Never show warning dialog box in command-line pkg installs.

Also,
 - add Background Music Device.driver to the array of bundles in
   pkgbuild.plist, and
 - don't warn about the permissions of the install dir for BGMXPCHelper
   in build_and_install.sh if it's only building.

.gitignore

@@ -2,6 +2,10 @@
 .*.swp
 /BGMDriver/BGMDriver/quick_install.conf
 /build_and_install.log
+.idea/
+tags
+cmake-build-debug/
+/Background-Music-*/
 
 # Everything below is from https://github.com/github/gitignore/blob/master/Objective-C.gitignore
 

.travis.yml

@@ -0,0 +1,90 @@
+language: objective-c
+matrix:
+  include:
+    - os: osx
+      osx_image: xcode8.3
+      xcode_sdk: macosx10.12
+      sudo: required
+      env: DEPLOY=true
+    - os: osx
+      osx_image: xcode8.2
+      xcode_sdk: macosx10.12
+      sudo: required
+    - os: osx
+      osx_image: xcode8.1
+      xcode_sdk: macosx10.12
+      sudo: required
+    - os: osx
+      osx_image: xcode8
+      xcode_sdk: macosx10.11
+      sudo: required
+    - os: osx
+      osx_image: xcode7.3
+      xcode_sdk: macosx10.11
+      sudo: required
+branches:
+  only:
+    - master
+install:
+# Install Apple's NullAudio device. Travis' VMs don't have any audio devices installed.
+  - sudo xcodebuild -project BGMApp/BGMAppTests/NullAudio/AudioDriverExamples.xcodeproj -target NullAudio DSTROOT="/" install
+  - sudo launchctl kickstart -kp system/com.apple.audio.coreaudiod || sudo killall coreaudiod
+script:
+# Build in a case-sensitive disk image to catch failures that only happen on case-sensitive filesystems.
+  - hdiutil create -type SPARSEBUNDLE -fs 'Case-sensitive Journaled HFS+' -volname bgmbuild -nospotlight -verbose -attach -size 50m bgmbuild.dmg
+  - sudo cp -r . /Volumes/bgmbuild
+  - cd /Volumes/bgmbuild
+# Install Background Music.
+  - yes | ./build_and_install.sh
+  - cat build_and_install.log
+  - find */build/Release/*/ -type f -exec md5 {} \;
+# Log the installed audio devices...
+  - system_profiler SPAudioDataType
+# ...and their IDs.
+  - say -a '?'
+# Check the BGM dirs and files were installed. (These fail if the dir/file isn't found.)
+  - ls -la "/Applications/Background Music.app"
+  - ls -la "/Library/Audio/Plug-Ins/HAL/Background Music Device.driver"
+  - ls -la "/usr/local/libexec/BGMXPCHelper.xpc" || ls -la "/Library/Application Support/Background Music/BGMXPCHelper.xpc"
+  - ls -la "/Library/LaunchDaemons/com.bearisdriving.BGM.XPCHelper.plist"
+# Close BGMApp (which the install script opened).
+  - osascript -e 'tell application "Background Music" to quit'
+# Skip the UI tests until Travis has support for them.
+  - BGMApp/BGMAppTests/UITests/travis-skip.py
+# Run the tests.
+  - xcodebuild -workspace BGM.xcworkspace -scheme 'Background Music Device' test
+  - xcodebuild -workspace BGM.xcworkspace -scheme 'Background Music' test
+  - xcodebuild -workspace BGM.xcworkspace -scheme 'BGMXPCHelper' test
+# Uninstall Background Music.
+  - yes | ./uninstall.sh
+# Check the BGM dirs and files were removed.
+  - if ls -la "/Applications/Background Music.app"; then false; fi
+  - if ls -la "/Library/Audio/Plug-Ins/HAL/Background Music Device.driver"; then false; fi
+  - if ls -la "/usr/local/libexec/BGMXPCHelper.xpc"; then false; fi
+  - if ls -la "/Library/Application Support/Background Music/BGMXPCHelper.xpc"; then false; fi
+  - if ls -la "/Library/LaunchDaemons/com.bearisdriving.BGM.XPCHelper.plist"; then false; fi
+# Build the .pkg installer.
+  - ./package.sh
+# Install the .pkg.
+  - sudo installer -pkg Background-Music-*/BackgroundMusic-*.pkg -target / -verbose -dumplog
+# Check the BGM dirs and files were installed again.
+  - ls -la "/Applications/Background Music.app"
+  - ls -la "/Library/Audio/Plug-Ins/HAL/Background Music Device.driver"
+  - ls -la "/usr/local/libexec/BGMXPCHelper.xpc" || ls -la "/Library/Application Support/Background Music/BGMXPCHelper.xpc"
+  - ls -la "/Library/LaunchDaemons/com.bearisdriving.BGM.XPCHelper.plist"
+# Post on IRC when Travis builds finish.
+notifications:
+  irc: "irc.freenode.org#backgroundmusic"
+# Upload the .pkg and dSYM zip to GitHub.
+deploy:
+  provider: releases
+  api_key:
+    secure: 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
+  file_glob: true
+  file: Background-Music-*/*
+  skip_cleanup: true
+  on:
+    repo: kyleneideck/BackgroundMusic
+    condition: $DEPLOY = true
+
+

BGM.xcworkspace/contents.xcworkspacedata

@@ -10,15 +10,33 @@
    <FileRef
       location = "group:README.md">
    </FileRef>
+   <FileRef
+      location = "group:MANUAL-INSTALL.md">
+   </FileRef>
+   <FileRef
+      location = "group:MANUAL-UNINSTALL.md">
+   </FileRef>
    <FileRef
       location = "group:TODO.md">
    </FileRef>
+   <FileRef
+      location = "group:DEVELOPING.md">
+   </FileRef>
    <FileRef
       location = "group:CONTRIBUTING.md">
    </FileRef>
    <FileRef
       location = "group:LICENSE">
    </FileRef>
+   <FileRef
+      location = "group:LICENSE-Apple-Sample-Code">
+   </FileRef>
+   <FileRef
+      location = "group:build_and_install.sh">
+   </FileRef>
+   <FileRef
+      location = "group:uninstall.sh">
+   </FileRef>
    <FileRef
       location = "group:Images">
    </FileRef>

BGMApp/BGMApp.xcodeproj/xcshareddata/xcschemes/BGMXPCHelper.xcscheme

@@ -1,6 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <Scheme
-   LastUpgradeVersion = "0720"
+   LastUpgradeVersion = "0820"
    version = "1.3">
    <BuildAction
       parallelizeBuildables = "YES"

BGMApp/BGMApp.xcodeproj/xcshareddata/xcschemes/Background Music.xcscheme

@@ -1,6 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <Scheme
-   LastUpgradeVersion = "0720"
+   LastUpgradeVersion = "0820"
    version = "1.3">
    <BuildAction
       parallelizeBuildables = "YES"
@@ -32,9 +32,19 @@
             skipped = "NO">
             <BuildableReference
                BuildableIdentifier = "primary"
-               BlueprintIdentifier = "1CB8B3481BBA75F0000E2DD1"
-               BuildableName = "BGMAppTests.xctest"
-               BlueprintName = "BGMAppTests"
+               BlueprintIdentifier = "2743C9F51D86CFF90089613B"
+               BuildableName = "BGMAppUnitTests.xctest"
+               BlueprintName = "BGMAppUnitTests"
+               ReferencedContainer = "container:BGMApp.xcodeproj">
+            </BuildableReference>
+         </TestableReference>
+         <TestableReference
+            skipped = "NO">
+            <BuildableReference
+               BuildableIdentifier = "primary"
+               BlueprintIdentifier = "1CCC4F531E584081008053E4"
+               BuildableName = "BGMAppUITests.xctest"
+               BlueprintName = "BGMAppUITests"
                ReferencedContainer = "container:BGMApp.xcodeproj">
             </BuildableReference>
          </TestableReference>
@@ -59,6 +69,7 @@
       useCustomWorkingDirectory = "NO"
       ignoresPersistentStateOnLaunch = "NO"
       debugDocumentVersioning = "YES"
+      enableAddressSanitizer = "YES"
       debugServiceExtension = "internal"
       allowLocationSimulation = "NO">
       <BuildableProductRunnable
@@ -74,7 +85,7 @@
       <EnvironmentVariables>
          <EnvironmentVariable
             key = "ASAN_OPTIONS"
-            value = "detect_odr_violation=0"
+            value = "detect_odr_violation=0,use_odr_indicator=1"
             isEnabled = "YES">
          </EnvironmentVariable>
       </EnvironmentVariables>

BGMApp/BGMApp/AppDelegate.mm

@@ -1,178 +0,0 @@
-// This file is part of Background Music.
-//
-// Background Music is free software: you can redistribute it and/or
-// modify it under the terms of the GNU General Public License as
-// published by the Free Software Foundation, either version 2 of the
-// License, or (at your option) any later version.
-//
-// Background Music is distributed in the hope that it will be useful,
-// but WITHOUT ANY WARRANTY; without even the implied warranty of
-// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
-// GNU General Public License for more details.
-//
-// You should have received a copy of the GNU General Public License
-// along with Background Music. If not, see <http://www.gnu.org/licenses/>.
-
-//
-//  AppDelegate.mm
-//  BGMApp
-//
-//  Copyright © 2016 Kyle Neideck
-//
-
-// Self Includes
-#import "AppDelegate.h"
-
-// Local Includes
-#include "BGM_Types.h"
-#import "BGMAudioDeviceManager.h"
-#import "BGMAutoPauseMusic.h"
-#import "BGMAppVolumes.h"
-#import "BGMPreferencesMenu.h"
-#import "BGMXPCListener.h"
-
-
-static float const kStatusBarIconPadding = 0.25;
-
-@implementation AppDelegate {
-    // The button in the system status bar (the bar with volume, battery, clock, etc.) to show the main menu
-    // for the app. These are called "menu bar extras" in the Human Interface Guidelines.
-    NSStatusItem* statusBarItem;
-    
-    BGMAutoPauseMusic* autoPauseMusic;
-    BGMAppVolumes* appVolumes;
-    BGMAudioDeviceManager* audioDevices;
-    BGMPreferencesMenu* prefsMenu;
-    BGMXPCListener* xpcListener;
-}
-
-- (void) awakeFromNib {
-    // Set up the status bar item
-    statusBarItem = [[NSStatusBar systemStatusBar] statusItemWithLength:NSSquareStatusItemLength];
-    
-    // Set the icon
-    NSImage* icon = [NSImage imageNamed:@"FermataIcon"];
-    if (icon != nil) {
-        CGFloat lengthMinusPadding = [[statusBarItem button] frame].size.height * (1 - kStatusBarIconPadding);
-        [icon setSize:NSMakeSize(lengthMinusPadding, lengthMinusPadding)];
-        // Make the icon a "template image" so it gets drawn colour-inverted when it's highlighted or the status
-        // bar's in dark mode
-        [icon setTemplate:YES];
-        statusBarItem.button.image = icon;
-    } else {
-        // If our icon is missing for some reason, fallback to a fermata character (1D110)
-        statusBarItem.button.title = @"𝄐";
-    }
-    
-    // Set the main menu
-    statusBarItem.menu = self.bgmMenu;
-}
-
-- (void) applicationDidFinishLaunching:(NSNotification*)aNotification {
-    #pragma unused (aNotification)
-    
-    // Set up the GUI and other external interfaces.
-
-    // Coordinates the audio devices (BGMDevice and the output device): manages playthrough, volume/mute controls, etc.
-    NSError* err;
-    audioDevices = [[BGMAudioDeviceManager alloc] initWithError:&err];
-    if (audioDevices == nil) {
-        [self showDeviceNotFoundErrorMessageAndExit:err.code];
-    }
-    [audioDevices setBGMDeviceAsOSDefault];
-    
-    autoPauseMusic = [[BGMAutoPauseMusic alloc] initWithAudioDevices:audioDevices];
-    
-    xpcListener = [[BGMXPCListener alloc] initWithAudioDevices:audioDevices
-                                  helperConnectionErrorHandler:^(NSError* error) {
-                                      [self showXPCHelperErrorMessageAndExit:error];
-                                  }];
-    
-    appVolumes = [[BGMAppVolumes alloc] initWithMenu:[self bgmMenu]
-                                       appVolumeView:[self appVolumeView]
-                                        audioDevices:audioDevices];
-    
-    prefsMenu = [[BGMPreferencesMenu alloc] initWithbgmMenu:[self bgmMenu]
-                                               audioDevices:audioDevices
-                                                 aboutPanel:[self aboutPanel]
-                                      aboutPanelLicenseView:[self aboutPanelLicenseView]];
-    
-    [self loadUserDefaults];
-}
-
-- (void) loadUserDefaults {
-    // Register the preference defaults. These are the preferences/state that only apply to BGMApp. The others are
-    // persisted on BGMDriver.
-    NSDictionary* appDefaults = [NSDictionary dictionaryWithObject:[NSNumber numberWithBool:YES]
-                                                            forKey:@"AutoPauseMusicEnabled"];
-    [[NSUserDefaults standardUserDefaults] registerDefaults:appDefaults];
-    
-    // Enable auto-pausing music if it's enabled in the user's preferences (which it is by default).
-    if ([[NSUserDefaults standardUserDefaults] boolForKey:@"AutoPauseMusicEnabled"]) {
-        [self toggleAutoPauseMusic:self];
-    }
-}
-
-- (void) showDeviceNotFoundErrorMessageAndExit:(NSInteger)code {
-    // Show an error dialog and exit if either BGMDevice wasn't found on the system or we couldn't find any output devices
-    
-    // NSAlert should only be used on the main thread.
-    dispatch_async(dispatch_get_main_queue(), ^{
-        NSAlert* alert = [NSAlert new];
-        
-        if (code == kBGMErrorCode_BGMDeviceNotFound) {
-            // TODO: Check whether the driver files are in /Library/Audio/Plug-Ins/HAL and offer to install them if not. Also,
-            //       it would be nice if we could restart coreaudiod automatically (using launchd).
-            [alert setMessageText:@"Could not find the Background Music virtual audio device."];
-            [alert setInformativeText:@"Make sure you've installed Background Music.driver to /Library/Audio/Plug-Ins/HAL and restarted coreaudiod (e.g. \"sudo killall coreaudiod\")."];
-        } else if (code == kBGMErrorCode_OutputDeviceNotFound) {
-            [alert setMessageText:@"Could not find an audio output device."];
-            [alert setInformativeText:@"If you do have one installed, this is probably a bug. Sorry about that. Feel free to file an issue on GitHub."];
-        }
-        
-        [alert runModal];
-        [NSApp terminate:self];
-    });
-}
-
-- (void) showXPCHelperErrorMessageAndExit:(NSError*)error {
-    // NSAlert should only be used on the main thread.
-    dispatch_async(dispatch_get_main_queue(), ^{
-        NSAlert* alert = [NSAlert new];
-        
-        // TODO: Offer to install BGMXPCHelper if it's missing.
-        [alert setMessageText:@"Error connecting to BGMXPCHelper."];
-        [alert setInformativeText:[NSString stringWithFormat:@"%s%s%@ (%lu)",
-                                   "Make sure you have BGMXPCHelper installed. There are instructions in the README.md file.",
-                                   "\n\nDetails:\n",
-                                   [error localizedDescription],
-                                   [error code]]];
-        
-        [alert runModal];
-        [NSApp terminate:self];
-    });
-}
-
-- (void) applicationWillTerminate:(NSNotification*)aNotification {
-    #pragma unused (aNotification)
-    [audioDevices unsetBGMDeviceAsOSDefault];
-}
-
-- (IBAction) toggleAutoPauseMusic:(id)sender {
-    #pragma unused (sender)
-    
-    if (self.autoPauseMenuItem.state == NSOnState) {
-        self.autoPauseMenuItem.state = NSOffState;
-        [autoPauseMusic disable];
-    } else {
-        self.autoPauseMenuItem.state = NSOnState;
-        [autoPauseMusic enable];
-    }
-    
-    // Persist the change in the user's preferences
-    [[NSUserDefaults standardUserDefaults] setBool:(self.autoPauseMenuItem.state == NSOnState)
-                                            forKey:@"AutoPauseMusicEnabled"];
-}
-
-@end
-

BGMApp/BGMApp/BGMAppDelegate.h

@@ -14,7 +14,7 @@
 // along with Background Music. If not, see <http://www.gnu.org/licenses/>.
 
 //
-//  AppDelegate.h
+//  BGMAppDelegate.h
 //  BGMApp
 //
 //  Copyright © 2016 Kyle Neideck
@@ -22,16 +22,22 @@
 //  Sets up and tears down the app.
 //
 
+// Local Includes
+#import "BGMAudioDeviceManager.h"
+
+// System Includes
 #import <Cocoa/Cocoa.h>
 
 
-@interface AppDelegate : NSObject <NSApplicationDelegate>
+@interface BGMAppDelegate : NSObject <NSApplicationDelegate, NSMenuDelegate>
 
 @property (weak) IBOutlet NSMenu* bgmMenu;
-@property (weak) IBOutlet NSMenuItem* autoPauseMenuItem;
 @property (weak) IBOutlet NSView* appVolumeView;
 @property (weak) IBOutlet NSPanel* aboutPanel;
-@property (unsafe_unretained) IBOutlet NSTextView *aboutPanelLicenseView;
+@property (unsafe_unretained) IBOutlet NSTextView* aboutPanelLicenseView;
+@property (weak) IBOutlet NSMenuItem* autoPauseMenuItemUnwrapped;
+
+@property (readonly) BGMAudioDeviceManager* audioDevices;
 
 @end
 

BGMApp/BGMApp/BGMAppDelegate.mm

@@ -0,0 +1,335 @@
+// This file is part of Background Music.
+//
+// Background Music is free software: you can redistribute it and/or
+// modify it under the terms of the GNU General Public License as
+// published by the Free Software Foundation, either version 2 of the
+// License, or (at your option) any later version.
+//
+// Background Music is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Background Music. If not, see <http://www.gnu.org/licenses/>.
+
+//
+//  BGMAppDelegate.mm
+//  BGMApp
+//
+//  Copyright © 2016, 2017 Kyle Neideck
+//
+
+// Self Includes
+#import "BGMAppDelegate.h"
+
+// Local Includes
+#import "BGM_Types.h"
+#import "BGMUserDefaults.h"
+#import "BGMMusicPlayers.h"
+#import "BGMAutoPauseMusic.h"
+#import "BGMAutoPauseMenuItem.h"
+#import "BGMAppVolumes.h"
+#import "BGMPreferencesMenu.h"
+#import "BGMXPCListener.h"
+#import "SystemPreferences.h"
+
+
+#pragma clang assume_nonnull begin
+
+static float const kStatusBarIconPadding = 0.25;
+
+@implementation BGMAppDelegate {
+    // The button in the system status bar (the bar with volume, battery, clock, etc.) to show the main menu
+    // for the app. These are called "menu bar extras" in the Human Interface Guidelines.
+    NSStatusItem* statusBarItem;
+    
+    // Only show the 'BGMXPCHelper is missing' error dialog once.
+    BOOL haveShownXPCHelperErrorMessage;
+    
+    BGMAutoPauseMusic* autoPauseMusic;
+    BGMAutoPauseMenuItem* autoPauseMenuItem;
+    BGMMusicPlayers* musicPlayers;
+    BGMAppVolumes* appVolumes;
+    BGMPreferencesMenu* prefsMenu;
+    BGMXPCListener* xpcListener;
+}
+
+@synthesize audioDevices = audioDevices;
+
+- (void) awakeFromNib {
+    // Show BGMApp in the dock, if the command-line option for that was passed. This is used by the UI tests.
+    if ([NSProcessInfo.processInfo.arguments indexOfObject:@"--show-dock-icon"] != NSNotFound) {
+        [NSApp setActivationPolicy:NSApplicationActivationPolicyRegular];
+    }
+    
+    haveShownXPCHelperErrorMessage = NO;
+
+    [self initStatusBarItem];
+}
+
+// Set up the status bar item. (The thing you click to show BGMApp's UI.)
+- (void) initStatusBarItem {
+    statusBarItem = [[NSStatusBar systemStatusBar] statusItemWithLength:NSSquareStatusItemLength];
+    
+    // Set the icon
+    NSImage* icon = [NSImage imageNamed:@"FermataIcon"];
+
+    // NSStatusItem doesn't have the "button" property on OS X 10.9.
+    BOOL buttonAvailable = (floor(NSAppKitVersionNumber) >= NSAppKitVersionNumber10_10);
+
+    if (icon != nil) {
+        NSRect statusBarItemFrame;
+
+        if (buttonAvailable) {
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wpartial-availability"
+            statusBarItemFrame = statusBarItem.button.frame;
+#pragma clang diagnostic pop
+        } else {
+            // OS X 10.9 fallback. I haven't tested this (or anything else on 10.9).
+            statusBarItemFrame = statusBarItem.view.frame;
+        }
+
+        CGFloat lengthMinusPadding = statusBarItemFrame.size.height * (1 - kStatusBarIconPadding);
+        [icon setSize:NSMakeSize(lengthMinusPadding, lengthMinusPadding)];
+
+        // Make the icon a "template image" so it gets drawn colour-inverted when it's highlighted or the status
+        // bar's in dark mode
+        [icon setTemplate:YES];
+
+        if (buttonAvailable) {
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wpartial-availability"
+            statusBarItem.button.image = icon;
+#pragma clang diagnostic pop
+        } else {
+            statusBarItem.image = icon;
+        }
+    } else {
+        // If our icon is missing for some reason, fallback to a fermata character (1D110)
+        if (buttonAvailable) {
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wpartial-availability"
+            statusBarItem.button.title = @"𝄐";
+#pragma clang diagnostic pop
+        } else {
+            statusBarItem.title = @"𝄐";
+        }
+    }
+    
+    // Set the main menu
+    statusBarItem.menu = self.bgmMenu;
+}
+
+- (void) applicationDidFinishLaunching:(NSNotification*)aNotification {
+    #pragma unused (aNotification)
+    
+    // Log the version/build number.
+    //
+    // TODO: NSLog should only be used for logging errors.
+    // TODO: Automatically add the commit ID to the end of the build number for unreleased builds. (In the
+    //       Info.plist or something -- not here.)
+    NSLog(@"BGMApp version: %@, BGMApp build number: %@",
+          NSBundle.mainBundle.infoDictionary[@"CFBundleShortVersionString"],
+          NSBundle.mainBundle.infoDictionary[@"CFBundleVersion"]);
+
+    // Set up the rest of the UI and other external interfaces.
+
+    // audioDevices coordinates BGMDevice and the output device. It manages playthrough, volume/mute controls, etc.
+    {
+        NSError* error;
+        audioDevices = [[BGMAudioDeviceManager alloc] initWithError:&error];
+        if (audioDevices == nil) {
+            [self showDeviceNotFoundErrorMessageAndExit:error.code];
+            return;
+        }
+    }
+
+    {
+        NSError* error = [audioDevices setBGMDeviceAsOSDefault];
+        if (error) {
+            [self showSetDeviceAsDefaultError:error
+                                      message:@"Could not set Background Music Device as your default audio device."
+                              informativeText:@"You might be able to set it yourself."];
+        }
+    }
+
+    BGMUserDefaults* userDefaults = [self createUserDefaults];
+
+    musicPlayers = [[BGMMusicPlayers alloc] initWithAudioDevices:audioDevices
+                                                    userDefaults:userDefaults];
+    
+    autoPauseMusic = [[BGMAutoPauseMusic alloc] initWithAudioDevices:audioDevices
+                                                        musicPlayers:musicPlayers];
+    
+    autoPauseMenuItem = [[BGMAutoPauseMenuItem alloc] initWithMenuItem:self.autoPauseMenuItemUnwrapped
+                                                        autoPauseMusic:autoPauseMusic
+                                                          musicPlayers:musicPlayers
+                                                          userDefaults:userDefaults];
+    
+    xpcListener = [[BGMXPCListener alloc] initWithAudioDevices:audioDevices
+                                  helperConnectionErrorHandler:^(NSError* error) {
+                                      NSLog(@"BGMAppDelegate::applicationDidFinishLaunching: (helperConnectionErrorHandler) "
+                                             "BGMXPCHelper connection error: %@",
+                                            error);
+                                      
+                                      [self showXPCHelperErrorMessage:error];
+                                  }];
+    
+    appVolumes = [[BGMAppVolumes alloc] initWithMenu:self.bgmMenu
+                                       appVolumeView:self.appVolumeView
+                                        audioDevices:audioDevices];
+    
+    prefsMenu = [[BGMPreferencesMenu alloc] initWithBGMMenu:self.bgmMenu
+                                               audioDevices:audioDevices
+                                               musicPlayers:musicPlayers
+                                                 aboutPanel:self.aboutPanel
+                                      aboutPanelLicenseView:self.aboutPanelLicenseView];
+    
+    // Handle events about the main menu. (See the NSMenuDelegate methods below.)
+    self.bgmMenu.delegate = self;
+}
+
+- (BGMUserDefaults*) createUserDefaults {
+    BOOL persistentDefaults = [NSProcessInfo.processInfo.arguments indexOfObject:@"--no-persistent-data"] == NSNotFound;
+    NSUserDefaults* wrappedDefaults = persistentDefaults ? [NSUserDefaults standardUserDefaults] : nil;
+    return [[BGMUserDefaults alloc] initWithDefaults:wrappedDefaults];
+}
+
+- (void) applicationWillTerminate:(NSNotification*)aNotification {
+    #pragma unused (aNotification)
+    
+    DebugMsg("BGMAppDelegate::applicationWillTerminate");
+
+    NSError* error = [audioDevices unsetBGMDeviceAsOSDefault];
+    
+    if (error) {
+        [self showSetDeviceAsDefaultError:error
+                                  message:@"Failed to reset your system's audio output device."
+                          informativeText:@"You'll have to change it yourself to get audio working again."];
+    }
+}
+
+#pragma mark Error messages
+
+- (void) showDeviceNotFoundErrorMessageAndExit:(NSInteger)code {
+    // Show an error dialog and exit if either BGMDevice wasn't found on the system or we couldn't find any output devices
+    
+    // NSAlert should only be used on the main thread.
+    dispatch_async(dispatch_get_main_queue(), ^{
+        NSAlert* alert = [NSAlert new];
+        
+        if (code == kBGMErrorCode_BGMDeviceNotFound) {
+            // TODO: Check whether the driver files are in /Library/Audio/Plug-Ins/HAL and offer to install them if not. Also,
+            //       it would be nice if we could restart coreaudiod automatically (using launchd).
+            [alert setMessageText:@"Could not find the Background Music virtual audio device."];
+            [alert setInformativeText:@"Make sure you've installed Background Music.driver to /Library/Audio/Plug-Ins/HAL and restarted coreaudiod (e.g. \"sudo killall coreaudiod\")."];
+        } else if (code == kBGMErrorCode_OutputDeviceNotFound) {
+            [alert setMessageText:@"Could not find an audio output device."];
+            [alert setInformativeText:@"If you do have one installed, this is probably a bug. Sorry about that. Feel free to file an issue on GitHub."];
+        }
+        
+        [alert runModal];
+        [NSApp terminate:self];
+    });
+}
+
+- (void) showXPCHelperErrorMessage:(NSError*)error {
+    if (!haveShownXPCHelperErrorMessage) {
+        haveShownXPCHelperErrorMessage = YES;
+        
+        // NSAlert should only be used on the main thread.
+        dispatch_async(dispatch_get_main_queue(), ^{
+            NSAlert* alert = [NSAlert new];
+            
+            // TODO: Offer to install BGMXPCHelper if it's missing.
+            // TODO: Show suppression button?
+            [alert setMessageText:@"Error connecting to BGMXPCHelper."];
+            [alert setInformativeText:[NSString stringWithFormat:@"%s%s%@ (%lu)",
+                                       "Make sure you have BGMXPCHelper installed. There are instructions in the "
+                                       "README.md file.\n\n"
+                                       "Background Music might still work, but it won't work as well as it could.",
+                                       "\n\nDetails:\n",
+                                       [error localizedDescription],
+                                       [error code]]];
+            [alert runModal];
+        });
+    }
+}
+
+- (void) showSetDeviceAsDefaultError:(NSError*)error
+                             message:(NSString*)msg
+                     informativeText:(NSString*)info {
+    dispatch_async(dispatch_get_main_queue(), ^{
+        NSLog(@"%@ %@ Error: %@", msg, info, error);
+        
+        NSAlert* alert = [NSAlert alertWithError:error];
+        alert.messageText = msg;
+        alert.informativeText = info;
+        
+        [alert addButtonWithTitle:@"OK"];
+        [alert addButtonWithTitle:@"Open Sound in System Preferences"];
+        
+        NSModalResponse buttonClicked = [alert runModal];
+        
+        if (buttonClicked != NSAlertFirstButtonReturn) {  // 'OK' is the first button.
+            [self openSysPrefsSoundOutput];
+        }
+    });
+}
+
+- (void) openSysPrefsSoundOutput {
+    SystemPreferencesApplication* __nullable sysPrefs =
+        [SBApplication applicationWithBundleIdentifier:@"com.apple.systempreferences"];
+    
+    if (!sysPrefs) {
+        NSLog(@"Could not open System Preferences");
+        return;
+    }
+    
+    // In System Preferences, go to the "Output" tab on the "Sound" pane.
+    for (SystemPreferencesPane* pane : [sysPrefs panes]) {
+        DebugMsg("BGMAppDelegate::openSysPrefsSoundOutput: pane = %s", [pane.name UTF8String]);
+        
+        if ([pane.id isEqualToString:@"com.apple.preference.sound"]) {
+            sysPrefs.currentPane = pane;
+            
+            for (SystemPreferencesAnchor* anchor : [pane anchors]) {
+                DebugMsg("BGMAppDelegate::openSysPrefsSoundOutput: anchor = %s", [anchor.name UTF8String]);
+                
+                if ([[anchor.name lowercaseString] isEqualToString:@"output"]) {
+                    DebugMsg("BGMAppDelegate::openSysPrefsSoundOutput: Showing Output in Sound pane.");
+                    
+                    [anchor reveal];
+                }
+            }
+        }
+    }
+    
+    // Bring System Preferences to the foreground.
+    [sysPrefs activate];
+}
+
+#pragma mark NSMenuDelegate
+
+- (void) menuNeedsUpdate:(NSMenu*)menu {
+    if ([menu isEqual:self.bgmMenu]) {
+        [autoPauseMenuItem parentMenuNeedsUpdate];
+    } else {
+        DebugMsg("BGMAppDelegate::menuNeedsUpdate: Warning: unexpected menu. menu=%s", menu.description.UTF8String);
+    }
+}
+
+- (void) menu:(NSMenu*)menu willHighlightItem:(NSMenuItem* __nullable)item {
+    if ([menu isEqual:self.bgmMenu]) {
+        [autoPauseMenuItem parentMenuItemWillHighlight:item];
+    } else {
+        DebugMsg("BGMAppDelegate::menu: Warning: unexpected menu. menu=%s", menu.description.UTF8String);
+    }
+}
+
+@end
+
+#pragma clang assume_nonnull end
+

BGMApp/BGMApp/BGMAppVolumes.h

@@ -35,23 +35,32 @@
 
 // Protocol for the UI custom classes
 
-@protocol BGMAppVolumeSubview <NSObject>
+@protocol BGMAppVolumeMenuItemSubview <NSObject>
 
-- (void) setUpWithApp:(NSRunningApplication*)app context:(BGMAppVolumes*)ctx;
+- (void) setUpWithApp:(NSRunningApplication*)app context:(BGMAppVolumes*)ctx menuItem:(NSMenuItem*)item;
 
 @end
 
 // Custom classes for the UI elements in the app volume menu items
 
-@interface BGMAVM_AppIcon : NSImageView <BGMAppVolumeSubview>
+@interface BGMAVM_AppIcon : NSImageView <BGMAppVolumeMenuItemSubview>
 @end
 
-@interface BGMAVM_AppNameLabel : NSTextField <BGMAppVolumeSubview>
+@interface BGMAVM_AppNameLabel : NSTextField <BGMAppVolumeMenuItemSubview>
 @end
 
-@interface BGMAVM_VolumeSlider : NSSlider <BGMAppVolumeSubview>
+@interface BGMAVM_ShowMoreControlsButton : NSButton <BGMAppVolumeMenuItemSubview>
+@end
+
+@interface BGMAVM_VolumeSlider : NSSlider <BGMAppVolumeMenuItemSubview>
 
 - (void) setRelativeVolume:(NSNumber*)relativeVolume;
 
 @end
 
+@interface BGMAVM_PanSlider : NSSlider <BGMAppVolumeMenuItemSubview>
+
+- (void) setPanPosition:(NSNumber*)panPosition;
+
+@end
+

BGMApp/BGMApp/BGMAppVolumes.mm

@@ -17,7 +17,8 @@
 //  BGMAppVolumes.m
 //  BGMApp
 //
-//  Copyright © 2016 Kyle Neideck
+//  Copyright © 2016, 2017 Kyle Neideck
+//  Copyright © 2017 Andrew Tonner
 //
 
 // Self Include
@@ -25,6 +26,7 @@
 
 // BGM Includes
 #include "BGM_Types.h"
+#include "BGM_Utils.h"
 
 // PublicUtility Includes
 #include "CACFDictionary.h"
@@ -32,14 +34,20 @@
 #include "CACFString.h"
 
 
-static NSInteger const kAppVolumesMenuItemTag = 3;
+// Tags for UI elements in MainMenu.xib
+static NSInteger const kAppVolumesHeadingMenuItemTag = 3;
 static NSInteger const kSeparatorBelowAppVolumesMenuItemTag = 4;
 
 static float const kSlidersSnapWithin = 5;
 
+static CGFloat const kAppVolumeViewInitialHeight = 20;
+
 @implementation BGMAppVolumes {
     NSMenu* bgmMenu;
+    
     NSView* appVolumeView;
+    CGFloat appVolumeViewFullHeight;
+    
     BGMAudioDeviceManager* audioDevices;
 }
 
@@ -47,6 +55,7 @@ static float const kSlidersSnapWithin = 5;
     if ((self = [super init])) {
         bgmMenu = menu;
         appVolumeView = view;
+        appVolumeViewFullHeight = appVolumeView.frame.size.height;
         audioDevices = devices;
         
         // Create the menu items for controlling app volumes
@@ -66,71 +75,88 @@ static float const kSlidersSnapWithin = 5;
     [[NSWorkspace sharedWorkspace] removeObserver:self forKeyPath:@"runningApplications" context:nil];
 }
 
+#pragma mark UI Modifications
+
 - (void) insertMenuItemsForApps:(NSArray<NSRunningApplication*>*)apps {
     NSAssert([NSThread isMainThread], @"insertMenuItemsForApps is not thread safe");
     
 #ifndef NS_BLOCK_ASSERTIONS  // If assertions are enabled
-    NSInteger numMenuItemsBeforeInsert =
-        [bgmMenu indexOfItemWithTag:kSeparatorBelowAppVolumesMenuItemTag] - [bgmMenu indexOfItemWithTag:kAppVolumesMenuItemTag] - 1;
+    auto numMenuItems = [&self]() {
+        NSInteger headingIdx = [bgmMenu indexOfItemWithTag:kAppVolumesHeadingMenuItemTag];
+        NSInteger separatorIdx = [bgmMenu indexOfItemWithTag:kSeparatorBelowAppVolumesMenuItemTag];
+        return separatorIdx - headingIdx - 1;
+    };
+    
+    NSInteger numMenuItemsBeforeInsert = numMenuItems();
     NSUInteger numApps = 0;
 #endif
     
-    // Create a blank menu item to copy as a template
-    NSMenuItem* blankItem = [[NSMenuItem alloc] initWithTitle:@"" action:nil keyEquivalent:@""];
-    [blankItem setView:appVolumeView];
-    
     // Get the app volumes currently set on the device
     CACFArray appVolumesOnDevice((CFArrayRef)[audioDevices bgmDevice].GetPropertyData_CFType(kBGMAppVolumesAddress), false);
     
-    NSInteger index = [bgmMenu indexOfItemWithTag:kAppVolumesMenuItemTag] + 1;
+    NSInteger index = [bgmMenu indexOfItemWithTag:kAppVolumesHeadingMenuItemTag] + 1;
     
     // Add a volume-control menu item for each app
     for (NSRunningApplication* app in apps) {
         // Only show apps that appear in the dock (at first)
         // TODO: Would it be better to only show apps that are registered as HAL clients?
-        if ([app activationPolicy] != NSApplicationActivationPolicyRegular) continue;
-        
-        // Don't show Finder
-        if ([[app bundleIdentifier] isEqualTo:@"com.apple.finder"]) continue;
+        if (app.activationPolicy != NSApplicationActivationPolicyRegular) continue;
         
 #ifndef NS_BLOCK_ASSERTIONS  // If assertions are enabled
         // Count how many apps we should add menu items for so we can check it at the end of the method
         numApps++;
 #endif
         
-        NSMenuItem* appVolItem = [blankItem copy];
+        NSMenuItem* appVolItem = [self createBlankAppVolumeMenuItem];
         
         // Look through the menu item's subviews for the ones we want to set up
-        for (NSView* subview in [[appVolItem view] subviews]) {
-            if ([subview conformsToProtocol:@protocol(BGMAppVolumeSubview)]) {
-                [subview performSelector:@selector(setUpWithApp:context:) withObject:app withObject:self];
+        for (NSView* subview in appVolItem.view.subviews) {
+            if ([subview conformsToProtocol:@protocol(BGMAppVolumeMenuItemSubview)]) {
+                [(NSView<BGMAppVolumeMenuItemSubview>*)subview setUpWithApp:app context:self menuItem:appVolItem];
             }
         }
         
         // Store the NSRunningApplication object with the menu item so when the app closes we can find the item to remove it
-        [appVolItem setRepresentedObject:app];
+        appVolItem.representedObject = app;
         
         // Set the slider to the volume for this app if we got one from the driver
         [self setVolumeOfMenuItem:appVolItem fromAppVolumes:appVolumesOnDevice];
-        
+
+        // NSMenuItem didn't implement NSAccessibility before OS X SDK 10.12.
+#if MAC_OS_X_VERSION_MAX_ALLOWED >= 101200  // MAC_OS_X_VERSION_10_12
+        if ([appVolItem respondsToSelector:@selector(setAccessibilityTitle:)]) {
+            // TODO: This doesn't show up in Accessibility Inspector for me. Not sure why.
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wpartial-availability"
+            appVolItem.accessibilityTitle = [NSString stringWithFormat:@"%@", [app localizedName]];
+#pragma clang diagnostic pop
+        }
+#endif
+
         [bgmMenu insertItem:appVolItem atIndex:index];
     }
     
-#ifndef NS_BLOCK_ASSERTIONS  // If assertions are enabled
-    NSInteger numMenuItemsAfterInsert =
-        [bgmMenu indexOfItemWithTag:kSeparatorBelowAppVolumesMenuItemTag] - [bgmMenu indexOfItemWithTag:kAppVolumesMenuItemTag] - 1;
-    NSAssert3(numMenuItemsAfterInsert == (numMenuItemsBeforeInsert + numApps),
-              @"Did not add the expected number of menu items. numMenuItemsBeforeInsert=%ld numMenuItemsAfterInsert=%ld numAppsToAdd=%lu",
+    NSAssert3(numMenuItems() == (numMenuItemsBeforeInsert + numApps),
+              @"Added more/fewer menu items than there were apps. Items before: %ld, items after: %ld, apps: %lu",
               (long)numMenuItemsBeforeInsert,
-              (long)numMenuItemsAfterInsert,
+              (long)numMenuItems(),
               (unsigned long)numApps);
-#endif
+}
+
+// Create a blank menu item to copy as a template.
+- (NSMenuItem*) createBlankAppVolumeMenuItem {
+    NSMenuItem* menuItem = [[NSMenuItem alloc] initWithTitle:@"" action:nil keyEquivalent:@""];
+    
+    menuItem.view = appVolumeView;
+    menuItem = [menuItem copy];  // So we can modify a copy of the view, rather than the template itself.
+    
+    return menuItem;
 }
 
 - (void) removeMenuItemsForApps:(NSArray<NSRunningApplication*>*)apps {
     NSAssert([NSThread isMainThread], @"removeMenuItemsForApps is not thread safe");
     
-    NSInteger firstItemIndex = [bgmMenu indexOfItemWithTag:kAppVolumesMenuItemTag] + 1;
+    NSInteger firstItemIndex = [bgmMenu indexOfItemWithTag:kAppVolumesHeadingMenuItemTag] + 1;
     NSInteger lastItemIndex = [bgmMenu indexOfItemWithTag:kSeparatorBelowAppVolumesMenuItemTag] - 1;
     
     // Check each app volume menu item, removing the items that control one of the given apps
@@ -138,7 +164,7 @@ static float const kSlidersSnapWithin = 5;
         NSMenuItem* item = [bgmMenu itemAtIndex:i];
         
         for (NSRunningApplication* appToBeRemoved in apps) {
-            NSRunningApplication* itemApp = [item representedObject];
+            NSRunningApplication* itemApp = item.representedObject;
             
             if ([itemApp isEqual:appToBeRemoved]) {
                 [bgmMenu removeItem:item];
@@ -153,7 +179,7 @@ static float const kSlidersSnapWithin = 5;
 - (void) setVolumeOfMenuItem:(NSMenuItem*)menuItem fromAppVolumes:(CACFArray&)appVolumes {
     // Set menuItem's volume slider to the volume of the app in appVolumes that menuItem represents
     // Leaves menuItem unchanged if it doesn't match any of the apps in appVolumes
-    NSRunningApplication* representedApp = [menuItem representedObject];
+    NSRunningApplication* representedApp = menuItem.representedObject;
     
     for (UInt32 i = 0; i < appVolumes.GetNumberItems(); i++) {
         CACFDictionary appVolume(false);
@@ -167,21 +193,76 @@ static float const kSlidersSnapWithin = 5;
         pid_t pid;
         appVolume.GetSInt32(CFSTR(kBGMAppVolumesKey_ProcessID), pid);
         
-        if ([representedApp processIdentifier] == pid ||
-            [[representedApp bundleIdentifier] isEqualToString:(__bridge NSString*)bundleID.GetCFString()]) {
+        if ((representedApp.processIdentifier == pid) ||
+            [representedApp.bundleIdentifier isEqualToString:(__bridge NSString*)bundleID.GetCFString()]) {
             CFTypeRef relativeVolume;
             appVolume.GetCFType(CFSTR(kBGMAppVolumesKey_RelativeVolume), relativeVolume);
             
+            CFTypeRef panPosition;
+            appVolume.GetCFType(CFSTR(kBGMAppVolumesKey_PanPosition), panPosition);
+            
             // Update the slider
-            for (NSView* subview in [[menuItem view] subviews]) {
+            for (NSView* subview in menuItem.view.subviews) {
                 if ([subview respondsToSelector:@selector(setRelativeVolume:)]) {
                     [subview performSelector:@selector(setRelativeVolume:) withObject:(__bridge NSNumber*)relativeVolume];
                 }
+                if ([subview respondsToSelector:@selector(setPanPosition:)]) {
+                    [subview performSelector:@selector(setPanPosition:) withObject:(__bridge NSNumber*)panPosition];
+                }
             }
         }
     }
 }
 
+- (void) showHideExtraControls:(BGMAVM_ShowMoreControlsButton*)button {
+    // Show or hide an app's extra controls, currently only pan, in its App Volumes menu item.
+    
+    NSMenuItem* menuItem = button.cell.representedObject;
+    
+    BGMAssert(button, "!button");
+    BGMAssert(menuItem, "!menuItem");
+    
+    CGFloat width = menuItem.view.frame.size.width;
+    CGFloat height = menuItem.view.frame.size.height;
+    
+#if DEBUG
+    const char* appName = [((NSRunningApplication*)menuItem.representedObject).localizedName UTF8String];
+#endif
+    
+    auto nearEnough = [](CGFloat x, CGFloat y) {  // Shouldn't be necessary, but just in case.
+        return fabs(x - y) < 0.01;  // We don't need much precision.
+    };
+    
+    if (nearEnough(button.frameCenterRotation, 0.0)) {
+        // Hide extra controls
+        DebugMsg("BGMAppVolumes::showHideExtraControls: Hiding extra controls (%s)", appName);
+        
+        BGMAssert(nearEnough(height, appVolumeViewFullHeight), "Extra controls were already hidden");
+        
+        // Make the menu item shorter to hide the extra controls. Keep the width unchanged.
+        menuItem.view.frameSize = { width, kAppVolumeViewInitialHeight };
+        // Turn the button upside down so the arrowhead points down.
+        button.frameCenterRotation = 180.0;
+        // Move the button up slightly so it aligns with the volume slider.
+        [button setFrameOrigin:NSMakePoint(button.frame.origin.x, button.frame.origin.y - 1)];
+    } else {
+        // Show extra controls
+        DebugMsg("BGMAppVolumes::showHideExtraControls: Showing extra controls (%s)", appName);
+        
+        BGMAssert(nearEnough(button.frameCenterRotation, 180.0), "Unexpected button rotation");
+        BGMAssert(nearEnough(height, kAppVolumeViewInitialHeight), "Extra controls were already shown");
+        
+        // Make the menu item taller to show the extra controls. Keep the width unchanged.
+        menuItem.view.frameSize = { width, appVolumeViewFullHeight };
+        // Turn the button rightside up so the arrowhead points up.
+        button.frameCenterRotation = 0.0;
+        // Move the button down slightly, back to it's original position.
+        [button setFrameOrigin:NSMakePoint(button.frame.origin.x, button.frame.origin.y + 1)];
+    }
+}
+
+#pragma mark KVO
+
 - (void) observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context
 {
     #pragma unused (object, context)
@@ -214,6 +295,8 @@ static float const kSlidersSnapWithin = 5;
     }
 }
 
+#pragma mark BGMDevice Communication
+
 - (void) sendVolumeChangeToBGMDevice:(SInt32)newVolume appProcessID:(pid_t)appProcessID appBundleID:(NSString*)appBundleID {
     CACFDictionary appVolumeChange(true);
     appVolumeChange.AddSInt32(CFSTR(kBGMAppVolumesKey_ProcessID), appProcessID);
@@ -227,26 +310,70 @@ static float const kSlidersSnapWithin = 5;
     [audioDevices bgmDevice].SetPropertyData_CFType(kBGMAppVolumesAddress, appVolumeChanges.AsPropertyList());
 }
 
+- (void) sendPanPositionChangeToBGMDevice:(SInt32)newPanPosition appProcessID:(pid_t)appProcessID appBundleID:(NSString*)appBundleID {
+    CACFDictionary appVolumeChange(true);
+    appVolumeChange.AddSInt32(CFSTR(kBGMAppVolumesKey_ProcessID), appProcessID);
+    appVolumeChange.AddString(CFSTR(kBGMAppVolumesKey_BundleID), (__bridge CFStringRef)appBundleID);
+    
+    // The values from our sliders are in [kAppPanLeftRawValue, kAppPanRightRawValue] already
+    appVolumeChange.AddSInt32(CFSTR(kBGMAppVolumesKey_PanPosition), newPanPosition);
+    
+    CACFArray appVolumeChanges(true);
+    appVolumeChanges.AppendDictionary(appVolumeChange.GetDict());
+    
+    [audioDevices bgmDevice].SetPropertyData_CFType(kBGMAppVolumesAddress, appVolumeChanges.AsPropertyList());
+}
+
 @end
 
+#pragma mark Custom Classes (IB)
+
 // Custom classes for the UI elements in the app volume menu items
 
 @implementation BGMAVM_AppIcon
 
-- (void) setUpWithApp:(NSRunningApplication*)app context:(BGMAppVolumes*)ctx {
-    #pragma unused (ctx)
+- (void) setUpWithApp:(NSRunningApplication*)app context:(BGMAppVolumes*)ctx menuItem:(NSMenuItem*)menuItem {
+    #pragma unused (ctx, menuItem)
     
-    [self setImage:[app icon]];
+    self.image = app.icon;
 }
 
 @end
 
 @implementation BGMAVM_AppNameLabel
 
-- (void) setUpWithApp:(NSRunningApplication*)app context:(BGMAppVolumes*)ctx {
-    #pragma unused (ctx)
+- (void) setUpWithApp:(NSRunningApplication*)app context:(BGMAppVolumes*)ctx menuItem:(NSMenuItem*)menuItem {
+    #pragma unused (ctx, menuItem)
     
-    [self setStringValue:[app localizedName]];
+    NSString* name = app.localizedName ? (NSString*)app.localizedName : @"";
+    self.stringValue = name;
+}
+
+@end
+
+@implementation BGMAVM_ShowMoreControlsButton
+
+- (void) setUpWithApp:(NSRunningApplication*)app context:(BGMAppVolumes*)ctx menuItem:(NSMenuItem*)menuItem {
+    #pragma unused (app)
+    
+    // Set up the button that show/hide the extra controls (currently only a pan slider) for the app.
+    self.cell.representedObject = menuItem;
+    self.target = ctx;
+    self.action = @selector(showHideExtraControls:);
+    
+    // The menu item starts out with the extra controls visible, so we hide them here.
+    //
+    // TODO: Leave them visible if any of the controls are set to non-default values. The user has no way to
+    //       tell otherwise. Maybe we should also make this button look different if the controls are hidden
+    //       when they have non-default values.
+    [ctx showHideExtraControls:self];
+
+    if ([self respondsToSelector:@selector(setAccessibilityTitle:)]) {
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wpartial-availability"
+        self.accessibilityTitle = @"More options";
+#pragma clang diagnostic pop
+    }
 }
 
 @end
@@ -258,40 +385,94 @@ static float const kSlidersSnapWithin = 5;
     BGMAppVolumes* context;
 }
 
-- (void) setUpWithApp:(NSRunningApplication*)app context:(BGMAppVolumes*)ctx {
+- (void) setUpWithApp:(NSRunningApplication*)app context:(BGMAppVolumes*)ctx menuItem:(NSMenuItem*)menuItem {
+    #pragma unused (menuItem)
+    
     context = ctx;
     
-    [self setTarget:self];
-    [self setAction:@selector(appVolumeChanged)];
+    self.target = self;
+    self.action = @selector(appVolumeChanged);
     
-    appProcessID = [app processIdentifier];
-    appBundleID = [app bundleIdentifier];
+    appProcessID = app.processIdentifier;
+    appBundleID = app.bundleIdentifier;
     
-    [self setMaxValue:kAppRelativeVolumeMaxRawValue];
-    [self setMinValue:kAppRelativeVolumeMinRawValue];
+    self.maxValue = kAppRelativeVolumeMaxRawValue;
+    self.minValue = kAppRelativeVolumeMinRawValue;
+
+    if ([self respondsToSelector:@selector(setAccessibilityTitle:)]) {
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wpartial-availability"
+        self.accessibilityTitle = [NSString stringWithFormat:@"Volume for %@", [app localizedName]];
+#pragma clang diagnostic pop
+    }
 }
 
+// We have to handle snapping for volume sliders ourselves because adding a tick mark (snap point) in Interface Builder
+// changes how the slider looks.
 - (void) snap {
-    // Snap to the 50% point
-    float midPoint = static_cast<float>(([self maxValue] - [self minValue]) / 2);
-    if ([self floatValue] > (midPoint - kSlidersSnapWithin) && [self floatValue] < (midPoint + kSlidersSnapWithin)) {
-        [self setFloatValue:midPoint];
+    // Snap to the 50% point.
+    float midPoint = static_cast<float>((self.maxValue + self.minValue) / 2);
+    if (self.floatValue > (midPoint - kSlidersSnapWithin) && self.floatValue < (midPoint + kSlidersSnapWithin)) {
+        self.floatValue = midPoint;
     }
 }
 
 - (void) setRelativeVolume:(NSNumber*)relativeVolume {
-    [self setIntValue:[relativeVolume intValue]];
+    self.intValue = relativeVolume.intValue;
     [self snap];
 }
 
 - (void) appVolumeChanged {
     // TODO: This (sending updates to the driver) should probably be rate-limited. It uses a fair bit of CPU for me.
     
-    DebugMsg("BGMAppVolumes::appVolumeChanged: App volume for %s changed to %d", [appBundleID UTF8String], [self intValue]);
+    DebugMsg("BGMAppVolumes::appVolumeChanged: App volume for %s changed to %d", appBundleID.UTF8String, self.intValue);
     
     [self snap];
     
-    [context sendVolumeChangeToBGMDevice:[self intValue] appProcessID:appProcessID appBundleID:appBundleID];
+    [context sendVolumeChangeToBGMDevice:self.intValue appProcessID:appProcessID appBundleID:appBundleID];
+}
+
+@end
+
+@implementation BGMAVM_PanSlider {
+    // Will be set to -1 for apps without a pid
+    pid_t appProcessID;
+    NSString* appBundleID;
+    BGMAppVolumes* context;
+}
+
+- (void) setUpWithApp:(NSRunningApplication*)app context:(BGMAppVolumes*)ctx menuItem:(NSMenuItem*)menuItem {
+    #pragma unused (menuItem)
+    
+    context = ctx;
+    
+    self.target = self;
+    self.action = @selector(appPanPositionChanged);
+    
+    appProcessID = app.processIdentifier;
+    appBundleID = app.bundleIdentifier;
+    
+    self.minValue = kAppPanLeftRawValue;
+    self.maxValue = kAppPanRightRawValue;
+
+    if ([self respondsToSelector:@selector(setAccessibilityTitle:)]) {
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wpartial-availability"
+        self.accessibilityTitle = [NSString stringWithFormat:@"Pan for %@", [app localizedName]];
+#pragma clang diagnostic pop
+    }
+}
+
+- (void) setPanPosition:(NSNumber *)panPosition {
+    self.intValue = panPosition.intValue;
+}
+
+- (void) appPanPositionChanged {
+    // TODO: This (sending updates to the driver) should probably be rate-limited. It uses a fair bit of CPU for me.
+    
+    DebugMsg("BGMAppVolumes::appPanPositionChanged: App pan position for %s changed to %d", appBundleID.UTF8String, self.intValue);
+    
+    [context sendPanPositionChangeToBGMDevice:self.intValue appProcessID:appProcessID appBundleID:appBundleID];
 }
 
 @end

BGMApp/BGMApp/BGMAudioDevice.cpp

@@ -0,0 +1,366 @@
+// This file is part of Background Music.
+//
+// Background Music is free software: you can redistribute it and/or
+// modify it under the terms of the GNU General Public License as
+// published by the Free Software Foundation, either version 2 of the
+// License, or (at your option) any later version.
+//
+// Background Music is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Background Music. If not, see <http://www.gnu.org/licenses/>.
+
+//
+//  BGMAudioDevice.cpp
+//  BGMApp
+//
+//  Copyright © 2017 Kyle Neideck
+//
+
+// Self Include
+#include "BGMAudioDevice.h"
+
+// Local Includes
+#include "BGM_Types.h"
+
+// System Includes
+#include <AudioToolbox/AudioServices.h>
+
+
+// AudioObjectPropertyElement docs: "Elements are numbered sequentially where 0 represents the
+// master element."
+static const AudioObjectPropertyElement kMasterChannel = 0;
+
+#pragma mark Construction/Destruction
+
+BGMAudioDevice::BGMAudioDevice(AudioObjectID inAudioDevice)
+:
+    CAHALAudioDevice(inAudioDevice)
+{
+}
+
+BGMAudioDevice::BGMAudioDevice(CFStringRef inUID)
+:
+    CAHALAudioDevice(inUID)
+{
+}
+
+BGMAudioDevice::BGMAudioDevice(const CAHALAudioDevice& inDevice)
+:
+    BGMAudioDevice(inDevice.GetObjectID())
+{
+};
+
+BGMAudioDevice::~BGMAudioDevice()
+{
+}
+
+bool    BGMAudioDevice::CanBeOutputDeviceInBGMApp() const
+{
+    CFStringRef uid = CopyDeviceUID();
+    bool isBGMDevice = CFEqual(uid, CFSTR(kBGMDeviceUID));
+    bool isNullDevice = CFEqual(uid, CFSTR(kBGMNullDeviceUID));
+    CFRelease(uid);
+
+    bool hasOutputChannels = GetTotalNumberChannels(/* inIsInput = */ false) > 0;
+    bool canBeDefault = CanBeDefaultDevice(/* inIsInput = */ false, /* inIsSystem = */ false);
+
+    return !isBGMDevice && !isNullDevice && !IsHidden() && hasOutputChannels && canBeDefault;
+}
+
+#pragma mark Available Controls
+
+bool    BGMAudioDevice::HasSettableMasterVolume(AudioObjectPropertyScope inScope) const
+{
+    return HasVolumeControl(inScope, kMasterChannel) &&
+        VolumeControlIsSettable(inScope, kMasterChannel);
+}
+
+bool    BGMAudioDevice::HasSettableVirtualMasterVolume(AudioObjectPropertyScope inScope) const
+{
+    AudioObjectPropertyAddress virtualMasterVolumeAddress = {
+        kAudioHardwareServiceDeviceProperty_VirtualMasterVolume,
+        inScope,
+        kAudioObjectPropertyElementMaster
+    };
+
+    // TODO: Replace these calls deprecated AudioToolbox functions. There are more below.
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wdeprecated-declarations"
+    Boolean virtualMasterVolumeIsSettable;
+    OSStatus err = AudioHardwareServiceIsPropertySettable(GetObjectID(),
+                                                          &virtualMasterVolumeAddress,
+                                                          &virtualMasterVolumeIsSettable);
+    virtualMasterVolumeIsSettable &= (err == kAudioServicesNoError);
+
+    bool hasVirtualMasterVolume =
+        AudioHardwareServiceHasProperty(GetObjectID(), &virtualMasterVolumeAddress);
+#pragma clang diagnostic pop
+
+    return hasVirtualMasterVolume && virtualMasterVolumeIsSettable;
+}
+
+bool    BGMAudioDevice::HasSettableMasterMute(AudioObjectPropertyScope inScope) const
+{
+    return HasMuteControl(inScope, kMasterChannel) &&
+        MuteControlIsSettable(inScope, kMasterChannel);
+}
+
+#pragma mark Control Values Accessors
+
+void    BGMAudioDevice::CopyMuteFrom(const BGMAudioDevice inDevice,
+                                     AudioObjectPropertyScope inScope)
+{
+    // TODO: Support for devices that have per-channel mute controls but no master mute control
+    if(HasSettableMasterMute(inScope) && inDevice.HasMuteControl(inScope, kMasterChannel))
+    {
+        SetMuteControlValue(inScope,
+                            kMasterChannel,
+                            inDevice.GetMuteControlValue(inScope, kMasterChannel));
+    }
+}
+
+void    BGMAudioDevice::CopyVolumeFrom(const BGMAudioDevice inDevice,
+                                       AudioObjectPropertyScope inScope)
+{
+    // Get the volume of the other device.
+    bool didGetVolume = false;
+    Float32 volume = FLT_MIN;
+
+    if(inDevice.HasVolumeControl(inScope, kMasterChannel))
+    {
+        volume = inDevice.GetVolumeControlScalarValue(inScope, kMasterChannel);
+        didGetVolume = true;
+    }
+
+    // Use the average channel volume of the other device if it has no master volume.
+    if(!didGetVolume)
+    {
+        UInt32 numChannels =
+            inDevice.GetTotalNumberChannels(inScope == kAudioObjectPropertyScopeInput);
+        volume = 0;
+
+        for(UInt32 channel = 1; channel <= numChannels; channel++)
+        {
+            if(inDevice.HasVolumeControl(inScope, channel))
+            {
+                volume += inDevice.GetVolumeControlScalarValue(inScope, channel);
+                didGetVolume = true;
+            }
+        }
+
+        if(numChannels > 0)  // Avoid divide by zero.
+        {
+            volume /= numChannels;
+        }
+    }
+
+    // Set the volume of this device.
+    if(didGetVolume && volume != FLT_MIN)
+    {
+        bool didSetVolume = false;
+
+        try
+        {
+            didSetVolume = SetMasterVolumeScalar(inScope, volume);
+        }
+        catch(CAException e)
+        {
+            OSStatus err = e.GetError();
+            char err4CC[5] = CA4CCToCString(err);
+            CFStringRef uid = CopyDeviceUID();
+            LogWarning("BGMAudioDevice::CopyVolumeFrom: CAException '%s' trying to set master "
+                       "volume of %s",
+                       err4CC,
+                       CFStringGetCStringPtr(uid, kCFStringEncodingUTF8));
+            CFRelease(uid);
+        }
+
+        if(!didSetVolume)
+        {
+            // Couldn't find a master volume control to set, so try to find a virtual one
+            Float32 virtualMasterVolume;
+            bool success = inDevice.GetVirtualMasterVolumeScalar(inScope, virtualMasterVolume);
+            if(success)
+            {
+                didSetVolume = SetVirtualMasterVolumeScalar(inScope, virtualMasterVolume);
+            }
+        }
+
+        if(!didSetVolume)
+        {
+            // Couldn't set a master or virtual master volume, so as a fallback try to set each
+            // channel individually.
+            UInt32 numChannels = GetTotalNumberChannels(inScope == kAudioObjectPropertyScopeInput);
+            for(UInt32 channel = 1; channel <= numChannels; channel++)
+            {
+                if(HasVolumeControl(inScope, channel) && VolumeControlIsSettable(inScope, channel))
+                {
+                    SetVolumeControlScalarValue(inScope, channel, volume);
+                }
+            }
+        }
+    }
+}
+
+bool    BGMAudioDevice::SetMasterVolumeScalar(AudioObjectPropertyScope inScope, Float32 inVolume)
+{
+    if(HasSettableMasterVolume(inScope))
+    {
+        SetVolumeControlScalarValue(inScope, kMasterChannel, inVolume);
+        return true;
+    }
+
+    return false;
+}
+
+bool    BGMAudioDevice::GetVirtualMasterVolumeScalar(AudioObjectPropertyScope inScope,
+                                                     Float32& outVirtualMasterVolume) const
+{
+    AudioObjectPropertyAddress virtualMasterVolumeAddress = {
+        kAudioHardwareServiceDeviceProperty_VirtualMasterVolume,
+        inScope,
+        kAudioObjectPropertyElementMaster
+    };
+
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wdeprecated-declarations"
+    if(!AudioHardwareServiceHasProperty(GetObjectID(), &virtualMasterVolumeAddress))
+    {
+        return false;
+    }
+#pragma clang diagnostic pop
+
+    UInt32 virtualMasterVolumePropertySize = sizeof(Float32);
+    return kAudioServicesNoError == AHSGetPropertyData(GetObjectID(),
+                                                       &virtualMasterVolumeAddress,
+                                                       &virtualMasterVolumePropertySize,
+                                                       &outVirtualMasterVolume);
+}
+
+bool    BGMAudioDevice::SetVirtualMasterVolumeScalar(AudioObjectPropertyScope inScope,
+                                                     Float32 inVolume)
+{
+    // TODO: For me, setting the virtual master volume sets all the device's channels to the same volume, meaning you can't
+    //       keep any channels quieter than the others. The expected behaviour is to scale the channel volumes
+    //       proportionally. So to do this properly I think we'd have to store BGMDevice's previous volume and calculate
+    //       each channel's new volume from its current volume and the distance between BGMDevice's old and new volumes.
+    //
+    //       The docs kAudioHardwareServiceDeviceProperty_VirtualMasterVolume for say
+    //           "If the device has individual channel volume controls, this property will apply to those identified by the
+    //           device's preferred multi-channel layout (or preferred stereo pair if the device is stereo only). Note that
+    //           this control maintains the relative balance between all the channels it affects.
+    //       so I'm not sure why that's not working here. As a workaround we take the to device's (virtual master) balance
+    //       before changing the volume and set it back after, but of course that'll only work for stereo devices.
+
+    bool didSetVolume = false;
+
+    if(HasSettableVirtualMasterVolume(inScope))
+    {
+        // Not sure why, but setting the virtual master volume sets all channels to the same volume. As a workaround, we store
+        // the current balance here so we can reset it after setting the volume.
+        Float32 virtualMasterBalance;
+        bool didGetVirtualMasterBalance = GetVirtualMasterBalance(inScope, virtualMasterBalance);
+
+        AudioObjectPropertyAddress virtualMasterVolumeAddress = {
+            kAudioHardwareServiceDeviceProperty_VirtualMasterVolume,
+            inScope,
+            kAudioObjectPropertyElementMaster
+        };
+
+        didSetVolume = (kAudioServicesNoError == AHSSetPropertyData(GetObjectID(),
+                                                                    &virtualMasterVolumeAddress,
+                                                                    sizeof(Float32),
+                                                                    &inVolume));
+
+        // Reset the balance
+        AudioObjectPropertyAddress virtualMasterBalanceAddress = {
+            kAudioHardwareServiceDeviceProperty_VirtualMasterBalance,
+            inScope,
+            kAudioObjectPropertyElementMaster
+        };
+
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wdeprecated-declarations"
+        if(didSetVolume &&
+           didGetVirtualMasterBalance &&
+           AudioHardwareServiceHasProperty(GetObjectID(), &virtualMasterBalanceAddress))
+        {
+            Boolean balanceIsSettable;
+            OSStatus err = AudioHardwareServiceIsPropertySettable(GetObjectID(),
+                                                                  &virtualMasterBalanceAddress,
+                                                                  &balanceIsSettable);
+            if(err == kAudioServicesNoError && balanceIsSettable)
+            {
+                AHSSetPropertyData(GetObjectID(),
+                                   &virtualMasterBalanceAddress,
+                                   sizeof(Float32),
+                                   &virtualMasterBalance);
+            }
+        }
+#pragma clang diagnostic pop
+    }
+
+    return didSetVolume;
+}
+
+bool    BGMAudioDevice::GetVirtualMasterBalance(AudioObjectPropertyScope inScope,
+                                                Float32& outVirtualMasterBalance) const
+{
+    AudioObjectPropertyAddress virtualMasterBalanceAddress = {
+        kAudioHardwareServiceDeviceProperty_VirtualMasterBalance,
+        inScope,
+        kAudioObjectPropertyElementMaster
+    };
+
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wdeprecated-declarations"
+    if(!AudioHardwareServiceHasProperty(GetObjectID(), &virtualMasterBalanceAddress))
+    {
+        return false;
+    }
+#pragma clang diagnostic pop
+
+    UInt32 virtualMasterVolumePropertySize = sizeof(Float32);
+    return kAudioServicesNoError == AHSGetPropertyData(GetObjectID(),
+                                                       &virtualMasterBalanceAddress,
+                                                       &virtualMasterVolumePropertySize,
+                                                       &outVirtualMasterBalance);
+}
+
+// static
+OSStatus    BGMAudioDevice::AHSGetPropertyData(AudioObjectID inObjectID,
+                                               const AudioObjectPropertyAddress* inAddress,
+                                               UInt32* ioDataSize,
+                                               void* outData)
+{
+    // The docs for AudioHardwareServiceGetPropertyData specifically allow passing NULL for
+    // inQualifierData as we do here, but it's declared in an assume_nonnull section so we have to
+    // disable the warning here. I'm not sure why inQualifierData isn't __nullable. I'm assuming
+    // it's either a backwards compatibility thing or just a bug.
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wnonnull"
+#pragma clang diagnostic ignored "-Wdeprecated-declarations"
+    // The non-depreciated version of this (and the setter below) doesn't seem to support devices
+    // other than the default
+    return AudioHardwareServiceGetPropertyData(inObjectID, inAddress, 0, NULL, ioDataSize, outData);
+#pragma clang diagnostic pop
+}
+
+// static
+OSStatus    BGMAudioDevice::AHSSetPropertyData(AudioObjectID inObjectID,
+                                               const AudioObjectPropertyAddress* inAddress,
+                                               UInt32 inDataSize,
+                                               const void* inData)
+{
+    // See the explanation about these pragmas in AHSGetPropertyData
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wnonnull"
+#pragma clang diagnostic ignored "-Wdeprecated-declarations"
+    return AudioHardwareServiceSetPropertyData(inObjectID, inAddress, 0, NULL, inDataSize, inData);
+#pragma clang diagnostic pop
+}
+

BGMApp/BGMApp/BGMAudioDevice.h

@@ -0,0 +1,93 @@
+// This file is part of Background Music.
+//
+// Background Music is free software: you can redistribute it and/or
+// modify it under the terms of the GNU General Public License as
+// published by the Free Software Foundation, either version 2 of the
+// License, or (at your option) any later version.
+//
+// Background Music is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Background Music. If not, see <http://www.gnu.org/licenses/>.
+
+//  BGMAudioDevice.h
+//  BGMApp
+//
+//  Copyright © 2017 Kyle Neideck
+//
+//  A HAL audio device. Note that this class's only state is the AudioObjectID of the device.
+//
+
+#ifndef BGMApp__BGMAudioDevice
+#define BGMApp__BGMAudioDevice
+
+// PublicUtility Includes
+#include "CAHALAudioDevice.h"
+
+
+class BGMAudioDevice
+:
+    public CAHALAudioDevice
+{
+
+#pragma mark Construction/Destruction
+
+public:
+                       BGMAudioDevice(AudioObjectID inAudioDevice);
+                       BGMAudioDevice(CFStringRef inUID);
+                       BGMAudioDevice(const CAHALAudioDevice& inDevice);
+    virtual            ~BGMAudioDevice();
+
+#if defined(__OBJC__)
+
+    // Hack/workaround for Objective-C classes so we don't have to use pointers for instance
+    // variables.
+                       BGMAudioDevice() : BGMAudioDevice(kAudioObjectUnknown) { }
+
+#endif /* defined(__OBJC__) */
+
+                       operator AudioObjectID() const { return GetObjectID(); }
+
+    /*! @throws CAException */
+    bool               CanBeOutputDeviceInBGMApp() const;
+
+#pragma mark Available Controls
+
+    bool               HasSettableMasterVolume(AudioObjectPropertyScope inScope) const;
+    bool               HasSettableVirtualMasterVolume(AudioObjectPropertyScope inScope) const;
+    bool               HasSettableMasterMute(AudioObjectPropertyScope inScope) const;
+
+#pragma mark Control Values Accessors
+
+    void               CopyMuteFrom(const BGMAudioDevice inDevice,
+                                    AudioObjectPropertyScope inScope);
+    void               CopyVolumeFrom(const BGMAudioDevice inDevice,
+                                      AudioObjectPropertyScope inScope);
+
+    bool               SetMasterVolumeScalar(AudioObjectPropertyScope inScope, Float32 inVolume);
+    
+    bool               GetVirtualMasterVolumeScalar(AudioObjectPropertyScope inScope,
+                                                    Float32& outVirtualMasterVolume) const;
+    bool               SetVirtualMasterVolumeScalar(AudioObjectPropertyScope inScope,
+                                                    Float32 inVolume);
+
+    bool               GetVirtualMasterBalance(AudioObjectPropertyScope inScope,
+                                               Float32& outVirtualMasterBalance) const;
+
+private:
+    static OSStatus    AHSGetPropertyData(AudioObjectID inObjectID,
+                                          const AudioObjectPropertyAddress* inAddress,
+                                          UInt32* ioDataSize,
+                                          void* outData);
+    static OSStatus    AHSSetPropertyData(AudioObjectID inObjectID,
+                                          const AudioObjectPropertyAddress* inAddress,
+                                          UInt32 inDataSize,
+                                          const void* inData);
+
+};
+
+#endif /* BGMApp__BGMAudioDevice */
+

BGMApp/BGMApp/BGMAudioDeviceManager.h

@@ -19,38 +19,70 @@
 //
 //  Copyright © 2016 Kyle Neideck
 //
-//  Manages the BGMDevice and the output device. Sets the system's current default device as the output device on init, then
-//  starts playthrough and mirroring the devices' controls. The output device can be changed but the BGMDevice is fixed.
+//  Manages the BGMDevice and the output device. Sets the system's current default device as the
+//  output device on init, then starts playthrough and mirroring the devices' controls. The output
+//  device can be changed but the BGMDevice is fixed.
 //
 
 // PublicUtility Includes
-#include "CAHALAudioDevice.h"
+#ifdef __cplusplus
+#import "CAHALAudioDevice.h"
+#endif
 
 // System Includes
 #import <Foundation/Foundation.h>
-#include <CoreAudio/AudioHardwareBase.h>
+#import <CoreAudio/AudioHardwareBase.h>
 
 
+#pragma clang assume_nonnull begin
+
 extern int const kBGMErrorCode_BGMDeviceNotFound;
 extern int const kBGMErrorCode_OutputDeviceNotFound;
 
 @interface BGMAudioDeviceManager : NSObject
 
-- (id) initWithError:(NSError**)error;
+- (instancetype) initWithError:(NSError**)error;
 
 // Set BGMDevice as the default audio device for all processes
-- (void) setBGMDeviceAsOSDefault;
+- (NSError* __nullable) setBGMDeviceAsOSDefault;
 // Replace BGMDevice as the default device with the output device
-- (void) unsetBGMDeviceAsOSDefault;
+- (NSError* __nullable) unsetBGMDeviceAsOSDefault;
 
+#ifdef __cplusplus
+// The virtual device published by BGMDriver.
 - (CAHALAudioDevice) bgmDevice;
 
-- (BOOL) isOutputDevice:(AudioObjectID)deviceID;
-// Returns NO if the output device couldn't be changed and has been reverted
-- (BOOL) setOutputDeviceWithID:(AudioObjectID)deviceID revertOnFailure:(BOOL)revertOnFailure;
+// The device BGMApp will play audio through, making it, from the user's perspective, the system's
+// default output device.
+- (CAHALAudioDevice) outputDevice;
+#endif
 
-// Returns when IO has started running on the output device (for playthrough).
+- (BOOL) isOutputDevice:(AudioObjectID)deviceID;
+- (BOOL) isOutputDataSource:(UInt32)dataSourceID;
+
+// Set the audio output device that BGMApp uses.
+//
+// Returns an error if the output device couldn't be changed. If revertOnFailure is true in that case,
+// this method will attempt to set the output device back to the original device. If it fails to
+// revert, an additional error will be included in the error's userInfo with the key "revertError".
+//
+// Both errors' codes will be the code of the exception that caused the failure, if any, generally one
+// of the error constants from AudioHardwareBase.h.
+//
+// Blocks while the old device stops IO (if there was one).
+- (NSError* __nullable) setOutputDeviceWithID:(AudioObjectID)deviceID
+                              revertOnFailure:(BOOL)revertOnFailure;
+
+// As above, but also sets the new output device's data source. See kAudioDevicePropertyDataSource in
+// AudioHardware.h.
+- (NSError* __nullable) setOutputDeviceWithID:(AudioObjectID)deviceID
+                                 dataSourceID:(UInt32)dataSourceID
+                              revertOnFailure:(BOOL)revertOnFailure;
+
+// Blocks until IO has started running on the output device (for playthrough).
 - (OSStatus) waitForOutputDeviceToStart;
 
 @end
 
+#pragma clang assume_nonnull end
+

BGMApp/BGMApp/BGMAudioDeviceManager.mm

@@ -17,7 +17,7 @@
 //  BGMAudioDeviceManager.mm
 //  BGMApp
 //
-//  Copyright © 2016 Kyle Neideck
+//  Copyright © 2016, 2017 Kyle Neideck
 //
 
 // Self Include
@@ -25,8 +25,10 @@
 
 // Local Includes
 #include "BGM_Types.h"
+#include "BGM_Utils.h"
 #include "BGMDeviceControlSync.h"
 #include "BGMPlayThrough.h"
+#include "BGMAudioDevice.h"
 
 // PublicUtility Includes
 #include "CAHALAudioSystemObject.h"
@@ -36,43 +38,44 @@
 int const kBGMErrorCode_BGMDeviceNotFound = 0;
 int const kBGMErrorCode_OutputDeviceNotFound = 1;
 
-// Hack/workaround that adds a default constructor to CAHALAudioDevice so we don't have to use pointers for the instance variables
-class BGMAudioDevice : public CAHALAudioDevice {
-    using CAHALAudioDevice::CAHALAudioDevice;
-public:
-    BGMAudioDevice() : CAHALAudioDevice(kAudioDeviceUnknown) { }
-};
-
 @implementation BGMAudioDeviceManager {
     BGMAudioDevice bgmDevice;
     BGMAudioDevice outputDevice;
+    
     BGMDeviceControlSync deviceControlSync;
     BGMPlayThrough playThrough;
+    
+    NSRecursiveLock* stateLock;
 }
 
 #pragma mark Construction/Destruction
 
 - (id) initWithError:(NSError**)error {
     if ((self = [super init])) {
+        stateLock = [NSRecursiveLock new];
+        
         bgmDevice = BGMAudioDevice(CFSTR(kBGMDeviceUID));
         
         if (bgmDevice.GetObjectID() == kAudioObjectUnknown) {
-            DebugMsg("BGMAudioDeviceManager::initWithError: BGMDevice not found");
+            LogError("BGMAudioDeviceManager::initWithError: BGMDevice not found");
+            
             if (error) {
                 *error = [NSError errorWithDomain:@kBGMAppBundleID code:kBGMErrorCode_BGMDeviceNotFound userInfo:nil];
             }
+            
             self = nil;
             return self;
         }
         
         [self initOutputDevice];
         
-        
-        if (outputDevice.GetObjectID() == kAudioDeviceUnknown) {
-            DebugMsg("BGMAudioDeviceManager::initWithError: output device not found");
+        if (outputDevice.GetObjectID() == kAudioObjectUnknown) {
+            LogError("BGMAudioDeviceManager::initWithError: output device not found");
+            
             if (error) {
                 *error = [NSError errorWithDomain:@kBGMAppBundleID code:kBGMErrorCode_OutputDeviceNotFound userInfo:nil];
             }
+            
             self = nil;
             return self;
         }
@@ -85,6 +88,7 @@ public:
     CAHALAudioSystemObject audioSystem;
     // outputDevice = BGMAudioDevice(CFSTR("AppleHDAEngineOutput:1B,0,1,1:0"));
     AudioObjectID defaultDeviceID = audioSystem.GetDefaultAudioDevice(false, false);
+
     if (defaultDeviceID == bgmDevice.GetObjectID()) {
         // TODO: If BGMDevice is already the default (because BGMApp didn't shutdown properly or it was set manually)
         //       we should temporarily disable BGMDevice so we can find out what the previous default was.
@@ -94,6 +98,7 @@ public:
         if (numDevices > 0) {
             SInt32 minLatencyDeviceIdx = -1;
             UInt32 minLatency = UINT32_MAX;
+
             CAAutoArrayDelete<AudioObjectID> devices(numDevices);
             audioSystem.GetAudioDevices(numDevices, devices);
             
@@ -115,16 +120,24 @@ public:
                 }
             }
             
-            [self setOutputDeviceWithID:devices[minLatencyDeviceIdx] revertOnFailure:NO];
+            BGMLogUnexpectedExceptionsMsg("BGMAudioDeviceManager::initOutputDevice",
+                                          "setOutputDeviceWithID:devices[minLatencyDeviceIdx]", [&]() {
+                // TODO: On error, try a different output device.
+                [self setOutputDeviceWithID:devices[minLatencyDeviceIdx] revertOnFailure:NO];
+            });
         }
     } else {
-        [self setOutputDeviceWithID:defaultDeviceID revertOnFailure:NO];
+        BGMLogUnexpectedExceptionsMsg("BGMAudioDeviceManager::initOutputDevice",
+                                      "setOutputDeviceWithID:defaultDeviceID", [&]() {
+            // TODO: Return the error from setOutputDeviceWithID so it can be returned by initWithError.
+            [self setOutputDeviceWithID:defaultDeviceID revertOnFailure:NO];
+        });
     }
     
     assert(outputDevice.GetObjectID() != bgmDevice.GetObjectID());
     
     // Log message
-    if (outputDevice.GetObjectID() == kAudioDeviceUnknown) {
+    if (outputDevice.GetObjectID() == kAudioObjectUnknown) {
         CFStringRef outputDeviceUID = outputDevice.CopyDeviceUID();
         DebugMsg("BGMAudioDeviceManager::initDevices: Set output device to %s",
                  CFStringGetCStringPtr(outputDeviceUID, kCFStringEncodingUTF8));
@@ -134,33 +147,120 @@ public:
 
 #pragma mark Systemwide Default Device
 
-- (void) setBGMDeviceAsOSDefault {
+// Note that there are two different "default" output devices on OS X: "output" and "system output". See
+// AudioHardwarePropertyDefaultSystemOutputDevice in AudioHardware.h.
+
+- (NSError* __nullable) setBGMDeviceAsOSDefault {
+    DebugMsg("BGMAudioDeviceManager::setBGMDeviceAsOSDefault: Setting the system's default audio "
+             "device to BGMDevice");
+
     CAHALAudioSystemObject audioSystem;
     
-    @synchronized (self) {
-        if (audioSystem.GetDefaultAudioDevice(false, true) == outputDevice.GetObjectID()) {
-            // The default system device was the same as the default device, so change that as well
-            audioSystem.SetDefaultAudioDevice(false, true, bgmDevice.GetObjectID());
-        }
-        
-        audioSystem.SetDefaultAudioDevice(false, false, bgmDevice.GetObjectID());
+    AudioDeviceID bgmDeviceID = kAudioObjectUnknown;
+    AudioDeviceID outputDeviceID = kAudioObjectUnknown;
+    
+    @try {
+        [stateLock lock];
+
+        bgmDeviceID = bgmDevice.GetObjectID();
+        outputDeviceID = outputDevice.GetObjectID();
+    } @finally {
+        [stateLock unlock];
     }
+
+    if (outputDeviceID == kAudioObjectUnknown) {
+        return [NSError errorWithDomain:@kBGMAppBundleID code:kBGMErrorCode_OutputDeviceNotFound userInfo:nil];
+    }
+    if (bgmDeviceID == kAudioObjectUnknown) {
+        return [NSError errorWithDomain:@kBGMAppBundleID code:kBGMErrorCode_BGMDeviceNotFound userInfo:nil];
+    }
+
+    try {
+        AudioDeviceID currentDefault = audioSystem.GetDefaultAudioDevice(false, true);
+        
+        try {
+            if (currentDefault == outputDeviceID) {
+                // The default system device was the same as the default device, so change that as well
+                audioSystem.SetDefaultAudioDevice(false, true, bgmDeviceID);
+            }
+        
+            audioSystem.SetDefaultAudioDevice(false, false, bgmDeviceID);
+        } catch (CAException e) {
+            NSLog(@"SetDefaultAudioDevice threw CAException (%d)", e.GetError());
+            return [NSError errorWithDomain:@kBGMAppBundleID code:e.GetError() userInfo:nil];
+        }
+    } catch (...) {
+        NSLog(@"Unexpected exception");
+        return [NSError errorWithDomain:@kBGMAppBundleID code:-1 userInfo:nil];
+    }
+    
+    return nil;
 }
 
-- (void) unsetBGMDeviceAsOSDefault {
+- (NSError* __nullable) unsetBGMDeviceAsOSDefault {
     CAHALAudioSystemObject audioSystem;
     
-    @synchronized (self) {
-        if (audioSystem.GetDefaultAudioDevice(false, true) == bgmDevice.GetObjectID()) {
-            // We changed the system output device to BGMDevice, which we only do if it initially matches the
-            // default output device, so change it back
-            audioSystem.SetDefaultAudioDevice(false, true, outputDevice.GetObjectID());
-        }
+    bool bgmDeviceIsDefault = true;
+    bool bgmDeviceIsSystemDefault = true;
+    
+    AudioDeviceID bgmDeviceID = kAudioObjectUnknown;
+    AudioDeviceID outputDeviceID = kAudioObjectUnknown;
+    
+    @try {
+        [stateLock lock];
+
+        bgmDeviceID = bgmDevice.GetObjectID();
+        outputDeviceID = outputDevice.GetObjectID();
+
+        BGMLogAndSwallowExceptions("unsetBGMDeviceAsOSDefault", [&]() {
+            bgmDeviceIsDefault =
+                (audioSystem.GetDefaultAudioDevice(false, false) == bgmDeviceID);
+            
+            bgmDeviceIsSystemDefault =
+                (audioSystem.GetDefaultAudioDevice(false, true) == bgmDeviceID);
+        });
+    } @finally {
+        [stateLock unlock];
+    }
+
+    if (outputDeviceID == kAudioObjectUnknown) {
+        return [NSError errorWithDomain:@kBGMAppBundleID code:kBGMErrorCode_OutputDeviceNotFound userInfo:nil];
+    }
+    if (bgmDeviceID == kAudioObjectUnknown) {
+        return [NSError errorWithDomain:@kBGMAppBundleID code:kBGMErrorCode_BGMDeviceNotFound userInfo:nil];
+    }
+    
+    if (bgmDeviceIsDefault) {
+        DebugMsg("BGMAudioDeviceManager::unsetBGMDeviceAsOSDefault: Setting the system's default output "
+                 "device back to device %d", outputDeviceID);
         
-        if (audioSystem.GetDefaultAudioDevice(false, false) == bgmDevice.GetObjectID()) {
-            audioSystem.SetDefaultAudioDevice(false, false, outputDevice.GetObjectID());
+        try {
+            audioSystem.SetDefaultAudioDevice(false, false, outputDeviceID);
+        } catch (CAException e) {
+            return [NSError errorWithDomain:@kBGMAppBundleID code:e.GetError() userInfo:nil];
+        } catch (...) {
+            BGMLogUnexpectedExceptionIn("BGMAudioDeviceManager::unsetBGMDeviceAsOSDefault "
+                                        "SetDefaultAudioDevice (output)");
         }
     }
+    
+    // If we changed the default system output device to BGMDevice, which we only do if it's set to
+    // the same device as the default output device, change it back to the previous device.
+    if (bgmDeviceIsSystemDefault) {
+        DebugMsg("BGMAudioDeviceManager::unsetBGMDeviceAsOSDefault: Setting the system's default system "
+                 "output device back to device %d", outputDeviceID);
+        
+        try {
+            audioSystem.SetDefaultAudioDevice(false, true, outputDeviceID);
+        } catch (CAException e) {
+            return [NSError errorWithDomain:@kBGMAppBundleID code:e.GetError() userInfo:nil];
+        } catch (...) {
+            BGMLogUnexpectedExceptionIn("BGMAudioDeviceManager::unsetBGMDeviceAsOSDefault "
+                                        "SetDefaultAudioDevice (system output)");
+        }
+    }
+    
+    return nil;
 }
 
 #pragma mark Accessors
@@ -169,62 +269,216 @@ public:
     return bgmDevice;
 }
 
+- (CAHALAudioDevice) outputDevice {
+    return outputDevice;
+}
+
 - (BOOL) isOutputDevice:(AudioObjectID)deviceID {
-    @synchronized (self) {
+    @try {
+        [stateLock lock];
         return deviceID == outputDevice.GetObjectID();
+    } @finally {
+        [stateLock unlock];
     }
 }
 
-- (BOOL) setOutputDeviceWithID:(AudioObjectID)deviceID revertOnFailure:(BOOL)revertOnFailure {
-    DebugMsg("BGMAudioDeviceManager::setOutputDeviceWithID: Setting output device. deviceID=%u", deviceID);
+- (BOOL) isOutputDataSource:(UInt32)dataSourceID {
+    @try {
+        [stateLock lock];
+        
+        try {
+            AudioObjectPropertyScope scope = kAudioDevicePropertyScopeOutput;
+            UInt32 channel = 0;
+            
+            return outputDevice.HasDataSourceControl(scope, channel) &&
+                (dataSourceID == outputDevice.GetCurrentDataSourceID(scope, channel));
+        } catch (CAException e) {
+            BGMLogException(e);
+            return false;
+        }
+    } @finally {
+        [stateLock unlock];
+    }
+}
+
+
+- (NSError* __nullable) setOutputDeviceWithID:(AudioObjectID)deviceID
+                              revertOnFailure:(BOOL)revertOnFailure {
+    return [self setOutputDeviceWithIDImpl:deviceID
+                              dataSourceID:nil
+                           revertOnFailure:revertOnFailure];
+}
+
+- (NSError* __nullable) setOutputDeviceWithID:(AudioObjectID)deviceID
+                                 dataSourceID:(UInt32)dataSourceID
+                              revertOnFailure:(BOOL)revertOnFailure {
+    return [self setOutputDeviceWithIDImpl:deviceID
+                              dataSourceID:&dataSourceID
+                           revertOnFailure:revertOnFailure];
+}
+
+- (NSError* __nullable) setOutputDeviceWithIDImpl:(AudioObjectID)newDeviceID
+                                     dataSourceID:(UInt32* __nullable)dataSourceID
+                                  revertOnFailure:(BOOL)revertOnFailure {
+    DebugMsg("BGMAudioDeviceManager::setOutputDeviceWithID: Setting output device. newDeviceID=%u",
+             newDeviceID);
+    
+    AudioDeviceID currentDeviceID = outputDevice.GetObjectID();  // (GetObjectID doesn't throw.)
     
     // Set up playthrough and control sync
-    BGMAudioDevice newOutputDevice(deviceID);
+    BGMAudioDevice newOutputDevice(newDeviceID);
     
-    try {
-        @synchronized (self) {
-            // Mirror changes in BGMDevice's controls to the new output device's.
-            deviceControlSync = BGMDeviceControlSync(bgmDevice, newOutputDevice);
+    @try {
+        [stateLock lock];
+        
+        try {
+            // Re-read the device ID after entering the monitor. (The initial read is because
+            // currentDeviceID is used in the catch blocks.)
+            currentDeviceID = outputDevice.GetObjectID();
             
-            // Stream audio from BGMDevice to the output device.
-            //
-            // TODO: Should this be done async? Some output devices take a long time to start IO (e.g. AirPlay) and I
-            //       assume this blocks the main thread. Haven't tried it to check, though.
-            playThrough = BGMPlayThrough(bgmDevice, newOutputDevice);
+            if (newDeviceID != currentDeviceID) {
+                // Deactivate playthrough rather than stopping it so it can't be started by HAL
+                // notifications while we're updating deviceControlSync.
+                playThrough.Deactivate();
 
-            outputDevice = BGMAudioDevice(deviceID);
+                deviceControlSync.SetDevices(bgmDevice, newOutputDevice);
+                deviceControlSync.Activate();
+
+                // Stream audio from BGMDevice to the new output device. This blocks while the old device
+                // stops IO.
+                playThrough.SetDevices(&bgmDevice, &newOutputDevice);
+                playThrough.Activate();
+
+                outputDevice = newOutputDevice;
+            }
+            
+            // Set the output device to use the new data source.
+            if (dataSourceID) {
+                // TODO: If this fails, ideally we'd still start playthrough and return an error, but not
+                //       revert the device. It would probably be a bit awkward, though.
+                [self setDataSource:*dataSourceID device:outputDevice];
+            }
+            
+            if (newDeviceID != currentDeviceID) {
+                // We successfully changed to the new device. Start playthrough on it, since audio might be
+                // playing. (If we only changed the data source, playthrough will already be running if it
+                // needs to be.)
+                playThrough.Start();
+                // But stop playthrough if audio isn't playing, since it uses CPU.
+                playThrough.StopIfIdle();
+            }
+        } catch (CAException e) {
+            BGMAssert(e.GetError() != kAudioHardwareNoError,
+                      "CAException with kAudioHardwareNoError");
+            
+            return [self failedToSetOutputDevice:newDeviceID
+                                       errorCode:e.GetError()
+                                        revertTo:(revertOnFailure ? &currentDeviceID : nullptr)];
+        } catch (...) {
+            return [self failedToSetOutputDevice:newDeviceID
+                                       errorCode:kAudioHardwareUnspecifiedError
+                                        revertTo:(revertOnFailure ? &currentDeviceID : nullptr)];
         }
-        
-        // Start playthrough because audio might be playing.
-        //
-        // TODO: If audio isn't playing, this makes playthrough run until the user plays audio and then stops it again,
-        //       which wastes CPU. I think we could just have Start() call StopIfIdle(), but I haven't tried it yet.
-        playThrough.Start();
-    } catch (CAException e) {
-        // Using LogWarning from PublicUtility instead of NSLog here crashes from a bad access. Not sure why.
-        NSLog(@"BGMAudioDeviceManager::setOutputDeviceWithID: Couldn't set device with ID %u as output device. %s %s%d.",
-              newOutputDevice.GetObjectID(),
-              (revertOnFailure ? "Will attempt to revert to the previous device." : ""),
-              "Error: ", e.GetError());
-        
-        if (revertOnFailure) {
-            // Try to reactivate the original device listener and playthrough
-            [self setOutputDeviceWithID:outputDevice.GetObjectID() revertOnFailure:NO];
-            return NO;
-        } else {
-            // TODO: Handle in callers. (Maybe show an error dialog and try to set the original default device as the
-            //       output device.)
-            Throw(e);
+    } @finally {
+        [stateLock unlock];
+    }
+
+    return nil;
+}
+
+- (void) setDataSource:(UInt32)dataSourceID device:(BGMAudioDevice)device {
+    BGMLogAndSwallowExceptions("BGMAudioDeviceManager::setDataSource", [&]() {
+        AudioObjectPropertyScope scope = kAudioObjectPropertyScopeOutput;
+        UInt32 channel = 0;
+
+        if (device.DataSourceControlIsSettable(scope, channel)) {
+            DebugMsg("BGMAudioDeviceManager::setOutputDeviceWithID: Setting dataSourceID=%u",
+                     dataSourceID);
+            
+            device.SetCurrentDataSourceByID(scope, channel, dataSourceID);
         }
+    });
+}
+
+- (NSError*) failedToSetOutputDevice:(AudioDeviceID)deviceID
+                           errorCode:(OSStatus)errorCode
+                            revertTo:(AudioDeviceID*)revertTo {
+    // Using LogWarning from PublicUtility instead of NSLog here crashes from a bad access. Not sure why.
+    NSLog(@"BGMAudioDeviceManager::failedToSetOutputDevice: Couldn't set device with ID %u as output device. "
+          "%s%d. %@",
+          deviceID,
+          "Error: ", errorCode,
+          (revertTo ? [NSString stringWithFormat:@"Will attempt to revert to the previous device. "
+                                                  "Previous device ID: %u.", *revertTo] : @""));
+    
+    NSDictionary* __nullable info = nil;
+    
+    if (revertTo) {
+        // Try to reactivate the original device listener and playthrough. (Sorry about the mutual recursion.)
+        NSError* __nullable revertError = [self setOutputDeviceWithID:*revertTo revertOnFailure:NO];
+        
+        if (revertError) {
+            info = @{ @"revertError": (NSError*)revertError };
+        }
+    } else {
+        // TODO: Handle this error better in callers. Maybe show an error dialog and try to set the original
+        //       default device as the output device.
+        NSLog(@"BGMAudioDeviceManager::failedToSetOutputDevice: Failed to revert to the previous device.");
     }
     
-    return YES;
+    return [NSError errorWithDomain:@kBGMAppBundleID code:errorCode userInfo:info];
 }
 
 - (OSStatus) waitForOutputDeviceToStart {
-    @synchronized (self) {
-        return playThrough.WaitForOutputDeviceToStart();
+    // We can only try for stateLock because setOutputDeviceWithID might have already taken it, then made a
+    // HAL request to BGMDevice and is now waiting for the response. Some of the requests setOutputDeviceWithID
+    // makes to BGMDevice block in the HAL if another thread is in BGM_Device::StartIO.
+    //
+    // Since BGM_Device::StartIO calls this method (via XPC), waiting for setOutputDeviceWithID to release
+    // stateLock could cause deadlocks. Instead we return early with an error code that BGMDriver knows to
+    // ignore, since the output device is (almost certainly) being changed and we can't avoid dropping frames
+    // while the output device starts up.
+    OSStatus err;
+    BOOL gotLock;
+    
+    @try {
+        gotLock = [stateLock tryLock];
+        
+        if (gotLock) {
+            err = playThrough.WaitForOutputDeviceToStart();
+        } else {
+            LogWarning("BGMAudioDeviceManager::waitForOutputDeviceToStart: Didn't get state lock. Returning "
+                       "early with kDeviceNotStarting.");
+            err = BGMPlayThrough::kDeviceNotStarting;
+        }
+        
+        if (err == BGMPlayThrough::kDeviceNotStarting) {
+            // I'm not sure if this block is currently reachable, but BGMDriver only starts waiting on the
+            // output device when IO is starting, so we should start playthrough even if BGMApp hasn't been
+            // notified by the HAL yet.
+            LogWarning("BGMAudioDeviceManager::waitForOutputDeviceToStart: Playthrough wasn't starting the "
+                       "output device. Will tell it to and then return early with kDeviceNotStarting.");
+
+            dispatch_async(dispatch_get_global_queue(QOS_CLASS_USER_INTERACTIVE, 0), ^{
+                @try {
+                    [stateLock lock];
+                    
+                    BGMLogAndSwallowExceptions("BGMAudioDeviceManager::waitForOutputDeviceToStart", [&]() {
+                        playThrough.Start();
+                        playThrough.StopIfIdle();
+                    });
+                } @finally {
+                    [stateLock unlock];
+                }
+            });
+        }
+    } @finally {
+        if (gotLock) {
+            [stateLock unlock];
+        }
     }
+    
+    return err;
 }
 
 @end

BGMApp/BGMApp/BGMAutoPauseMenuItem.h

@@ -0,0 +1,48 @@
+// This file is part of Background Music.
+//
+// Background Music is free software: you can redistribute it and/or
+// modify it under the terms of the GNU General Public License as
+// published by the Free Software Foundation, either version 2 of the
+// License, or (at your option) any later version.
+//
+// Background Music is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Background Music. If not, see <http://www.gnu.org/licenses/>.
+
+//
+//  BGMAutoPauseMenuItem.h
+//  BGMApp
+//
+//  Copyright © 2016 Kyle Neideck
+//
+
+// Local Includes
+#import "BGMAutoPauseMusic.h"
+#import "BGMMusicPlayers.h"
+#import "BGMUserDefaults.h"
+
+// System Includes
+#import <Cocoa/Cocoa.h>
+
+
+#pragma clang assume_nonnull begin
+
+@interface BGMAutoPauseMenuItem : NSObject
+
+- (instancetype) initWithMenuItem:(NSMenuItem*)item
+                   autoPauseMusic:(BGMAutoPauseMusic*)autoPause
+                     musicPlayers:(BGMMusicPlayers*)players
+                     userDefaults:(BGMUserDefaults*)defaults;
+
+// Handle events passed along by the delegate (NSMenuDelegate) of the menu containing this menu item.
+- (void) parentMenuNeedsUpdate;
+- (void) parentMenuItemWillHighlight:(NSMenuItem* __nullable)item;
+
+@end
+
+#pragma clang assume_nonnull end
+

BGMApp/BGMApp/BGMAutoPauseMenuItem.m

@@ -0,0 +1,201 @@
+// This file is part of Background Music.
+//
+// Background Music is free software: you can redistribute it and/or
+// modify it under the terms of the GNU General Public License as
+// published by the Free Software Foundation, either version 2 of the
+// License, or (at your option) any later version.
+//
+// Background Music is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Background Music. If not, see <http://www.gnu.org/licenses/>.
+
+//
+//  BGMAutoPauseMenuItem.m
+//  BGMApp
+//
+//  Copyright © 2016 Kyle Neideck
+//  Copyright © 2016 Tanner Hoke
+//
+
+// Self Include
+#import "BGMAutoPauseMenuItem.h"
+
+// Local Includes
+#import "BGMMusicPlayer.h"
+
+
+#pragma clang assume_nonnull begin
+
+static NSString* const kMenuItemTitleFormat = @"Auto-pause %@";
+static NSString* const kMenuItemDisabledToolTipFormat = @"%@ doesn't appear to be running.";
+
+// Wait time to disable/enable the auto-pause menu item, in seconds.
+static SInt64 const kMenuItemUpdateWaitTime = 1;
+
+@implementation BGMAutoPauseMenuItem {
+    BGMUserDefaults* userDefaults;
+    NSMenuItem* menuItem;
+    BGMAutoPauseMusic* autoPauseMusic;
+    BGMMusicPlayers* musicPlayers;
+    id<NSObject> didLaunchToken, didTerminateToken;
+}
+
+- (instancetype) initWithMenuItem:(NSMenuItem*)item
+                   autoPauseMusic:(BGMAutoPauseMusic*)autoPause
+                     musicPlayers:(BGMMusicPlayers*)players
+                     userDefaults:(BGMUserDefaults*)defaults {
+    if ((self = [super init])) {
+        menuItem = item;
+        autoPauseMusic = autoPause;
+        musicPlayers = players;
+        userDefaults = defaults;
+        
+        // Enable/disable auto-pause to match the user's preferences setting.
+        if (userDefaults.autoPauseMusicEnabled) {
+            menuItem.state = NSOnState;
+            [autoPauseMusic enable];
+        } else {
+            menuItem.state = NSOffState;
+            [autoPauseMusic disable];
+        }
+        
+        // Toggle auto-pause when the menu item is clicked.
+        menuItem.target = self;
+        menuItem.action = @selector(toggleAutoPauseMusic);
+        
+        [self updateMenuItemTitle];
+        [self initMusicPlayerObservers];
+    }
+    
+    return self;
+}
+
+- (void) initMusicPlayerObservers {
+    // Add observers that enable/disable the Auto-pause Music menu item when the music player is launched/terminated.
+    NSNotificationCenter* center = [[NSWorkspace sharedWorkspace] notificationCenter];
+    
+    id<NSObject> (^addObserver)(NSString*) = ^(NSString* name) {
+        return [center addObserverForName:name
+                                   object:nil
+                                    queue:nil
+                               usingBlock:^(NSNotification* note) {
+                                   NSString* appBundleID = [note.userInfo[NSWorkspaceApplicationKey] bundleIdentifier];
+                                   BOOL isAboutThisMusicPlayer = musicPlayers.selectedMusicPlayer.bundleID &&
+                                       [appBundleID isEqualToString:(NSString*)musicPlayers.selectedMusicPlayer.bundleID];
+                                   
+                                   if (isAboutThisMusicPlayer) {
+                                       dispatch_after(dispatch_time(DISPATCH_TIME_NOW,
+                                                                    kMenuItemUpdateWaitTime * NSEC_PER_SEC),
+                                                      dispatch_get_main_queue(),
+                                                      ^{
+                                                          [self updateMenuItemTitle];
+                                                      });
+                                   }
+                               }];
+    };
+    
+    didLaunchToken = addObserver(NSWorkspaceDidLaunchApplicationNotification);
+    didTerminateToken = addObserver(NSWorkspaceDidTerminateApplicationNotification);
+}
+
+- (void) dealloc {
+    // Remove the application launch/termination observers.
+    NSNotificationCenter* center = [[NSWorkspace sharedWorkspace] notificationCenter];
+    
+    if (didLaunchToken) {
+        [center removeObserver:didLaunchToken];
+    }
+    
+    if (didTerminateToken) {
+        [center removeObserver:didTerminateToken];
+    }
+}
+
+- (void) toggleAutoPauseMusic {
+    // The menu item was clicked.
+    
+    if (menuItem.state == NSOnState) {
+        menuItem.state = NSOffState;
+        [autoPauseMusic disable];
+    } else {
+        menuItem.state = NSOnState;
+        [autoPauseMusic enable];
+    }
+    
+    // Persist the change in the user's preferences.
+    userDefaults.autoPauseMusicEnabled = (menuItem.state == NSOnState);
+}
+
+- (void) updateMenuItemTitle {
+    [self updateMenuItemTitleWithHighlight:menuItem.isHighlighted];
+}
+
+- (void) updateMenuItemTitleWithHighlight:(BOOL)highlight {
+    // Set the title of the Auto-pause Music menu item, including the name of the selected music player.
+    NSString* musicPlayerName = musicPlayers.selectedMusicPlayer.name;
+    menuItem.title = [NSString stringWithFormat:kMenuItemTitleFormat, musicPlayerName];
+    
+    // Make the Auto-pause Music menu item appear disabled if the application is not running.
+    //
+    // We don't actually disable it just in case the user decides to disable auto-pause and their music player isn't
+    // running. E.g. someone who only recently installed Background Music and doesn't want to use auto-pause at all.
+    if (musicPlayers.selectedMusicPlayer.isRunning) {
+        menuItem.attributedTitle = nil;
+        menuItem.toolTip = nil;
+    } else {
+        // Hardcode the text colour grey to match disabled menu items (unless the menu item is highlighted, in which
+        // case use white).
+        //
+        // I couldn't figure out a way to do this without hardcoding the colours. There's no colour constant for this,
+        // except possibly disabledControlTextColor, which just leaves the text black for me. I also couldn't get the
+        // colours from the built-in NSColorLists.
+        //
+        // TODO: Can we make the tick mark grey as well?
+        NSString* __nullable appleInterfaceStyle =
+            [[NSUserDefaults standardUserDefaults] stringForKey:@"AppleInterfaceStyle"];
+        BOOL darkMode = [appleInterfaceStyle isEqualToString:@"Dark"];
+        NSColor* textColor = [NSColor colorWithHue:0
+                                        saturation:0
+                                        brightness:(highlight ? 1 : (darkMode ? 0.25 : 0.75))
+                                             alpha:1];
+        
+        NSDictionary* attributes = @{ NSFontAttributeName: [NSFont menuBarFontOfSize:0],  // Default font size
+                                      NSForegroundColorAttributeName: textColor };
+        NSAttributedString* pseudoDisabledTitle = [[NSAttributedString alloc] initWithString:menuItem.title
+                                                                                  attributes:attributes];
+        menuItem.attributedTitle = pseudoDisabledTitle;
+
+        menuItem.toolTip = [NSString stringWithFormat:kMenuItemDisabledToolTipFormat, musicPlayerName];
+    }
+}
+
+#pragma mark Parent menu events
+
+- (void) parentMenuNeedsUpdate {
+    [self updateMenuItemTitle];
+}
+
+- (void) parentMenuItemWillHighlight:(NSMenuItem* __nullable)item {
+    // Used to make the auto-pause menu item's text white when it's highlighted and change it back after.
+    //
+    // TODO: If you click the auto-pause menu item while it's disabled, it will initially appear highlighted next time
+    //       you open the main menu.
+    
+    // If item is nil or any other menu item, the auto-pause menu item will be unhighlighted.
+    BOOL willHighlightMenuItem = [item isEqual:menuItem];
+    
+    // Only update the menu item if it's changing (from highlighted to unhighlighted or vice versa) to save a little
+    // CPU.
+    if (willHighlightMenuItem != menuItem.highlighted) {
+        [self updateMenuItemTitleWithHighlight:willHighlightMenuItem];
+    }
+}
+
+@end
+
+#pragma clang assume_nonnull end
+

BGMApp/BGMApp/BGMAutoPauseMusic.h

@@ -25,16 +25,22 @@
 
 // Local Includes
 #import "BGMAudioDeviceManager.h"
+#import "BGMMusicPlayers.h"
 
 // System Includes
 #import <Foundation/Foundation.h>
 
 
+#pragma clang assume_nonnull begin
+
 @interface BGMAutoPauseMusic : NSObject
 
-- (id) initWithAudioDevices:(BGMAudioDeviceManager*)inAudioDevices;
+- (id) initWithAudioDevices:(BGMAudioDeviceManager*)inAudioDevices musicPlayers:(BGMMusicPlayers*)inMusicPlayers;
+
 - (void) enable;
 - (void) disable;
 
 @end
 
+#pragma clang assume_nonnull end
+

BGMApp/BGMApp/BGMAutoPauseMusic.mm

@@ -17,7 +17,7 @@
 //  BGMAutoPauseMusic.m
 //  BGMApp
 //
-//  Copyright © 2016 Kyle Neideck
+//  Copyright © 2016, 2017 Kyle Neideck
 //
 
 // Self Include
@@ -27,6 +27,9 @@
 #include "BGM_Types.h"
 #import "BGMMusicPlayer.h"
 
+// STL Includes
+#import <algorithm>  // std::max, std::min
+
 // System Includes
 #include <CoreAudio/AudioHardware.h>
 #include <mach/mach_time.h>
@@ -36,34 +39,63 @@
 // and other audio can have short periods of silence without causing music to play and quickly pause again. Of course, it's a
 // trade-off against how long the music will overlap the other audio before it gets paused and how long the music will stay paused
 // after a sound that was only slightly longer than the pause delay.
+static UInt64 const kPauseDelayNSec = 1500 * NSEC_PER_MSEC;
+// The delay before unpausing the music player is proportional to how long we paused it for, bounded by these limits. This makes it
+// a bit less annoying when a sound is just long enough to cause an auto-pause.
 //
-// TODO: Make these settable in advanced settings?
-static int const kPauseDelayMSecs = 1500;
-static int const kUnpauseDelayMSecs = 3000;
+// I haven't spent much time experimenting with different values for these constants, so they could probably be improved a fair
+// bit.
+//
+// TODO: Would it be worth listening for kAudioDeviceCustomPropertyDeviceIsRunningSomewhereOtherThanBGMApp so we can unpause
+//       immediately if we haven't been paused for long and the non-music-player client stops IO? That would usually indicate that
+//       it doesn't intend to start playing audio again soon. We'd also have to deal with music players that don't stop IO when
+//       they're paused.
+static UInt64 const kMaxUnpauseDelayNSec = 3000 * NSEC_PER_MSEC;
+static UInt64 const kMinUnpauseDelayNSec = kMaxUnpauseDelayNSec / 10;
+// We multiply the time spent paused by this factor to calculate the delay before we consider unpausing.
+static Float32 const kUnpauseDelayWeightingFactor = 0.25f;
 
 @implementation BGMAutoPauseMusic {
     BOOL enabled;
+    
     BGMAudioDeviceManager* audioDevices;
+    BGMMusicPlayers* musicPlayers;
+    
     dispatch_queue_t listenerQueue;
-    // Have to keep track of the listener block we add so we can remove it later
+    // Have to keep track of the listener block we add so we can remove it later.
     AudioObjectPropertyListenerBlock listenerBlock;
-    // True if BGMApp has paused musicPlayer and hasn't unpaused it yet. (Will be out of sync with the music player app if the user
-    // has unpaused it themselves.)
+    
+    dispatch_queue_t pauseUnpauseMusicQueue;
+    
+    // True if BGMApp has paused musicPlayer and hasn't unpaused it yet. (Will be out of sync with the music player app if the
+    // user has unpaused it themselves.)
     BOOL wePaused;
     // The times, in absolute time, that the BGMDevice last changed its audible state to silent...
     UInt64 wentSilent;
-    // ...and to audible
+    // ...and to audible.
     UInt64 wentAudible;
-    dispatch_queue_t pauseUnpauseMusicQueue;
 }
 
-- (id) initWithAudioDevices:(BGMAudioDeviceManager*)inAudioDevices {
+- (id) initWithAudioDevices:(BGMAudioDeviceManager*)inAudioDevices musicPlayers:(BGMMusicPlayers*)inMusicPlayers {
     if ((self = [super init])) {
-        enabled = NO;
         audioDevices = inAudioDevices;
+        musicPlayers = inMusicPlayers;
+        
+        enabled = NO;
         wePaused = NO;
         
-        dispatch_queue_attr_t attr = dispatch_queue_attr_make_with_qos_class(DISPATCH_QUEUE_SERIAL, QOS_CLASS_DEFAULT, 0);
+        dispatch_queue_attr_t attr;
+
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wpartial-availability"
+        if (&dispatch_queue_attr_make_with_qos_class) {
+            attr = dispatch_queue_attr_make_with_qos_class(DISPATCH_QUEUE_SERIAL, QOS_CLASS_DEFAULT, 0);
+        } else {
+            // OS X 10.9 fallback
+            attr = DISPATCH_QUEUE_SERIAL;
+        }
+#pragma clang diagnostic pop
+
         listenerQueue = dispatch_queue_create("com.bearisdriving.BGM.AutoPauseMusic.Listener", attr);
         pauseUnpauseMusicQueue = dispatch_queue_create("com.bearisdriving.BGM.AutoPauseMusic.PauseUnpauseMusic", attr);
         
@@ -94,6 +126,8 @@ static int const kUnpauseDelayMSecs = 3000;
                          audibleStateStr);
 #endif
                 
+                // TODO: We shouldn't assume this block will only get called when BGMDevice's audible state changes. (Even if
+                //       the Core Audio docs did specify that, there's no reason not to be fault tolerant.)
                 if (audibleState == kBGMDeviceIsAudible) {
                     [weakSelf queuePauseBlock];
                 } else if (audibleState == kBGMDeviceIsSilent) {
@@ -112,9 +146,12 @@ static int const kUnpauseDelayMSecs = 3000;
 
 - (SInt32) deviceAudibleState {
     SInt32 audibleState;
-    CFNumberRef audibleStateRef = static_cast<CFNumberRef>([audioDevices bgmDevice].GetPropertyData_CFType(kBGMAudibleStateAddress));
+    CFNumberRef audibleStateRef =
+        static_cast<CFNumberRef>([audioDevices bgmDevice].GetPropertyData_CFType(kBGMAudibleStateAddress));
+    
     CFNumberGetValue(audibleStateRef, kCFNumberSInt32Type, &audibleState);
     CFRelease(audibleStateRef);
+    
     return audibleState;
 }
 
@@ -124,10 +161,10 @@ static int const kUnpauseDelayMSecs = 3000;
     UInt64 startedPauseDelay = now;
     
     DebugMsg("BGMAutoPauseMusic::queuePauseBlock: Dispatching pause block at %llu", now);
-    dispatch_after(dispatch_time(DISPATCH_TIME_NOW, kPauseDelayMSecs * NSEC_PER_MSEC),
+    dispatch_after(dispatch_time(DISPATCH_TIME_NOW, kPauseDelayNSec),
                    pauseUnpauseMusicQueue,
                    ^{
-                       BOOL stillAudible = [self deviceAudibleState] == kBGMDeviceIsAudible;
+                       BOOL stillAudible = ([self deviceAudibleState] == kBGMDeviceIsAudible);
                        
                        DebugMsg("BGMAutoPauseMusic::queuePauseBlock: Running pause block dispatched at %llu.%s wentAudible=%llu",
                                 startedPauseDelay,
@@ -137,8 +174,8 @@ static int const kUnpauseDelayMSecs = 3000;
                        // Pause if this is the most recent pause block and the device is still audible, which means the audible
                        // state hasn't changed since this block was queued. Also set wePaused to true if the player wasn't
                        // already paused.
-                       if (!wePaused && startedPauseDelay == wentAudible && stillAudible) {
-                           wePaused = [[BGMMusicPlayer selectedMusicPlayer] pause] || wePaused;
+                       if (!wePaused && (startedPauseDelay == wentAudible) && stillAudible) {
+                           wePaused = ([musicPlayers.selectedMusicPlayer pause] || wePaused);
                        }
                    });
 }
@@ -148,11 +185,31 @@ static int const kUnpauseDelayMSecs = 3000;
     wentSilent = now;
     UInt64 startedUnpauseDelay = now;
     
-    DebugMsg("BGMAutoPauseMusic::queueUnpauseBlock: Dispatched unpause block at %llu", now);
-    dispatch_after(dispatch_time(DISPATCH_TIME_NOW, kUnpauseDelayMSecs * NSEC_PER_MSEC),
+    // Unpause sooner if we've only been paused for a short time. This is so a notification sound causing an auto-pause is
+    // less of an interruption.
+    //
+    // TODO: Would it help much if we ignored all audio played on the "system default" device rather than the "default"
+    //       device? IIRC apps are supposed to use the former for UI sounds.
+    UInt64 unpauseDelayNsec =
+        static_cast<UInt64>((wentSilent - wentAudible) * kUnpauseDelayWeightingFactor);
+    
+    // Convert from absolute time to nanos.
+    mach_timebase_info_data_t info;
+    mach_timebase_info(&info);
+    unpauseDelayNsec = unpauseDelayNsec * info.numer / info.denom;
+    
+    // Clamp.
+    unpauseDelayNsec = std::min(kMaxUnpauseDelayNSec, unpauseDelayNsec);
+    unpauseDelayNsec = std::max(kMinUnpauseDelayNSec, unpauseDelayNsec);
+    
+    DebugMsg("BGMAutoPauseMusic::queueUnpauseBlock: Dispatched unpause block at %llu. unpauseDelayNsec=%llu",
+             now,
+             unpauseDelayNsec);
+    
+    dispatch_after(dispatch_time(DISPATCH_TIME_NOW, unpauseDelayNsec),
                    pauseUnpauseMusicQueue,
                    ^{
-                       BOOL stillSilent = [self deviceAudibleState] == kBGMDeviceIsSilent;
+                       BOOL stillSilent = ([self deviceAudibleState] == kBGMDeviceIsSilent);
                        
                        DebugMsg("BGMAutoPauseMusic::queueUnpauseBlock: Running unpause block dispatched at %llu.%s%s wentSilent=%llu",
                                 startedUnpauseDelay,
@@ -162,9 +219,9 @@ static int const kUnpauseDelayMSecs = 3000;
                        
                        // Unpause if we were the one who paused. Also check that this is the most recent unpause block and the
                        // device is still silent, which means the audible state hasn't changed since this block was queued.
-                       if (wePaused && startedUnpauseDelay == wentSilent && stillSilent) {
+                       if (wePaused && (startedUnpauseDelay == wentSilent) && stillSilent) {
                            wePaused = NO;
-                           [[BGMMusicPlayer selectedMusicPlayer] unpause];
+                           [musicPlayers.selectedMusicPlayer unpause];
                        }
                    });
 }

BGMApp/BGMApp/BGMDeviceControlSync.cpp

@@ -17,7 +17,7 @@
 //  BGMDeviceControlSync.cpp
 //  BGMApp
 //
-//  Copyright © 2016 Kyle Neideck
+//  Copyright © 2016, 2017 Kyle Neideck
 //
 
 // Self Include
@@ -25,13 +25,13 @@
 
 // Local Includes
 #include "BGM_Types.h"
+#include "BGM_Utils.h"
 
-// System Includes
-#include <AudioToolbox/AudioServices.h>
+// PublicUtility Includes
+#include "CAPropertyAddress.h"
 
 
-// AudioObjectPropertyElement docs: "Elements are numbered sequentially where 0 represents the master element."
-static const AudioObjectPropertyElement kMasterChannel = 0;
+#pragma clang assume_nonnull begin
 
 static const AudioObjectPropertyAddress kMutePropertyAddress =
     { kAudioDevicePropertyMute, kAudioObjectPropertyScopeOutput, kAudioObjectPropertyElementMaster };
@@ -41,31 +41,55 @@ static const AudioObjectPropertyAddress kVolumePropertyAddress =
 
 #pragma mark Construction/Destruction
 
-BGMDeviceControlSync::BGMDeviceControlSync(CAHALAudioDevice inBGMDevice, CAHALAudioDevice inOutputDevice)
+BGMDeviceControlSync::BGMDeviceControlSync(AudioObjectID inBGMDevice,
+                                           AudioObjectID inOutputDevice,
+                                           CAHALAudioSystemObject inAudioSystem)
 :
     mBGMDevice(inBGMDevice),
-    mOutputDevice(inOutputDevice)
+    mOutputDevice(inOutputDevice),
+    mAudioSystem(inAudioSystem),
+    mBGMDeviceControlsList(inBGMDevice)
 {
-    Activate();
 }
 
 BGMDeviceControlSync::~BGMDeviceControlSync()
 {
-    Deactivate();
+    BGMLogAndSwallowExceptions("BGMDeviceControlSync::~BGMDeviceControlSync", [&] {
+        CAMutex::Locker locker(mMutex);
+
+        Deactivate();
+    });
 }
 
 void    BGMDeviceControlSync::Activate()
 {
-    ThrowIf((mBGMDevice.GetObjectID() == kAudioDeviceUnknown || mOutputDevice.GetObjectID() == kAudioDeviceUnknown),
+    CAMutex::Locker locker(mMutex);
+
+    ThrowIf((mBGMDevice.GetObjectID() == kAudioObjectUnknown || mOutputDevice.GetObjectID() == kAudioObjectUnknown),
             BGM_DeviceNotSetException(),
             "BGMDeviceControlSync::Activate: Both the output device and BGMDevice must be set to start synchronizing their controls");
-    
-    // Init BGMDevice controls to match output device
-    CopyVolume(mOutputDevice, mBGMDevice, kAudioObjectPropertyScopeOutput);
-    CopyMute(mOutputDevice, mBGMDevice, kAudioObjectPropertyScopeOutput);
-    
+
     if(!mActive)
     {
+        DebugMsg("BGMDeviceControlSync::Activate: Activating control sync");
+
+        // Disable BGMDevice controls that the output device doesn't have and reenable any that were
+        // disabled for the previous output device.
+        //
+        // Continue anyway if this fails because it's better to have extra/missing controls than to
+        // be unable to use the device.
+        BGMLogAndSwallowExceptionsMsg("BGMDeviceControlSync::Activate", "Controls list", [&] {
+            bool wasUpdated = mBGMDeviceControlsList.MatchControlsListOf(mOutputDevice);
+            if(wasUpdated)
+            {
+                mBGMDeviceControlsList.PropagateControlListChange();
+            }
+        });
+
+        // Init BGMDevice controls to match output device
+        mBGMDevice.CopyVolumeFrom(mOutputDevice, kAudioObjectPropertyScopeOutput);
+        mBGMDevice.CopyMuteFrom(mOutputDevice, kAudioObjectPropertyScopeOutput);
+
         // Register listeners for volume and mute values
         mBGMDevice.AddPropertyListener(kVolumePropertyAddress, &BGMDeviceControlSync::BGMDeviceListenerProc, this);
         
@@ -75,284 +99,140 @@ void    BGMDeviceControlSync::Activate()
         }
         catch(CAException)
         {
+            CATry
             mBGMDevice.RemovePropertyListener(kVolumePropertyAddress, &BGMDeviceControlSync::BGMDeviceListenerProc, this);
+            CACatch
+            
             throw;
         }
         
         mActive = true;
     }
+    else
+    {
+        DebugMsg("BGMDeviceControlSync::Activate: Already active");
+    }
 }
 
 void    BGMDeviceControlSync::Deactivate()
 {
-    if(mActive && mBGMDevice.GetObjectID() != kAudioDeviceUnknown)
+    CAMutex::Locker locker(mMutex);
+
+    if(mActive)
     {
-        // Unregister listeners
-        mBGMDevice.RemovePropertyListener(kVolumePropertyAddress, &BGMDeviceControlSync::BGMDeviceListenerProc, this);
-        mBGMDevice.RemovePropertyListener(kMutePropertyAddress, &BGMDeviceControlSync::BGMDeviceListenerProc, this);
-    }
-}
+        DebugMsg("BGMDeviceControlSync::Deactivate: Deactivating control sync");
 
-
-void    BGMDeviceControlSync::Swap(BGMDeviceControlSync& inDeviceControlSync)
-{
-    mBGMDevice = inDeviceControlSync.mBGMDevice;
-    mOutputDevice = inDeviceControlSync.mOutputDevice;
-    inDeviceControlSync.Deactivate();
-    Activate();
-}
-
-#pragma mark Get/Set Control Values
-
-// static
-void    BGMDeviceControlSync::CopyMute(CAHALAudioDevice inFromDevice, CAHALAudioDevice inToDevice, AudioObjectPropertyScope inScope)
-{
-    // TODO: Support for devices that have per-channel mute controls but no master mute control
-    bool toHasSettableMasterMute = inToDevice.HasMuteControl(inScope, kMasterChannel) && inToDevice.MuteControlIsSettable(inScope, kMasterChannel);
-    if(toHasSettableMasterMute && inFromDevice.HasMuteControl(inScope, kMasterChannel))
-    {
-        inToDevice.SetMuteControlValue(inScope,
-                                       kMasterChannel,
-                                       inFromDevice.GetMuteControlValue(inScope, kMasterChannel));
-    }
-}
-
-// static
-void    BGMDeviceControlSync::CopyVolume(CAHALAudioDevice inFromDevice, CAHALAudioDevice inToDevice, AudioObjectPropertyScope inScope)
-{
-    // Get the volume of the from device
-    bool didGetFromVolume = false;
-    Float32 fromVolume = FLT_MIN;
-    
-    if(inFromDevice.HasVolumeControl(inScope, kMasterChannel))
-    {
-        fromVolume = inFromDevice.GetVolumeControlScalarValue(inScope, kMasterChannel);
-        didGetFromVolume = true;
-    }
-
-    // Use the average channel volume of the from device if it has no master volume
-    if(!didGetFromVolume)
-    {
-        UInt32 fromNumChannels = inFromDevice.GetTotalNumberChannels(inScope == kAudioObjectPropertyScopeInput);
-        fromVolume = 0;
-        
-        for(UInt32 channel = 1; channel <= fromNumChannels; channel++)
+        // Deregister listeners
+        if(mBGMDevice.GetObjectID() != kAudioDeviceUnknown)
         {
-            if(inFromDevice.HasVolumeControl(inScope, channel))
-            {
-                fromVolume += inFromDevice.GetVolumeControlScalarValue(inScope, channel);
-                didGetFromVolume = true;
-            }
-        }
-        
-        fromVolume /= fromNumChannels;
-    }
+            BGMLogAndSwallowExceptions("BGMDeviceControlSync::Deactivate", [&] {
+                mBGMDevice.RemovePropertyListener(kVolumePropertyAddress,
+                                                  &BGMDeviceControlSync::BGMDeviceListenerProc,
+                                                  this);
+            });
 
-    // Set the volume of the to device
-    if(didGetFromVolume && fromVolume != FLT_MIN)
-    {
-        bool didSetVolume = false;
-        
-        try
-        {
-            didSetVolume = SetMasterVolumeScalar(inToDevice, inScope, fromVolume);
-        }
-        catch(CAException e)
-        {
-            OSStatus err = e.GetError();
-            char err4CC[5] = CA4CCToCString(err);
-            CFStringRef uid = inToDevice.CopyDeviceUID();
-            LogWarning("BGMDeviceControlSync::CopyVolume: CAException '%s' trying to set master volume of %s", err4CC, uid);
-            CFRelease(uid);
+            BGMLogAndSwallowExceptions("BGMDeviceControlSync::Deactivate", [&] {
+                mBGMDevice.RemovePropertyListener(kMutePropertyAddress,
+                                                  &BGMDeviceControlSync::BGMDeviceListenerProc,
+                                                  this);
+            });
         }
 
-        if(!didSetVolume)
-        {
-            // Couldn't find a master volume control to set, so try to find a virtual one
-            Float32 fromVirtualMasterVolume;
-            bool success = GetVirtualMasterVolume(inFromDevice, inScope, fromVirtualMasterVolume);
-            if(success)
-            {
-                didSetVolume = SetVirtualMasterVolume(inToDevice, inScope, fromVirtualMasterVolume);
-            }
-        }
-    
-        if(!didSetVolume)
-        {
-            // Couldn't set a master or virtual master volume, so as a fallback try to set each channel individually
-            UInt32 numChannels = inToDevice.GetTotalNumberChannels(inScope == kAudioObjectPropertyScopeInput);
-            for(UInt32 channel = 1; channel <= numChannels; channel++)
-            {
-                if(inToDevice.HasVolumeControl(inScope, channel) && inToDevice.VolumeControlIsSettable(inScope, channel))
-                {
-                    inToDevice.SetVolumeControlScalarValue(inScope, channel, fromVolume);
-                }
-            }
-        }
+        mActive = false;
     }
-}
-
-// static
-bool    BGMDeviceControlSync::SetMasterVolumeScalar(CAHALAudioDevice inDevice, AudioObjectPropertyScope inScope, Float32 inVolume)
-{
-    bool hasSettableMasterVolume =
-        inDevice.HasVolumeControl(inScope, kMasterChannel) && inDevice.VolumeControlIsSettable(inScope, kMasterChannel);
-    
-    if(hasSettableMasterVolume)
+    else
     {
-        inDevice.SetVolumeControlScalarValue(inScope, kMasterChannel, inVolume);
-        return true;
+        DebugMsg("BGMDeviceControlSync::Deactivate: Not active");
     }
-    
-    return false;
 }
 
-// static
-bool    BGMDeviceControlSync::GetVirtualMasterVolume(CAHALAudioDevice inDevice, AudioObjectPropertyScope inScope, Float32& outVirtualMasterVolume)
+#pragma mark Accessors
+
+void    BGMDeviceControlSync::SetDevices(AudioObjectID inBGMDevice, AudioObjectID inOutputDevice)
 {
-    AudioObjectPropertyAddress virtualMasterVolumeAddress =
-        { kAudioHardwareServiceDeviceProperty_VirtualMasterVolume, inScope, kAudioObjectPropertyElementMaster };
+    CAMutex::Locker locker(mMutex);
+
+    bool wasActive = mActive;
+
+    Deactivate();
+
+    mBGMDevice = inBGMDevice;
+    mBGMDeviceControlsList.SetBGMDevice(inBGMDevice);
+    mOutputDevice = inOutputDevice;
     
-    if(!AudioHardwareServiceHasProperty(inDevice.GetObjectID(), &virtualMasterVolumeAddress))
+    if(wasActive)
     {
-        return false;
+        Activate();
     }
-    
-    UInt32 virtualMasterVolumePropertySize = sizeof(Float32);
-    return kAudioServicesNoError == AHSGetPropertyData(inDevice.GetObjectID(),
-                                                       &virtualMasterVolumeAddress,
-                                                       &virtualMasterVolumePropertySize,
-                                                       &outVirtualMasterVolume);
 }
 
-// static
-bool    BGMDeviceControlSync::SetVirtualMasterVolume(CAHALAudioDevice inDevice, AudioObjectPropertyScope inScope, Float32 inVolume)
-{
-    // TODO: For me, setting the virtual master volume sets all the device's channels to the same volume, meaning you can't
-    //       keep any channels quieter than the others. The expected behaviour is to scale the channel volumes
-    //       proportionally. So to do this properly I think we'd have to store BGMDevice's previous volume and calculate
-    //       each channel's new volume from its current volume and the distance between BGMDevice's old and new volumes.
-    //
-    //       The docs kAudioHardwareServiceDeviceProperty_VirtualMasterVolume for say
-    //           "If the device has individual channel volume controls, this property will apply to those identified by the
-    //           device's preferred multi-channel layout (or preferred stereo pair if the device is stereo only). Note that
-    //           this control maintains the relative balance between all the channels it affects.
-    //       so I'm not sure why that's not working here. As a workaround we take the to device's (virtual master) balance
-    //       before changing the volume and set it back after, but of course that'll only work for stereo devices.
-    
-    bool didSetVolume = false;
-    AudioObjectPropertyAddress virtualMasterVolumeAddress =
-        { kAudioHardwareServiceDeviceProperty_VirtualMasterVolume, inScope, kAudioObjectPropertyElementMaster };
-    bool hasVirtualMasterVolume = AudioHardwareServiceHasProperty(inDevice.GetObjectID(), &virtualMasterVolumeAddress);
-    
-    Boolean virtualMasterVolumeIsSettable;
-    OSStatus err = AudioHardwareServiceIsPropertySettable(inDevice.GetObjectID(), &virtualMasterVolumeAddress, &virtualMasterVolumeIsSettable);
-    virtualMasterVolumeIsSettable &= (err == kAudioServicesNoError);
-    
-    if(hasVirtualMasterVolume && virtualMasterVolumeIsSettable)
-    {
-        // Not sure why, but setting the virtual master volume sets all channels to the same volume. As a workaround, we store
-        // the current balance here so we can reset it after setting the volume.
-        Float32 virtualMasterBalance;
-        bool didGetVirtualMasterBalance = GetVirtualMasterBalance(inDevice, inScope, virtualMasterBalance);
-        
-        didSetVolume = kAudioServicesNoError == AHSSetPropertyData(inDevice.GetObjectID(), &virtualMasterVolumeAddress, sizeof(Float32), &inVolume);
-        
-        // Reset the balance
-        AudioObjectPropertyAddress virtualMasterBalanceAddress =
-            { kAudioHardwareServiceDeviceProperty_VirtualMasterBalance, inScope, kAudioObjectPropertyElementMaster };
-        
-        if(didSetVolume && didGetVirtualMasterBalance && AudioHardwareServiceHasProperty(inDevice.GetObjectID(), &virtualMasterBalanceAddress))
-        {
-            Boolean balanceIsSettable;
-            err = AudioHardwareServiceIsPropertySettable(inDevice.GetObjectID(), &virtualMasterBalanceAddress, &balanceIsSettable);
-            if(err == kAudioServicesNoError && balanceIsSettable)
-            {
-                AHSSetPropertyData(inDevice.GetObjectID(), &virtualMasterBalanceAddress, sizeof(Float32), &virtualMasterBalance);
-            }
-        }
-    }
-    
-    return didSetVolume;
-}
+#pragma mark Listener Procs
 
 // static
-bool    BGMDeviceControlSync::GetVirtualMasterBalance(CAHALAudioDevice inDevice, AudioObjectPropertyScope inScope, Float32& outVirtualMasterBalance)
+OSStatus    BGMDeviceControlSync::BGMDeviceListenerProc(AudioObjectID inObjectID, UInt32 inNumberAddresses, const AudioObjectPropertyAddress* inAddresses, void* __nullable inClientData)
 {
-    AudioObjectPropertyAddress virtualMasterBalanceAddress =
-        { kAudioHardwareServiceDeviceProperty_VirtualMasterBalance, inScope, kAudioObjectPropertyElementMaster };
-    
-    if(!AudioHardwareServiceHasProperty(inDevice.GetObjectID(), &virtualMasterBalanceAddress))
-    {
-        return false;
-    }
-    
-    UInt32 virtualMasterVolumePropertySize = sizeof(Float32);
-    return kAudioServicesNoError == AHSGetPropertyData(inDevice.GetObjectID(),
-                                                       &virtualMasterBalanceAddress,
-                                                       &virtualMasterVolumePropertySize,
-                                                       &outVirtualMasterBalance);
-}
-
-// static
-OSStatus    BGMDeviceControlSync::AHSGetPropertyData(AudioObjectID inObjectID, const AudioObjectPropertyAddress* inAddress, UInt32* ioDataSize, void* outData)
-{
-    // The docs for AudioHardwareServiceGetPropertyData specifically allow passing NULL for inQualifierData as we do here,
-    // but it's declared in an assume_nonnull section so we have to disable the warning here. I'm not sure why inQualifierData
-    // isn't __nullable. I'm assuming it's either a backwards compatibility thing or just a bug.
-    #pragma clang diagnostic push
-    #pragma clang diagnostic ignored "-Wnonnull"
-    // The non-depreciated version of this (and the setter below) doesn't seem to support devices other than the default
-    return AudioHardwareServiceGetPropertyData(inObjectID, inAddress, 0, NULL, ioDataSize, outData);
-    #pragma clang diagnostic pop
-}
-
-// static
-OSStatus    BGMDeviceControlSync::AHSSetPropertyData(AudioObjectID inObjectID, const AudioObjectPropertyAddress* inAddress, UInt32 inDataSize, const void* inData)
-{
-    // See the explanation about these pragmas in AHSGetPropertyData
-    #pragma clang diagnostic push
-    #pragma clang diagnostic ignored "-Wnonnull"
-    return AudioHardwareServiceSetPropertyData(inObjectID, inAddress, 0, NULL, inDataSize, inData);
-    #pragma clang diagnostic pop
-}
-
-#pragma mark Listener
-
-// static
-OSStatus    BGMDeviceControlSync::BGMDeviceListenerProc(AudioObjectID inObjectID, UInt32 inNumberAddresses, const AudioObjectPropertyAddress* __nonnull inAddresses, void* __nullable inClientData)
-{
-    // refCon (reference context) is the instance that registered this listener proc
+    // refCon (reference context) is the instance that registered this listener proc.
     BGMDeviceControlSync* refCon = static_cast<BGMDeviceControlSync*>(inClientData);
-    
-    if(refCon->mActive)
-    {
-        ThrowIf(inObjectID != refCon->mBGMDevice.GetObjectID(),
-                CAException(kAudioHardwareBadObjectError),
-                "BGMDeviceControlSync::BGMDeviceListenerProc: notified about audio object other than BGMDevice");
-        
-        for(int i = 0; i < inNumberAddresses; i++)
+
+    auto checkState = [&] {
+        if(!refCon)
         {
-            AudioObjectPropertyScope scope = inAddresses[i].mScope;
-            
-            switch(inAddresses[i].mSelector)
-            {
-                case kAudioDevicePropertyVolumeScalar:
-                    // Update the output device
-                    CopyVolume(refCon->mBGMDevice, refCon->mOutputDevice, scope);
-                    break;
-                    
-                case kAudioDevicePropertyMute:
-                    // Update the output device. Note that this also runs when you change the volume (on BGMDevice)
-                    CopyMute(refCon->mBGMDevice, refCon->mOutputDevice, scope);
-                    break;
-                    
-                default:
-                    break;
-            }
+            LogError("BGMDeviceControlSync::BGMDeviceListenerProc: !refCon");
+            return false;
+        }
+
+        if(!refCon->mActive ||
+           (refCon->mBGMDevice.GetObjectID() == kAudioObjectUnknown) ||
+           (refCon->mOutputDevice.GetObjectID() == kAudioObjectUnknown))
+        {
+            return false;
+        }
+
+        if(inObjectID != refCon->mBGMDevice.GetObjectID())
+        {
+            LogError("BGMDeviceControlSync::BGMDeviceListenerProc: notified about audio object other than BGMDevice");
+            return false;
+        }
+        
+        return true;
+    };
+
+    for(int i = 0; i < inNumberAddresses; i++)
+    {
+        AudioObjectPropertyScope scope = inAddresses[i].mScope;
+        
+        switch(inAddresses[i].mSelector)
+        {
+            case kAudioDevicePropertyVolumeScalar:
+                {
+                    CAMutex::Locker locker(refCon->mMutex);
+
+                    // Update the output device's volume.
+                    if(checkState())
+                    {
+                        refCon->mOutputDevice.CopyVolumeFrom(refCon->mBGMDevice, scope);
+                    }
+                }
+                break;
+                
+            case kAudioDevicePropertyMute:
+                {
+                    CAMutex::Locker locker(refCon->mMutex);
+
+                    // Update the output device's mute control. Note that this also runs when you
+                    // change the volume (on BGMDevice).
+                    if(checkState())
+                    {
+                        refCon->mOutputDevice.CopyMuteFrom(refCon->mBGMDevice, scope);
+                    }
+                }
+                break;
         }
     }
-    
+
+    // "The return value [of an AudioObjectPropertyListenerProc] is currently unused and should always be 0."
     return 0;
 }
 
+#pragma clang assume_nonnull end
+

BGMApp/BGMApp/BGMDeviceControlSync.h

@@ -17,65 +17,105 @@
 //  BGMDeviceControlSync.h
 //  BGMApp
 //
-//  Copyright © 2016 Kyle Neideck
+//  Copyright © 2016, 2017 Kyle Neideck
 //
-//  Listens for notifications that BGMDevice's controls (just volume and mute currently) have changed value, and
-//  copies the new values to the output device.
+//  Synchronises BGMDevice's controls (just volume and mute currently) with the output device's
+//  controls. This allows the user to control the output device normally while BGMDevice is set as
+//  the default device.
+//
+//  BGMDeviceControlSync disables any BGMDevice controls that the output device doesn't also have.
+//  When the value of one of BGMDevice's controls is changed, BGMDeviceControlSync copies the new
+//  value to the output device.
+//
+//  Thread safe.
 //
 
-#ifndef __BGMApp__BGMDeviceControlSync__
-#define __BGMApp__BGMDeviceControlSync__
+#ifndef BGMApp__BGMDeviceControlSync
+#define BGMApp__BGMDeviceControlSync
+
+// Local Includes
+#include "BGMAudioDevice.h"
+#include "BGMDeviceControlsList.h"
 
 // PublicUtility Includes
-#include "CAHALAudioDevice.h"
+#include "CAHALAudioSystemObject.h"
+#include "CAMutex.h"
+
+// System Includes
+#include <AudioToolbox/AudioServices.h>
 
 
 #pragma clang assume_nonnull begin
 
 class BGMDeviceControlSync
 {
-    
+
+#pragma mark Construction/Destruction
+
 public:
-                        BGMDeviceControlSync(CAHALAudioDevice inBGMDevice, CAHALAudioDevice inOutputDevice);
+                        BGMDeviceControlSync(AudioObjectID inBGMDevice,
+                                             AudioObjectID inOutputDevice,
+                                             CAHALAudioSystemObject inAudioSystem
+                                                     = CAHALAudioSystemObject());
                         ~BGMDeviceControlSync();
                         // Disallow copying
                         BGMDeviceControlSync(const BGMDeviceControlSync&) = delete;
                         BGMDeviceControlSync& operator=(const BGMDeviceControlSync&) = delete;
-                        // Move constructor/assignment
-                        BGMDeviceControlSync(BGMDeviceControlSync&& inDeviceControlSync) { Swap(inDeviceControlSync); }
-                        BGMDeviceControlSync& operator=(BGMDeviceControlSync&& inDeviceControlSync) { Swap(inDeviceControlSync); return *this; }
-    
+
 #ifdef __OBJC__
                         // Only intended as a convenience for Objective-C instance vars
-                        BGMDeviceControlSync() { };
+                        BGMDeviceControlSync()
+                        : BGMDeviceControlSync(kAudioObjectUnknown, kAudioObjectUnknown) { };
 #endif
-    
-private:
+
+    /*!
+     Begin synchronising BGMDevice's controls with the output device's.
+
+     @throws BGM_DeviceNotSetException if BGMDevice isn't set.
+     @throws CAException if the HAL or one of the devices returns an error when this function
+                         registers for device property notifications or when it copies the current
+                         values of the output device's controls to BGMDevice. This
+                         BGMDeviceControlSync will remain inactive if this function throws.
+     */
     void                Activate();
+    /*! Stop synchronising BGMDevice's controls with the output device's. */
     void                Deactivate();
-    void                Swap(BGMDeviceControlSync& inDeviceControlSync);
-    
-    static void         CopyMute(CAHALAudioDevice inFromDevice, CAHALAudioDevice inToDevice, AudioObjectPropertyScope inScope);
-    static void         CopyVolume(CAHALAudioDevice inFromDevice, CAHALAudioDevice inToDevice, AudioObjectPropertyScope inScope);
-    
-    static bool         SetMasterVolumeScalar(CAHALAudioDevice inDevice, AudioObjectPropertyScope inScope, Float32 inVolume);
-    static bool         GetVirtualMasterVolume(CAHALAudioDevice inDevice, AudioObjectPropertyScope inScope, Float32& outVirtualMasterVolume);
-    static bool         SetVirtualMasterVolume(CAHALAudioDevice inDevice, AudioObjectPropertyScope inScope, Float32 inVolume);
-    static bool         GetVirtualMasterBalance(CAHALAudioDevice inDevice, AudioObjectPropertyScope inScope, Float32& outVirtualMasterBalance);
-    
-    static OSStatus     AHSGetPropertyData(AudioObjectID inObjectID, const AudioObjectPropertyAddress* inAddress, UInt32* ioDataSize, void* outData);
-    static OSStatus     AHSSetPropertyData(AudioObjectID inObjectID, const AudioObjectPropertyAddress* inAddress, UInt32 inDataSize, const void* inData);
-    
-    static OSStatus     BGMDeviceListenerProc(AudioObjectID inObjectID, UInt32 inNumberAddresses, const AudioObjectPropertyAddress* inAddresses, void* __nullable inClientData);
+
+#pragma mark Accessors
+
+    /*!
+     Set the IDs of BGMDevice and the output device to synchronise with.
+
+     @throws BGM_DeviceNotSetException if BGMDevice isn't set.
+     @throws CAException if the HAL or one of the new devices returns an error while restarting
+                         synchronisation. This BGMDeviceControlSync will be deactivated if this
+                         function throws, but its devices will still be set.
+     */
+    void                SetDevices(AudioObjectID inBGMDevice, AudioObjectID inOutputDevice);
+
+#pragma mark Listener Procs
     
 private:
-    bool                mActive = false;
-    CAHALAudioDevice    mBGMDevice { kAudioDeviceUnknown };
-    CAHALAudioDevice    mOutputDevice { kAudioDeviceUnknown };
+    /*! Receives HAL notifications about the BGMDevice properties this class listens to. */
+    static OSStatus     BGMDeviceListenerProc(AudioObjectID inObjectID,
+                                              UInt32 inNumberAddresses,
+                                              const AudioObjectPropertyAddress* inAddresses,
+                                              void* __nullable inClientData);
+    
+private:
+    CAMutex             mMutex         { "Device Control Sync" };
+    bool                mActive        = false;
+
+    CAHALAudioSystemObject mAudioSystem;
+    
+    BGMAudioDevice      mBGMDevice     { (AudioObjectID)kAudioObjectUnknown };
+    BGMAudioDevice      mOutputDevice  { (AudioObjectID)kAudioObjectUnknown };
+
+    BGMDeviceControlsList mBGMDeviceControlsList;
     
 };
 
 #pragma clang assume_nonnull end
 
-#endif /* __BGMApp__BGMDeviceControlSync__ */
+#endif /* BGMApp__BGMDeviceControlSync */
 

BGMApp/BGMApp/BGMDeviceControlsList.cpp

@@ -0,0 +1,507 @@
+// This file is part of Background Music.
+//
+// Background Music is free software: you can redistribute it and/or
+// modify it under the terms of the GNU General Public License as
+// published by the Free Software Foundation, either version 2 of the
+// License, or (at your option) any later version.
+//
+// Background Music is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Background Music. If not, see <http://www.gnu.org/licenses/>.
+
+//
+//  BGMDeviceControlsList.cpp
+//  BGMApp
+//
+//  Copyright © 2017 Kyle Neideck
+//
+
+// Self Include
+#include "BGMDeviceControlsList.h"
+
+// Local Includes
+#include "BGM_Types.h"
+#include "BGM_Utils.h"
+
+// PublicUtility Includes
+#include "CAPropertyAddress.h"
+#include "CACFArray.h"
+
+
+#pragma clang assume_nonnull begin
+
+static const SInt64 kToggleDeviceInitialDelay = 50 * NSEC_PER_MSEC;
+static const SInt64 kToggleDeviceBackDelay    = 500 * NSEC_PER_MSEC;
+static const SInt64 kDisableNullDeviceDelay   = 500 * NSEC_PER_MSEC;
+static const SInt64 kDisableNullDeviceTimeout = 5000 * NSEC_PER_MSEC;
+
+#pragma mark Construction/Destruction
+
+BGMDeviceControlsList::BGMDeviceControlsList(AudioObjectID inBGMDevice,
+                                             CAHALAudioSystemObject inAudioSystem)
+:
+    mBGMDevice(inBGMDevice),
+    mAudioSystem(inAudioSystem)
+{
+    BGMAssert((mBGMDevice.GetObjectID() == mAudioSystem.GetAudioDeviceForUID(CFSTR(kBGMDeviceUID)) ||
+                    mBGMDevice.GetObjectID() == kAudioObjectUnknown),
+              "BGMDeviceControlsList::BGMDeviceControlsList: Given device is not BGMDevice");
+
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wpartial-availability"
+    mCanToggleDeviceOnSystem = (&dispatch_block_wait &&
+                                &dispatch_block_cancel &&
+                                &dispatch_block_testcancel &&
+                                &dispatch_queue_attr_make_with_qos_class);
+#pragma clang diagnostic pop
+}
+
+BGMDeviceControlsList::~BGMDeviceControlsList()
+{
+    CAMutex::Locker locker(mMutex);
+
+    if(!mDeviceTogglingInitialised)
+    {
+        return;
+    }
+
+    BGMLogAndSwallowExceptions("BGMDeviceControlsList::~BGMDeviceControlsList", [&] {
+        mAudioSystem.RemovePropertyListenerBlock(CAPropertyAddress(kAudioHardwarePropertyDevices),
+                                                 mListenerQueue,
+                                                 mListenerBlock);
+    });
+
+    // If we're in the middle of toggling the default device, block until we've finished.
+    if(mDisableNullDeviceBlock && mDeviceToggleState != ToggleState::NotToggling)
+    {
+        DebugMsg("BGMDeviceControlsList::~BGMDeviceControlsList: Waiting for device toggle");
+
+        // Copy the reference so we can unlock the mutex and allow any remaining blocks to run.
+        dispatch_block_t disableNullDeviceBlock = mDisableNullDeviceBlock;
+
+        CAMutex::Unlocker unlocker(mMutex);
+
+        // Note that if mDisableNullDeviceBlock is currently running this will return after it
+        // finishes and if it's already run this will return immediately. So we don't have to
+        // worry about ending up waiting for mDisableNullDeviceBlock when it isn't queued.
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wpartial-availability"
+        bool timedOut = dispatch_block_wait(disableNullDeviceBlock, kDisableNullDeviceTimeout);
+#pragma clang diagnostic pop
+
+        if(timedOut)
+        {
+            LogWarning("BGMDeviceControlsList::~BGMDeviceControlsList: Device toggle timed out");
+        }
+    }
+
+    mDeviceToggleState = ToggleState::NotToggling;
+
+    DestroyBlock(mDeviceToggleBlock);
+    DestroyBlock(mDeviceToggleBackBlock);
+    DestroyBlock(mDisableNullDeviceBlock);
+
+    Block_release(mListenerBlock);
+    dispatch_release(mListenerQueue);
+}
+
+#pragma mark Accessors
+
+void    BGMDeviceControlsList::SetBGMDevice(AudioObjectID inBGMDeviceID)
+{
+    CAMutex::Locker locker(mMutex);
+
+    mBGMDevice = inBGMDeviceID;
+
+    BGMAssert(mBGMDevice.GetObjectID() == mAudioSystem.GetAudioDeviceForUID(CFSTR(kBGMDeviceUID)),
+              "BGMDeviceControlsList::SetBGMDevice: Given device is not BGMDevice");
+}
+
+#pragma mark Update Controls List
+
+bool    BGMDeviceControlsList::MatchControlsListOf(AudioObjectID inDeviceID)
+{
+    CAMutex::Locker locker(mMutex);
+
+    if(mBGMDevice.GetObjectID() != mAudioSystem.GetAudioDeviceForUID(CFSTR(kBGMDeviceUID)))
+    {
+        LogWarning("BGMDeviceControlsList::MatchControlsListOf: BGMDevice ID not set");
+        return false;
+    }
+
+    // If the output device doesn't have a control that BGMDevice does, disable it on BGMDevice so
+    // the system's audio UI isn't confusing.
+
+    // No need to change input controls.
+    AudioObjectPropertyScope inScope = kAudioObjectPropertyScopeOutput;
+
+    // Check which of BGMDevice's controls are currently enabled. We need to know whether we're
+    // actually enabling/disabling any controls so we know whether we need to call
+    // PropagateControlListChange afterward.
+    CFTypeRef __nullable enabledControlsRef =
+        mBGMDevice.GetPropertyData_CFType(kBGMEnabledOutputControlsAddress);
+
+    ThrowIf(!enabledControlsRef || (CFGetTypeID(enabledControlsRef) != CFArrayGetTypeID()),
+            CAException(kAudioHardwareIllegalOperationError),
+            "BGMDeviceControlsList::MatchControlsListOf: Expected a CFArray for "
+            "kAudioDeviceCustomPropertyEnabledOutputControls");
+
+    CACFArray enabledControls(static_cast<CFArrayRef>(enabledControlsRef), true);
+
+    BGMAssert(enabledControls.GetNumberItems() == 2,
+              "BGMDeviceControlsList::MatchControlsListOf: Expected 2 array elements for "
+              "kAudioDeviceCustomPropertyEnabledOutputControls");
+
+    bool volumeEnabled;
+    bool didGetBool = enabledControls.GetBool(kBGMEnabledOutputControlsIndex_Volume, volumeEnabled);
+    ThrowIf(!didGetBool,
+            CAException(kAudioHardwareIllegalOperationError),
+            "BGMDeviceControlsList::MatchControlsListOf: Expected volume element of "
+            "kAudioDeviceCustomPropertyEnabledOutputControls to be a CFBoolean");
+
+    bool muteEnabled;
+    didGetBool = enabledControls.GetBool(kBGMEnabledOutputControlsIndex_Mute, muteEnabled);
+    ThrowIf(!didGetBool,
+            CAException(kAudioHardwareIllegalOperationError),
+            "BGMDeviceControlsList::MatchControlsListOf: Expected mute element of "
+            "kAudioDeviceCustomPropertyEnabledOutputControls to be a CFBoolean");
+
+    DebugMsg("BGMDeviceControlsList::MatchControlsListOf: BGMDevice has volume %s, mute %s",
+             (volumeEnabled ? "enabled" : "disabled"),
+             (muteEnabled ? "enabled" : "disabled"));
+
+    // Check which controls the other device has.
+    BGMAudioDevice device(inDeviceID);
+    bool hasMute = device.HasSettableMasterMute(inScope);
+
+    bool hasVolume =
+        device.HasSettableMasterVolume(inScope) || device.HasSettableVirtualMasterVolume(inScope);
+
+    if(!hasVolume)
+    {
+        // Check for per-channel volume controls.
+        UInt32 numChannels =
+            device.GetTotalNumberChannels(inScope == kAudioObjectPropertyScopeInput);
+
+        for(UInt32 channel = 1; channel <= numChannels; channel++)
+        {
+            BGMLogAndSwallowExceptionsMsg("BGMDeviceControlsList::MatchControlsListOf",
+                                          "Checking for channel volume controls",
+                                          ([&] {
+                hasVolume =
+                    (device.HasVolumeControl(inScope, channel)
+                            && device.VolumeControlIsSettable(inScope, channel));
+            }));
+
+            if(hasVolume)
+            {
+                break;
+            }
+        }
+    }
+
+    // Tell BGMDevice to enable/disable its controls to match the output device.
+    bool deviceUpdated = false;
+
+    CACFArray newEnabledControls;
+    newEnabledControls.SetCFMutableArrayFromCopy(enabledControls.GetCFArray());
+
+    // Update volume.
+    if(volumeEnabled != hasVolume)
+    {
+        DebugMsg("BGMDeviceControlsList::MatchControlsListOf: %s BGMDevice volume control.",
+                 hasVolume ? "Enabling" : "Disabling");
+
+        newEnabledControls.SetBool(kBGMEnabledOutputControlsIndex_Volume, hasVolume);
+        deviceUpdated = true;
+    }
+
+    // Update mute.
+    if(muteEnabled != hasMute)
+    {
+        DebugMsg("BGMDeviceControlsList::MatchControlsListOf: %s BGMDevice mute control.",
+                 hasMute ? "Enabling" : "Disabling");
+
+        newEnabledControls.SetBool(kBGMEnabledOutputControlsIndex_Mute, hasMute);
+        deviceUpdated = true;
+    }
+
+    if(deviceUpdated)
+    {
+        mBGMDevice.SetPropertyData_CFType(kBGMEnabledOutputControlsAddress,
+                                          newEnabledControls.GetCFMutableArray());
+    }
+
+    return deviceUpdated;
+}
+
+void    BGMDeviceControlsList::PropagateControlListChange()
+{
+    CAMutex::Locker locker(mMutex);
+
+    if((mBGMDevice == kAudioObjectUnknown) || !mCanToggleDeviceOnSystem)
+    {
+        return;
+    }
+
+    InitDeviceToggling();
+
+    // Leave the default device alone if the user has changed it since launching BGMApp.
+    bool bgmDeviceIsDefault = true;
+
+    BGMLogAndSwallowExceptions("BGMDeviceControlsList::PropagateControlListChange", ([&] {
+        bgmDeviceIsDefault =
+            (mBGMDevice.GetObjectID() == mAudioSystem.GetDefaultAudioDevice(false, false));
+    }));
+
+    if(bgmDeviceIsDefault)
+    {
+        mDeviceToggleState = ToggleState::SettingNullDeviceAsDefault;
+
+        // We'll get a notification from the HAL after the Null Device is enabled. Then we can
+        // temporarily make it the default device, which gets other programs to notice that
+        // BGMDevice's controls have changed.
+        try
+        {
+            CAMutex::Unlocker unlocker(mMutex);
+            SetNullDeviceEnabled(true);
+        }
+        catch (...)
+        {
+            mDeviceToggleState = ToggleState::NotToggling;
+            LogError("BGMDeviceControlsList::PropagateControlListChange: Could not enable the Null "
+                     "Device");
+            throw;
+        }
+    }
+}
+
+#pragma mark Implementation
+
+void    BGMDeviceControlsList::InitDeviceToggling()
+{
+    CAMutex::Locker locker(mMutex);
+
+    if(mDeviceTogglingInitialised || !mCanToggleDeviceOnSystem)
+    {
+        return;
+    }
+
+    BGMAssert(mBGMDevice.GetObjectID() == mAudioSystem.GetAudioDeviceForUID(CFSTR(kBGMDeviceUID)),
+              "BGMDeviceControlsList::InitDeviceToggling: mBGMDevice device is not set to "
+              "BGMDevice's ID");
+
+    mDeviceToggleBlock = CreateDeviceToggleBlock();
+    mDeviceToggleBackBlock = CreateDeviceToggleBackBlock();
+    mDisableNullDeviceBlock = CreateDisableNullDeviceBlock();
+
+    // Register a listener to find out when the Null Device becomes available/unavailable. See
+    // ToggleDefaultDevice.
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wpartial-availability"
+    dispatch_queue_attr_t attr =
+        dispatch_queue_attr_make_with_qos_class(DISPATCH_QUEUE_SERIAL, QOS_CLASS_DEFAULT, 0);
+#pragma clang diagnostic pop
+    mListenerQueue = dispatch_queue_create("com.bearisdriving.BGM.BGMDeviceControlsList", attr);
+
+    mListenerBlock = ^(UInt32 inNumberAddresses, const AudioObjectPropertyAddress* inAddresses) {
+        // Ignore the notification if we're not toggling the default device, which would just mean
+        // the default device has been changed for an unrelated reason.
+        if(mDeviceToggleState == ToggleState::NotToggling)
+        {
+            return;
+        }
+
+        for(int i = 0; i < inNumberAddresses; i++)
+        {
+            switch(inAddresses[i].mSelector)
+            {
+                case kAudioHardwarePropertyDevices:
+                    {
+                        CAMutex::Locker innerLocker(mMutex);
+
+                        DebugMsg("BGMDeviceControlsList::InitDeviceToggling: Got "
+                                 "kAudioHardwarePropertyDevices");
+
+                        // Cancel the previous block in case it hasn't run yet.
+                        DestroyBlock(mDeviceToggleBlock);
+
+                        mDeviceToggleBlock = CreateDeviceToggleBlock();
+
+                        // Changing the default device too quickly after enabling the Null Device
+                        // seems to cause problems with some programs. Not sure why.
+                        dispatch_after(dispatch_time(DISPATCH_TIME_NOW, kToggleDeviceInitialDelay),
+                                       dispatch_get_global_queue(QOS_CLASS_USER_INITIATED, 0),
+                                       mDeviceToggleBlock);
+                    }
+                    break;
+            }
+        }
+    };
+
+    BGMLogAndSwallowExceptions("BGMDeviceControlsList::InitDeviceToggling", [&] {
+        mAudioSystem.AddPropertyListenerBlock(CAPropertyAddress(kAudioHardwarePropertyDevices),
+                                              mListenerQueue,
+                                              mListenerBlock);
+    });
+
+    mDeviceTogglingInitialised = true;
+}
+
+void    BGMDeviceControlsList::ToggleDefaultDevice()
+{
+    // Set the Null Device as the OS X default device.
+    AudioObjectID nullDeviceID = mAudioSystem.GetAudioDeviceForUID(CFSTR(kBGMNullDeviceUID));
+
+    if(nullDeviceID == kAudioObjectUnknown)
+    {
+        // It's unlikely, but we might have been notified about an unrelated device so just log a
+        // warning.
+        LogWarning("BGMDeviceControlsList::ToggleDefaultDevice: Null Device not found");
+        return;
+    }
+
+    DebugMsg("BGMDeviceControlsList::ToggleDefaultDevice: Setting Null Device as default. "
+             "nullDeviceID = %u", nullDeviceID);
+    mAudioSystem.SetDefaultAudioDevice(false, false, nullDeviceID);
+
+    mDeviceToggleState = ToggleState::SettingBGMDeviceAsDefault;
+
+    // A small number of apps (e.g. Firefox) seem to have trouble with the default device being
+    // changed back immediately, so for now we insert a short delay here and before disabling the
+    // Null Device.
+
+    // Cancel the previous block in case it hasn't run yet.
+    DestroyBlock(mDeviceToggleBackBlock);
+
+    mDeviceToggleBackBlock = CreateDeviceToggleBackBlock();
+
+    dispatch_after(dispatch_time(DISPATCH_TIME_NOW, kToggleDeviceBackDelay),
+                   dispatch_get_global_queue(QOS_CLASS_USER_INITIATED, 0),
+                   mDeviceToggleBackBlock);
+}
+
+void    BGMDeviceControlsList::SetNullDeviceEnabled(bool inEnabled)
+{
+    DebugMsg("BGMDeviceControlsList::SetNullDeviceEnabled: %s the null device",
+             inEnabled ? "Enabling" : "Disabling");
+
+    // Get the audio object for BGMDriver, which is the object the Null Device belongs to.
+    AudioObjectID bgmDriverID = mAudioSystem.GetAudioPlugInForBundleID(CFSTR(kBGMDriverBundleID));
+
+    if(bgmDriverID == kAudioObjectUnknown)
+    {
+        LogError("BGMDeviceControlsList::SetNullDeviceEnabled: BGMDriver plug-in audio object not "
+                 "found");
+        throw CAException(kAudioHardwareUnspecifiedError);
+    }
+
+    CAHALAudioObject bgmDriver(bgmDriverID);
+    bgmDriver.SetPropertyData_CFType(CAPropertyAddress(kAudioPlugInCustomPropertyNullDeviceActive),
+                                     (inEnabled ? kCFBooleanTrue : kCFBooleanFalse));
+}
+
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wpartial-availability"
+
+dispatch_block_t    BGMDeviceControlsList::CreateDeviceToggleBlock()
+{
+    return dispatch_block_create((dispatch_block_flags_t)0, ^{
+        CAMutex::Locker locker(mMutex);
+
+        if(mDeviceToggleState == ToggleState::SettingNullDeviceAsDefault)
+        {
+            BGMLogAndSwallowExceptions("BGMDeviceControlsList::CreateDeviceToggleBlock",
+                                       ([&] {
+                ToggleDefaultDevice();
+            }));
+        }
+    });
+}
+
+dispatch_block_t    BGMDeviceControlsList::CreateDeviceToggleBackBlock()
+{
+    return dispatch_block_create((dispatch_block_flags_t)0, ^{
+        CAMutex::Locker locker(mMutex);
+
+        if(mDeviceToggleState != ToggleState::SettingBGMDeviceAsDefault)
+        {
+            return;
+        }
+
+        // Set BGMDevice back as the default device.
+        DebugMsg("BGMDeviceControlsList::ToggleDefaultDevice: Setting BGMDevice as default");
+        BGMLogAndSwallowExceptions("BGMDeviceControlsList::CreateDeviceToggleBackBlock", ([&] {
+            mAudioSystem.SetDefaultAudioDevice(false, false, mBGMDevice.GetObjectID());
+        }));
+
+        mDeviceToggleState = ToggleState::DisablingNullDevice;
+
+        // Cancel the previous block in case it hasn't run yet.
+        DestroyBlock(mDisableNullDeviceBlock);
+
+        mDisableNullDeviceBlock = CreateDisableNullDeviceBlock();
+
+        dispatch_after(dispatch_time(DISPATCH_TIME_NOW, kDisableNullDeviceDelay),
+                       dispatch_get_global_queue(QOS_CLASS_DEFAULT, 0),
+                       mDisableNullDeviceBlock);
+    });
+}
+
+dispatch_block_t    BGMDeviceControlsList::CreateDisableNullDeviceBlock()
+{
+    return dispatch_block_create((dispatch_block_flags_t)0, ^{
+        CAMutex::Locker locker(mMutex);
+
+        if(mDeviceToggleState != ToggleState::DisablingNullDevice)
+        {
+            return;
+        }
+
+        mDeviceToggleState = ToggleState::NotToggling;
+
+        BGMLogAndSwallowExceptions("BGMDeviceControlsList::CreateDisableNullDeviceBlock",
+                                   ([&] {
+            CAMutex::Unlocker unlocker(mMutex);
+            // Hide the null device from the user again.
+            SetNullDeviceEnabled(false);
+        }));
+
+        BGMAssert(mBGMDevice.GetObjectID() == mAudioSystem.GetAudioDeviceForUID(CFSTR(kBGMDeviceUID)),
+                  "BGMDevice's AudioObjectID changed");
+    });
+}
+
+void    BGMDeviceControlsList::DestroyBlock(dispatch_block_t __nullable & block)
+{
+    if(!block)
+    {
+        return;
+    }
+
+    dispatch_block_t& blockNN = (dispatch_block_t&)block;
+    if(!dispatch_block_testcancel(blockNN))
+    {
+        // Stop the block from running if it's currently queued.
+        dispatch_block_cancel(blockNN);
+
+        // Make sure the block isn't currently running. That should almost never be the case.
+        while(!dispatch_block_testcancel(blockNN))
+        {
+            CAMutex::Unlocker unlocker(mMutex);
+            usleep(10);
+        }
+        
+        Block_release(block);
+        block = nullptr;
+    }
+}
+
+#pragma clang diagnostic pop /* -Wpartial-availability */
+
+#pragma clang assume_nonnull end
+

BGMApp/BGMApp/BGMDeviceControlsList.h

@@ -0,0 +1,137 @@
+// This file is part of Background Music.
+//
+// Background Music is free software: you can redistribute it and/or
+// modify it under the terms of the GNU General Public License as
+// published by the Free Software Foundation, either version 2 of the
+// License, or (at your option) any later version.
+//
+// Background Music is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Background Music. If not, see <http://www.gnu.org/licenses/>.
+
+//
+//  BGMDeviceControlsList.h
+//  BGMApp
+//
+//  Copyright © 2017 Kyle Neideck
+//
+
+#ifndef BGMApp__BGMDeviceControlsList
+#define BGMApp__BGMDeviceControlsList
+
+// Local Includes
+#include "BGMAudioDevice.h"
+
+// PublicUtility Includes
+#include "CAHALAudioDevice.h"
+#include "CAHALAudioSystemObject.h"
+#include "CAMutex.h"
+
+// System Includes
+#include <dispatch/dispatch.h>
+#include <AudioToolbox/AudioServices.h>
+
+
+#pragma clang assume_nonnull begin
+
+class BGMDeviceControlsList
+{
+
+#pragma mark Construction/Destruction
+
+public:
+
+                        BGMDeviceControlsList(AudioObjectID inBGMDevice,
+                                              CAHALAudioSystemObject inAudioSystem
+                                                      = CAHALAudioSystemObject());
+                        ~BGMDeviceControlsList();
+                        // Disallow copying
+                        BGMDeviceControlsList(const BGMDeviceControlsList&) = delete;
+                        BGMDeviceControlsList& operator=(const BGMDeviceControlsList&) = delete;
+
+#pragma mark Accessors
+
+    /*! @param inBGMDeviceID The ID of BGMDevice. */
+    void                SetBGMDevice(AudioObjectID inBGMDeviceID);
+
+#pragma mark Update Controls List
+
+    /*!
+     Enable the BGMDevice controls (volume and mute currently) that can be matched to controls of
+     the given device, and disable the ones that can't.
+
+     @param inDeviceID The ID of the device.
+     @return True if BGMDevice's list of controls was updated.
+     @throws CAException if an error is received from either device.
+     */
+    bool                MatchControlsListOf(AudioObjectID inDeviceID);
+    /*!
+     After updating BGMDevice's controls list, we need to change the default device so programs
+     (including OS X's audio UI) will update themselves. We could just change to the real output
+     device and change back, but that could have side effects the user wouldn't expect. For example,
+     an app the user has muted might be unmuted for a short period.
+
+     Instead we tell BGMDriver to enable the Null Device -- a device that does nothing -- so we can
+     use it to toggle the default device. The Null Device is normally disabled so it can be hidden
+     from the user. OS X won't let us make a hidden device temporarily visible or set a hidden
+     device as the default, so we have to completely remove the Null Device from the system while
+     we're not using it.
+     
+     @throws CAException if it fails to enable the Null Device.
+     */
+    void                PropagateControlListChange();
+
+#pragma mark Implementation
+
+private:
+    /*! Lazily initialises the fields used to toggle the default device. */
+    void                InitDeviceToggling();
+    /*! Changes the OS X default audio device to the Null Device and then back to BGMDevice. */
+    void                ToggleDefaultDevice();
+    /*!
+     Enable or disable the Null Device. See PropagateControlListChange and BGM_NullDevice in 
+     BGMDriver.
+
+     @throws CAException if we can't get the BGMDriver plug-in audio object from the HAL or the HAL
+                         returns an error when setting kAudioPlugInCustomPropertyNullDeviceActive.
+     */
+    void                SetNullDeviceEnabled(bool inEnabled);
+
+    dispatch_block_t    CreateDeviceToggleBlock();
+    dispatch_block_t    CreateDeviceToggleBackBlock();
+    dispatch_block_t    CreateDisableNullDeviceBlock();
+
+    void                DestroyBlock(dispatch_block_t __nullable & block);
+
+private:
+    CAMutex             mMutex { "Device Controls List" };
+    bool                mDeviceTogglingInitialised = false;
+    // OS X 10.9 doesn't have the functions we use for PropagateControlListChange.
+    bool                mCanToggleDeviceOnSystem;
+
+    BGMAudioDevice      mBGMDevice;
+    CAHALAudioSystemObject mAudioSystem;  // Not guarded by the mutex.
+
+    enum ToggleState
+    {
+        NotToggling, SettingNullDeviceAsDefault, SettingBGMDeviceAsDefault, DisablingNullDevice
+    };
+    BGMDeviceControlsList::ToggleState mDeviceToggleState = ToggleState::NotToggling;
+
+    dispatch_block_t    mDeviceToggleBlock;
+    dispatch_block_t    mDeviceToggleBackBlock;
+    dispatch_block_t    mDisableNullDeviceBlock;
+
+    dispatch_queue_t    mListenerQueue;
+    AudioObjectPropertyListenerBlock mListenerBlock;
+
+};
+
+#pragma clang assume_nonnull end
+
+#endif /* BGMApp__BGMDeviceControlsList */
+

BGMApp/BGMApp/BGMPlayThrough.h

@@ -17,7 +17,7 @@
 //  BGMPlayThrough.h
 //  BGMApp
 //
-//  Copyright © 2016 Kyle Neideck
+//  Copyright © 2016, 2017 Kyle Neideck
 //
 //  Reads audio from an input device and immediately writes it to an output device. We currently use this class with the input
 //  device always set to BGMDevice and the output device set to the one selected in the preferences menu.
@@ -28,7 +28,7 @@
 //  sample code from 2004. This class's main addition is pausing playthrough when idle to save CPU.
 //
 //  Playing audio with this class uses more CPU, mostly in the coreaudiod process, than playing audio normally because we need
-//  an input IO proc as well as an output one, and BGMDriver is running in addition to the output device's driver. For me, it
+//  an input IOProc as well as an output one, and BGMDriver is running in addition to the output device's driver. For me, it
 //  usually adds around 1-2% (as a percentage of total usage -- it doesn't seem to be relative to the CPU used when playing
 //  audio normally).
 //
@@ -36,14 +36,18 @@
 //  a future release.
 //
 
-#ifndef __BGMApp__BGMPlayThrough__
-#define __BGMApp__BGMPlayThrough__
+#ifndef BGMApp__BGMPlayThrough
+#define BGMApp__BGMPlayThrough
 
 // PublicUtility Includes
 #include "CARingBuffer.h"
 #include "CAHALAudioDevice.h"
 #include "CAMutex.h"
 
+// STL Includes
+#include <atomic>
+#include <algorithm>
+
 // System Includes
 #include <mach/semaphore.h>
 
@@ -52,6 +56,10 @@
 
 class BGMPlayThrough
 {
+    
+public:
+    // Error codes
+    static const OSStatus kDeviceNotStarting = 100;
 
 public:
                         BGMPlayThrough(CAHALAudioDevice inInputDevice, CAHALAudioDevice inOutputDevice);
@@ -59,41 +67,70 @@ public:
                         // Disallow copying
                         BGMPlayThrough(const BGMPlayThrough&) = delete;
                         BGMPlayThrough& operator=(const BGMPlayThrough&) = delete;
-                        // Move constructor/assignment
-                        BGMPlayThrough(BGMPlayThrough&& inPlayThrough) { Swap(inPlayThrough); }
-                        BGMPlayThrough& operator=(BGMPlayThrough&& inPlayThrough) { Swap(inPlayThrough); return *this; }
 
 #ifdef __OBJC__
-                        // Only intended as a convenience for Objective-C instance vars
+                        // Only intended as a convenience (hack) for Objective-C instance vars. Call
+                        // SetDevices to initialise the instance before using it.
                         BGMPlayThrough() { }
 #endif
     
 private:
-    void                Swap(BGMPlayThrough& inPlayThrough);
-    
+    /*! @throws CAException */
+    void                Init(CAHALAudioDevice inInputDevice, CAHALAudioDevice inOutputDevice);
+
+public:
+    /*! @throws CAException */
     void                Activate();
+    /*! @throws CAException */
     void                Deactivate();
-    
+
+private:
     void                AllocateBuffer();
     
     static bool         IsBGMDevice(CAHALAudioDevice inDevice);
 
-    void                CreateIOProcs();
-    void                DestroyIOProcs();
+    /*! @throws CAException */
+    void                CreateIOProcIDs();
+    /*! @throws CAException */
+    void                DestroyIOProcIDs();
+    /*!
+        @return True if both IOProcs are stopped.
+        @nonthreadsafe
+     */
+    bool                CheckIOProcsAreStopped() const noexcept; // TODO: REQUIRES(mStateMutex);
 	
 public:
-    OSStatus            Start();
-    OSStatus            WaitForOutputDeviceToStart();
+    /*!
+     Pass null for either param to only change one of the devices.
+     @throws CAException
+     */
+    void                SetDevices(CAHALAudioDevice* __nullable inInputDevice,
+                                   CAHALAudioDevice* __nullable inOutputDevice);
+    
+    /*! @throws CAException */
+    void                Start();
+    
+    // Blocks until the output device has started our IOProc. Returns one of the error constants
+    // from AudioHardwareBase.h (e.g. kAudioHardwareNoError).
+    OSStatus            WaitForOutputDeviceToStart() noexcept;
     
 private:
+    void                ReleaseThreadsWaitingForOutputToStart() const;
+    
+public:
     OSStatus            Stop();
     void                StopIfIdle();
     
+private:
+    
     static OSStatus     BGMDeviceListenerProc(AudioObjectID inObjectID,
                                               UInt32 inNumberAddresses,
                                               const AudioObjectPropertyAddress* inAddresses,
                                               void* __nullable inClientData);
-    static bool         RunningSomewhereOtherThanBGMApp(const CAHALAudioDevice inBGMDevice);
+    static void         HandleBGMDeviceIsRunning(BGMPlayThrough* refCon);
+    static void         HandleBGMDeviceIsRunningSomewhereOtherThanBGMApp(BGMPlayThrough* refCon);
+    
+    static bool         IsRunningSomewhereOtherThanBGMApp(const CAHALAudioDevice& inBGMDevice);
 
     static OSStatus     InputDeviceIOProc(AudioObjectID           inDevice,
                                           const AudioTimeStamp*   inNow,
@@ -109,6 +146,22 @@ private:
                                            AudioBufferList*        outOutputData,
                                            const AudioTimeStamp*   inOutputTime,
                                            void* __nullable        inClientData);
+    
+    // The state of an IOProc. Used by the IOProc to tell other threads when it's finished starting. Used by other
+    // threads to tell the IOProc to stop itself. (Probably used for other things as well.)
+    enum class          IOState
+                        {
+                            Stopped, Starting, Running, Stopping
+                        };
+    
+    // The IOProcs call this to update their IOState member. Also stops the IOProc if its state has been set to Stopping.
+    // Returns true if it changes the state.
+    static bool         UpdateIOProcState(const char* __nullable callerName,
+                                          std::atomic<IOState>& inState,
+                                          AudioDeviceIOProcID __nullable inIOProcID,
+                                          CAHALAudioDevice& inDevice,
+                                          IOState& outNewState);
+    
     static void         HandleRingBufferError(CARingBufferError err,
                                               const char* methodName,
                                               const char* callReturningErr);
@@ -116,31 +169,31 @@ private:
 private:
     CARingBuffer        mBuffer;
     
-    AudioDeviceIOProcID mInputDeviceIOProcID;
-    AudioDeviceIOProcID mOutputDeviceIOProcID;
+    AudioDeviceIOProcID __nullable mInputDeviceIOProcID;
+    AudioDeviceIOProcID __nullable mOutputDeviceIOProcID;
     
-    CAHALAudioDevice    mInputDevice { kAudioDeviceUnknown };
-    CAHALAudioDevice    mOutputDevice { kAudioDeviceUnknown };
+    CAHALAudioDevice    mInputDevice { kAudioObjectUnknown };
+    CAHALAudioDevice    mOutputDevice { kAudioObjectUnknown };
     
     CAMutex             mStateMutex { "Playthrough state" };
     
-    // Signalled when the output IO proc runs. We use it to tell BGMDriver when the output device is ready to receive audio data.
+    // Signalled when the output IOProc runs. We use it to tell BGMDriver when the output device is ready to receive audio data.
     semaphore_t         mOutputDeviceIOProcSemaphore { SEMAPHORE_NULL };
     
     bool                mActive = false;
     bool                mPlayingThrough = false;
-    
+
     UInt64              mLastNotifiedIOStoppedOnBGMDevice;
-    
-    bool                mInputDeviceIOProcShouldStop = false;
-    bool                mOutputDeviceIOProcShouldStop = false;
+
+    std::atomic<IOState>    mInputDeviceIOProcState { IOState::Stopped };
+    std::atomic<IOState>    mOutputDeviceIOProcState { IOState::Stopped };
     
     // For debug logging.
     UInt64              mToldOutputDeviceToStartAt;
 
-    // IO proc vars. (Should only be used inside IO procs.)
+    // IOProc vars. (Should only be used inside IOProcs.)
     
-    // The earliest/latest sample times seen by the IO procs since starting playthrough. -1 for unset.
+    // The earliest/latest sample times seen by the IOProcs since starting playthrough. -1 for unset.
     Float64             mFirstInputSampleTime = -1;
     Float64             mLastInputSampleTime = -1;
     Float64             mLastOutputSampleTime = -1;
@@ -152,5 +205,5 @@ private:
 
 #pragma clang assume_nonnull end
 
-#endif /* __BGMApp__BGMPlayThrough__ */
+#endif /* BGMApp__BGMPlayThrough */
 

BGMApp/BGMApp/BGMUserDefaults.h

@@ -0,0 +1,46 @@
+// This file is part of Background Music.
+//
+// Background Music is free software: you can redistribute it and/or
+// modify it under the terms of the GNU General Public License as
+// published by the Free Software Foundation, either version 2 of the
+// License, or (at your option) any later version.
+//
+// Background Music is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Background Music. If not, see <http://www.gnu.org/licenses/>.
+
+//
+//  BGMUserDefaults.h
+//  BGMApp
+//
+//  Copyright © 2016, 2017 Kyle Neideck
+//
+//  A simple wrapper around our use of NSUserDefaults. Used to store the preferences/state that only
+//  apply to BGMApp. The others are stored on BGMDriver.
+//
+
+// System includes
+#import <Cocoa/Cocoa.h>
+
+
+#pragma clang assume_nonnull begin
+
+@interface BGMUserDefaults : NSObject
+
+// If inDefaults is nil, settings are not loaded from or saved to disk, which is useful for testing.
+- (instancetype) initWithDefaults:(NSUserDefaults* __nullable)inDefaults;
+
+// The musicPlayerID (see BGMMusicPlayer.h), as a string, of the music player selected by the user.
+// Must be either null or a string that can be parsed by NSUUID.
+@property NSString* __nullable selectedMusicPlayerID;
+
+@property BOOL autoPauseMusicEnabled;
+
+@end
+
+#pragma clang assume_nonnull end
+

BGMApp/BGMApp/BGMUserDefaults.m

@@ -0,0 +1,106 @@
+// This file is part of Background Music.
+//
+// Background Music is free software: you can redistribute it and/or
+// modify it under the terms of the GNU General Public License as
+// published by the Free Software Foundation, either version 2 of the
+// License, or (at your option) any later version.
+//
+// Background Music is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Background Music. If not, see <http://www.gnu.org/licenses/>.
+
+//
+//  BGMUserDefaults.m
+//  BGMApp
+//
+//  Copyright © 2016, 2017 Kyle Neideck
+//
+
+// Self include
+#import "BGMUserDefaults.h"
+
+
+#pragma clang assume_nonnull begin
+
+// Keys
+static NSString* const BGMDefaults_AutoPauseMusicEnabled = @"AutoPauseMusicEnabled";
+static NSString* const BGMDefaults_SelectedMusicPlayerID = @"SelectedMusicPlayerID";
+
+@implementation BGMUserDefaults {
+    // The defaults object wrapped by this object.
+    NSUserDefaults* defaults;
+    // When we're not persisting defaults, settings are stored in this dictionary instead. This
+    // var should only be accessed if 'defaults' is nil.
+    NSMutableDictionary<NSString*,id>* transientDefaults;
+}
+
+- (instancetype) initWithDefaults:(NSUserDefaults* __nullable)inDefaults {
+    if ((self = [super init])) {
+        defaults = inDefaults;
+
+        // Register the settings defaults.
+        //
+        // iTunes is the default music player, but we don't set BGMDefaults_SelectedMusicPlayerID
+        // here so we know when it's never been set. (If it hasn't, we try using BGMDevice's
+        // kAudioDeviceCustomPropertyMusicPlayerBundleID property to tell which music player should
+        // be selected. See BGMMusicPlayers.)
+        NSDictionary* defaultsDict = @{ BGMDefaults_AutoPauseMusicEnabled: @YES };
+
+        if (defaults) {
+            [defaults registerDefaults:defaultsDict];
+        } else {
+            transientDefaults = [defaultsDict mutableCopy];
+        }
+    }
+
+    return self;
+}
+
+- (NSString* __nullable) selectedMusicPlayerID {
+    return [self get:BGMDefaults_SelectedMusicPlayerID];
+}
+
+- (void) setSelectedMusicPlayerID:(NSString* __nullable)selectedMusicPlayerID {
+    [self set:BGMDefaults_SelectedMusicPlayerID to:selectedMusicPlayerID];
+}
+
+- (BOOL) autoPauseMusicEnabled {
+    return [self getBool:BGMDefaults_AutoPauseMusicEnabled];
+}
+
+- (void) setAutoPauseMusicEnabled:(BOOL)autoPauseMusicEnabled {
+    [self setBool:BGMDefaults_AutoPauseMusicEnabled to:autoPauseMusicEnabled];
+}
+
+- (id __nullable) get:(NSString*)key {
+    return defaults ? [defaults objectForKey:key] : transientDefaults[key];
+}
+
+- (void) set:(NSString*)key to:(NSObject<NSCopying,NSSecureCoding>* __nullable)value {
+    if (defaults) {
+        [defaults setObject:value forKey:key];
+    } else {
+        transientDefaults[key] = value;
+    }
+}
+
+- (BOOL) getBool:(NSString*)key {
+    return defaults ? [defaults boolForKey:key] : [transientDefaults[key] boolValue];
+}
+
+- (void) setBool:(NSString*)key to:(BOOL)value {
+    if (defaults) {
+        [defaults setBool:value forKey:key];
+    } else {
+        transientDefaults[key] = [NSNumber numberWithBool:value];
+    }
+}
+
+@end
+
+#pragma clang assume_nonnull end
+

BGMApp/BGMApp/BGMXPCListener.mm

@@ -22,6 +22,7 @@
 
 // Self Include
 #import "BGMXPCListener.h"
+#import "BGMPlayThrough.h"  // For kDeviceNotStarting.
 
 
 #pragma clang assume_nonnull begin
@@ -175,11 +176,26 @@
 }
 
 - (void) waitForOutputDeviceToStartWithReply:(void (^)(NSError*))reply {
-    OSStatus err = [audioDevices waitForOutputDeviceToStart];
     NSString* description;
+    OSStatus err;
+    
+    try {
+        err = [audioDevices waitForOutputDeviceToStart];
+    } catch (CAException e) {
+        // waitForOutputDeviceToStart should never throw a CAException, but check anyway in case we change that at some point.
+        LogError("BGMXPCListener::waitForOutputDeviceToStartWithReply: Caught CAException (%d). Replying kBGMXPC_HardwareError.",
+                 e.GetError());
+        err = kBGMXPC_HardwareError;
+    } catch (...) {
+        LogError("BGMXPCListener::waitForOutputDeviceToStartWithReply: Caught unknown exception. Replying kBGMXPC_InternalError.");
+        err = kBGMXPC_InternalError;
+#if DEBUG
+        throw;
+#endif
+    }
     
     switch (err) {
-        case noErr:
+        case kAudioHardwareNoError:
             description = @"BGMApp started the output device.";
             err = kBGMXPC_Success;
             break;
@@ -194,6 +210,12 @@
             err = kBGMXPC_HardwareError;
             break;
             
+        case BGMPlayThrough::kDeviceNotStarting:
+            // We have to send a more specific error in this case because BGMDevice handles this case differently.
+            description = @"The output device is not starting.";
+            err = kBGMXPC_HardwareNotStartingError;
+            break;
+            
         default:
             description = @"Unknown error while waiting for the output device.";
             err = kBGMXPC_InternalError;

BGMApp/BGMApp/Base.lproj/MainMenu.xib

@@ -1,8 +1,9 @@
-<?xml version="1.0" encoding="UTF-8" standalone="no"?>
-<document type="com.apple.InterfaceBuilder3.Cocoa.XIB" version="3.0" toolsVersion="9531" systemVersion="14F1509" targetRuntime="MacOSX.Cocoa" propertyAccessControl="none" useAutolayout="YES" customObjectInstantitationMethod="direct">
+<?xml version="1.0" encoding="UTF-8"?>
+<document type="com.apple.InterfaceBuilder3.Cocoa.XIB" version="3.0" toolsVersion="12120" systemVersion="16E195" targetRuntime="MacOSX.Cocoa" propertyAccessControl="none" useAutolayout="YES" customObjectInstantitationMethod="direct">
     <dependencies>
         <deployment identifier="macosx"/>
-        <plugIn identifier="com.apple.InterfaceBuilder.CocoaPlugin" version="9531"/>
+        <development version="7000" identifier="xcode"/>
+        <plugIn identifier="com.apple.InterfaceBuilder.CocoaPlugin" version="12120"/>
     </dependencies>
     <objects>
         <customObject id="-2" userLabel="File's Owner" customClass="NSApplication">
@@ -12,12 +13,12 @@
         </customObject>
         <customObject id="-1" userLabel="First Responder" customClass="FirstResponder"/>
         <customObject id="-3" userLabel="Application" customClass="NSObject"/>
-        <customObject id="Voe-Tx-rLC" customClass="AppDelegate">
+        <customObject id="Voe-Tx-rLC" customClass="BGMAppDelegate">
             <connections>
                 <outlet property="aboutPanel" destination="Cf4-3V-gl1" id="cgo-Hw-rE2"/>
                 <outlet property="aboutPanelLicenseView" destination="LSG-PF-cl8" id="mbu-kv-Jfc"/>
                 <outlet property="appVolumeView" destination="MWB-XH-kFI" id="eFA-RN-VMC"/>
-                <outlet property="autoPauseMenuItem" destination="nHv-T8-1nb" id="skN-ap-dre"/>
+                <outlet property="autoPauseMenuItemUnwrapped" destination="nHv-T8-1nb" id="Lie-Cx-jw6"/>
                 <outlet property="bgmMenu" destination="8AN-nh-rEe" id="UWn-BX-eLy"/>
             </connections>
         </customObject>
@@ -26,9 +27,7 @@
             <items>
                 <menuItem title="Auto-pause Music" tag="2" id="nHv-T8-1nb">
                     <modifierMask key="keyEquivalentModifierMask"/>
-                    <connections>
-                        <action selector="toggleAutoPauseMusic:" target="Voe-Tx-rLC" id="fL3-wA-voV"/>
-                    </connections>
+                    <accessibility description="Enable to automatically pause your selected music player when a different app starts playing audio." identifier="Auto-pause enabled"/>
                 </menuItem>
                 <menuItem isSeparatorItem="YES" id="ZGd-Pq-YeA"/>
                 <menuItem title="App Volumes" tag="3" enabled="NO" id="8PP-wA-Pae">
@@ -60,14 +59,16 @@
                     </connections>
                 </menuItem>
             </items>
+            <accessibility description="Background Music Main Menu" identifier="MainMenu"/>
             <point key="canvasLocation" x="-184" y="-69.5"/>
         </menu>
-        <customView id="MWB-XH-kFI">
-            <rect key="frame" x="0.0" y="0.0" width="264" height="20"/>
+        <customView wantsLayer="YES" id="MWB-XH-kFI">
+            <rect key="frame" x="0.0" y="0.0" width="269" height="47"/>
             <autoresizingMask key="autoresizingMask" flexibleMaxX="YES" flexibleMinY="YES"/>
             <subviews>
-                <textField identifier="AppName" horizontalHuggingPriority="251" verticalHuggingPriority="750" fixedFrame="YES" translatesAutoresizingMaskIntoConstraints="NO" id="Xmd-bg-huG" customClass="BGMAVM_AppNameLabel">
-                    <rect key="frame" x="58" y="4" width="115" height="14"/>
+                <textField identifier="AppName" horizontalHuggingPriority="251" verticalHuggingPriority="750" fixedFrame="YES" allowsCharacterPickerTouchBarItem="YES" translatesAutoresizingMaskIntoConstraints="NO" id="Xmd-bg-huG" customClass="BGMAVM_AppNameLabel">
+                    <rect key="frame" x="42" y="28" width="115" height="14"/>
+                    <autoresizingMask key="autoresizingMask" flexibleMaxX="YES" flexibleMinY="YES"/>
                     <textFieldCell key="cell" controlSize="small" lineBreakMode="truncatingTail" allowsUndo="NO" sendsActionOnEndEditing="YES" alignment="left" title="App name here" usesSingleLineMode="YES" id="ZHF-ZW-Oqg">
                         <font key="font" metaFont="smallSystem"/>
                         <color key="textColor" name="labelColor" catalog="System" colorSpace="catalog"/>
@@ -75,92 +76,152 @@
                     </textFieldCell>
                 </textField>
                 <imageView identifier="AppIcon" horizontalHuggingPriority="251" verticalHuggingPriority="251" fixedFrame="YES" translatesAutoresizingMaskIntoConstraints="NO" id="W04-iT-IUw" customClass="BGMAVM_AppIcon">
-                    <rect key="frame" x="36" y="3" width="16" height="16"/>
+                    <rect key="frame" x="20" y="27" width="16" height="16"/>
+                    <autoresizingMask key="autoresizingMask" flexibleMaxX="YES" flexibleMinY="YES"/>
                     <imageCell key="cell" refusesFirstResponder="YES" alignment="left" imageScaling="proportionallyDown" id="6QQ-oO-HxF"/>
                 </imageView>
                 <slider verticalHuggingPriority="750" fixedFrame="YES" translatesAutoresizingMaskIntoConstraints="NO" id="I1l-Ci-4md" customClass="BGMAVM_VolumeSlider">
-                    <rect key="frame" x="179" y="2" width="74" height="17"/>
+                    <rect key="frame" x="163" y="27" width="74" height="15"/>
+                    <autoresizingMask key="autoresizingMask" flexibleMaxX="YES" flexibleMinY="YES"/>
                     <sliderCell key="cell" controlSize="small" continuous="YES" state="on" alignment="left" maxValue="100" doubleValue="50" tickMarkPosition="above" sliderType="linear" id="Jmg-df-9Xl"/>
+                    <accessibility description="Volume"/>
                 </slider>
+                <slider toolTip="Pan" verticalHuggingPriority="750" fixedFrame="YES" translatesAutoresizingMaskIntoConstraints="NO" id="2mh-uO-kOV" customClass="BGMAVM_PanSlider">
+                    <rect key="frame" x="163" y="7" width="74" height="15"/>
+                    <autoresizingMask key="autoresizingMask" flexibleMaxX="YES" flexibleMinY="YES"/>
+                    <sliderCell key="cell" controlSize="mini" continuous="YES" state="on" alignment="left" minValue="-100" maxValue="100" tickMarkPosition="below" numberOfTickMarks="1" sliderType="linear" id="ccM-Mt-93g"/>
+                    <accessibility description="Pan"/>
+                </slider>
+                <button verticalHuggingPriority="750" fixedFrame="YES" tag="1" springLoaded="YES" translatesAutoresizingMaskIntoConstraints="NO" id="vTG-n6-GxY" customClass="BGMAVM_ShowMoreControlsButton">
+                    <rect key="frame" x="243" y="27" width="15" height="17"/>
+                    <autoresizingMask key="autoresizingMask" flexibleMaxX="YES" flexibleMinY="YES"/>
+                    <contentFilters>
+                        <ciFilter name="CIAffineTransform">
+                            <configuration>
+                                <null key="inputImage"/>
+                                <affineTransform key="inputTransform" m11="1" m12="0.0" m21="0.0" m22="1" tX="0.0" tY="2"/>
+                            </configuration>
+                        </ciFilter>
+                    </contentFilters>
+                    <buttonCell key="cell" type="square" title="⌃" bezelStyle="shadowlessSquare" image="buttonCell:IXo-C7-3uE:image" alignment="center" lineBreakMode="truncatingTail" imageScaling="proportionallyDown" inset="2" id="IXo-C7-3uE">
+                        <behavior key="behavior" pushIn="YES" lightByBackground="YES" lightByGray="YES"/>
+                        <font key="font" metaFont="system"/>
+                    </buttonCell>
+                </button>
+                <textField toolTip="Pan" horizontalHuggingPriority="251" verticalHuggingPriority="750" fixedFrame="YES" allowsCharacterPickerTouchBarItem="NO" translatesAutoresizingMaskIntoConstraints="NO" id="9jc-9i-jw2">
+                    <rect key="frame" x="162" y="-1" width="12" height="17"/>
+                    <autoresizingMask key="autoresizingMask" flexibleMaxX="YES" flexibleMinY="YES"/>
+                    <textFieldCell key="cell" scrollable="YES" lineBreakMode="clipping" sendsActionOnEndEditing="YES" title="L" id="hgE-7A-bez">
+                        <font key="font" metaFont="miniSystem"/>
+                        <color key="textColor" name="labelColor" catalog="System" colorSpace="catalog"/>
+                        <color key="backgroundColor" name="controlColor" catalog="System" colorSpace="catalog"/>
+                    </textFieldCell>
+                    <accessibility description="Pan left"/>
+                </textField>
+                <textField toolTip="Pan" horizontalHuggingPriority="251" verticalHuggingPriority="750" fixedFrame="YES" allowsCharacterPickerTouchBarItem="NO" translatesAutoresizingMaskIntoConstraints="NO" id="1lZ-hX-6Kl">
+                    <rect key="frame" x="228" y="-1" width="12" height="17"/>
+                    <autoresizingMask key="autoresizingMask" flexibleMaxX="YES" flexibleMinY="YES"/>
+                    <textFieldCell key="cell" scrollable="YES" lineBreakMode="clipping" sendsActionOnEndEditing="YES" title="R" id="lzr-NO-0Na">
+                        <font key="font" metaFont="miniSystem"/>
+                        <color key="textColor" name="labelColor" catalog="System" colorSpace="catalog"/>
+                        <color key="backgroundColor" name="controlColor" catalog="System" colorSpace="catalog"/>
+                    </textFieldCell>
+                    <accessibility description="Pan right"/>
+                </textField>
             </subviews>
-            <point key="canvasLocation" x="81" y="-111"/>
+            <point key="canvasLocation" x="117.5" y="-117.5"/>
         </customView>
-        <window allowsToolTipsWhenApplicationIsInactive="NO" autorecalculatesKeyViewLoop="NO" restorable="NO" hidesOnDeactivate="YES" oneShot="NO" releasedWhenClosed="NO" showsToolbarButton="NO" visibleAtLaunch="NO" animationBehavior="default" id="Cf4-3V-gl1" customClass="NSPanel">
+        <window allowsToolTipsWhenApplicationIsInactive="NO" autorecalculatesKeyViewLoop="NO" restorable="NO" hidesOnDeactivate="YES" oneShot="NO" showsToolbarButton="NO" visibleAtLaunch="NO" animationBehavior="default" id="Cf4-3V-gl1" customClass="NSPanel">
             <windowStyleMask key="styleMask" titled="YES" closable="YES" utility="YES"/>
             <windowPositionMask key="initialPositionMask" topStrut="YES"/>
-            <rect key="contentRect" x="248" y="350" width="748" height="293"/>
-            <rect key="screenRect" x="0.0" y="0.0" width="1280" height="777"/>
+            <rect key="contentRect" x="248" y="350" width="1002" height="335"/>
+            <rect key="screenRect" x="0.0" y="0.0" width="1440" height="877"/>
             <view key="contentView" id="HlB-hX-Y0Y">
-                <rect key="frame" x="0.0" y="0.0" width="748" height="293"/>
+                <rect key="frame" x="0.0" y="0.0" width="1002" height="335"/>
                 <autoresizingMask key="autoresizingMask"/>
                 <subviews>
-                    <textField horizontalHuggingPriority="251" verticalHuggingPriority="750" fixedFrame="YES" translatesAutoresizingMaskIntoConstraints="NO" id="r51-dd-LGP">
-                        <rect key="frame" x="18" y="78" width="240" height="22"/>
+                    <textField horizontalHuggingPriority="251" verticalHuggingPriority="750" fixedFrame="YES" allowsCharacterPickerTouchBarItem="YES" translatesAutoresizingMaskIntoConstraints="NO" id="r51-dd-LGP">
+                        <rect key="frame" x="71" y="125" width="240" height="22"/>
+                        <autoresizingMask key="autoresizingMask" flexibleMaxX="YES" flexibleMinY="YES"/>
                         <textFieldCell key="cell" scrollable="YES" lineBreakMode="clipping" sendsActionOnEndEditing="YES" alignment="center" title="Background Music" id="Dw2-nu-eBQ">
                             <font key="font" size="18" name=".HelveticaNeueDeskInterface-Regular"/>
                             <color key="textColor" name="labelColor" catalog="System" colorSpace="catalog"/>
                             <color key="backgroundColor" name="controlColor" catalog="System" colorSpace="catalog"/>
                         </textFieldCell>
                     </textField>
-                    <textField horizontalHuggingPriority="251" verticalHuggingPriority="750" fixedFrame="YES" tag="1" translatesAutoresizingMaskIntoConstraints="NO" id="ekc-h0-I43">
-                        <rect key="frame" x="18" y="53" width="240" height="17"/>
+                    <textField horizontalHuggingPriority="251" verticalHuggingPriority="750" fixedFrame="YES" tag="1" allowsCharacterPickerTouchBarItem="YES" translatesAutoresizingMaskIntoConstraints="NO" id="ekc-h0-I43">
+                        <rect key="frame" x="71" y="100" width="240" height="17"/>
+                        <autoresizingMask key="autoresizingMask" flexibleMaxX="YES" flexibleMinY="YES"/>
                         <textFieldCell key="cell" scrollable="YES" lineBreakMode="clipping" sendsActionOnEndEditing="YES" alignment="center" title="Version 0.1.0" id="FDH-7l-wFf">
                             <font key="font" metaFont="system"/>
                             <color key="textColor" name="labelColor" catalog="System" colorSpace="catalog"/>
                             <color key="backgroundColor" name="controlColor" catalog="System" colorSpace="catalog"/>
                         </textFieldCell>
                     </textField>
-                    <textField horizontalHuggingPriority="251" verticalHuggingPriority="750" fixedFrame="YES" translatesAutoresizingMaskIntoConstraints="NO" id="L5P-Lw-aCd">
-                        <rect key="frame" x="299" y="256" width="270" height="17"/>
-                        <textFieldCell key="cell" scrollable="YES" lineBreakMode="clipping" sendsActionOnEndEditing="YES" alignment="left" title="Licensed under GPLv2 or any later version." id="ETh-En-bzX">
+                    <textField horizontalHuggingPriority="251" verticalHuggingPriority="750" fixedFrame="YES" allowsCharacterPickerTouchBarItem="YES" translatesAutoresizingMaskIntoConstraints="NO" id="L5P-Lw-aCd">
+                        <rect key="frame" x="413" y="298" width="270" height="17"/>
+                        <autoresizingMask key="autoresizingMask" flexibleMaxX="YES" flexibleMinY="YES"/>
+                        <textFieldCell key="cell" scrollable="YES" lineBreakMode="clipping" sendsActionOnEndEditing="YES" alignment="left" title="Licensed under GPL v2 or any later version." id="ETh-En-bzX">
                             <font key="font" metaFont="system"/>
                             <color key="textColor" name="labelColor" catalog="System" colorSpace="catalog"/>
                             <color key="backgroundColor" name="controlColor" catalog="System" colorSpace="catalog"/>
                         </textFieldCell>
                     </textField>
-                    <box horizontalHuggingPriority="750" fixedFrame="YES" title="Box" boxType="separator" titlePosition="noTitle" translatesAutoresizingMaskIntoConstraints="NO" id="Zc9-gs-X8C">
-                        <rect key="frame" x="264" y="71" width="5" height="150"/>
-                        <color key="borderColor" white="0.0" alpha="0.41999999999999998" colorSpace="calibratedWhite"/>
-                        <color key="fillColor" white="0.0" alpha="0.0" colorSpace="calibratedWhite"/>
-                        <font key="titleFont" metaFont="system"/>
+                    <box horizontalHuggingPriority="750" fixedFrame="YES" boxType="separator" translatesAutoresizingMaskIntoConstraints="NO" id="Zc9-gs-X8C">
+                        <rect key="frame" x="383" y="93" width="5" height="150"/>
+                        <autoresizingMask key="autoresizingMask" flexibleMaxX="YES" flexibleMinY="YES"/>
                     </box>
-                    <textField horizontalHuggingPriority="251" verticalHuggingPriority="750" fixedFrame="YES" tag="2" translatesAutoresizingMaskIntoConstraints="NO" id="Vy4-dv-jQB">
-                        <rect key="frame" x="18" y="28" width="240" height="17"/>
-                        <textFieldCell key="cell" scrollable="YES" lineBreakMode="clipping" sendsActionOnEndEditing="YES" alignment="center" title="Copyright © 2016 Kyle Neideck" placeholderString="" id="ctF-95-uVu">
+                    <textField horizontalHuggingPriority="251" verticalHuggingPriority="750" fixedFrame="YES" tag="2" allowsCharacterPickerTouchBarItem="YES" translatesAutoresizingMaskIntoConstraints="NO" id="Vy4-dv-jQB">
+                        <rect key="frame" x="18" y="75" width="346" height="17"/>
+                        <autoresizingMask key="autoresizingMask" flexibleMaxX="YES" flexibleMinY="YES"/>
+                        <textFieldCell key="cell" scrollable="YES" lineBreakMode="clipping" sendsActionOnEndEditing="YES" alignment="center" title="Copyright © 2016, 2017 Background Music contributors" placeholderString="" id="ctF-95-uVu">
                             <font key="font" metaFont="system"/>
                             <color key="textColor" name="labelColor" catalog="System" colorSpace="catalog"/>
                             <color key="backgroundColor" name="controlColor" catalog="System" colorSpace="catalog"/>
                         </textFieldCell>
                     </textField>
+                    <textField horizontalHuggingPriority="251" verticalHuggingPriority="750" fixedFrame="YES" tag="3" allowsCharacterPickerTouchBarItem="YES" translatesAutoresizingMaskIntoConstraints="NO" id="nx6-kQ-N8Z" customClass="BGMLinkField">
+                        <rect key="frame" x="36" y="50" width="310" height="17"/>
+                        <autoresizingMask key="autoresizingMask" flexibleMaxX="YES" flexibleMinY="YES"/>
+                        <textFieldCell key="cell" scrollable="YES" lineBreakMode="clipping" sendsActionOnEndEditing="YES" alignment="center" tag="3" title="https://github.com/kyleneideck/BackgroundMusic" placeholderString="" id="VOb-5X-o3R">
+                            <font key="font" metaFont="system"/>
+                            <color key="textColor" red="0.20000000000000001" green="0.40000000000000002" blue="0.59999999999999998" alpha="1" colorSpace="calibratedRGB"/>
+                            <color key="backgroundColor" name="controlColor" catalog="System" colorSpace="catalog"/>
+                        </textFieldCell>
+                    </textField>
                     <imageView wantsLayer="YES" fixedFrame="YES" translatesAutoresizingMaskIntoConstraints="NO" id="Tui-Hf-FLv">
-                        <rect key="frame" x="63" y="108" width="150" height="150"/>
+                        <rect key="frame" x="116" y="155" width="150" height="150"/>
+                        <autoresizingMask key="autoresizingMask" flexibleMaxX="YES" flexibleMinY="YES"/>
                         <shadow key="shadow">
                             <color key="color" white="0.0" alpha="1" colorSpace="calibratedWhite"/>
                         </shadow>
                         <imageCell key="cell" refusesFirstResponder="YES" alignment="left" animates="YES" imageScaling="proportionallyUpOrDown" image="FermataIcon" id="dBU-ZS-ZzA"/>
                     </imageView>
                     <imageView wantsLayer="YES" fixedFrame="YES" translatesAutoresizingMaskIntoConstraints="NO" id="R1R-Rd-xPC">
-                        <rect key="frame" x="63" y="108" width="150" height="150"/>
+                        <rect key="frame" x="116" y="155" width="150" height="150"/>
+                        <autoresizingMask key="autoresizingMask" flexibleMaxX="YES" flexibleMinY="YES"/>
                         <shadow key="shadow">
                             <color key="color" white="0.0" alpha="1" colorSpace="calibratedWhite"/>
                         </shadow>
                         <imageCell key="cell" refusesFirstResponder="YES" alignment="left" animates="YES" imageScaling="proportionallyUpOrDown" image="FermataIcon" id="1VP-dU-RCe"/>
                     </imageView>
                     <scrollView fixedFrame="YES" horizontalLineScroll="10" horizontalPageScroll="10" verticalLineScroll="10" verticalPageScroll="10" hasHorizontalScroller="NO" usesPredominantAxisScrolling="NO" translatesAutoresizingMaskIntoConstraints="NO" id="eqz-ap-PAC">
-                        <rect key="frame" x="301" y="28" width="427" height="220"/>
+                        <rect key="frame" x="415" y="45" width="567" height="245"/>
+                        <autoresizingMask key="autoresizingMask" flexibleMaxX="YES" flexibleMinY="YES"/>
                         <clipView key="contentView" ambiguous="YES" id="Cdb-RA-YK0">
-                            <rect key="frame" x="1" y="1" width="425" height="218"/>
-                            <autoresizingMask key="autoresizingMask" widthSizable="YES" heightSizable="YES"/>
+                            <rect key="frame" x="1" y="1" width="565" height="243"/>
+                            <autoresizingMask key="autoresizingMask"/>
                             <subviews>
-                                <textView ambiguous="YES" editable="NO" importsGraphics="NO" findStyle="panel" continuousSpellChecking="YES" allowsUndo="YES" usesRuler="YES" usesFontPanel="YES" verticallyResizable="YES" allowsNonContiguousLayout="YES" quoteSubstitution="YES" dashSubstitution="YES" smartInsertDelete="YES" id="LSG-PF-cl8">
-                                    <rect key="frame" x="0.0" y="0.0" width="425" height="218"/>
+                                <textView ambiguous="YES" editable="NO" importsGraphics="NO" richText="NO" id="LSG-PF-cl8">
+                                    <rect key="frame" x="-4" y="0.0" width="572" height="243"/>
                                     <autoresizingMask key="autoresizingMask" widthSizable="YES" heightSizable="YES"/>
                                     <color key="backgroundColor" white="1" alpha="1" colorSpace="calibratedWhite"/>
-                                    <size key="minSize" width="425" height="218"/>
-                                    <size key="maxSize" width="477" height="10000000"/>
+                                    <size key="minSize" width="565" height="243"/>
+                                    <size key="maxSize" width="594" height="10000000"/>
                                     <color key="insertionPointColor" name="controlTextColor" catalog="System" colorSpace="catalog"/>
-                                    <size key="minSize" width="425" height="218"/>
-                                    <size key="maxSize" width="477" height="10000000"/>
+                                    <allowedInputSourceLocales>
+                                        <string>NSAllRomanInputSourcesLocaleIdentifier</string>
+                                    </allowedInputSourceLocales>
                                 </textView>
                             </subviews>
                             <color key="backgroundColor" white="1" alpha="1" colorSpace="calibratedWhite"/>
@@ -170,15 +231,24 @@
                             <autoresizingMask key="autoresizingMask"/>
                         </scroller>
                         <scroller key="verticalScroller" verticalHuggingPriority="750" horizontal="NO" id="qCC-lY-zQ6">
-                            <rect key="frame" x="410" y="1" width="16" height="218"/>
+                            <rect key="frame" x="-15" y="1" width="16" height="0.0"/>
                             <autoresizingMask key="autoresizingMask"/>
                         </scroller>
                     </scrollView>
+                    <textField verticalHuggingPriority="750" horizontalCompressionResistancePriority="250" fixedFrame="YES" allowsCharacterPickerTouchBarItem="YES" translatesAutoresizingMaskIntoConstraints="NO" id="6qu-yI-r00">
+                        <rect key="frame" x="413" y="20" width="203" height="11"/>
+                        <autoresizingMask key="autoresizingMask" flexibleMaxX="YES" flexibleMinY="YES"/>
+                        <textFieldCell key="cell" lineBreakMode="truncatingTail" sendsActionOnEndEditing="YES" title="The AirPlay Logo is a trademark of Apple Inc." id="lx7-k3-q16">
+                            <font key="font" metaFont="miniSystem"/>
+                            <color key="textColor" name="labelColor" catalog="System" colorSpace="catalog"/>
+                            <color key="backgroundColor" name="controlColor" catalog="System" colorSpace="catalog"/>
+                        </textFieldCell>
+                    </textField>
                 </subviews>
             </view>
-            <point key="canvasLocation" x="101" y="211.5"/>
+            <point key="canvasLocation" x="-200" y="232.5"/>
         </window>
-        <textField verticalHuggingPriority="750" horizontalCompressionResistancePriority="250" setsMaxLayoutWidthAtFirstLayout="YES" id="IoN-sN-cCx">
+        <textField verticalHuggingPriority="750" horizontalCompressionResistancePriority="250" setsMaxLayoutWidthAtFirstLayout="YES" allowsCharacterPickerTouchBarItem="YES" id="IoN-sN-cCx">
             <rect key="frame" x="0.0" y="0.0" width="471" height="180"/>
             <autoresizingMask key="autoresizingMask" flexibleMaxX="YES" flexibleMinY="YES"/>
             <textFieldCell key="cell" controlSize="mini" sendsActionOnEndEditing="YES" drawsBackground="YES" id="Ay8-8n-FHi">
@@ -188,10 +258,61 @@
                 <color key="textColor" red="0.11543657067200695" green="0.4338699494949495" blue="0.0" alpha="1" colorSpace="calibratedRGB"/>
                 <color key="backgroundColor" red="0.99215692281723022" green="0.9960784912109375" blue="0.9960784912109375" alpha="1" colorSpace="deviceRGB"/>
             </textFieldCell>
-            <point key="canvasLocation" x="101.5" y="496"/>
+            <point key="canvasLocation" x="-559" y="-118"/>
         </textField>
     </objects>
     <resources>
         <image name="FermataIcon" width="284" height="284"/>
+        <image name="buttonCell:IXo-C7-3uE:image" width="1" height="1">
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+CiEKKQosCjEKOQo8Ck4KUQpWAAAAAAAAAgEAAAAAAAAAQQAAAAAAAAAAAAAAAAAAClg
+</mutableData>
+        </image>
     </resources>
 </document>

BGMApp/BGMApp/Images.xcassets/AirPlayIcon.imageset/Contents.json

@@ -0,0 +1,21 @@
+{
+  "images" : [
+    {
+      "idiom" : "universal",
+      "filename" : "AirPlay.pdf",
+      "scale" : "1x"
+    },
+    {
+      "idiom" : "universal",
+      "scale" : "2x"
+    },
+    {
+      "idiom" : "universal",
+      "scale" : "3x"
+    }
+  ],
+  "info" : {
+    "version" : 1,
+    "author" : "xcode"
+  }
+}

BGMApp/BGMApp/Info.plist

@@ -29,10 +29,18 @@
 	<key>LSUIElement</key>
 	<true/>
 	<key>NSHumanReadableCopyright</key>
-	<string>Copyright © 2016 Kyle Neideck</string>
+	<string>Copyright © 2016, 2017 Background Music contributors</string>
 	<key>NSMainNibFile</key>
 	<string>MainMenu</string>
 	<key>NSPrincipalClass</key>
 	<string>NSApplication</string>
+	<key>NSAppleScriptEnabled</key>
+	<true/>
+	<key>OSAScriptingDefinition</key>
+	<string>BGMApp.sdef</string>
+	<key>NSServices</key>
+	<array>
+		<dict/>
+	</array>
 </dict>
 </plist>

BGMApp/BGMApp/Music Players/BGMDecibel.h

@@ -0,0 +1,30 @@
+// This file is part of Background Music.
+//
+// Background Music is free software: you can redistribute it and/or
+// modify it under the terms of the GNU General Public License as
+// published by the Free Software Foundation, either version 2 of the
+// License, or (at your option) any later version.
+//
+// Background Music is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Background Music. If not, see <http://www.gnu.org/licenses/>.
+
+//
+//  BGMDecibel.h
+//  BGMApp
+//
+//  Copyright © 2016 Kyle Neideck
+//
+
+// Superclass/Protocol Import
+#import "BGMMusicPlayer.h"
+
+
+@interface BGMDecibel : BGMMusicPlayerBase<BGMMusicPlayer>
+
+@end
+

BGMApp/BGMApp/Music Players/BGMDecibel.m

@@ -0,0 +1,103 @@
+// This file is part of Background Music.
+//
+// Background Music is free software: you can redistribute it and/or
+// modify it under the terms of the GNU General Public License as
+// published by the Free Software Foundation, either version 2 of the
+// License, or (at your option) any later version.
+//
+// Background Music is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Background Music. If not, see <http://www.gnu.org/licenses/>.
+
+//
+//  BGMDecibel.m
+//  BGMApp
+//
+//  Copyright © 2016 Kyle Neideck
+//  Copyright © 2016 Tanner Hoke
+//
+
+// Self Include
+#import "BGMDecibel.h"
+
+// Auto-generated Scripting Bridge header
+#import "Decibel.h"
+
+// Local Includes
+#import "BGMScriptingBridge.h"
+
+// PublicUtility Includes
+#undef CoreAudio_ThreadStampMessages
+#define CoreAudio_ThreadStampMessages 0  // Requires C++
+#include "CADebugMacros.h"
+
+
+#pragma clang assume_nonnull begin
+
+@implementation BGMDecibel {
+    BGMScriptingBridge* scriptingBridge;
+}
+
+- (id) init {
+    if ((self = [super initWithMusicPlayerID:[BGMMusicPlayerBase makeID:@"A9790CD5-4886-47C7-9FFC-DD70743CF2BF"]
+                                        name:@"Decibel"
+                                    bundleID:@"org.sbooth.Decibel"])) {
+        scriptingBridge = [[BGMScriptingBridge alloc] initWithBundleID:(NSString*)self.bundleID];
+    }
+    
+    return self;
+}
+
+- (DecibelApplication* __nullable) decibel {
+    return (DecibelApplication* __nullable)scriptingBridge.application;
+}
+
+- (BOOL) isRunning {
+    return self.decibel.running;
+}
+
+- (BOOL) isPlaying {
+    return self.running && self.decibel.playing;
+}
+
+- (BOOL) isPaused {
+    // We don't want to return true when Decibel is stopped, rather than paused. At least for me, Decibel
+    // returns -1 for playbackTime and playbackPosition when it's neither playing nor paused.
+    BOOL probablyNotStopped =
+        self.decibel.playbackTime >= 0 || self.decibel.playbackPosition >= 0;
+    
+    return self.running && !self.decibel.playing && probablyNotStopped;
+}
+
+- (BOOL) pause {
+    // isPlaying checks isRunning, so we don't need to check it here and waste an Apple event
+    BOOL wasPlaying = self.playing;
+    
+    if (wasPlaying) {
+        DebugMsg("BGMDecibel::pause: Pausing Decibel");
+        [self.decibel pause];
+    }
+    
+    return wasPlaying;
+}
+
+- (BOOL) unpause {
+    // isPaused checks isRunning, so we don't need to check it here and waste an Apple event
+    BOOL wasPaused = self.paused;
+    
+    if (wasPaused) {
+        DebugMsg("BGMDecibel::unpause: Unpausing Decibel");
+        [self.decibel play];
+    }
+    
+    return wasPaused;
+}
+
+@end
+
+#pragma clang assume_nonnull end
+

BGMApp/BGMApp/Music Players/BGMHermes.h

@@ -0,0 +1,30 @@
+// This file is part of Background Music.
+//
+// Background Music is free software: you can redistribute it and/or
+// modify it under the terms of the GNU General Public License as
+// published by the Free Software Foundation, either version 2 of the
+// License, or (at your option) any later version.
+//
+// Background Music is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Background Music. If not, see <http://www.gnu.org/licenses/>.
+
+//
+//  BGMHermes.h
+//  BGMApp
+//
+//  Copyright © 2016 Kyle Neideck
+//
+
+// Superclass/Protocol Import
+#import "BGMMusicPlayer.h"
+
+
+@interface BGMHermes : BGMMusicPlayerBase<BGMMusicPlayer>
+
+@end
+

BGMApp/BGMApp/Music Players/BGMHermes.m

@@ -0,0 +1,102 @@
+// This file is part of Background Music.
+//
+// Background Music is free software: you can redistribute it and/or
+// modify it under the terms of the GNU General Public License as
+// published by the Free Software Foundation, either version 2 of the
+// License, or (at your option) any later version.
+//
+// Background Music is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Background Music. If not, see <http://www.gnu.org/licenses/>.
+
+//
+//  BGMHermes.m
+//  BGMApp
+//
+//  Copyright © 2016 Kyle Neideck
+//
+
+// Self Include
+#import "BGMHermes.h"
+
+// Auto-generated Scripting Bridge header
+#import "Hermes.h"
+
+// Local Includes
+#import "BGMScriptingBridge.h"
+
+// PublicUtility Includes
+#undef CoreAudio_ThreadStampMessages
+#define CoreAudio_ThreadStampMessages 0  // Requires C++
+#include "CADebugMacros.h"
+
+
+#pragma clang assume_nonnull begin
+
+@implementation BGMHermes {
+    BGMScriptingBridge* scriptingBridge;
+}
+
+- (id) init {
+    // If you're copying this class, replace the ID string with a new one generated by uuidgen. (Command line tool.)
+    if ((self = [super initWithMusicPlayerID:[BGMMusicPlayerBase makeID:@"0CDC67B0-56D3-4D94-BC06-6E380D8F5E34"]
+                                        name:@"Hermes"
+                                    bundleID:@"com.alexcrichton.Hermes"])) {
+        scriptingBridge = [[BGMScriptingBridge alloc] initWithBundleID:(NSString*)self.bundleID];
+    }
+    
+    return self;
+}
+
+- (HermesApplication* __nullable) hermes {
+    return (HermesApplication* __nullable)scriptingBridge.application;
+}
+
+- (BOOL) isRunning {
+    // Note that this will return NO if is self.hermes is nil (i.e. Hermes isn't running).
+    return self.hermes.running;
+}
+
+// isPlaying and isPaused check self.running first just in case Hermes is closed but self.hermes hasn't become
+// nil yet. In that case, reading self.hermes.playerState could make Scripting Bridge open Hermes.
+
+- (BOOL) isPlaying {
+    return self.running && (self.hermes.playbackState == HermesPlayerStatesPlaying);
+}
+
+- (BOOL) isPaused {
+    return self.running && (self.hermes.playbackState == HermesPlayerStatesPaused);
+}
+
+- (BOOL) pause {
+    // isPlaying checks isRunning, so we don't need to check it here and waste an Apple event
+    BOOL wasPlaying = self.playing;
+    
+    if (wasPlaying) {
+        DebugMsg("BGMHermes::pause: Pausing Hermes");
+        [self.hermes pause];
+    }
+    
+    return wasPlaying;
+}
+
+- (BOOL) unpause {
+    // isPaused checks isRunning, so we don't need to check it here and waste an Apple event
+    BOOL wasPaused = self.paused;
+    
+    if (wasPaused) {
+        DebugMsg("BGMHermes::unpause: Unpausing Hermes");
+        [self.hermes play];
+    }
+    
+    return wasPaused;
+}
+
+@end
+
+#pragma clang assume_nonnull end
+

BGMApp/BGMApp/Music Players/BGMMusicPlayer.h

@@ -19,62 +19,83 @@
 //
 //  Copyright © 2016 Kyle Neideck
 //
-//  The base class and protocol for music player apps. Also holds the state of the currently
-//  selected music player.
+//  The base classes and protocol for objects that represent a music player app.
 //
-//  To add support for a music player, create a subclass of BGMMusicPlayerBase that implements
-//  BGMMusicPlayerProtocol. BGMSpotify will probably be the most useful example.
+//  To add support for a music player, create a class that implements the BGMMusicPlayer protocol
+//  and add it to initWithAudioDevices in BGMMusicPlayers.mm.
 //
-//  Include the BGM_MUSIC_PLAYER_DEFAULT_LOAD_METHOD macro somewhere in the @implementation block.
-//  You might also want to override the icon method if the default implementation from
-//  BGMMusicPlayerBase doesn't work.
+//  You'll probably want to subclass BGMMusicPlayerBase and, if the music player supports
+//  AppleScript, use BGMScriptingBridge. Your class might need to override the icon method if the
+//  default implementation from BGMMusicPlayerBase doesn't work.
 //
-//  The music player classes written so far use Scripting Bridge to communicate with the music
-//  player apps (see iTunes.h/Spotify.h) but any other way is fine too.
+//  BGMSpotify will probably be the most useful example to follow, but they're all pretty
+//  similar. The music player classes written so far all use Scripting Bridge to communicate with
+//  the music player apps (see iTunes.h/Spotify.h) but any other way is fine too.
+//
+//  BGMDriver will use either the music player's bundle ID or PID to match it to the audio it
+//  plays. (Though using PIDs hasn't been tested yet.)
+//
+//  If you're not sure what bundle ID the music player uses, install a debug build of BGMDriver
+//  and play something in the music player. The easiest way is to do
+//      build_and_install.sh -d
+//  BGMDriver will log the bundle ID to system.log when it becomes aware of the music player.
 //
 
 // System Includes
-#import <Foundation/Foundation.h>
-#import <ScriptingBridge/ScriptingBridge.h>
+#import <Cocoa/Cocoa.h>
 
 
 #pragma clang assume_nonnull begin
 
-#define BGM_MUSIC_PLAYER_ADD_SELF_TO_CLASSES_LIST \
-    [BGMMusicPlayerBase addToMusicPlayerClasses:[self class]];
+@protocol BGMMusicPlayer <NSObject>
 
-#define BGM_MUSIC_PLAYER_DEFAULT_LOAD_METHOD \
-    + (void) load { \
-        BGM_MUSIC_PLAYER_ADD_SELF_TO_CLASSES_LIST \
-    }
+// Classes return an instance of themselves for each music player app they make available in
+// BGMApp. So far that's always been a single instance, and classes haven't needed to override
+// the default implementation of createInstances from BGMMusicPlayerBase. But that will probably
+// change eventually.
+//
+// For example, a class for custom music players would probably return an instance for each
+// custom player the user has created. (Also note that it could return an empty array.) In that
+// case the class would probably restore some state from user defaults in its createInstances.
+//
+// TODO: I think the return type should actually be NSArray<instancetype>*, but that doesn't seem
+//       to work. There's a Clang bug about this: https://llvm.org/bugs/show_bug.cgi?id=27323
+//       (though it hasn't been confirmed yet).
++ (NSArray<id<BGMMusicPlayer>>*) createInstances;
 
-// Forward declarations (just for the typedef)
-@class BGMMusicPlayerBase;
-@protocol BGMMusicPlayerProtocol;
+// We need a unique ID for each music player to store in user defaults. In the most common case,
+// classes that provide a static (or at least bounded) number of music players, you can generate
+// IDs with uuidgen (the command line tool) and include them in your class as constants. Otherwise,
+// you'll probably want to store them in user defaults and retrieve them in your createInstances.
+@property (readonly) NSUUID* musicPlayerID;
 
-typedef BGMMusicPlayerBase<BGMMusicPlayerProtocol> BGMMusicPlayer;
+// The name and icon of the music player, to be used in the UI.
+@property (readonly) NSString* name;
+@property (readonly) NSImage* __nullable icon;
 
-@protocol BGMMusicPlayerProtocol
+@property (readonly) NSString* __nullable bundleID;
 
-@optional
-// Subclasses usually won't need to implement these unless the music player has no bundle ID.
-+ (id) initWithPID:(pid_t)pid;
-+ (id) initWithPIDFromNSNumber:(NSNumber*)pid;
-+ (id) initWithPIDFromCFNumber:(CFNumberRef)pid;
-// The pid of each instance of the music player app currently running
-+ (NSArray<NSNumber*>*) pidsOfRunningInstances;
+// Classes will usually ignore this property and leave it nil unless the music player has no
+// bundle ID.
+//
+// TODO: If we ever add a music player class that uses this property, it'll need a way to inform
+//       BGMDevice of changes. It might be easiest to have BGMMusicPlayers to observe this property,
+//       on the selected music player, with KVO and update BGMDevice when it changes. Or
+//       BGMMusicPlayers could pass a pointer to itself to createInstances.
+@property NSNumber* __nullable pid;
 
-@required
-// The name of the music player, to be used in the UI
-+ (NSString*) name;
-
-// The refs returned by the bundleID and pid methods don't need to be released by users, but may be
-// released by the class/instance at some point (get rule applies).
-+ (CFStringRef __nullable) bundleID;
-// Subclasses will usually always return NULL unless they implement the optional methods above.
-- (CFNumberRef __nullable) pid;
-
-- (BOOL) isRunning;
+// The state of the music player.
+//
+// True if the music player app is open.
+@property (readonly, getter=isRunning) BOOL running;
+// True if the music player is playing a song or some other user-selected audio file. Note that
+// the music player playing audio for UI, notifications, etc. won't make this true (which is why we
+// need this property and can't just ask BGMDriver if the music player is playing audio).
+@property (readonly, getter=isPlaying) BOOL playing;
+// True if the music player has a current/open song (or whatever) and will continue playing it if
+// BGMMusicPlayer::unpause is called. Normally because the user was playing a song and they or
+// BGMApp paused it.
+@property (readonly, getter=isPaused) BOOL paused;
 
 // Pause the music player. Does nothing if the music player is already paused or isn't running.
 // Returns YES if the music player is paused now but wasn't before, returns NO otherwise.
@@ -84,27 +105,31 @@ typedef BGMMusicPlayerBase<BGMMusicPlayerProtocol> BGMMusicPlayer;
 // Returns YES if the music player is playing now but wasn't before, returns NO otherwise.
 - (BOOL) unpause;
 
-- (BOOL) isPlaying;
-
-- (BOOL) isPaused;
-
 @end
 
-@interface BGMMusicPlayerBase : NSObject <SBApplicationDelegate>
 
-+ (NSArray*) musicPlayerClasses;
-+ (void) addToMusicPlayerClasses:(Class)musicPlayerClass;
+@interface BGMMusicPlayerBase : NSObject
 
-// The music player currently selected in the preferences menu. (There's no real reason for this to be
-// global or in this class. I was just trying it out of curiosity.)
-+ (BGMMusicPlayer*) selectedMusicPlayer;
-+ (void) setSelectedMusicPlayer:(BGMMusicPlayer*)musicPlayer;
+- (instancetype) initWithMusicPlayerID:(NSUUID*)musicPlayerID
+                                  name:(NSString*)name
+                              bundleID:(NSString* __nullable)bundleID;
 
-+ (NSImage* __nullable) icon;
+- (instancetype) initWithMusicPlayerID:(NSUUID*)musicPlayerID
+                                  name:(NSString*)name
+                              bundleID:(NSString* __nullable)bundleID
+                                   pid:(NSNumber* __nullable)pid;
 
-// If the music player application is running, the scripting bridge object representing it. Otherwise
-// nil.
-@property (readonly) __kindof SBApplication* __nullable sbApplication;
+// Convenience wrapper around NSUUID's initWithUUIDString. musicPlayerIDString must be a string
+// generated by uuidgen (command line tool), e.g. "60BA9739-B6DD-4E6A-8134-51410A45BB84".
++ (NSUUID*) makeID:(NSString*)musicPlayerIDString;
+
+// BGMMusicPlayer default implementations
++ (NSArray<id<BGMMusicPlayer>>*) createInstances;
+@property (readonly) NSImage* __nullable icon;
+@property (readonly) NSUUID* musicPlayerID;
+@property (readonly) NSString* name;
+@property (readonly) NSString* __nullable bundleID;
+@property NSNumber* __nullable pid;
 
 @end
 

BGMApp/BGMApp/Music Players/BGMMusicPlayer.m

@@ -28,135 +28,60 @@
 #define CoreAudio_ThreadStampMessages 0  // Requires C++
 #include "CADebugMacros.h"
 
-// System Includes
-#import <Cocoa/Cocoa.h>
-
 
 #pragma clang assume_nonnull begin
 
-@implementation BGMMusicPlayerBase {
-    // Tokens for the notification observers. We need these to remove the observers in dealloc.
-    id didLaunchToken;
-    id didTerminateToken;
+@implementation BGMMusicPlayerBase
+
+@synthesize musicPlayerID = _musicPlayerID;
+@synthesize name = _name;
+@synthesize bundleID = _bundleID;
+@synthesize pid = _pid;
+
+- (instancetype) initWithMusicPlayerID:(NSUUID*)musicPlayerID
+                                  name:(NSString*)name
+                              bundleID:(NSString* __nullable)bundleID {
+    return [self initWithMusicPlayerID:musicPlayerID name:name bundleID:bundleID pid:nil];
 }
 
-@synthesize sbApplication = sbApplication;
-
-// A array of the subclasses of BGMMusicPlayer
-static NSArray* sMusicPlayerClasses;
-
-// The user-selected music player. One of BGMMusicPlayer's subclasses declares itself the default music player by
-// setting this to an instance of itself in its load method.
-static BGMMusicPlayer* sSelectedMusicPlayer;
-
-// Load-time static initializer
-+ (void) load {
-    sMusicPlayerClasses = @[];
-}
-
-- (id) init {
+- (instancetype) initWithMusicPlayerID:(NSUUID*)musicPlayerID
+                                  name:(NSString*)name
+                              bundleID:(NSString* __nullable)bundleID
+                                   pid:(NSNumber* __nullable)pid {
     if ((self = [super init])) {
-        NSString* bundleID = (__bridge NSString*)[[self class] bundleID];
+        NSAssert(musicPlayerID, @"BGMMusicPlayerBase::initWithMusicPlayerID: !musicPlayerID");
         
-        void (^createSBApplication)(void) = ^{
-            sbApplication = [SBApplication applicationWithBundleIdentifier:bundleID];
-            sbApplication.delegate = self;
-        };
+        NSAssert([self conformsToProtocol:@protocol(BGMMusicPlayer)],
+                 @"BGMMusicPlayerBase::initWithMusicPlayerID: !conformsToProtocol");
         
-        BOOL (^isAboutThisMusicPlayer)(NSNotification*) = ^(NSNotification* note){
-            return [[note.userInfo[NSWorkspaceApplicationKey] bundleIdentifier] isEqualToString:bundleID];
-        };
-        
-        // Add observers that create/destroy the SBApplication when the music player is launched/terminated. We
-        // only create the SBApplication when the music player is open because, if it isn't, creating the
-        // SBApplication, or sending it events, could launch the music player. Whether it does or not depends on
-        // the music player, and possibly the version of the music player, so to be safe we assume they all do.
-        //
-        // From the docs for SBApplication's applicationWithBundleIdentifier method:
-        //     "For applications that declare themselves to have a dynamic scripting interface, this method will
-        //     launch the application if it is not already running."
-        NSNotificationCenter* center = [[NSWorkspace sharedWorkspace] notificationCenter];
-#if DEBUG
-        const char* mpName = [[[self class] name] UTF8String];
-#endif
-        didLaunchToken = [center addObserverForName:NSWorkspaceDidLaunchApplicationNotification
-                                             object:nil
-                                              queue:nil
-                                         usingBlock:^(NSNotification* note) {
-                                             if (isAboutThisMusicPlayer(note)) {
-                                                 DebugMsg("BGMMusicPlayer::init: %s launched", mpName);
-                                                 createSBApplication();
-                                             }
-                                         }];
-        didTerminateToken = [center addObserverForName:NSWorkspaceDidTerminateApplicationNotification
-                                                object:nil
-                                                 queue:nil
-                                            usingBlock:^(NSNotification* note) {
-                                             if (isAboutThisMusicPlayer(note)) {
-                                                 DebugMsg("BGMMusicPlayer::init: %s terminated", mpName);
-                                                 sbApplication = nil;
-                                                }
-                                            }];
-        
-        // Create the SBApplication if the music player is already running.
-        if ([[NSRunningApplication runningApplicationsWithBundleIdentifier:bundleID] count] > 0) {
-            createSBApplication();
-        }
+        _musicPlayerID = musicPlayerID;
+        _name = name;
+        _bundleID = bundleID;
+        _pid = pid;
     }
-    
+
     return self;
 }
 
-- (id) eventDidFail:(const AppleEvent*)event withError:(NSError*)error {
-    // SBApplicationDelegate method. So far, this just logs the error.
++ (NSUUID*) makeID:(NSString*)musicPlayerIDString {
+    NSUUID* __nullable musicPlayerID = [[NSUUID alloc] initWithUUIDString:musicPlayerIDString];
+    NSAssert(musicPlayerID, @"BGMMusicPlayerBase::makeID: !musicPlayerID");
     
-#if DEBUG
-    NSString* vars = [NSString stringWithFormat:@"event=%@ error=%@ sbApplication=%@", event, error, sbApplication];
-    DebugMsg("BGMMusicPlayer::eventDidFail: Apple event sent to %s failed. %s",
-             [[[self class] name] UTF8String],
-             [vars UTF8String]);
-#else
-    #pragma unused (event, error)
-#endif
+    return (NSUUID*)musicPlayerID;
+}
+
+#pragma mark BGMMusicPlayer default implementations
+
++ (NSArray<id<BGMMusicPlayer>>*) createInstances {
+    return @[ [self new] ];
+}
+
+- (NSImage* __nullable) icon {
+    NSString* __nullable bundleID = self.bundleID;
+    NSString* __nullable bundlePath =
+        (!bundleID ? nil : [[NSWorkspace sharedWorkspace] absolutePathForAppBundleWithIdentifier:(NSString*)bundleID]);
     
-    return nil;
-}
-
-- (void) dealloc {
-    // Remove the application launch/termination observers.
-    NSNotificationCenter* center = [[NSWorkspace sharedWorkspace] notificationCenter];
-    
-    if (didLaunchToken) {
-        [center removeObserver:didLaunchToken];
-    }
-    
-    if (didTerminateToken) {
-        [center removeObserver:didTerminateToken];
-    }
-}
-
-+ (void) addToMusicPlayerClasses:(Class)musicPlayerClass {
-    sMusicPlayerClasses = [sMusicPlayerClasses arrayByAddingObject:musicPlayerClass];
-}
-
-+ (NSArray*) musicPlayerClasses {
-    return sMusicPlayerClasses;
-}
-
-+ (BGMMusicPlayer*) selectedMusicPlayer {
-    NSAssert(sSelectedMusicPlayer != nil, @"One of BGMMusicPlayer's subclasses should set itself as the default "
-                                           "music player (i.e. set sSelectedMusicPlayer) in its initialize method");
-    return sSelectedMusicPlayer;
-}
-
-+ (void) setSelectedMusicPlayer:(BGMMusicPlayer*)musicPlayer {
-    sSelectedMusicPlayer = musicPlayer;
-}
-
-+ (NSImage* __nullable) icon {
-    NSString* bundleID = (__bridge NSString*)[(id<BGMMusicPlayerProtocol>)self bundleID];
-    NSString* bundlePath = [[NSWorkspace sharedWorkspace] absolutePathForAppBundleWithIdentifier:bundleID];
-    return bundlePath == nil ? nil : [[NSWorkspace sharedWorkspace] iconForFile:bundlePath];
+    return (!bundlePath ? nil : [[NSWorkspace sharedWorkspace] iconForFile:(NSString*)bundlePath]);
 }
 
 @end

BGMApp/BGMApp/Music Players/BGMMusicPlayers.h

@@ -0,0 +1,62 @@
+// This file is part of Background Music.
+//
+// Background Music is free software: you can redistribute it and/or
+// modify it under the terms of the GNU General Public License as
+// published by the Free Software Foundation, either version 2 of the
+// License, or (at your option) any later version.
+//
+// Background Music is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Background Music. If not, see <http://www.gnu.org/licenses/>.
+
+//
+//  BGMMusicPlayers.h
+//  BGMApp
+//
+//  Copyright © 2016 Kyle Neideck
+//
+//  Holds the music players (i.e. BGMMusicPlayer objects) available in BGMApp. Also keeps track of
+//  which music player is currently selected by the user.
+//
+
+// Local Includes
+#import "BGMAudioDeviceManager.h"
+#import "BGMMusicPlayer.h"
+#import "BGMUserDefaults.h"
+
+// System Includes
+#import <Foundation/Foundation.h>
+
+
+#pragma clang assume_nonnull begin
+
+@interface BGMMusicPlayers : NSObject
+
+// Calls initWithAudioDevices:musicPlayers: with sensible defaults.
+- (instancetype) initWithAudioDevices:(BGMAudioDeviceManager*)devices
+                         userDefaults:(BGMUserDefaults*)defaults;
+
+// defaultMusicPlayerID is the musicPlayerID (see BGMMusicPlayer.h) of the music player that should be
+// selected by default.
+//
+// The createInstances method of each class in musicPlayerClasses will be called, and the results stored
+// in the musicPlayers property.
+- (instancetype) initWithAudioDevices:(BGMAudioDeviceManager*)devices
+                 defaultMusicPlayerID:(NSUUID*)defaultMusicPlayerID
+                   musicPlayerClasses:(NSArray<Class<BGMMusicPlayer>>*)musicPlayerClasses
+                         userDefaults:(BGMUserDefaults*)defaults;
+
+@property (readonly) NSArray<id<BGMMusicPlayer>>* musicPlayers;
+
+// The music player currently selected in the preferences menu. BGMDevice is informed when this property
+// is changed.
+@property id<BGMMusicPlayer> selectedMusicPlayer;
+
+@end
+
+#pragma clang assume_nonnull end
+

BGMApp/BGMApp/Music Players/BGMMusicPlayers.mm

@@ -0,0 +1,240 @@
+// This file is part of Background Music.
+//
+// Background Music is free software: you can redistribute it and/or
+// modify it under the terms of the GNU General Public License as
+// published by the Free Software Foundation, either version 2 of the
+// License, or (at your option) any later version.
+//
+// Background Music is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Background Music. If not, see <http://www.gnu.org/licenses/>.
+
+//
+//  BGMMusicPlayers.mm
+//  BGMApp
+//
+//  Copyright © 2016 Kyle Neideck
+//
+
+// Self include
+#import "BGMMusicPlayers.h"
+
+// Local includes
+#import "BGM_Types.h"
+
+// Music player includes
+#import "BGMiTunes.h"
+#import "BGMSpotify.h"
+#import "BGMVLC.h"
+#import "BGMVOX.h"
+#import "BGMDecibel.h"
+#import "BGMHermes.h"
+
+
+#pragma clang assume_nonnull begin
+
+@implementation BGMMusicPlayers {
+    BGMAudioDeviceManager* audioDevices;
+    BGMUserDefaults* userDefaults;
+}
+
+@synthesize selectedMusicPlayer = _selectedMusicPlayer;
+
+- (instancetype) initWithAudioDevices:(BGMAudioDeviceManager*)devices
+                         userDefaults:(BGMUserDefaults*)defaults {
+    return [self initWithAudioDevices:devices
+                 defaultMusicPlayerID:[BGMiTunes sharedMusicPlayerID]
+                   // If you write a new music player class, add it to this array.
+                   musicPlayerClasses:@[ [BGMVOX class],
+                                         [BGMVLC class],
+                                         [BGMSpotify class],
+                                         [BGMiTunes class],
+                                         [BGMDecibel class],
+                                         [BGMHermes class] ]
+                         userDefaults:defaults];
+}
+
+- (instancetype) initWithAudioDevices:(BGMAudioDeviceManager*)devices
+                 defaultMusicPlayerID:(NSUUID*)defaultMusicPlayerID
+                   musicPlayerClasses:(NSArray<Class<BGMMusicPlayer>>*)musicPlayerClasses
+                         userDefaults:(BGMUserDefaults*)defaults {
+    if ((self = [super init])) {
+        audioDevices = devices;
+        userDefaults = defaults;
+        
+        // Init _musicPlayers, an array containing one object for each music player in BGMApp.
+        //
+        // Each music player class has a factory method, createInstances, that returns all the instances of that
+        // class BGMApp will use. (Though so far it's always just one instance.)
+        NSMutableArray* musicPlayers = [NSMutableArray new];
+        for (Class<BGMMusicPlayer> musicPlayerClass in musicPlayerClasses) {
+            [musicPlayers addObjectsFromArray:[musicPlayerClass createInstances]];
+        }
+        
+        _musicPlayers = [NSArray arrayWithArray:musicPlayers];
+        
+        // Set _selectedMusicPlayer to its setting from last time BGMApp ran. (Unless this is the first run or
+        // that music player isn't available this time.)
+        [self initSelectedMusicPlayerFromUserDefaults];
+        
+        if (!_selectedMusicPlayer) {
+            // Couldn't set _selectedMusicPlayer from user defaults, so try BGMDevice's music player property.
+            [self initSelectedMusicPlayerFromBGMDevice];
+        }
+        
+        if (!_selectedMusicPlayer) {
+            // The user hasn't changed the music player yet, so we set the default music player as selected.
+            [self setSelectedMusicPlayerByID:defaultMusicPlayerID];
+        }
+        
+        NSAssert(_selectedMusicPlayer, @"BGMMusicPlayers::initWithAudioDevices: !_selectedMusicPlayer");
+    }
+    
+    return self;
+}
+
+- (void) initSelectedMusicPlayerFromUserDefaults {
+    // Load the selected music player setting from user defaults.
+    
+    NSString* __nullable selectedMusicPlayerIDStr = userDefaults.selectedMusicPlayerID;
+    NSUUID* __nullable selectedMusicPlayerID = nil;
+    
+    if (selectedMusicPlayerIDStr) {
+        NSString* idStrNN = selectedMusicPlayerIDStr;
+        selectedMusicPlayerID = [[NSUUID alloc] initWithUUIDString:idStrNN];
+        
+        NSAssert(selectedMusicPlayerID,
+                 @"BGMMusicPlayers::initSelectedMusicPlayerFromUserDefaults: !selectedMusicPlayerID");
+    }
+    
+    if (selectedMusicPlayerID) {
+        NSUUID* idNN = selectedMusicPlayerID;
+        BOOL didChangeMusicPlayer = [self setSelectedMusicPlayerByID:idNN];
+        
+#if DEBUG
+        DebugMsg("BGMMusicPlayers::initSelectedMusicPlayerFromUserDefaults: %s selectedMusicPlayerIDStr=%s",
+                 (didChangeMusicPlayer ?
+                     "Selected music player restored from user defaults." :
+                     "The selected music player setting found in user defaults didn't match an available music player."),
+                 selectedMusicPlayerIDStr.UTF8String);
+#else
+        #pragma unused (didChangeMusicPlayer)
+#endif
+    }
+}
+
+- (void) initSelectedMusicPlayerFromBGMDevice {
+    // When the selected music player setting hasn't been stored in user defaults yet, we get the music player
+    // bundle ID from the driver and look for the music player with that bundle ID. This is mainly done for
+    // backwards compatability.
+    
+    NSString* __nullable bundleID =
+        (__bridge_transfer NSString* __nullable)[audioDevices bgmDevice].GetPropertyData_CFString(kBGMMusicPlayerBundleIDAddress);
+    
+    DebugMsg("BGMMusicPlayers::initSelectedMusicPlayerFromBGMDevice: "
+             "Trying to set selected music player by bundle ID (from BGMDriver). bundleID=%s",
+             (bundleID ? bundleID.UTF8String : "(null)"));
+    
+    if (bundleID && ![bundleID isEqualToString:@""]) {
+        // Find any music players with a bundle ID matching the one from BGMDriver.
+        NSArray<id<BGMMusicPlayer>>* matchingMusicPlayers = @[ ];
+        
+        for (id<BGMMusicPlayer> musicPlayer in _musicPlayers) {
+            NSString* bundleIDNN = bundleID;
+            if ([musicPlayer.bundleID isEqualToString:bundleIDNN]) {
+                DebugMsg("BGMMusicPlayers::initSelectedMusicPlayerFromBGMDevice: Bundle ID on BGMDevice matches %s",
+                         musicPlayer.name.UTF8String);
+                
+                matchingMusicPlayers = [matchingMusicPlayers arrayByAddingObject:musicPlayer];
+            }
+        }
+        
+        // Currently, the music players all have different bundle IDs, but that might change at some point. We
+        // might want to consider some websites as music players, for example. So we don't change the setting
+        // unless the bundle ID only matches one music player.
+        if (matchingMusicPlayers.count == 1) {
+            // (Use setSelectedMusicPlayerImpl to avoid setSelectedMusicPlayer being called in init.)
+            [self setSelectedMusicPlayerImpl:matchingMusicPlayers[0]];
+        }
+    }
+}
+
+- (id<BGMMusicPlayer>) selectedMusicPlayer {
+    return _selectedMusicPlayer;
+}
+
+- (void) setSelectedMusicPlayer:(id<BGMMusicPlayer>)newSelectedMusicPlayer {
+    // Apparently you shouldn't call properties' setter methods in init (KVO notifications might trigger, etc.)
+    // so the actual work is done in setSelectedMusicPlayerImpl.
+    [self setSelectedMusicPlayerImpl:newSelectedMusicPlayer];
+    
+    NSAssert(self.selectedMusicPlayer == newSelectedMusicPlayer,
+             @"BGMMusicPlayers::setSelectedMusicPlayer: selectedMusicPlayer wasn't set to the object expected");
+}
+
+- (BOOL) setSelectedMusicPlayerByID:(NSUUID*)newSelectedMusicPlayerID {
+    id<BGMMusicPlayer> __nullable newSelectedMusicPlayer = nil;
+    
+    // Find the music player with the given ID, if there is one.
+    for (id<BGMMusicPlayer> musicPlayer in _musicPlayers) {
+        if ([musicPlayer.musicPlayerID isEqual:newSelectedMusicPlayerID]) {
+            NSAssert(!newSelectedMusicPlayer, @"BGMMusicPlayers::setSelectedMusicPlayerByID: Non-unique musicPlayerID");
+            
+            newSelectedMusicPlayer = musicPlayer;
+        }
+    }
+    
+    if (newSelectedMusicPlayer) {
+        // (Use setSelectedMusicPlayerImpl to avoid setSelectedMusicPlayer being called in init.)
+        id<BGMMusicPlayer> newPlayerNN = newSelectedMusicPlayer;
+        [self setSelectedMusicPlayerImpl:newPlayerNN];
+        
+        return YES;
+    } else {
+        return NO;
+    }
+}
+
+- (void) setSelectedMusicPlayerImpl:(id<BGMMusicPlayer>)newSelectedMusicPlayer {
+    NSAssert([_musicPlayers containsObject:newSelectedMusicPlayer],
+             @"BGMMusicPlayers::setSelectedMusicPlayerImpl: Only the music players in the musicPlayers array can be selected. "
+              "newSelectedMusicPlayer=%@",
+             newSelectedMusicPlayer.name);
+    
+    _selectedMusicPlayer = newSelectedMusicPlayer;
+    
+    DebugMsg("BGMMusicPlayers::setSelectedMusicPlayerImpl: Set selected music player to %s",
+             _selectedMusicPlayer.name.UTF8String);
+    
+    // Update the selected music player on the driver.
+    [self updateBGMDeviceMusicPlayerProperties];
+    
+    // Save the new setting in user defaults.
+    userDefaults.selectedMusicPlayerID = _selectedMusicPlayer.musicPlayerID.UUIDString;
+}
+
+- (void) updateBGMDeviceMusicPlayerProperties {
+    // Send the music player's PID and/or bundle ID to the driver.
+    
+    NSAssert(self.selectedMusicPlayer.pid || self.selectedMusicPlayer.bundleID,
+             @"BGMMusicPlayers::updateBGMDeviceMusicPlayerProperties: Music player has neither bundle ID nor PID");
+
+    if (self.selectedMusicPlayer.pid) {
+        [audioDevices bgmDevice].SetPropertyData_CFType(kBGMMusicPlayerProcessIDAddress,
+                                                        (__bridge CFNumberRef)self.selectedMusicPlayer.pid);
+    }
+    
+    if (self.selectedMusicPlayer.bundleID) {
+        [audioDevices bgmDevice].SetPropertyData_CFString(kBGMMusicPlayerBundleIDAddress,
+                                                          (__bridge CFStringRef)self.selectedMusicPlayer.bundleID);
+    }
+}
+
+@end
+
+#pragma clang assume_nonnull end
+

BGMApp/BGMApp/Music Players/BGMScriptingBridge.h

@@ -0,0 +1,59 @@
+// This file is part of Background Music.
+//
+// Background Music is free software: you can redistribute it and/or
+// modify it under the terms of the GNU General Public License as
+// published by the Free Software Foundation, either version 2 of the
+// License, or (at your option) any later version.
+//
+// Background Music is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Background Music. If not, see <http://www.gnu.org/licenses/>.
+
+//
+//  BGMScriptingBridge.h
+//  BGMApp
+//
+//  Copyright © 2016 Kyle Neideck
+//
+//  A wrapper around Scripting Bridge's SBApplication that tries to avoid ever launching the application.
+//
+//  We use Scripting Bridge to communicate with music player apps, which we never want to launch
+//  ourselves. But creating an SBApplication for an app, or sending messages/events to an existing one,
+//  can launch the app.
+//
+//  As a workaround, this class has an SBApplication property, application (see below), which is nil
+//  unless the music player app is running. That way messages sent while the app is closed are ignored.
+//
+
+// System Includes
+#import <Cocoa/Cocoa.h>
+#import <ScriptingBridge/ScriptingBridge.h>
+
+
+#pragma clang assume_nonnull begin
+
+@interface BGMScriptingBridge : NSObject <SBApplicationDelegate>
+
+- (instancetype) initWithBundleID:(NSString*)bundleID;
+
+// If the music player application is running, this property is the Scripting Bridge object representing
+// it. If not, it's set to nil. Used to send Apple events to the music player app.
+@property (readonly) __kindof SBApplication* __nullable application;
+
+// SBApplicationDelegate
+
+// On 10.11, SBApplicationDelegate.h declares eventDidFail with a non-null return type, but the docs
+// specifically say that returning nil is allowed.
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wnullability"
+- (id __nullable) eventDidFail:(const AppleEvent*)event withError:(NSError*)error;
+#pragma clang diagnostic pop
+
+@end
+
+#pragma clang assume_nonnull end
+

BGMApp/BGMApp/Music Players/BGMScriptingBridge.m

@@ -0,0 +1,135 @@
+// This file is part of Background Music.
+//
+// Background Music is free software: you can redistribute it and/or
+// modify it under the terms of the GNU General Public License as
+// published by the Free Software Foundation, either version 2 of the
+// License, or (at your option) any later version.
+//
+// Background Music is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Background Music. If not, see <http://www.gnu.org/licenses/>.
+
+//
+//  BGMScriptingBridge.m
+//  BGMApp
+//
+//  Copyright © 2016 Kyle Neideck
+//
+
+// Self Include
+#import "BGMScriptingBridge.h"
+
+// PublicUtility Includes
+#undef CoreAudio_ThreadStampMessages
+#define CoreAudio_ThreadStampMessages 0  // Requires C++
+#include "CADebugMacros.h"
+
+
+#pragma clang assume_nonnull begin
+
+@implementation BGMScriptingBridge {
+    NSString* bundleID;
+    // Tokens for the notification observers. We need these to remove the observers in dealloc.
+    id didLaunchToken, didTerminateToken;
+}
+
+@synthesize application = _application;
+
+- (instancetype) initWithBundleID:(NSString*)inBundleID {
+    if ((self = [super init])) {
+        bundleID = inBundleID;
+        
+        [self initApplication];
+    }
+    
+    return self;
+}
+
+- (void) initApplication {
+    void (^createSBApplication)(void) = ^{
+        _application = [SBApplication applicationWithBundleIdentifier:bundleID];
+        _application.delegate = self;
+    };
+    
+    BOOL (^isAboutThisMusicPlayer)(NSNotification*) = ^(NSNotification* note) {
+        return [[note.userInfo[NSWorkspaceApplicationKey] bundleIdentifier] isEqualToString:bundleID];
+    };
+    
+    // Add observers that create/destroy the SBApplication when the music player is launched/terminated. We
+    // only create the SBApplication when the music player is open. If it isn't open, creating the
+    // SBApplication or sending it events could launch the music player. Whether or not it does depends on
+    // the music player, and possibly the version of the music player, so to be safe we assume they all do.
+    //
+    // From the docs for SBApplication's applicationWithBundleIdentifier method:
+    //     "For applications that declare themselves to have a dynamic scripting interface, this method will
+    //     launch the application if it is not already running."
+    NSNotificationCenter* center = [[NSWorkspace sharedWorkspace] notificationCenter];
+    didLaunchToken = [center addObserverForName:NSWorkspaceDidLaunchApplicationNotification
+                                         object:nil
+                                          queue:nil
+                                     usingBlock:^(NSNotification* note) {
+                                         if (isAboutThisMusicPlayer(note)) {
+                                             DebugMsg("BGMScriptingBridge::initApplication: %s launched",
+                                                      bundleID.UTF8String);
+                                             createSBApplication();
+                                         }
+                                     }];
+    didTerminateToken = [center addObserverForName:NSWorkspaceDidTerminateApplicationNotification
+                                            object:nil
+                                             queue:nil
+                                        usingBlock:^(NSNotification* note) {
+                                            if (isAboutThisMusicPlayer(note)) {
+                                                DebugMsg("BGMScriptingBridge::initApplication: %s terminated",
+                                                         bundleID.UTF8String);
+                                                _application = nil;
+                                            }
+                                        }];
+    
+    // Create the SBApplication if the music player is already running.
+    if ([NSRunningApplication runningApplicationsWithBundleIdentifier:bundleID].count > 0) {
+        createSBApplication();
+    }
+}
+
+- (void) dealloc {
+    // Remove the application launch/termination observers.
+    NSNotificationCenter* center = [NSWorkspace sharedWorkspace].notificationCenter;
+    
+    if (didLaunchToken) {
+        [center removeObserver:didLaunchToken];
+    }
+    
+    if (didTerminateToken) {
+        [center removeObserver:didTerminateToken];
+    }
+}
+
+#pragma mark SBApplicationDelegate
+
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wnullability"  // See explanation in the header file.
+- (id __nullable) eventDidFail:(const AppleEvent*)event withError:(NSError*)error {
+#pragma clang diagnostic pop
+    // So far, this just logs the error.
+    
+#if DEBUG
+    NSString* vars = [NSString stringWithFormat:@"event='%4.4s' error=%@ application=%@",
+                         (char*)&(event->descriptorType), error, self.application];
+    DebugMsg("BGMScriptingBridge::eventDidFail: Apple event sent to %s failed. %s",
+             bundleID.UTF8String,
+             vars.UTF8String);
+#else
+    #pragma unused (event, error)
+#endif
+
+    return nil;
+}
+
+@end
+
+#pragma clang assume_nonnull end
+

BGMApp/BGMApp/Music Players/BGMSpotify.h

@@ -24,7 +24,7 @@
 #import "BGMMusicPlayer.h"
 
 
-@interface BGMSpotify : BGMMusicPlayer
+@interface BGMSpotify : BGMMusicPlayerBase<BGMMusicPlayer>
 
 @end
 

BGMApp/BGMApp/Music Players/BGMSpotify.m

@@ -29,39 +29,55 @@
 // Auto-generated Scripting Bridge header
 #import "Spotify.h"
 
+// Local Includes
+#import "BGMScriptingBridge.h"
+
 // PublicUtility Includes
 #undef CoreAudio_ThreadStampMessages
 #define CoreAudio_ThreadStampMessages 0  // Requires C++
 #include "CADebugMacros.h"
 
 
-@implementation BGMSpotify
+#pragma clang assume_nonnull begin
 
-BGM_MUSIC_PLAYER_DEFAULT_LOAD_METHOD
-
-+ (NSString*) name {
-    return @"Spotify";
+@implementation BGMSpotify {
+    BGMScriptingBridge* scriptingBridge;
 }
 
-- (CFNumberRef) pid {
-    return NULL;
-}
-
-+ (CFStringRef) bundleID {
-    return CFSTR("com.spotify.client");
+- (id) init {
+    // If you're copying this class, replace the ID string with a new one generated by uuidgen. (Command line tool.)
+    if ((self = [super initWithMusicPlayerID:[BGMMusicPlayerBase makeID:@"EC2A907F-8515-4687-9570-1BF63176E6D8"]
+                                        name:@"Spotify"
+                                    bundleID:@"com.spotify.client"])) {
+        scriptingBridge = [[BGMScriptingBridge alloc] initWithBundleID:(NSString*)self.bundleID];
+    }
+    
+    return self;
 }
 
 - (SpotifyApplication* __nullable) spotify {
-    return (SpotifyApplication*) self.sbApplication;
+    return (SpotifyApplication* __nullable)scriptingBridge.application;
 }
 
 - (BOOL) isRunning {
-    return self.spotify && [self.spotify isRunning];
+    // Note that this will return NO if is self.spotify is nil (i.e. Spotify isn't running).
+    return self.spotify.running;
+}
+
+// isPlaying and isPaused check self.running first just in case Spotify is closed but self.spotify hasn't become
+// nil yet. In that case, reading self.spotify.playerState could make Scripting Bridge open Spotify.
+
+- (BOOL) isPlaying {
+    return self.running && (self.spotify.playerState == SpotifyEPlSPlaying);
+}
+
+- (BOOL) isPaused {
+    return self.running && (self.spotify.playerState == SpotifyEPlSPaused);
 }
 
 - (BOOL) pause {
     // isPlaying checks isRunning, so we don't need to check it here and waste an Apple event
-    BOOL wasPlaying = [self isPlaying];
+    BOOL wasPlaying = self.playing;
     
     if (wasPlaying) {
         DebugMsg("BGMSpotify::pause: Pausing Spotify");
@@ -73,7 +89,7 @@ BGM_MUSIC_PLAYER_DEFAULT_LOAD_METHOD
 
 - (BOOL) unpause {
     // isPaused checks isRunning, so we don't need to check it here and waste an Apple event
-    BOOL wasPaused = [self isPaused];
+    BOOL wasPaused = self.paused;
     
     if (wasPaused) {
         DebugMsg("BGMSpotify::unpause: Unpausing Spotify");
@@ -83,13 +99,7 @@ BGM_MUSIC_PLAYER_DEFAULT_LOAD_METHOD
     return wasPaused;
 }
 
-- (BOOL) isPlaying {
-    return [self isRunning] && [self.spotify playerState] == SpotifyEPlSPlaying;
-}
-
-- (BOOL) isPaused {
-    return [self isRunning] && [self.spotify playerState] == SpotifyEPlSPaused;
-}
-
 @end
 
+#pragma clang assume_nonnull end
+

BGMApp/BGMApp/Music Players/BGMVLC.h

@@ -24,7 +24,7 @@
 #import "BGMMusicPlayer.h"
 
 
-@interface BGMVLC : BGMMusicPlayer
+@interface BGMVLC : BGMMusicPlayerBase<BGMMusicPlayer>
 
 @end
 

BGMApp/BGMApp/Music Players/BGMVLC.m

@@ -27,43 +27,58 @@
 // Auto-generated Scripting Bridge header
 #import "VLC.h"
 
+// Local Includes
+#import "BGMScriptingBridge.h"
+
 // PublicUtility Includes
 #undef CoreAudio_ThreadStampMessages
 #define CoreAudio_ThreadStampMessages 0  // Requires C++
 #include "CADebugMacros.h"
 
 
-@implementation BGMVLC
+#pragma clang assume_nonnull begin
 
-BGM_MUSIC_PLAYER_DEFAULT_LOAD_METHOD
-
-+ (NSString*) name {
-    return @"VLC";
+@implementation BGMVLC {
+    BGMScriptingBridge* scriptingBridge;
 }
 
-- (CFNumberRef) pid {
-    return NULL;
-}
-
-+ (CFStringRef) bundleID {
-    return CFSTR("org.videolan.vlc");
+- (id) init {
+    if ((self = [super initWithMusicPlayerID:[BGMMusicPlayerBase makeID:@"5226F4B9-C740-4045-A273-4B8EABC0E8FC"]
+                                        name:@"VLC"
+                                    bundleID:@"org.videolan.vlc"])) {
+        scriptingBridge = [[BGMScriptingBridge alloc] initWithBundleID:(NSString*)self.bundleID];
+    }
+    
+    return self;
 }
 
 - (VLCApplication* __nullable) vlc {
-    return (VLCApplication*) self.sbApplication;
+    return (VLCApplication*)scriptingBridge.application;
 }
 
 - (BOOL) isRunning {
-    return self.vlc && [self.vlc isRunning];
+    return self.vlc.running;
+}
+
+// isPlaying and isPaused check self.running first just in case VLC is closed but self.vlc hasn't become
+// nil yet. In that case, reading other properties of self.vlc could make Scripting Bridge open VLC.
+
+- (BOOL) isPlaying {
+    return self.running && self.vlc.playing;
+}
+
+- (BOOL) isPaused {
+    // VLC is paused if it has a file open but isn't playing it
+    return self.running && (self.vlc.nameOfCurrentItem != nil) && !self.vlc.playing;
 }
 
 - (BOOL) pause {
     // isPlaying checks isRunning, so we don't need to check it here and waste an Apple event
-    BOOL wasPlaying = [self isPlaying];
+    BOOL wasPlaying = self.playing;
     
     if (wasPlaying) {
         DebugMsg("BGMVLC::pause: Pausing VLC");
-        [self togglePlay];
+        [BGMVLC togglePlay];
     }
     
     return wasPlaying;
@@ -71,30 +86,21 @@ BGM_MUSIC_PLAYER_DEFAULT_LOAD_METHOD
 
 - (BOOL) unpause {
     // isPaused checks isRunning, so we don't need to check it here and waste an Apple event
-    BOOL wasPaused = [self isPaused];
+    BOOL wasPaused = self.paused;
     
     if (wasPaused) {
         DebugMsg("BGMVLC::unpause: Unpausing VLC");
-        [self togglePlay];
+        [BGMVLC togglePlay];
     }
     
     return wasPaused;
 }
 
-- (BOOL) isPlaying {
-    return [self isRunning] && [self.vlc playing];
-}
-
-- (BOOL) isPaused {
-    // VLC is paused if it has a file open but isn't playing it
-    return [self isRunning] && [self.vlc nameOfCurrentItem] != nil && ![self.vlc playing];
-}
-
 // This is from SubTTS's STVLCPlayer class:
 // https://github.com/heatherleaf/subtts-mac/blob/master/SubTTS/STVLCPlayer.m
 //
 // VLC's Scripting Bridge interface doesn't seem to have a cleaner way to do this.
-- (void) togglePlay {
++ (void) togglePlay {
     NSString* src = @"tell application \"VLC\" to play";
     NSAppleScript* script = [[NSAppleScript alloc] initWithSource:src];
     [script executeAndReturnError:nil];
@@ -102,3 +108,5 @@ BGM_MUSIC_PLAYER_DEFAULT_LOAD_METHOD
 
 @end
 
+#pragma clang assume_nonnull end
+

BGMApp/BGMApp/Music Players/BGMVOX.h

@@ -14,7 +14,7 @@
 // along with Background Music. If not, see <http://www.gnu.org/licenses/>.
 
 //
-//  BGMVox.h
+//  BGMVOX.h
 //  BGMApp
 //
 //  Copyright © 2016 Kyle Neideck
@@ -24,7 +24,7 @@
 #import "BGMMusicPlayer.h"
 
 
-@interface BGMVox : BGMMusicPlayer
+@interface BGMVOX : BGMMusicPlayerBase<BGMMusicPlayer>
 
 @end
 

BGMApp/BGMApp/Music Players/BGMVOX.m

@@ -14,17 +14,20 @@
 // along with Background Music. If not, see <http://www.gnu.org/licenses/>.
 
 //
-//  BGMVox.m
+//  BGMVOX.m
 //  BGMApp
 //
 //  Copyright © 2016 Kyle Neideck
 //
 
 // Self Include
-#import "BGMVox.h"
+#import "BGMVOX.h"
 
 // Auto-generated Scripting Bridge header
-#import "Vox.h"
+#import "VOX.h"
+
+// Local Includes
+#import "BGMScriptingBridge.h"
 
 // PublicUtility Includes
 #undef CoreAudio_ThreadStampMessages
@@ -32,36 +35,49 @@
 #include "CADebugMacros.h"
 
 
-@implementation BGMVox
+#pragma clang assume_nonnull begin
 
-BGM_MUSIC_PLAYER_DEFAULT_LOAD_METHOD
-
-+ (NSString*) name {
-    return @"VOX";
+@implementation BGMVOX {
+    BGMScriptingBridge* scriptingBridge;
 }
 
-- (CFNumberRef) pid {
-    return NULL;
-}
-
-+ (CFStringRef) bundleID {
-    return CFSTR("com.coppertino.Vox");
+- (id) init {
+    if ((self = [super initWithMusicPlayerID:[BGMMusicPlayerBase makeID:@"26498C5D-C18B-4689-8B41-9DA91A78FFAD"]
+                                        name:@"VOX"
+                                    bundleID:@"com.coppertino.Vox"])) {
+        scriptingBridge = [[BGMScriptingBridge alloc] initWithBundleID:(NSString*)self.bundleID];
+    }
+    
+    return self;
 }
 
 - (VoxApplication* __nullable) vox {
-    return (VoxApplication*) self.sbApplication;
+    return (VoxApplication*)scriptingBridge.application;
 }
 
 - (BOOL) isRunning {
-    return self.vox && [self.vox isRunning];
+    return self.vox.running;
+}
+
+// isPlaying and isPaused check self.running first just in case VOX is closed but self.vox hasn't become
+// nil yet. In that case, reading self.vox.playerState could make Scripting Bridge open VOX.
+//
+// VOX's comment for its playerState property says "playing = 1, paused = 0".
+
+- (BOOL) isPlaying {
+    return self.running && (self.vox.playerState == 1);
+}
+
+- (BOOL) isPaused {
+    return self.running && (self.vox.playerState == 0);
 }
 
 - (BOOL) pause {
     // isPlaying checks isRunning, so we don't need to check it here and waste an Apple event
-    BOOL wasPlaying = [self isPlaying];
+    BOOL wasPlaying = self.playing;
     
     if (wasPlaying) {
-        DebugMsg("BGMVox::pause: Pausing VOX");
+        DebugMsg("BGMVOX::pause: Pausing VOX");
         [self.vox pause];
     }
     
@@ -70,25 +86,17 @@ BGM_MUSIC_PLAYER_DEFAULT_LOAD_METHOD
 
 - (BOOL) unpause {
     // isPaused checks isRunning, so we don't need to check it here and waste an Apple event
-    BOOL wasPaused = [self isPaused];
+    BOOL wasPaused = self.paused;
     
     if (wasPaused) {
-        DebugMsg("BGMVox::unpause: Unpausing VOX");
+        DebugMsg("BGMVOX::unpause: Unpausing VOX");
         [self.vox playpause];
     }
     
     return wasPaused;
 }
 
-// Vox's comment for playerState says "playing = 1, paused = 0"
-
-- (BOOL) isPlaying {
-    return [self isRunning] && [self.vox playerState] == 1;
-}
-
-- (BOOL) isPaused {
-    return [self isRunning] && [self.vox playerState] == 0;
-}
-
 @end
 
+#pragma clang assume_nonnull end
+

BGMApp/BGMApp/Music Players/BGMiTunes.h

@@ -24,8 +24,11 @@
 #import "BGMMusicPlayer.h"
 
 
-@interface BGMiTunes : BGMMusicPlayer
+@interface BGMiTunes : BGMMusicPlayerBase<BGMMusicPlayer>
+
+// The music player ID (see BGMMusicPlayer.h) used by BGMiTunes instances. (Though BGMApp only ever creates one instance of
+// BGMiTunes, sharedMusicPlayerID is exposed so iTunes can be set as the default music player.)
++ (NSUUID*) sharedMusicPlayerID;
 
 @end
 
-

BGMApp/BGMApp/Music Players/BGMiTunes.m

@@ -26,44 +26,59 @@
 // Auto-generated Scripting Bridge header
 #import "iTunes.h"
 
+// Local Includes
+#import "BGMScriptingBridge.h"
+
 // PublicUtility Includes
 #undef CoreAudio_ThreadStampMessages
 #define CoreAudio_ThreadStampMessages 0  // Requires C++
 #include "CADebugMacros.h"
 
 
-@implementation BGMiTunes
+#pragma clang assume_nonnull begin
 
-+ (void) load {
-    BGM_MUSIC_PLAYER_ADD_SELF_TO_CLASSES_LIST
+@implementation BGMiTunes {
+    BGMScriptingBridge* scriptingBridge;
+}
+
++ (NSUUID*) sharedMusicPlayerID {
+    NSUUID* __nullable musicPlayerID = [[NSUUID alloc] initWithUUIDString:@"7B62B5BF-CF90-4938-84E3-F16DEDC3F608"];
+    NSAssert(musicPlayerID, @"BGMiTunes::sharedMusicPlayerID: !musicPlayerID");
+    return (NSUUID*)musicPlayerID;
+}
+
+- (id) init {
+    if ((self = [super initWithMusicPlayerID:[BGMiTunes sharedMusicPlayerID]
+                                        name:@"iTunes"
+                                    bundleID:@"com.apple.iTunes"])) {
+        scriptingBridge = [[BGMScriptingBridge alloc] initWithBundleID:(NSString* __nonnull)self.bundleID];
+    }
     
-    // iTunes is selected as the music player when the user hasn't changed the setting yet
-    [self setSelectedMusicPlayer:[BGMiTunes new]];
-}
-
-+ (NSString*) name {
-    return @"iTunes";
-}
-
-- (CFNumberRef) pid {
-    return NULL;
-}
-
-+ (CFStringRef) bundleID {
-    return CFSTR("com.apple.iTunes");
+    return self;
 }
 
 - (iTunesApplication* __nullable) iTunes {
-    return (iTunesApplication*) self.sbApplication;
+    return (iTunesApplication*)scriptingBridge.application;
 }
 
 - (BOOL) isRunning {
-    return self.iTunes && [self.iTunes isRunning];
+    return self.iTunes.running;
+}
+
+// isPlaying and isPaused check self.running first just in case iTunes is closed but self.iTunes hasn't become
+// nil yet. In that case, reading self.iTunes.playerState could make Scripting Bridge open iTunes.
+
+- (BOOL) isPlaying {
+    return self.running && (self.iTunes.playerState == iTunesEPlSPlaying);
+}
+
+- (BOOL) isPaused {
+    return self.running && (self.iTunes.playerState == iTunesEPlSPaused);
 }
 
 - (BOOL) pause {
     // isPlaying checks isRunning, so we don't need to check it here and waste an Apple event
-    BOOL wasPlaying = [self isPlaying];
+    BOOL wasPlaying = self.playing;
     
     if (wasPlaying) {
         DebugMsg("BGMiTunes::pause: Pausing iTunes");
@@ -75,7 +90,7 @@
 
 - (BOOL) unpause {
     // isPaused checks isRunning, so we don't need to check it here and waste an Apple event
-    BOOL wasPaused = [self isPaused];
+    BOOL wasPaused = self.paused;
     
     if (wasPaused) {
         DebugMsg("BGMiTunes::unpause: Unpausing iTunes");
@@ -85,13 +100,7 @@
     return wasPaused;
 }
 
-- (BOOL) isPlaying {
-    return [self isRunning] && [self.iTunes playerState] == iTunesEPlSPlaying;
-}
-
-- (BOOL) isPaused {
-    return [self isRunning] && [self.iTunes playerState] == iTunesEPlSPaused;
-}
-
 @end
 
+#pragma clang assume_nonnull end
+

BGMApp/BGMApp/Music Players/Decibel.h

@@ -0,0 +1,181 @@
+/*
+ * Decibel.h
+ *
+ * Generated with
+ * sdef /Applications/Decibel.app | sdp -fh --basename Decibel
+ */
+
+#import <AppKit/AppKit.h>
+#import <ScriptingBridge/ScriptingBridge.h>
+
+
+@class DecibelApplication, DecibelDocument, DecibelWindow, DecibelApplication, DecibelTrack;
+
+enum DecibelSaveOptions {
+	DecibelSaveOptionsYes = 'yes ' /* Save the file. */,
+	DecibelSaveOptionsNo = 'no  ' /* Do not save the file. */,
+	DecibelSaveOptionsAsk = 'ask ' /* Ask the user whether or not to save the file. */
+};
+typedef enum DecibelSaveOptions DecibelSaveOptions;
+
+enum DecibelPrintingErrorHandling {
+	DecibelPrintingErrorHandlingStandard = 'lwst' /* Standard PostScript error handling */,
+	DecibelPrintingErrorHandlingDetailed = 'lwdt' /* print a detailed report of PostScript errors */
+};
+typedef enum DecibelPrintingErrorHandling DecibelPrintingErrorHandling;
+
+enum DecibelShuffleMode {
+	DecibelShuffleModeOff = 'off ' /* Off */,
+	DecibelShuffleModeTrack = 'trck' /* Track */,
+	DecibelShuffleModeAlbum = 'albm' /* Album */,
+	DecibelShuffleModeArtist = 'arts' /* Artist */
+};
+typedef enum DecibelShuffleMode DecibelShuffleMode;
+
+enum DecibelRepeatMode {
+	DecibelRepeatModeOff = 'off ' /* Off */,
+	DecibelRepeatModeTrack = 'trck' /* Track */,
+	DecibelRepeatModeAlbum = 'albm' /* Album */,
+	DecibelRepeatModeArtist = 'arts' /* Artist */,
+	DecibelRepeatModeAll = 'all ' /* All */
+};
+typedef enum DecibelRepeatMode DecibelRepeatMode;
+
+@protocol DecibelGenericMethods
+
+- (void) closeSaving:(DecibelSaveOptions)saving savingIn:(NSURL *)savingIn;  // Close a document.
+- (void) saveIn:(NSURL *)in_ as:(id)as;  // Save a document.
+- (void) printWithProperties:(NSDictionary *)withProperties printDialog:(BOOL)printDialog;  // Print a document.
+- (void) delete;  // Delete an object.
+- (void) duplicateTo:(SBObject *)to withProperties:(NSDictionary *)withProperties;  // Copy an object.
+- (void) moveTo:(SBObject *)to;  // Move an object to a new location.
+
+@end
+
+
+
+/*
+ * Standard Suite
+ */
+
+// The application's top-level scripting object.
+@interface DecibelApplication : SBApplication
+
+- (SBElementArray<DecibelDocument *> *) documents;
+- (SBElementArray<DecibelWindow *> *) windows;
+
+@property (copy, readonly) NSString *name;  // The name of the application.
+@property (readonly) BOOL frontmost;  // Is this the active application?
+@property (copy, readonly) NSString *version;  // The version number of the application.
+
+- (id) open:(id)x;  // Open a document.
+- (void) print:(id)x withProperties:(NSDictionary *)withProperties printDialog:(BOOL)printDialog;  // Print a document.
+- (void) quitSaving:(DecibelSaveOptions)saving;  // Quit the application.
+- (BOOL) exists:(id)x;  // Verify that an object exists.
+- (void) play;  // Begin audio playback
+- (void) pause;  // Suspend audio playback
+- (void) stop;  // Stop audio playback
+- (void) playPause;  // Begin or suspend audio playback
+- (void) seekForward;  // Seek forward three seconds
+- (void) seekBackward;  // Seek backward three seconds
+- (void) playSelection;  // Play the selected track, or the first track if more than one are selected
+- (void) playPreviousTrack;  // Play the previous logical track in the playlist
+- (void) playNextTrack;  // Play the next logical track in the playlist
+- (void) addFile:(NSURL *)x;  // Add a file to the playlist
+- (void) playFile:(NSURL *)x;  // Add a file to the playlist and play it
+- (void) playTrackAtIndex:(NSInteger)x;  // Play a track in the playlist
+- (void) increaseDeviceVolume;  // Increase the device volume
+- (void) decreaseDeviceVolume;  // Decrease the device volume
+- (void) increaseDigitalVolume;  // Increase the digital volume
+- (void) decreaseDigitalVolume;  // Decrease the digital volume
+- (void) clearPlaylist;  // Clear the playlist
+- (void) scramblePlaylist;  // Scramble the playlist
+
+@end
+
+// A document.
+@interface DecibelDocument : SBObject <DecibelGenericMethods>
+
+@property (copy, readonly) NSString *name;  // Its name.
+@property (readonly) BOOL modified;  // Has it been modified since the last save?
+@property (copy, readonly) NSURL *file;  // Its location on disk, if it has one.
+
+
+@end
+
+// A window.
+@interface DecibelWindow : SBObject <DecibelGenericMethods>
+
+@property (copy, readonly) NSString *name;  // The title of the window.
+- (NSInteger) id;  // The unique identifier of the window.
+@property NSInteger index;  // The index of the window, ordered front to back.
+@property NSRect bounds;  // The bounding rectangle of the window.
+@property (readonly) BOOL closeable;  // Does the window have a close button?
+@property (readonly) BOOL miniaturizable;  // Does the window have a minimize button?
+@property BOOL miniaturized;  // Is the window minimized right now?
+@property (readonly) BOOL resizable;  // Can the window be resized?
+@property BOOL visible;  // Is the window visible right now?
+@property (readonly) BOOL zoomable;  // Does the window have a zoom button?
+@property BOOL zoomed;  // Is the window zoomed right now?
+@property (copy, readonly) DecibelDocument *document;  // The document whose contents are displayed in the window.
+
+
+@end
+
+
+
+/*
+ * Decibel Scripting Suite
+ */
+
+// The Decibel application class.
+@interface DecibelApplication (DecibelScriptingSuite)
+
+- (SBElementArray<DecibelTrack *> *) tracks;
+
+@property (readonly) BOOL playing;  // Is the player currently playing?
+@property (readonly) BOOL shuffling;  // Is the player currently shuffling?
+@property (readonly) BOOL repeating;  // Is the player currently repeating?
+@property (copy, readonly) DecibelTrack *nowPlaying;  // The track that is currently playing?
+@property double deviceVolume;  // The current device volume
+@property double digitalVolume;  // The current digital volume
+@property double playbackPosition;  // The current playback position [0, 1]
+@property double playbackTime;  // The current playback time in seconds
+@property (readonly) BOOL canPlay;  // Is the player currently playing?
+@property (readonly) BOOL canPlayPreviousTrack;  // Is the player currently playing?
+@property (readonly) BOOL canPlayNextTrack;  // Is the player currently playing?
+@property (readonly) BOOL canAdjustDeviceVolume;  // Can the device volume be adjusted?
+@property DecibelShuffleMode shuffleMode;  // Player shuffle mode
+@property DecibelRepeatMode repeatMode;  // Player repeat mode
+@property (copy, readonly) SBObject *currentPlaylist;  // The current playlist
+
+@end
+
+// A track in the playlist
+@interface DecibelTrack : SBObject <DecibelGenericMethods>
+
+- (NSString *) id;  // The track's ID
+@property (copy, readonly) NSURL *file;  // The track's location
+@property (readonly) double duration;  // The track's duration in seconds
+@property (readonly) double sampleRate;  // The track's sample rate in Hz
+@property (readonly) NSInteger bitDepth;  // The bit depth
+@property (readonly) NSInteger channels;  // The track's channels
+@property (copy) NSString *title;  // The track's title
+@property (copy) NSString *artist;  // The track's artist
+@property (copy) NSString *albumTitle;  // The track's album title
+@property (copy) NSString *albumArtist;  // The track's album artist
+@property NSInteger trackNumber;  // The track's track number
+@property NSInteger trackTotal;  // The total number of tracks on the album
+@property NSInteger discNumber;  // The disc number containing the track
+@property NSInteger discTotal;  // The total number of discs (for multidisc albums)
+@property BOOL partOfACompilation;  // Is the track part of a compilation?
+@property (copy) NSString *genre;  // The track's genre
+@property (copy) NSString *composer;  // The track's composer
+@property (copy) NSString *releaseDate;  // The track's release date
+@property (copy) NSString *ISRC;  // The track's ISRC
+@property (copy) id MCN;  // The track's MCN
+
+- (void) playTrack;  // Play a track in the playlist
+
+@end
+

BGMApp/BGMApp/Music Players/Hermes.h

@@ -0,0 +1,78 @@
+/*
+ * Hermes.h
+ *
+ * Generated with
+ * sdef /Applications/Hermes.app | sdp -fh --basename Hermes
+ */
+
+#import <AppKit/AppKit.h>
+#import <ScriptingBridge/ScriptingBridge.h>
+
+
+@class HermesApplication, HermesSong, HermesStation;
+
+// Legal player states
+enum HermesPlayerStates {
+	HermesPlayerStatesStopped = 'stop' /* Player is stopped */,
+	HermesPlayerStatesPlaying = 'play' /* Player is playing */,
+	HermesPlayerStatesPaused = 'paus' /* Player is paused */
+};
+typedef enum HermesPlayerStates HermesPlayerStates;
+
+
+
+/*
+ * Hermes Suite
+ */
+
+// The Pandora player.
+@interface HermesApplication : SBApplication
+
+- (SBElementArray<HermesStation *> *) stations;
+
+@property NSInteger playbackVolume;  // The current playback volume (0–100).
+@property HermesPlayerStates playbackState;  // The current playback state.
+@property (readonly) double playbackPosition;  // The current song’s playback position, in seconds.
+@property (readonly) double currentSongDuration;  // The duration (length) of the current song, in seconds.
+@property (copy) HermesStation *currentStation;  // The currently selected Pandora station.
+@property (copy, readonly) HermesSong *currentSong;  // The currently playing (or paused) Pandora song (WARNING: This is an invalid reference in current versions of Hermes; you must access the current song’s properties individually or as a group directly instead.)
+
+- (void) playpause;  // Play the current song if it is paused; pause the current song if it is playing.
+- (void) pause;  // Pause the currently playing song.
+- (void) play;  // Resume playing the current song.
+- (void) nextSong;  // Skip to the next song on the current station.
+- (void) thumbsUp;  // Tell Pandora you like the current song.
+- (void) thumbsDown;  // Tell Pandora you don’t like the current song.
+- (void) tiredOfSong;  // Tell Pandora you’re tired of the current song.
+- (void) increaseVolume;  // Increase the playback volume.
+- (void) decreaseVolume;  // Decrease the playback volume.
+- (void) maximizeVolume;  // Set the playback volume to its maximum level.
+- (void) mute;  // Mutes playback, saving the current volume level.
+- (void) unmute;  // Restores the volume to the level prior to muting.
+
+@end
+
+// A Pandora song (track).
+@interface HermesSong : SBObject
+
+@property (copy, readonly) NSString *title;  // The song’s title.
+@property (copy, readonly) NSString *artist;  // The song’s artist.
+@property (copy, readonly) NSString *album;  // The song’s album.
+@property (copy, readonly) NSString *artworkURL;  // An image URL for the album’s cover artwork.
+@property (readonly) NSInteger rating;  // The song’s numeric rating.
+@property (copy, readonly) NSString *albumURL;  // A Pandora URL for more information on the album.
+@property (copy, readonly) NSString *artistURL;  // A Pandora URL for more information on the artist.
+@property (copy, readonly) NSString *trackURL;  // A Pandora URL for more information on the track.
+
+
+@end
+
+// A Pandora station.
+@interface HermesStation : SBObject
+
+@property (copy, readonly) NSString *name;  // The station’s name.
+@property (copy, readonly) NSString *stationID;  // The station’s ID.
+
+
+@end
+

BGMApp/BGMApp/Music Players/VOX.h

@@ -1,8 +1,8 @@
 /*
- * Vox.h
+ * VOX.h
  *
  * Generated with
- * sdef /Applications/Vox.app | sdp -fh --basename Vox
+ * sdef /Applications/VOX.app | sdp -fh --basename VOX
  */
 
 #import <AppKit/AppKit.h>

BGMApp/BGMApp/Preferences/BGMAboutPanel.h

@@ -14,45 +14,30 @@
 // along with Background Music. If not, see <http://www.gnu.org/licenses/>.
 
 //
-//  BGMAppTests.m
-//  BGMAppTests
+//  BGMAboutPanel.h
+//  BGMApp
 //
 //  Copyright © 2016 Kyle Neideck
 //
+//  This class manages the "About Background Music" window.
+//
 
+// System Includes
 #import <Cocoa/Cocoa.h>
-#import <XCTest/XCTest.h>
 
 
-@interface BGMAppTests : XCTestCase
+NS_ASSUME_NONNULL_BEGIN
+
+@interface BGMAboutPanel : NSObject
+
+- (instancetype)initWithPanel:(NSPanel*)inAboutPanel licenseView:(NSTextView*)inLicenseView;
+- (void) show;
 
 @end
 
-@implementation BGMAppTests
-
-// TODO: More than no tests
-
-- (void)setUp {
-    [super setUp];
-    // Put setup code here. This method is called before the invocation of each test method in the class.
-}
-
-- (void)tearDown {
-    // Put teardown code here. This method is called after the invocation of each test method in the class.
-    [super tearDown];
-}
-
-- (void)testExample {
-    // This is an example of a functional test case.
-    XCTAssert(YES, @"Pass");
-}
-
-- (void)testPerformanceExample {
-    // This is an example of a performance test case.
-    [self measureBlock:^{
-        // Put the code you want to measure the time of here.
-    }];
-}
 
+@interface BGMLinkField : NSTextField
 @end
 
+NS_ASSUME_NONNULL_END
+

BGMApp/BGMApp/Preferences/BGMAboutPanel.m

@@ -0,0 +1,144 @@
+// This file is part of Background Music.
+//
+// Background Music is free software: you can redistribute it and/or
+// modify it under the terms of the GNU General Public License as
+// published by the Free Software Foundation, either version 2 of the
+// License, or (at your option) any later version.
+//
+// Background Music is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Background Music. If not, see <http://www.gnu.org/licenses/>.
+
+//
+//  BGMAboutPanel.m
+//  BGMApp
+//
+//  Copyright © 2016 Kyle Neideck
+//
+
+// Self Include
+#import "BGMAboutPanel.h"
+
+// Local Includes
+#import "BGM_Types.h"
+
+// PublicUtility Includes
+#undef CoreAudio_ThreadStampMessages
+#define CoreAudio_ThreadStampMessages 0  // Requires C++
+#include "CADebugMacros.h"
+
+
+NS_ASSUME_NONNULL_BEGIN
+
+static NSInteger const kVersionLabelTag = 1;
+static NSInteger const kCopyrightLabelTag = 2;
+static NSInteger const kProjectWebsiteLabelTag = 3;
+
+@implementation BGMAboutPanel {
+    NSPanel* aboutPanel;
+    
+    NSTextField* versionLabel;
+    NSTextField* copyrightLabel;
+    NSTextField* websiteLabel;
+    
+    NSTextView* licenseView;
+}
+
+- (instancetype)initWithPanel:(NSPanel*)inAboutPanel licenseView:(NSTextView*)inLicenseView {
+    if ((self = [super init])) {
+        aboutPanel = inAboutPanel;
+        
+        versionLabel = [[aboutPanel contentView] viewWithTag:kVersionLabelTag];
+        copyrightLabel = [[aboutPanel contentView] viewWithTag:kCopyrightLabelTag];
+        websiteLabel = [[aboutPanel contentView] viewWithTag:kProjectWebsiteLabelTag];
+        
+        licenseView = inLicenseView;
+        
+        [self initAboutPanel];
+    }
+    
+    return self;
+}
+
+- (void) initAboutPanel {
+    // Set up the About Background Music window
+    
+    NSBundle* bundle = [NSBundle mainBundle];
+    
+    if (bundle == nil) {
+        NSLog(@"Background Music: BGMAboutPanel::initAboutPanel: Could not find main bundle");
+    } else {
+        // Version number label
+        NSString* __nullable version =
+            [[bundle infoDictionary] objectForKey:@"CFBundleShortVersionString"];
+        
+        if (version) {
+            versionLabel.stringValue = [NSString stringWithFormat:@"Version %@", version];
+        }
+        
+        // Copyright notice label
+        NSString* __nullable copyrightNotice =
+            [[bundle infoDictionary] objectForKey:@"NSHumanReadableCopyright"];
+        
+        if (copyrightNotice) {
+            copyrightLabel.stringValue = (NSString*)copyrightNotice;
+        }
+        
+        // Project website link label
+        websiteLabel.selectable = YES;
+        websiteLabel.allowsEditingTextAttributes = YES;
+        
+        NSString* projectURL = [NSString stringWithUTF8String:kBGMProjectURL];
+        websiteLabel.attributedStringValue =
+            [[NSAttributedString alloc] initWithString:projectURL
+                                            attributes:@{ NSLinkAttributeName: projectURL,
+                                                          NSFontAttributeName: websiteLabel.font }];
+        
+        // Load the text of the license into the text view
+        NSString* __nullable licensePath = [bundle pathForResource:@"LICENSE" ofType:nil];
+        
+        NSError* err;
+        NSString* __nullable licenseStr = (!licensePath ? nil :
+            [NSString stringWithContentsOfFile:(NSString*)licensePath
+                                      encoding:NSASCIIStringEncoding
+                                         error:&err]);
+        
+        if (err || !licenseStr || [licenseStr isEqualToString:@""]) {
+            NSLog(@"Error loading license file: %@", err);
+            licenseStr = @"Error: could not open license file.";
+        }
+        
+        licenseView.string = licenseStr;
+        
+        NSFont* __nullable font = [NSFont fontWithName:@"Andale Mono" size:0.0];
+        if (font) {
+            licenseView.textStorage.font = font;
+        }
+    }
+}
+
+- (void) show {
+    DebugMsg("BGMAboutPanel::showAboutPanel: Opening \"About Background Music\" panel");
+    [NSApp activateIgnoringOtherApps:YES];
+    [aboutPanel setIsVisible:YES];
+    [aboutPanel makeKeyAndOrderFront:self];
+}
+
+@end
+
+@implementation BGMLinkField
+
+- (void) resetCursorRects {
+    // Change the mouse cursor when hovering over the link. (It does change by default, but only after
+    // you've clicked it once.)
+    [self addCursorRect:self.bounds cursor:[NSCursor pointingHandCursor]];
+}
+
+@end
+
+NS_ASSUME_NONNULL_END
+

BGMApp/BGMApp/Preferences/BGMAutoPauseMusicPrefs.h

@@ -20,21 +20,23 @@
 //  Copyright © 2016 Kyle Neideck
 //
 
-// PublicUtility Includes
-#include "BGMAudioDeviceManager.h"
+// Local Includes
+#import "BGMAudioDeviceManager.h"
+#import "BGMMusicPlayers.h"
 
 // System Includes
-#import <AppKit/AppKit.h>
+#import <Cocoa/Cocoa.h>
 
 
+#pragma clang assume_nonnull begin
+
 @interface BGMAutoPauseMusicPrefs : NSObject
 
-// Note that toggleAutoPauseMusicMenuItem is the item in the main menu that enables/disables auto-pausing, rather than the
-// disabled "Auto-pause" menu item in the preferences menu that acts as a section heading. This class updates the text of
-// toggleAutoPauseMusicMenuItem when the user changes the music player.
 - (id) initWithPreferencesMenu:(NSMenu*)inPrefsMenu
-  toggleAutoPauseMusicMenuItem:(NSMenuItem*)inToggleAutoPauseMusicMenuItem
-                  audioDevices:(BGMAudioDeviceManager*)inAudioDevices;
+                  audioDevices:(BGMAudioDeviceManager*)inAudioDevices
+                  musicPlayers:(BGMMusicPlayers*)inMusicPlayers;
 
 @end
 
+#pragma clang assume_nonnull end 
+

BGMApp/BGMApp/Preferences/BGMAutoPauseMusicPrefs.mm

@@ -24,182 +24,94 @@
 #import "BGMAutoPauseMusicPrefs.h"
 
 // Local Includes
-#include "BGM_Types.h"
+#import "BGM_Types.h"
 #import "BGMMusicPlayer.h"
 
 
-static NSString* const kToggleAutoPauseMusicMenuItemTitleFormat = @"Auto-pause %@";
+#pragma clang assume_nonnull begin
+
 static float const kMenuItemIconScalingFactor = 1.15f;
 static NSInteger const kPrefsMenuAutoPauseHeaderTag = 1;
 
 @implementation BGMAutoPauseMusicPrefs {
     BGMAudioDeviceManager* audioDevices;
-    NSMenuItem* toggleAutoPauseMusicMenuItem;
+    BGMMusicPlayers* musicPlayers;
     NSMenu* prefsMenu;
     NSArray<NSMenuItem*>* musicPlayerMenuItems;
 }
 
 - (id) initWithPreferencesMenu:(NSMenu*)inPrefsMenu
-  toggleAutoPauseMusicMenuItem:(NSMenuItem*)inToggleAutoPauseMusicMenuItem
-                  audioDevices:(BGMAudioDeviceManager*)inAudioDevices {
+                  audioDevices:(BGMAudioDeviceManager*)inAudioDevices
+                  musicPlayers:(BGMMusicPlayers*)inMusicPlayers {
     if ((self = [super init])) {
         prefsMenu = inPrefsMenu;
-        toggleAutoPauseMusicMenuItem = inToggleAutoPauseMusicMenuItem;
         audioDevices = inAudioDevices;
+        musicPlayers = inMusicPlayers;
+        
         musicPlayerMenuItems = @[];
         
-        [self initSelectedMusicPlayer];
-        [self initMenuSection];
-        [self updateMenuItemTitle];
+        [self initPreferencesMenuSection];
     }
     
     return self;
 }
 
-- (void) initSelectedMusicPlayer {
-    // TODO: It would make more sense to either just save the music player setting in the User Defaults (the same way AppDelegate saves
-    //       whether auto-pause is enabled) or to send a "musicPlayerID" to the driver, which would only be used by BGMApp. If the latter,
-    //       we might as well save the auto-pause setting on the driver as well just so all the settings are saved in the same place.
-    
-    // Get the currently selected music player from the driver and update the global in BGMMusicPlayerBase
-    
-    // The bundle ID and PID set on the driver
-    CFNumberRef selectedPID = static_cast<CFNumberRef>([audioDevices bgmDevice].GetPropertyData_CFType(kBGMMusicPlayerProcessIDAddress));
-    CFStringRef selectedBundleID = [audioDevices bgmDevice].GetPropertyData_CFString(kBGMMusicPlayerBundleIDAddress);
-    
-    DebugMsg("BGMAutoPauseMusicPrefs::initSelectedMusicPlayer: Music player on BGMDriver: bundleID=%s PID=%s",
-             selectedBundleID == NULL ? "null" : CFStringGetCStringPtr(selectedBundleID, kCFStringEncodingUTF8),
-             selectedPID == NULL ? "null" : [[(__bridge NSNumber*)selectedPID stringValue] UTF8String]);
-    
-    // If no music player is set on the driver, set it to the one set in the app and return
-    if ((selectedBundleID == NULL || CFEqual(selectedBundleID, CFSTR(""))) &&
-        (selectedPID == NULL || [(__bridge NSNumber*)selectedPID intValue] < 1)) {
-        [self updateBGMDevice];
-        return;
-    }
-    
-    // The IDs set in the app, which will be updated if they don't match the values from the driver
-    CFNumberRef selectedPIDInBGMApp = [[BGMMusicPlayerBase selectedMusicPlayer] pid];
-    CFStringRef selectedBundleIDInBGMApp = [[[BGMMusicPlayerBase selectedMusicPlayer] class] bundleID];
-    
-    // Return early if the music player selected in the app already matches the driver
-    if ((selectedPID != NULL && selectedPIDInBGMApp != NULL && CFEqual(selectedPID, selectedPIDInBGMApp)) ||
-        (selectedBundleID != NULL && selectedBundleIDInBGMApp != NULL && CFEqual(selectedBundleID, selectedBundleIDInBGMApp))) {
-        return;
-    }
-    
-    // Check each selectable music player
-    for (Class mpClass in [BGMMusicPlayerBase musicPlayerClasses]) {
-        // Look for a running instance of the music player by PID
-        if (selectedPID != NULL &&
-            [mpClass respondsToSelector:@selector(pidsOfRunningInstances)] &&
-            [mpClass respondsToSelector:@selector(initWithPIDFromNSNumber:)]) {
-            NSArray<NSNumber*>* mpPIDs = [mpClass pidsOfRunningInstances];
-            for (NSNumber* mpPID in mpPIDs) {
-                if (CFEqual((__bridge CFNumberRef)mpPID, selectedPID)) {
-                    DebugMsg("BGMAutoPauseMusicPrefs::initSelectedMusicPlayer: Selected music player on driver was %s (found by pid)",
-                             [[mpClass name] UTF8String]);
-                    [BGMMusicPlayerBase setSelectedMusicPlayer:[[mpClass alloc] initWithPIDFromNSNumber:mpPID]];
-                    return;
-                }
-            }
-        }
-        
-        // Check by bundle ID
-        CFStringRef mpBundleID = [mpClass bundleID];
-        if (selectedBundleID != NULL &&
-            mpBundleID != NULL &&
-            CFEqual(mpBundleID, selectedBundleID)) {
-            // Found the selected music player. Update the app to match the driver and return.
-            DebugMsg("BGMAutoPauseMusicPrefs::initSelectedMusicPlayer: Selected music player on driver was %s",
-                     [[mpClass name] UTF8String]);
-            
-            [BGMMusicPlayerBase setSelectedMusicPlayer:[mpClass new]];
-            return;
-        }
-    }
-}
-
-- (void) initMenuSection {
-    // Add the menu items related to auto-pausing music to the settings submenu
+- (void) initPreferencesMenuSection {
+    // Add the menu items related to auto-pausing music to the Preferences submenu
     
     // The index to start inserting music player menu items at
     NSInteger musicPlayerItemsIndex = [prefsMenu indexOfItemWithTag:kPrefsMenuAutoPauseHeaderTag] + 1;
     
-    // Insert the options to change the music player app
-    for (Class musicPlayerClass in [BGMMusicPlayerBase musicPlayerClasses]) {
-        NSMenuItem* menuItem = [prefsMenu insertItemWithTitle:[musicPlayerClass name]
+    // Insert the menu items used to change the music player app.
+    for (id<BGMMusicPlayer> musicPlayer in musicPlayers.musicPlayers) {
+        // Create an menu item for this music player.
+        NSMenuItem* menuItem = [prefsMenu insertItemWithTitle:musicPlayer.name
                                                        action:@selector(handleMusicPlayerChange:)
                                                 keyEquivalent:@""
-                                                       atIndex:musicPlayerItemsIndex];
+                                                      atIndex:musicPlayerItemsIndex];
         
         musicPlayerMenuItems = [musicPlayerMenuItems arrayByAddingObject:menuItem];
         
-        // Create an instance for this music player and associate it with the menu item
-        [menuItem setRepresentedObject:[musicPlayerClass new]];
+        // Associate the music player with the menu item
+        menuItem.representedObject = musicPlayer;
         
-        // Show the default music player as selected
-        if (musicPlayerClass == [[BGMMusicPlayerBase selectedMusicPlayer] class]) {
-            [menuItem setState:NSOnState];
+        // Show the menu item for the selected music player as selected
+        if (musicPlayers.selectedMusicPlayer == musicPlayer) {
+            menuItem.state = NSOnState;
         }
         
-        // Set the item's icon
-        NSImage* icon = [musicPlayerClass icon];
+        // Set the menu item's icon
+        NSImage* __nullable icon = musicPlayer.icon;
         if (icon == nil) {
             // Set a blank icon so the text lines up
             icon = [NSImage new];
         }
-        // Size the icon relative to the size of the item's text
-        CGFloat length = [[NSFont menuBarFontOfSize:0] pointSize] * kMenuItemIconScalingFactor;
-        [icon setSize:NSMakeSize(length, length)];
-        [menuItem setImage:icon];
         
-        [menuItem setTarget:self];
-        [menuItem setIndentationLevel:1];
+        // Size the icon relative to the size of the item's text
+        CGFloat length = [NSFont menuBarFontOfSize:0].pointSize * kMenuItemIconScalingFactor;
+        icon.size = NSMakeSize(length, length);
+        menuItem.image = icon;
+        
+        menuItem.target = self;
+        menuItem.indentationLevel = 1;
     }
 }
 
 - (void) handleMusicPlayerChange:(NSMenuItem*)sender {
     // Set the new music player as the selected music player
-    BGMMusicPlayer* musicPlayer = [sender representedObject];
-    assert(musicPlayer != nil);
-    [BGMMusicPlayerBase setSelectedMusicPlayer:musicPlayer];
+    id<BGMMusicPlayer> musicPlayer = sender.representedObject;
+    NSAssert(musicPlayer, @"BGMAutoPauseMusicPrefs::handleMusicPlayerChange: !musicPlayer");
     
-    // Select/Deselect the menu items
+    musicPlayers.selectedMusicPlayer = musicPlayer;
+    
+    // Select/deselect the menu items
     for (NSMenuItem* item in musicPlayerMenuItems) {
-        BOOL isNewlySelectedMusicPlayer = item == sender;
-        [item setState:(isNewlySelectedMusicPlayer ? NSOnState : NSOffState)];
+        BOOL isNewlySelectedMusicPlayer = (item == sender);
+        item.state = (isNewlySelectedMusicPlayer ? NSOnState : NSOffState);
     }
-    
-    [self updateMenuItemTitle];
-    [self updateBGMDevice];
-}
-
-- (void) updateBGMDevice {
-    // Send the music player's PID or bundle ID to the driver
-    
-    DebugMsg("BGMAutoPauseMusicPrefs::updateBGMDevice: Setting the music player to %s on the driver",
-             [[[[BGMMusicPlayer selectedMusicPlayer] class] name] UTF8String]);
-    
-    CFNumberRef __nullable pid = [[BGMMusicPlayer selectedMusicPlayer] pid];
-    
-    if (pid != NULL) {
-        [audioDevices bgmDevice].SetPropertyData_CFType(kBGMMusicPlayerProcessIDAddress, pid);
-    } else {
-        CFStringRef __nullable bundleID = [[[BGMMusicPlayer selectedMusicPlayer] class] bundleID];
-        
-        if (bundleID != NULL) {
-            [audioDevices bgmDevice].SetPropertyData_CFString(kBGMMusicPlayerBundleIDAddress, bundleID);
-        }
-    }
-}
-
-- (void) updateMenuItemTitle {
-    // Set the title of the Auto-pause Music menu item, including the name of the selected music player
-    NSString* musicPlayerName = [[[BGMMusicPlayer selectedMusicPlayer] class] name];
-    NSString* title = [NSString stringWithFormat:kToggleAutoPauseMusicMenuItemTitleFormat, musicPlayerName];
-    [toggleAutoPauseMusicMenuItem setTitle:title];
 }
 
 @end
 
+#pragma clang assume_nonnull end
+

BGMApp/BGMApp/Preferences/BGMOutputDevicePrefs.h

@@ -27,6 +27,8 @@
 #import <AppKit/AppKit.h>
 
 
+#pragma clang assume_nonnull begin
+
 @interface BGMOutputDevicePrefs : NSObject
 
 - (id) initWithAudioDevices:(BGMAudioDeviceManager*)inAudioDevices;
@@ -34,3 +36,5 @@
 
 @end
 
+#pragma clang assume_nonnull end
+

BGMApp/BGMApp/Preferences/BGMOutputDevicePrefs.mm

@@ -23,12 +23,19 @@
 // Self Include
 #import "BGMOutputDevicePrefs.h"
 
+// Local Includes
+#import "BGM_Utils.h"
+#import "BGM_Types.h"
+#import "BGMAudioDevice.h"
+
 // PublicUtility Includes
 #include "CAHALAudioSystemObject.h"
 #include "CAHALAudioDevice.h"
 #include "CAAutoDisposer.h"
 
 
+#pragma clang assume_nonnull begin
+
 static NSInteger const kOutputDeviceMenuItemTag = 2;
 
 @implementation BGMOutputDevicePrefs {
@@ -50,58 +57,209 @@ static NSInteger const kOutputDeviceMenuItemTag = 2;
     for (NSMenuItem* item in outputDeviceMenuItems) {
         [prefsMenu removeItem:item];
     }
-    [outputDeviceMenuItems removeAllObjects];
     
-    // Insert menu items after the item for the "Output Device" heading
-    const NSInteger menuItemsIdx = [prefsMenu indexOfItemWithTag:kOutputDeviceMenuItemTag] + 1;
+    [outputDeviceMenuItems removeAllObjects];
     
     // Add a menu item for each output device
     CAHALAudioSystemObject audioSystem;
     UInt32 numDevices = audioSystem.GetNumberAudioDevices();
+    
     if (numDevices > 0) {
         CAAutoArrayDelete<AudioObjectID> devices(numDevices);
         audioSystem.GetAudioDevices(numDevices, devices);
         
         for (UInt32 i = 0; i < numDevices; i++) {
-            CAHALAudioDevice device(devices[i]);
-            BOOL hasOutputChannels = device.GetTotalNumberChannels(/* inIsInput = */ false) > 0;
-            
-            if (device.GetObjectID() != [audioDevices bgmDevice].GetObjectID() && hasOutputChannels) {
-                NSString* deviceName = CFBridgingRelease(device.CopyName());
-                NSMenuItem* item = [[NSMenuItem alloc] initWithTitle:deviceName
-                                                              action:@selector(outputDeviceWasChanged:)
-                                                       keyEquivalent:@""];
-                
-                BOOL isSelected = [audioDevices isOutputDevice:device.GetObjectID()];
-                [item setState:(isSelected ? NSOnState : NSOffState)];
-                [item setTarget:self];
-                [item setIndentationLevel:1];
-                [item setRepresentedObject:[NSNumber numberWithUnsignedInt:device.GetObjectID()]];
-                
-                [prefsMenu insertItem:item atIndex:menuItemsIdx];
-                
-                [outputDeviceMenuItems addObject:item];
-            }
+            [self insertMenuItemsForDevice:devices[i] preferencesMenu:prefsMenu];
         }
     }
 }
 
-- (void) outputDeviceWasChanged:(NSMenuItem*)menuItem {
-    BOOL success = [audioDevices setOutputDeviceWithID:[[menuItem representedObject] unsignedIntValue] revertOnFailure:YES];
+- (void) insertMenuItemsForDevice:(BGMAudioDevice)device preferencesMenu:(NSMenu*)prefsMenu {
+    // Insert menu items after the item for the "Output Device" heading.
+    const NSInteger menuItemsIdx = [prefsMenu indexOfItemWithTag:kOutputDeviceMenuItemTag] + 1;
+
+    BOOL canBeOutputDevice = YES;
+    BGMLogAndSwallowExceptions("BGMOutputDevicePrefs::insertMenuItemsForDevice", ([&] {
+        canBeOutputDevice = device.CanBeOutputDeviceInBGMApp();
+    }));
+
+    if (canBeOutputDevice) {
+        for (NSMenuItem* item : [self createMenuItemsForDevice:device]) {
+            [prefsMenu insertItem:item atIndex:menuItemsIdx];
+            [outputDeviceMenuItems addObject:item];
+        }
+    }
+}
+
+- (NSArray<NSMenuItem*>*) createMenuItemsForDevice:(CAHALAudioDevice)device {
+    // We fill this array with a menu item for each output device (or each data source for each device) on
+    // the system.
+    NSMutableArray<NSMenuItem*>* items = [NSMutableArray new];
+
+    AudioObjectPropertyScope scope = kAudioObjectPropertyScopeOutput;
+    UInt32 channel = 0;  // 0 is the master channel.
     
-    if (!success) {
-        // Couldn't change the output device, so show a warning and change the menu selection back
-        NSAlert* alert = [NSAlert new];
-        NSString* deviceName = [menuItem title];
-        [alert setMessageText:[NSString stringWithFormat:@"Failed to set %@ as the output device", deviceName]];
-        [alert setInformativeText:@"This is probably a bug. Feel free to report it."];
-        [alert runModal];
+    // If the device has data sources, create a menu item for each. Otherwise, create a single menu item
+    // for the device. This way the menu items' titles will be, for example, "Internal Speakers" rather
+    // than "Built-in Output".
+    //
+    // TODO: Handle data destinations as well? I don't have (or know of) any hardware with them.
+    // TODO: Use the current data source's name when the control isn't settable, but only add one menu item.
+    UInt32 numDataSources = 0;
+    
+    BGMLogAndSwallowExceptions("BGMOutputDevicePrefs::createMenuItemsForDevice", [&] {
+        if (device.HasDataSourceControl(scope, channel) &&
+                device.DataSourceControlIsSettable(scope, channel)) {
+            numDataSources = device.GetNumberAvailableDataSources(scope, channel);
+        }
+    });
+    
+    if (numDataSources > 0) {
+        UInt32 dataSourceIDs[numDataSources];
+        // This call updates numDataSources to the real number of IDs it added to our array.
+        device.GetAvailableDataSources(scope, channel, numDataSources, dataSourceIDs);
         
-        [menuItem setState:NSOffState];
+        for (UInt32 i = 0; i < numDataSources; i++) {
+            DebugMsg("BGMOutputDevicePrefs::createMenuItemsForDevice: Creating item. %s%u %s%u",
+                     "Device ID:", device.GetObjectID(),
+                     ", Data source ID:", dataSourceIDs[i]);
+            
+            BGMLogAndSwallowExceptionsMsg("BGMOutputDevicePrefs::createMenuItemsForDevice", "(DS)", [&]() {
+                NSNumber* dataSourceID = [NSNumber numberWithUnsignedInt:dataSourceIDs[i]];
+                NSString* dataSourceName =
+                    CFBridgingRelease(device.CopyDataSourceNameForID(scope, channel, dataSourceIDs[i]));
+                NSString* deviceName = CFBridgingRelease(device.CopyName());
+                
+                [items addObject:[self createMenuItemForDevice:device
+                                                  dataSourceID:dataSourceID
+                                                         title:dataSourceName
+                                                       toolTip:deviceName]];
+            });
+        }
+    } else {
+        DebugMsg("BGMOutputDevicePrefs::createMenuItemsForDevice: Creating item. %s%u",
+                 "Device ID:", device.GetObjectID());
         
-        // TODO: Reselect previous menu item
+        BGMLogAndSwallowExceptions("BGMOutputDevicePrefs::createMenuItemsForDevice", ([&] {
+            [items addObject:[self createMenuItemForDevice:device
+                                              dataSourceID:nil
+                                                     title:CFBridgingRelease(device.CopyName())
+                                                   toolTip:nil]];
+        }));
+    }
+    
+    return items;
+}
+
+- (NSMenuItem*) createMenuItemForDevice:(CAHALAudioDevice)device
+                           dataSourceID:(NSNumber* __nullable)dataSourceID
+                                  title:(NSString* __nullable)title
+                                toolTip:(NSString* __nullable)toolTip {
+    // If we don't have a title, use the tool-tip text instead.
+    if (!title) {
+        title = (toolTip ? toolTip : @"");
+    }
+    
+    NSMenuItem* item = [[NSMenuItem alloc] initWithTitle:BGMNN(title)
+                                                  action:@selector(outputDeviceWasChanged:)
+                                           keyEquivalent:@""];
+    
+    // Add the AirPlay icon to the labels of AirPlay devices.
+    //
+    // TODO: Test this with real hardware that supports AirPlay. (I don't have any.)
+    BGMLogAndSwallowExceptions("BGMOutputDevicePrefs::createMenuItemForDevice", [&] {
+        if (device.GetTransportType() == kAudioDeviceTransportTypeAirPlay) {
+            item.image = [NSImage imageNamed:@"AirPlayIcon"];
+            
+            // Make the icon a "template image" so it gets drawn colour-inverted when it's highlighted or
+            // OS X is in dark mode.
+            [item.image setTemplate:YES];
+        }
+    });
+    
+    // The menu item should be selected if it's the menu item for the current output device. If the device
+    // has data sources, only the menu item for the current data source should be selected.
+    BOOL isSelected =
+        [audioDevices isOutputDevice:device.GetObjectID()] &&
+            (!dataSourceID || [audioDevices isOutputDataSource:[dataSourceID unsignedIntValue]]);
+    
+    item.state = (isSelected ? NSOnState : NSOffState);
+    item.toolTip = toolTip;
+    item.target = self;
+    item.indentationLevel = 1;
+    item.representedObject = @{ @"deviceID": [NSNumber numberWithUnsignedInt:device.GetObjectID()],
+                                @"dataSourceID": dataSourceID ? BGMNN(dataSourceID) : [NSNull null] };
+    
+    return item;
+}
+
+- (void) outputDeviceWasChanged:(NSMenuItem*)menuItem {
+    DebugMsg("BGMOutputDevicePrefs::outputDeviceWasChanged: '%s' menu item selected",
+             [menuItem.title UTF8String]);
+    
+    // Make sure the menu item is actually for an output device.
+    if (![outputDeviceMenuItems containsObject:menuItem]) {
+        return;
+    }
+    
+    // Change to the new output device.
+    AudioDeviceID newDeviceID = [[menuItem representedObject][@"deviceID"] unsignedIntValue];
+    id newDataSourceID = [menuItem representedObject][@"dataSourceID"];
+    
+    BOOL changingDevice = ![audioDevices isOutputDevice:newDeviceID];
+    BOOL changingDataSource =
+        (newDataSourceID != [NSNull null]) &&
+            ![audioDevices isOutputDataSource:[newDataSourceID unsignedIntValue]];
+
+    if (changingDevice || changingDataSource) {
+        NSString* deviceName =
+            menuItem.toolTip ?
+                [NSString stringWithFormat:@"%@ (%@)", menuItem.title, menuItem.toolTip] :
+                menuItem.title;
+        
+        // Dispatched because it usually blocks. (Note that we're using QOS_CLASS_USER_INITIATED
+        // rather than QOS_CLASS_USER_INTERACTIVE.)
+        dispatch_async(dispatch_get_global_queue(QOS_CLASS_USER_INITIATED, 0), ^{
+            [self changeToOutputDevice:newDeviceID
+                         newDataSource:newDataSourceID
+                            deviceName:deviceName];
+        });
+    }
+}
+
+- (void) changeToOutputDevice:(AudioDeviceID)deviceID
+                newDataSource:(id)dataSourceID
+                   deviceName:(NSString*)deviceName {
+    NSError* __nullable error;
+    
+    if (dataSourceID == [NSNull null]) {
+        error = [audioDevices setOutputDeviceWithID:deviceID revertOnFailure:YES];
+    } else {
+        error = [audioDevices setOutputDeviceWithID:deviceID
+                                       dataSourceID:[dataSourceID unsignedIntValue]
+                                    revertOnFailure:YES];
+    }
+    
+    if (error) {
+        // Couldn't change the output device, so show a warning. (No need to change the menu
+        // selection back because it gets repopulated every time it's opened.)
+        
+        // NSAlerts should only be shown on the main thread.
+        dispatch_async(dispatch_get_main_queue(), ^{
+            NSLog(@"Failed to set output device: %@", deviceName);
+            
+            NSAlert* alert = [NSAlert new];
+            
+            alert.messageText =
+                [NSString stringWithFormat:@"Failed to set %@ as the output device.", deviceName];
+            alert.informativeText = @"This is probably a bug. Feel free to report it.";
+            
+            [alert runModal];
+        });
     }
 }
 
 @end
 
+#pragma clang assume_nonnull end
+

BGMApp/BGMApp/Preferences/BGMPreferencesMenu.h

@@ -25,6 +25,7 @@
 
 // Local Includes
 #import "BGMAudioDeviceManager.h"
+#import "BGMMusicPlayers.h"
 
 // System Includes
 #import <Cocoa/Cocoa.h>
@@ -34,8 +35,9 @@ NS_ASSUME_NONNULL_BEGIN
 
 @interface BGMPreferencesMenu : NSObject <NSMenuDelegate>
 
-- (id) initWithbgmMenu:(NSMenu*)inBGMMenu
+- (id) initWithBGMMenu:(NSMenu*)inBGMMenu
           audioDevices:(BGMAudioDeviceManager*)inAudioDevices
+          musicPlayers:(BGMMusicPlayers*)inMusicPlayers
             aboutPanel:(NSPanel*)inAboutPanel
  aboutPanelLicenseView:(NSTextView*)inAboutPanelLicenseView;
 

BGMApp/BGMApp/Preferences/BGMPreferencesMenu.mm

@@ -26,105 +26,56 @@
 // Local Includes
 #import "BGMAutoPauseMusicPrefs.h"
 #import "BGMOutputDevicePrefs.h"
+#import "BGMAboutPanel.h"
 
 
 NS_ASSUME_NONNULL_BEGIN
 
 // Interface Builder tags
-static NSInteger const kToggleAutoPauseMusicMenuItemTag = 2;
-
 static NSInteger const kPreferencesMenuItemTag = 1;
 static NSInteger const kAboutPanelMenuItemTag = 3;
 
-static NSInteger const kAboutPanelVersionLabelTag = 1;
-static NSInteger const kAboutPanelCopyrightLabelTag = 2;
-
 @implementation BGMPreferencesMenu {
-    BGMAudioDeviceManager* audioDevices;
-    
     // Menu sections
     BGMAutoPauseMusicPrefs* autoPauseMusicPrefs;
     BGMOutputDevicePrefs* outputDevicePrefs;
     
-    // About Background Music window
-    NSPanel* aboutPanel;
-    NSTextField* aboutPanelVersionLabel;
-    NSTextField* aboutPanelCopyrightLabel;
-    NSTextView* aboutPanelLicenceView;
+    // The About Background Music window
+    BGMAboutPanel* aboutPanel;
 }
 
-- (id) initWithbgmMenu:(NSMenu*)inBGMMenu
+- (id) initWithBGMMenu:(NSMenu*)inBGMMenu
           audioDevices:(BGMAudioDeviceManager*)inAudioDevices
+          musicPlayers:(BGMMusicPlayers*)inMusicPlayers
             aboutPanel:(NSPanel*)inAboutPanel
  aboutPanelLicenseView:(NSTextView*)inAboutPanelLicenseView {
     if ((self = [super init])) {
-        audioDevices = inAudioDevices;
-        aboutPanel = inAboutPanel;
-        
-        aboutPanelVersionLabel = [[aboutPanel contentView] viewWithTag:kAboutPanelVersionLabelTag];
-        aboutPanelCopyrightLabel = [[aboutPanel contentView] viewWithTag:kAboutPanelCopyrightLabelTag];
-        aboutPanelLicenceView = inAboutPanelLicenseView;
-
         NSMenu* prefsMenu = [[inBGMMenu itemWithTag:kPreferencesMenuItemTag] submenu];
         [prefsMenu setDelegate:self];
         
-        NSMenuItem* toggleAutoPauseMusicMenuItem = [inBGMMenu itemWithTag:kToggleAutoPauseMusicMenuItemTag];
         autoPauseMusicPrefs = [[BGMAutoPauseMusicPrefs alloc] initWithPreferencesMenu:prefsMenu
-                                                         toggleAutoPauseMusicMenuItem:toggleAutoPauseMusicMenuItem
-                                                                         audioDevices:audioDevices];
+                                                                         audioDevices:inAudioDevices
+                                                                         musicPlayers:inMusicPlayers];
         
-        outputDevicePrefs = [[BGMOutputDevicePrefs alloc] initWithAudioDevices:audioDevices];
+        outputDevicePrefs = [[BGMOutputDevicePrefs alloc] initWithAudioDevices:inAudioDevices];
+        
+        aboutPanel = [[BGMAboutPanel alloc] initWithPanel:inAboutPanel licenseView:inAboutPanelLicenseView];
         
         // Set up the "About Background Music" menu item
         NSMenuItem* aboutMenuItem = [prefsMenu itemWithTag:kAboutPanelMenuItemTag];
-        [aboutMenuItem setTarget:self];
-        [aboutMenuItem setAction:@selector(showAboutPanel)];
-        
-        [self initAboutPanel];
+        [aboutMenuItem setTarget:aboutPanel];
+        [aboutMenuItem setAction:@selector(show)];
     }
     
     return self;
 }
 
-- (void) initAboutPanel {
-    // Set up the About Background Music window
-    
-    NSBundle* bundle = [NSBundle mainBundle];
-    
-    if (bundle == nil) {
-        LogWarning("Background Music: BGMPreferencesMenu::initAboutPanel: Could not find main bundle");
-    } else {
-        // Version number label
-        NSString* version = [[bundle infoDictionary] objectForKey:@"CFBundleShortVersionString"];
-        [aboutPanelVersionLabel setStringValue:[NSString stringWithFormat:@"Version %@", version]];
-        
-        // Copyright notice label
-        NSString* copyrightNotice = [[bundle infoDictionary] objectForKey:@"NSHumanReadableCopyright"];
-        [aboutPanelCopyrightLabel setStringValue:copyrightNotice];
-        
-        // Load the text of the license into the text view
-        NSString* licensePath = [bundle pathForResource:@"LICENSE" ofType:nil];
-        NSError* err;
-        NSString* licenseStr = [NSString stringWithContentsOfFile:licensePath encoding:NSASCIIStringEncoding error:&err];
-        if (err != nil || [licenseStr isEqualToString:@""]) {
-            NSLog(@"Error loading license file: %@", err);
-            licenseStr = @"Error: could not open license file.";
-        }
-        [aboutPanelLicenceView setString:licenseStr];
-    }
-}
+#pragma mark NSMenuDelegate
 
 - (void) menuNeedsUpdate:(NSMenu*)menu {
     [outputDevicePrefs populatePreferencesMenu:menu];
 }
 
-- (void) showAboutPanel {
-    DebugMsg("BGMPreferencesMenu::showAboutPanel: Opening \"About Background Music\" panel");
-    [NSApp activateIgnoringOtherApps:YES];
-    [aboutPanel setIsVisible:YES];
-    [aboutPanel makeKeyAndOrderFront:self];
-}
-
 @end
 
 NS_ASSUME_NONNULL_END

BGMApp/BGMApp/Scripting/BGMASOutputDevice.h

@@ -0,0 +1,46 @@
+// This file is part of Background Music.
+//
+// Background Music is free software: you can redistribute it and/or
+// modify it under the terms of the GNU General Public License as
+// published by the Free Software Foundation, either version 2 of the
+// License, or (at your option) any later version.
+//
+// Background Music is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Background Music. If not, see <http://www.gnu.org/licenses/>.
+
+//
+//  BGMASOutputDevice.h
+//  BGMApp
+//
+//  Copyright © 2017 Kyle Neideck
+//
+//  An AppleScript class for the output devices that can be selected in the preferences menu.
+//
+
+// Local Includes
+#import "BGMAudioDeviceManager.h"
+
+// System Includes
+#import <Foundation/Foundation.h>
+
+
+#pragma clang assume_nonnull begin
+
+@interface BGMASOutputDevice : NSObject
+
+- (instancetype) initWithAudioObjectID:(AudioObjectID)objID
+                          audioDevices:(BGMAudioDeviceManager*)devices
+                       parentSpecifier:(NSScriptObjectSpecifier* __nullable)parentSpecifier;
+
+@property (readonly) NSString* name;
+@property BOOL selected;  // is this the device to be used for audio output?
+
+@end
+
+#pragma clang assume_nonnull end
+

BGMApp/BGMApp/Scripting/BGMASOutputDevice.mm

@@ -0,0 +1,83 @@
+// This file is part of Background Music.
+//
+// Background Music is free software: you can redistribute it and/or
+// modify it under the terms of the GNU General Public License as
+// published by the Free Software Foundation, either version 2 of the
+// License, or (at your option) any later version.
+//
+// Background Music is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Background Music. If not, see <http://www.gnu.org/licenses/>.
+
+//
+//  BGMASOutputDevice.mm
+//  BGMApp
+//
+//  Copyright © 2017 Kyle Neideck
+//
+
+// Self Include
+#import "BGMASOutputDevice.h"
+
+// Local Includes
+#import "BGMAudioDevice.h"
+
+// PublicUtility Includes
+#import "CADebugMacros.h"
+
+
+#pragma clang assume_nonnull begin
+
+@implementation BGMASOutputDevice {
+    NSScriptObjectSpecifier* parentSpecifier;
+    BGMAudioDevice device;
+    BGMAudioDeviceManager* audioDevices;
+}
+
+- (instancetype) initWithAudioObjectID:(AudioObjectID)objID
+                          audioDevices:(BGMAudioDeviceManager*)devices
+                       parentSpecifier:(NSScriptObjectSpecifier* __nullable)parent {
+    if ((self = [super init])) {
+        parentSpecifier = parent;
+        device = objID;
+        audioDevices = devices;
+    }
+
+    return self;
+}
+
+- (NSString*) name {
+    return (NSString*)CFBridgingRelease(device.CopyName());
+}
+
+- (BOOL) selected {
+    return [audioDevices isOutputDevice:device];
+}
+
+- (void) setSelected:(BOOL)selected {
+    if (selected && ![self selected]) {
+        DebugMsg("BGMASOutputDevice::setSelected: A script is setting output device to %s",
+                 [[self name] UTF8String]);
+
+        NSError* err = [audioDevices setOutputDeviceWithID:device revertOnFailure:YES];
+        (void)err;  // TODO: Return an error to the script somehow if this isn't nil. Also, should
+                    //       we return an error if the script tries to set this property to false?     
+    }
+}
+
+- (NSScriptObjectSpecifier* __nullable) objectSpecifier {
+    NSScriptClassDescription* parentClassDescription = [parentSpecifier keyClassDescription];
+    return [[NSNameSpecifier alloc] initWithContainerClassDescription:parentClassDescription
+                                                   containerSpecifier:parentSpecifier
+                                                                  key:@"output devices"
+                                                                 name:self.name];
+}
+
+@end
+
+#pragma clang assume_nonnull end
+

BGMApp/BGMApp/Scripting/BGMApp.sdef

@@ -0,0 +1,59 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE dictionary SYSTEM "file://localhost/System/Library/DTDs/sdef.dtd">
+<dictionary>
+    <suite name="Background Music" code="BGMs" description="Background Music specific classes">
+             <!-- TODO: Figure out why Script Editor returns output device objects as
+                      «class» "Built-in Output" of application "Background Music"
+                  instead of
+                      device "Built-in Output" of application "Background Music" -->
+        <class name="output device"
+               code="aDev"
+               description="A hardware device that can play audio"
+               plural="output devices"
+               inherits="item">
+            <synonym name="audio device"/>
+
+            <cocoa class="BGMASOutputDevice"/>
+
+            <property name="name"
+                      code="pnam"
+                      description="The name of the output device."
+                      type="text"
+                      access="r"/>
+
+            <property name="selected"
+                      code="Slcd"
+                      type="boolean"
+                      access="rw"
+                      description="Is this the device to be used for audio output?">
+                <synonym name="default"/>
+            </property>
+        </class>
+
+        <class name="application"
+               code="capp"
+               description="The application program">
+            <cocoa class="NSApplication"/>
+
+            <!-- We have a class called "output device", so we have to call this class something
+                 else. -->
+            <property name="selected output device"
+                      type="output device"
+                      code="selO"
+                      access="rw"
+                      description="The device to be used for audio output">
+                <synonym name="selected device"/>
+                <synonym name="default device"/>
+                <synonym name="default output device"/>
+
+                <cocoa key="selectedOutputDevice"/>
+            </property>
+
+            <!-- Unintuitively, this is for the array of output devices. -->
+            <element type="output device" access="r">
+                <cocoa key="outputDevices"/>
+            </element>
+        </class>
+    </suite>
+</dictionary>
+

BGMApp/BGMApp/Scripting/BGMAppDelegate+AppleScript.h

@@ -0,0 +1,44 @@
+// This file is part of Background Music.
+//
+// Background Music is free software: you can redistribute it and/or
+// modify it under the terms of the GNU General Public License as
+// published by the Free Software Foundation, either version 2 of the
+// License, or (at your option) any later version.
+//
+// Background Music is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Background Music. If not, see <http://www.gnu.org/licenses/>.
+
+//
+//  BGMAppDelegate+AppleScript.h
+//  BGMApp
+//
+//  Copyright © 2017 Kyle Neideck
+//
+
+#import "BGMAppDelegate.h"
+
+// Local Includes
+#import "BGMASOutputDevice.h"
+
+// System Includes
+#import <Foundation/Foundation.h>
+
+
+#pragma clang assume_nonnull begin
+
+@interface BGMAppDelegate (AppleScript)
+
+- (BOOL) application:(NSApplication*)sender delegateHandlesKey:(NSString*)key;
+
+@property BGMASOutputDevice* selectedOutputDevice;
+@property (readonly) NSArray<BGMASOutputDevice*>* outputDevices;
+
+@end
+
+#pragma clang assume_nonnull end
+

BGMApp/BGMApp/Scripting/BGMAppDelegate+AppleScript.mm

@@ -0,0 +1,85 @@
+// This file is part of Background Music.
+//
+// Background Music is free software: you can redistribute it and/or
+// modify it under the terms of the GNU General Public License as
+// published by the Free Software Foundation, either version 2 of the
+// License, or (at your option) any later version.
+//
+// Background Music is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Background Music. If not, see <http://www.gnu.org/licenses/>.
+
+//
+//  BGMAppDelegate+AppleScript.mm
+//  BGMApp
+//
+//  Copyright © 2017 Kyle Neideck
+//
+
+// Self Include
+#import "BGMAppDelegate+AppleScript.h"
+
+// Local Includes
+#import "BGMAudioDevice.h"
+
+// PublicUtility Includes
+#import "CAHALAudioSystemObject.h"
+#import "CAAutoDisposer.h"
+
+
+#pragma clang assume_nonnull begin
+
+@implementation BGMAppDelegate (AppleScript)
+
+- (BOOL) application:(NSApplication*)sender delegateHandlesKey:(NSString*)key {
+    #pragma unused (sender)
+    DebugMsg("BGMAppDelegate:application:delegateHandlesKey: Key queried: '%s'", [key UTF8String]);
+
+    return [@[@"selectedOutputDevice", @"outputDevices"] containsObject:key];
+}
+
+- (BGMASOutputDevice*) selectedOutputDevice {
+    AudioObjectID outputDeviceID = [self.audioDevices outputDevice].GetObjectID();
+
+    return [[BGMASOutputDevice alloc] initWithAudioObjectID:outputDeviceID
+                                               audioDevices:self.audioDevices
+                                            parentSpecifier:[self objectSpecifier]];
+}
+
+- (void) setSelectedOutputDevice:(BGMASOutputDevice*)device {
+    [device setSelected:YES];
+}
+
+- (NSArray<BGMASOutputDevice*>*) outputDevices {
+    UInt32 numDevices = CAHALAudioSystemObject().GetNumberAudioDevices();
+    
+    CAAutoArrayDelete<AudioObjectID> devices(numDevices);
+    CAHALAudioSystemObject().GetAudioDevices(numDevices, devices);
+
+    NSMutableArray<BGMASOutputDevice*>* outputDevices =
+        [NSMutableArray arrayWithCapacity:numDevices];
+
+    for (UInt32 i = 0; i < numDevices; i++) {
+        BGMAudioDevice device(devices[i]);
+
+        if (device.CanBeOutputDeviceInBGMApp()) {
+            BGMASOutputDevice* outputDevice =
+                [[BGMASOutputDevice alloc] initWithAudioObjectID:device.GetObjectID()
+                                                    audioDevices:self.audioDevices
+                                                 parentSpecifier:[self objectSpecifier]];
+
+            [outputDevices addObject:outputDevice];
+        }
+    }
+
+    return outputDevices;
+}
+
+@end
+
+#pragma clang assume_nonnull end
+

BGMApp/BGMApp/SystemPreferences.h

@@ -0,0 +1,258 @@
+/*
+ * SystemPreferences.h
+ */
+
+#import <AppKit/AppKit.h>
+#import <ScriptingBridge/ScriptingBridge.h>
+
+
+@class SystemPreferencesItem, SystemPreferencesApplication, SystemPreferencesColor, SystemPreferencesDocument, SystemPreferencesWindow, SystemPreferencesAttributeRun, SystemPreferencesCharacter, SystemPreferencesParagraph, SystemPreferencesText, SystemPreferencesAttachment, SystemPreferencesWord, SystemPreferencesAnchor, SystemPreferencesPane, SystemPreferencesPrintSettings;
+
+enum SystemPreferencesSavo {
+	SystemPreferencesSavoAsk = 'ask ' /* Ask the user whether or not to save the file. */,
+	SystemPreferencesSavoNo = 'no  ' /* Do not save the file. */,
+	SystemPreferencesSavoYes = 'yes ' /* Save the file. */
+};
+typedef enum SystemPreferencesSavo SystemPreferencesSavo;
+
+enum SystemPreferencesEnum {
+	SystemPreferencesEnumStandard = 'lwst' /* Standard PostScript error handling */,
+	SystemPreferencesEnumDetailed = 'lwdt' /* print a detailed report of PostScript errors */
+};
+typedef enum SystemPreferencesEnum SystemPreferencesEnum;
+
+
+
+/*
+ * Standard Suite
+ */
+
+// A scriptable object.
+@interface SystemPreferencesItem : SBObject
+
+@property (copy) NSDictionary *properties;  // All of the object's properties.
+
+- (void)closeSaving:(SystemPreferencesSavo) saving savingIn:(NSURL *)savingIn;  // Close an object.
+- (void)delete;   // Delete an object.
+- (void)duplicateTo:(SBObject *)to withProperties:(NSDictionary *)withProperties;   // Copy object(s) and put the copies at a new location.
+- (BOOL)exists;   // Verify if an object exists.
+- (void)moveTo:(SBObject *)to;   // Move object(s) to a new location.
+- (void)saveAs:(NSString *)as in:(NSURL *)in_;   // Save an object.
+
+@end
+
+// An application's top level scripting object.
+@interface SystemPreferencesApplication : SBApplication
+
+- (SBElementArray *)documents;
+- (SBElementArray *)windows;
+
+@property (readonly) BOOL frontmost;  // Is this the frontmost (active) application?
+@property (copy, readonly) NSString *name;  // The name of the application.
+@property (copy, readonly) NSString *version;  // The version of the application.
+
+- (SystemPreferencesDocument *)open:(NSURL *)x;   // Open an object.
+- (void)print:(NSURL *)x printDialog:(BOOL) printDialog withProperties:(SystemPreferencesPrintSettings *)withProperties;  // Print an object.
+- (void)quitSaving:(SystemPreferencesSavo)saving;   // Quit an application.
+
+@end
+
+// A color.
+@interface SystemPreferencesColor : SystemPreferencesItem
+
+
+@end
+
+// A document.
+@interface SystemPreferencesDocument : SystemPreferencesItem
+
+@property (readonly) BOOL modified;  // Has the document been modified since the last save?
+@property (copy) NSString *name;  // The document's name.
+@property (copy) NSString *path;  // The document's path.
+
+
+@end
+
+// A window.
+@interface SystemPreferencesWindow : SystemPreferencesItem
+
+@property NSRect bounds;  // The bounding rectangle of the window.
+@property (readonly) BOOL closeable;  // Whether the window has a close box.
+@property (copy, readonly) SystemPreferencesDocument *document;  // The document whose contents are being displayed in the window.
+@property (readonly) BOOL floating;  // Whether the window floats.
+- (NSInteger)id;   // The unique identifier of the window.
+@property NSInteger index;  // The index of the window, ordered front to back.
+@property (readonly) BOOL miniaturizable;  // Whether the window can be miniaturized.
+@property BOOL miniaturized;  // Whether the window is currently miniaturized.
+@property (readonly) BOOL modal;  // Whether the window is the application's current modal window.
+@property (copy) NSString *name;  // The full title of the window.
+@property (readonly) BOOL resizable;  // Whether the window can be resized.
+@property (readonly) BOOL titled;  // Whether the window has a title bar.
+@property BOOL visible;  // Whether the window is currently visible.
+@property (readonly) BOOL zoomable;  // Whether the window can be zoomed.
+@property BOOL zoomed;  // Whether the window is currently zoomed.
+
+
+@end
+
+
+
+/*
+ * Text Suite
+ */
+
+// This subdivides the text into chunks that all have the same attributes.
+@interface SystemPreferencesAttributeRun : SystemPreferencesItem
+
+- (SBElementArray *)attachments;
+- (SBElementArray *)attributeRuns;
+- (SBElementArray *)characters;
+- (SBElementArray *)paragraphs;
+- (SBElementArray *)words;
+
+@property (copy) NSColor *color;  // The color of the first character.
+@property (copy) NSString *font;  // The name of the font of the first character.
+@property NSInteger size;  // The size in points of the first character.
+
+
+@end
+
+// This subdivides the text into characters.
+@interface SystemPreferencesCharacter : SystemPreferencesItem
+
+- (SBElementArray *)attachments;
+- (SBElementArray *)attributeRuns;
+- (SBElementArray *)characters;
+- (SBElementArray *)paragraphs;
+- (SBElementArray *)words;
+
+@property (copy) NSColor *color;  // The color of the first character.
+@property (copy) NSString *font;  // The name of the font of the first character.
+@property NSInteger size;  // The size in points of the first character.
+
+
+@end
+
+// This subdivides the text into paragraphs.
+@interface SystemPreferencesParagraph : SystemPreferencesItem
+
+- (SBElementArray *)attachments;
+- (SBElementArray *)attributeRuns;
+- (SBElementArray *)characters;
+- (SBElementArray *)paragraphs;
+- (SBElementArray *)words;
+
+@property (copy) NSColor *color;  // The color of the first character.
+@property (copy) NSString *font;  // The name of the font of the first character.
+@property NSInteger size;  // The size in points of the first character.
+
+
+@end
+
+// Rich (styled) text
+@interface SystemPreferencesText : SystemPreferencesItem
+
+- (SBElementArray *)attachments;
+- (SBElementArray *)attributeRuns;
+- (SBElementArray *)characters;
+- (SBElementArray *)paragraphs;
+- (SBElementArray *)words;
+
+@property (copy) NSColor *color;  // The color of the first character.
+@property (copy) NSString *font;  // The name of the font of the first character.
+@property NSInteger size;  // The size in points of the first character.
+
+
+@end
+
+// Represents an inline text attachment.  This class is used mainly for make commands.
+@interface SystemPreferencesAttachment : SystemPreferencesText
+
+@property (copy) NSString *fileName;  // The path to the file for the attachment
+
+
+@end
+
+// This subdivides the text into words.
+@interface SystemPreferencesWord : SystemPreferencesItem
+
+- (SBElementArray *)attachments;
+- (SBElementArray *)attributeRuns;
+- (SBElementArray *)characters;
+- (SBElementArray *)paragraphs;
+- (SBElementArray *)words;
+
+@property (copy) NSColor *color;  // The color of the first character.
+@property (copy) NSString *font;  // The name of the font of the first character.
+@property NSInteger size;  // The size in points of the first character.
+
+
+@end
+
+
+
+/*
+ * System Preferences
+ */
+
+// an anchor within a preference pane
+@interface SystemPreferencesAnchor : SystemPreferencesItem
+
+@property (copy, readonly) NSString *name;  // name of the anchor within a preference pane
+
+- (SystemPreferencesAnchor *)reveal;   // Reveals an anchor within a preference pane or preference pane itself
+
+@end
+
+// System Preferences top level scripting object
+@interface SystemPreferencesApplication (SystemPreferences)
+
+- (SBElementArray *)panes;
+
+@property (copy) SystemPreferencesPane *currentPane;  // the currently selected pane
+@property (copy, readonly) SystemPreferencesWindow *preferencesWindow;  // the main preferences window
+@property BOOL showAll;  // Is SystemPrefs in show all view. (Setting to false will do nothing)
+
+@end
+
+// a preference pane
+@interface SystemPreferencesPane : SystemPreferencesItem
+
+- (SBElementArray *)anchors;
+
+- (NSString *)id;   // locale independent name of the preference pane; can refer to a pane using the expression: pane id "<name>"
+@property (copy, readonly) NSString *localizedName;  // localized name of the preference pane
+@property (copy, readonly) NSString *name;  // name of the preference pane as it appears in the title bar; can refer to a pane using the expression: pane "<name>"
+
+- (NSInteger)timedLoad;   // This command does xxxx.
+
+@end
+
+
+
+/*
+ * Type Definitions
+ */
+
+@interface SystemPreferencesPrintSettings : SBObject
+
+@property NSInteger copies;  // the number of copies of a document to be printed
+@property BOOL collating;  // Should printed copies be collated?
+@property NSInteger startingPage;  // the first page of the document to be printed
+@property NSInteger endingPage;  // the last page of the document to be printed
+@property NSInteger pagesAcross;  // number of logical pages laid across a physical page
+@property NSInteger pagesDown;  // number of logical pages laid out down a physical page
+@property (copy) NSDate *requestedPrintTime;  // the time at which the desktop printer should print the document
+@property SystemPreferencesEnum errorHandling;  // how errors are handled
+@property (copy) NSString *faxNumber;  // for fax number
+@property (copy) NSString *targetPrinter;  // for target printer
+
+- (void)closeSaving:(SystemPreferencesSavo) saving savingIn:(NSURL *)savingIn;  // Close an object.
+- (void)delete;   // Delete an object.
+- (void)duplicateTo:(SBObject *)to withProperties:(NSDictionary *)withProperties;   // Copy object(s) and put the copies at a new location.
+- (BOOL)exists;   // Verify if an object exists.
+- (void)moveTo:(SBObject *)to;   // Move object(s) to a new location.
+- (void)saveAs:(NSString *)as in:(NSURL *)in_;   // Save an object.
+
+@end
+

BGMApp/BGMAppTests/NullAudio/AudioDriverExamples.xcodeproj/project.pbxproj

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+			isa = XCBuildConfiguration;
+			buildSettings = {
+				CLANG_WARN__EXIT_TIME_DESTRUCTORS = NO;
+				GCC_PREPROCESSOR_DEFINITIONS = "DEBUG=1";
+				INFOPLIST_FILE = "SimpleAudio/Driver/SimpleAudioDriver-Info.plist";
+				INSTALL_PATH = "$(SYSTEM_LIBRARY_DIR)/Extensions";
+				MODULE_NAME = com.apple.audio.SimpleAudioDriver;
+				MODULE_VERSION = 1.0;
+				PRODUCT_NAME = "$(TARGET_NAME)";
+				WRAPPER_EXTENSION = kext;
+			};
+			name = Debug;
+		};
+		2DED184815C357180091BE97 /* Debug-Opt */ = {
+			isa = XCBuildConfiguration;
+			buildSettings = {
+				CLANG_WARN__EXIT_TIME_DESTRUCTORS = NO;
+				GCC_PREPROCESSOR_DEFINITIONS = "DEBUG=1";
+				INFOPLIST_FILE = "SimpleAudio/Driver/SimpleAudioDriver-Info.plist";
+				INSTALL_PATH = "$(SYSTEM_LIBRARY_DIR)/Extensions";
+				MODULE_NAME = com.apple.audio.SimpleAudioDriver;
+				MODULE_VERSION = 1.0;
+				PRODUCT_NAME = "$(TARGET_NAME)";
+				WRAPPER_EXTENSION = kext;
+			};
+			name = "Debug-Opt";
+		};
+/* End XCBuildConfiguration section */
+
+/* Begin XCConfigurationList section */
+		2D7477A01578162B00412279 /* Build configuration list for PBXProject "AudioDriverExamples" */ = {
+			isa = XCConfigurationList;
+			buildConfigurations = (
+				2D7477A21578162B00412279 /* Release */,
+				2D7477A31578162B00412279 /* Debug */,
+				2D7477A41578164E00412279 /* Debug-Opt */,
+			);
+			defaultConfigurationIsVisible = 0;
+			defaultConfigurationName = Release;
+		};
+		2D7477B51578168D00412279 /* Build configuration list for PBXNativeTarget "NullAudio" */ = {
+			isa = XCConfigurationList;
+			buildConfigurations = (
+				2D7477B61578168D00412279 /* Release */,
+				2D7477B71578168D00412279 /* Debug */,
+				2D7477B81578168D00412279 /* Debug-Opt */,
+			);
+			defaultConfigurationIsVisible = 0;
+			defaultConfigurationName = Release;
+		};
+		2D76D97215E48B2000FF0F33 /* Build configuration list for PBXNativeTarget "SimpleAudioPlugIn" */ = {
+			isa = XCConfigurationList;
+			buildConfigurations = (
+				2D76D96F15E48B2000FF0F33 /* Release */,
+				2D76D97015E48B2000FF0F33 /* Debug */,
+				2D76D97115E48B2000FF0F33 /* Debug-Opt */,
+			);
+			defaultConfigurationIsVisible = 0;
+			defaultConfigurationName = Release;
+		};
+		2DED184515C357180091BE97 /* Build configuration list for PBXNativeTarget "SimpleAudioDriver" */ = {
+			isa = XCConfigurationList;
+			buildConfigurations = (
+				2DED184615C357180091BE97 /* Release */,
+				2DED184715C357180091BE97 /* Debug */,
+				2DED184815C357180091BE97 /* Debug-Opt */,
+			);
+			defaultConfigurationIsVisible = 0;
+			defaultConfigurationName = Release;
+		};
+/* End XCConfigurationList section */
+	};
+	rootObject = 2D74779D1578162B00412279 /* Project object */;
+}

BGMApp/BGMAppTests/NullAudio/AudioDriverExamples.xcodeproj/project.xcworkspace/contents.xcworkspacedata

@@ -0,0 +1,7 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<Workspace
+   version = "1.0">
+   <FileRef
+      location = "self:">
+   </FileRef>
+</Workspace>

BGMApp/BGMAppTests/NullAudio/NullAudio/NullAudio-Info.plist

@@ -0,0 +1,38 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
+<plist version="1.0">
+<dict>
+	<key>CFBundleDevelopmentRegion</key>
+	<string>English</string>
+	<key>CFBundleExecutable</key>
+	<string>${EXECUTABLE_NAME}</string>
+	<key>CFBundleIconFile</key>
+	<string></string>
+	<key>CFBundleIdentifier</key>
+	<string>com.apple.audio.${PRODUCT_NAME:rfc1034identifier}</string>
+	<key>CFBundleInfoDictionaryVersion</key>
+	<string>6.0</string>
+	<key>CFBundleName</key>
+	<string>${PRODUCT_NAME}</string>
+	<key>CFBundlePackageType</key>
+	<string>BNDL</string>
+	<key>CFBundleShortVersionString</key>
+	<string>1.0.1</string>
+	<key>CFBundleSignature</key>
+	<string>????</string>
+	<key>CFBundleVersion</key>
+	<string>1</string>
+	<key>CFPlugInFactories</key>
+	<dict>
+		<key>99A15A8B-DA3C-42C3-BD5D-D035A0C2377A</key>
+		<string>NullAudio_Create</string>
+	</dict>
+	<key>CFPlugInTypes</key>
+	<dict>
+		<key>443ABAB8-E7B3-491A-B985-BEB9187030DB</key>
+		<array>
+			<string>99A15A8B-DA3C-42C3-BD5D-D035A0C2377A</string>
+		</array>
+	</dict>
+</dict>
+</plist>

BGMApp/BGMAppTests/NullAudio/README

@@ -0,0 +1,6 @@
+TravisCI's OS X VMs don't have any audio devices installed by default, so we
+install Apple's NullAudio sample driver before the tests run. Otherwise the
+tests would fail because BGMApp currently crashes on launch if you don't have
+any audio devices.
+
+

BGMApp/BGMAppTests/UITests/BGMApp.h

@@ -0,0 +1,31 @@
+/*
+ * BGMApp.h
+ */
+
+#import <AppKit/AppKit.h>
+#import <ScriptingBridge/ScriptingBridge.h>
+
+
+@class BGMAppOutputDevice, BGMAppApplication;
+
+
+
+/*
+ * Background Music
+ */
+
+// an output audio device
+@interface BGMAppOutputDevice : SBObject
+
+@property (copy, readonly) NSString *name;
+@property BOOL selected;  // is this the device to be used for audio output?
+
+@end
+
+// The application program
+@interface BGMAppApplication : SBApplication
+
+- (SBElementArray<BGMAppOutputDevice *> *) outputDevices;
+
+@end
+

BGMApp/BGMAppTests/UITests/BGMAppUITests-Info.plist

@@ -16,8 +16,6 @@
 	<string>BNDL</string>
 	<key>CFBundleShortVersionString</key>
 	<string>1.0</string>
-	<key>CFBundleSignature</key>
-	<string>????</string>
 	<key>CFBundleVersion</key>
 	<string>1</string>
 </dict>

BGMApp/BGMAppTests/UITests/BGMAppUITests.m

@@ -0,0 +1,173 @@
+// This file is part of Background Music.
+//
+// Background Music is free software: you can redistribute it and/or
+// modify it under the terms of the GNU General Public License as
+// published by the Free Software Foundation, either version 2 of the
+// License, or (at your option) any later version.
+//
+// Background Music is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Background Music. If not, see <http://www.gnu.org/licenses/>.
+
+//
+//  BGMAppUITests.m
+//  BGMAppUITests
+//
+//  Copyright © 2017 Kyle Neideck
+//
+//  You might want to use Xcode's UI test recording feature if you add new tests.
+//
+
+// Local Includes
+#import "BGM_TestUtils.h"
+#import "BGM_Types.h"
+
+// Scripting Bridge Includes
+#import "BGMApp.h"
+
+
+// TODO: Skip these tests if macOS SDK 10.11 or higher isn't available.
+// TODO: Mock BGMDevice and music players.
+
+@interface BGMAppUITests : XCTestCase
+@end
+
+@implementation BGMAppUITests {
+    // The BGMApp instance.
+    XCUIApplication* app;
+
+    // Convenience vars.
+    //
+    // The menu bar icon. (Called the status bar icon in some places.)
+    XCUIElement* icon;
+    // The menu items in the main menu.
+    XCUIElementQuery* menuItems;
+    // The Preferences menu item.
+    XCUIElement* prefs;
+}
+
+- (void) setUp {
+    [super setUp];
+    
+    // In UI tests it is usually best to stop immediately when a failure occurs.
+    self.continueAfterFailure = NO;
+
+    // Set up the app object and some convenience vars.
+    app = [[XCUIApplication alloc] init];
+    menuItems = app.menuBars.menuItems;
+    icon = [app.menuBars childrenMatchingType:XCUIElementTypeMenuBarItem].element;
+    prefs = menuItems[@"Preferences"];
+
+    // TODO: Make sure BGMDevice isn't set as the OS X default device before launching BGMApp.
+
+    // Tell BGMApp not to load/store user defaults (settings) and to use
+    // NSApplicationActivationPolicyRegular. If it used the "accessory" policy as usual, the tests
+    // would fail to start because of a bug in Xcode.
+    app.launchArguments = @[ @"--no-persistent-data", @"--show-dock-icon" ];
+
+    // Launch BGMApp.
+    [app launch];
+}
+
+- (void) tearDown {
+    // Click the quit menu item.
+    if (!menuItems.count) {
+        [icon click];
+    }
+
+    [menuItems[@"Quit Background Music"] click];
+
+    // BGMApp should quit.
+    XCTAssert(!app.exists);
+    
+    [super tearDown];
+}
+
+- (void) testCycleOutputDevices {
+    const int NUM_CYCLES = 2;
+
+    // Get the list of output devices from the preferences menu.
+    [icon click];
+    [prefs hover];
+    NSArray<XCUIElement*>* outputDeviceMenuItems = [self outputDeviceMenuItems];
+
+    // For debugging certain issues, it can be useful to repeatedly switch between two
+    // devices:
+    // outputDeviceMenuItems = [outputDeviceMenuItems subarrayWithRange:NSMakeRange(0,2)];
+
+    XCTAssertGreaterThan(outputDeviceMenuItems.count, 0);
+
+    // Click the last device to close the menu again.
+    [outputDeviceMenuItems.lastObject click];
+
+    BGMAppApplication* sbApp = [SBApplication applicationWithBundleIdentifier:@kBGMAppBundleID];
+
+    for (int i = 0; i < NUM_CYCLES; i++) {
+        // Select each output device.
+        for (XCUIElement* item in outputDeviceMenuItems) {
+            [icon click];
+            [prefs hover];
+
+            [item click];
+
+            // Assert that the device we clicked is the selected device now.
+            for (BGMAppOutputDevice* device in [sbApp outputDevices]) {
+                // TODO: This seems a bit fragile. Would it still work with long device names?
+                if ([device.name isEqualToString:[item title]]) {
+                    XCTAssert(device.selected);
+                } else {
+                    XCTAssertFalse(device.selected);
+                }
+            }
+        }
+    }
+}
+
+// Find the menu items for the output devices in the preferences menu.
+- (NSArray<XCUIElement*>*) outputDeviceMenuItems {
+    NSArray<XCUIElement*>* items = @[];
+    BOOL inOutputDeviceSection = NO;
+
+    for (int i = 0; i < prefs.menuItems.count; i++) {
+        XCUIElement* menuItem = [prefs.menuItems elementBoundByIndex:i];
+
+        if ([menuItem.title isEqual:@"Output Device"]) {
+            inOutputDeviceSection = YES;
+        } else if (inOutputDeviceSection) {
+            // Assume that finding a separator menu item means we've reached the end of the section.
+            if (((NSMenuItem*)menuItem.value).separatorItem || [menuItem.title isEqual:@""]) {
+                break;
+            }
+
+            items = [items arrayByAddingObject:menuItem];
+        }
+    }
+
+    return items;
+}
+
+- (void) testSelectMusicPlayer {
+    // Select VLC as the music player.
+    [icon click];
+    [prefs hover];
+    [prefs.menuItems[@"VLC"] click];
+
+    // The name of the Auto-pause menu item should change. Also check the accessibility identifier.
+    [icon click];
+    XCTAssertEqualObjects(menuItems[@"Auto-pause VLC"].identifier, @"Auto-pause enabled");
+    
+    // Select iTunes as the music player.
+    [prefs hover];
+    [prefs.menuItems[@"iTunes"] click];
+
+    // The name of the Auto-pause menu item should change back.
+    [icon click];
+    XCTAssert(menuItems[@"Auto-pause iTunes"].exists);
+}
+
+@end
+

BGMApp/BGMAppTests/UITests/travis-skip.py

@@ -0,0 +1,49 @@
+#!/usr/bin/python2.7
+
+# This file is part of Background Music.
+#
+# Background Music is free software: you can redistribute it and/or
+# modify it under the terms of the GNU General Public License as
+# published by the Free Software Foundation, either version 2 of the
+# License, or (at your option) any later version.
+#
+# Background Music is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with Background Music. If not, see <http://www.gnu.org/licenses/>.
+
+#
+# travis-skip.py
+# BGMAppUITests
+#
+# Copyright (c) 2017 Kyle Neideck
+#
+# Skip the UI tests in Travis builds because they aren't supported.
+#
+# We can't run the tests on Travis because Xcode needs permission to use the Accessibility API
+# to control BGMApp. There's no way to set that up programmatically without disabling SIP and
+# Travis doesn't support that.
+#
+# See https://github.com/travis-ci/travis-ci/issues/5819
+#
+# TODO: Figure out a better way to do this.
+#
+
+import xml.etree.ElementTree as ET
+
+SCHEME_FILE = "BGMApp/BGMApp.xcodeproj/xcshareddata/xcschemes/Background Music.xcscheme"
+UI_REF_XPATH = ".//BuildableReference[@BlueprintName='BGMAppUITests']/.."
+
+# Parse the Xcode scheme.
+tree = ET.parse(SCHEME_FILE)
+
+# Set the TestableReference for the UI tests to skipped.
+tree.getroot().findall(UI_REF_XPATH)[0].set("skipped", "YES")
+
+# Save the scheme.
+tree.write(SCHEME_FILE)
+
+

BGMApp/BGMAppTests/UnitTests/BGMAppUnitTests-Info.plist

@@ -0,0 +1,22 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
+<plist version="1.0">
+<dict>
+	<key>CFBundleDevelopmentRegion</key>
+	<string>en</string>
+	<key>CFBundleExecutable</key>
+	<string>$(EXECUTABLE_NAME)</string>
+	<key>CFBundleIdentifier</key>
+	<string>$(PRODUCT_BUNDLE_IDENTIFIER)</string>
+	<key>CFBundleInfoDictionaryVersion</key>
+	<string>6.0</string>
+	<key>CFBundleName</key>
+	<string>$(PRODUCT_NAME)</string>
+	<key>CFBundlePackageType</key>
+	<string>BNDL</string>
+	<key>CFBundleShortVersionString</key>
+	<string>1.0</string>
+	<key>CFBundleVersion</key>
+	<string>1</string>
+</dict>
+</plist>

BGMApp/BGMAppTests/UnitTests/BGMMusicPlayersUnitTests.mm

@@ -0,0 +1,210 @@
+// This file is part of Background Music.
+//
+// Background Music is free software: you can redistribute it and/or
+// modify it under the terms of the GNU General Public License as
+// published by the Free Software Foundation, either version 2 of the
+// License, or (at your option) any later version.
+//
+// Background Music is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Background Music. If not, see <http://www.gnu.org/licenses/>.
+
+//
+//  BGMMusicPlayersUnitTests.mm
+//  BGMAppUnitTests
+//
+//  Copyright © 2016 Kyle Neideck
+//
+
+// Unit include
+#import "BGMMusicPlayers.h"
+
+// Local includes
+#import "BGM_TestUtils.h"
+
+#import "BGM_Types.h"
+#import "BGMAudioDeviceManager.h"
+#import "BGMiTunes.h"
+#import "BGMVLC.h"
+#import "BGMDecibel.h"
+#import "BGMSpotify.h"
+
+// PublicUtility includes
+#import "CAHALAudioDevice.h"  // Mocked
+
+// System includes
+#import <Foundation/Foundation.h>
+
+
+@interface BGMMockAudioDeviceManager : BGMAudioDeviceManager
+@end
+
+@implementation BGMMockAudioDeviceManager
+
++ (CAHALAudioDevice) bgmDevice {
+    static CAHALAudioDevice device(CFSTR("MockBGMDevice"));
+    return device;
+}
+
+@end
+
+// ----
+
+@interface BGMMockUserDefaults : BGMUserDefaults
+
+@property NSUUID* selectedPlayerID;
+
+@end
+
+@implementation BGMMockUserDefaults
+
+- (void) registerDefaults {
+}
+
+- (NSString* __nullable) selectedMusicPlayerID {
+    return [self.selectedPlayerID UUIDString];
+}
+
+- (void) setSelectedMusicPlayerID:(NSString* __nullable)selectedMusicPlayerID {
+    #pragma unused (selectedMusicPlayerID)
+}
+
+- (BOOL) autoPauseMusicEnabled {
+    return YES;
+}
+
+- (void) setAutoPauseMusicEnabled:(BOOL)autoPauseMusicEnabled {
+    #pragma unused (autoPauseMusicEnabled)
+}
+
+@end
+
+// ----
+
+@interface BGMMusicPlayersUnitTests : XCTestCase
+@end
+
+@implementation BGMMusicPlayersUnitTests {
+    BGMMockAudioDeviceManager* devices;
+    BGMMockUserDefaults* defaults;
+    
+    NSUUID* spotifyID;
+    NSUUID* vlcID;
+}
+
+- (void) setUp {
+    [super setUp];
+    
+    devices = [BGMMockAudioDeviceManager new];
+    defaults = [BGMMockUserDefaults new];
+    
+    // These are the IDs hardcoded in BGMSpotify and BGMVLC.
+    spotifyID = [[NSUUID alloc] initWithUUIDString:@"EC2A907F-8515-4687-9570-1BF63176E6D8"];
+    vlcID = [[NSUUID alloc] initWithUUIDString:@"5226F4B9-C740-4045-A273-4B8EABC0E8FC"];
+}
+
+- (void) tearDown {
+    [self resetDevice];
+    
+    [super tearDown];
+}
+
+- (void) testNoSelectedMusicPlayerStored {
+    // Test the case where the user has never changed the music player preference.
+    
+    // Test with iTunes as the default.
+    BGMMusicPlayers* players = [[BGMMusicPlayers alloc] initWithAudioDevices:devices
+                                                        defaultMusicPlayerID:[BGMiTunes sharedMusicPlayerID]
+                                                          musicPlayerClasses:@[ BGMiTunes.class, BGMVLC.class ]
+                                                                userDefaults:defaults];
+    
+    XCTAssertEqual(players.musicPlayers.count, 2);
+    
+    for (id<BGMMusicPlayer> player in players.musicPlayers) {
+        XCTAssertTrue([player isKindOfClass:BGMiTunes.class] || [player isKindOfClass:BGMVLC.class]);
+    }
+    
+    XCTAssertEqualObjects(players.selectedMusicPlayer.musicPlayerID, [BGMiTunes sharedMusicPlayerID]);
+    XCTAssertEqualObjects(players.selectedMusicPlayer.name, @"iTunes");
+    
+    [self resetDevice];
+    
+    // Test with VLC as the default.
+    players = [[BGMMusicPlayers alloc] initWithAudioDevices:devices
+                                       defaultMusicPlayerID:vlcID
+                                         musicPlayerClasses:@[ BGMiTunes.class,
+                                                               BGMVLC.class,
+                                                               BGMDecibel.class ]
+                                               userDefaults:defaults];
+    
+    XCTAssertEqual(players.musicPlayers.count, 3);
+    
+    for (id<BGMMusicPlayer> player in players.musicPlayers) {
+        XCTAssertTrue([player isKindOfClass:BGMiTunes.class] ||
+                      [player isKindOfClass:BGMVLC.class] ||
+                      [player isKindOfClass:BGMDecibel.class]);
+    }
+    
+    XCTAssertEqualObjects(players.selectedMusicPlayer.musicPlayerID, vlcID);
+    XCTAssertEqualObjects(players.selectedMusicPlayer.name, @"VLC");
+}
+
+- (void) testSelectedMusicPlayerInUserDefaults {
+    defaults.selectedPlayerID = spotifyID;
+    
+    BGMMusicPlayers* players = [[BGMMusicPlayers alloc] initWithAudioDevices:devices
+                                                        defaultMusicPlayerID:[BGMiTunes sharedMusicPlayerID]
+                                                          musicPlayerClasses:@[ BGMiTunes.class,
+                                                                                BGMVLC.class,
+                                                                                BGMSpotify.class ]
+                                                                userDefaults:defaults];
+    
+    XCTAssertEqual(players.musicPlayers.count, 3);
+    
+    XCTAssertEqualObjects(players.selectedMusicPlayer.musicPlayerID, spotifyID);
+    XCTAssertEqualObjects(players.selectedMusicPlayer.name, @"Spotify");
+    
+    [self resetDevice];
+    
+    // If there's an unrecognized ID in user defaults, the default music player should be selected.
+    defaults.selectedPlayerID = [[NSUUID alloc] initWithUUIDString:@"11111111-1111-1111-0000-000000000000"];
+    
+    // This initializer sets iTunes as the default music player and adds all the other music players.
+    players = [[BGMMusicPlayers alloc] initWithAudioDevices:devices
+                                               userDefaults:defaults];
+    
+    XCTAssert(players.musicPlayers.count >= 6);
+    
+    XCTAssertEqualObjects(players.selectedMusicPlayer.musicPlayerID, [BGMiTunes sharedMusicPlayerID]);
+    XCTAssertEqualObjects(players.selectedMusicPlayer.name, @"iTunes");
+}
+
+- (void) testSelectedMusicPlayerInBGMDeviceProperties {
+    // When it doesn't find a selected music player in user defaults, it should check BGMDevice's music
+    // player properties.
+    
+    [devices bgmDevice].SetPropertyData_CFString(kBGMMusicPlayerBundleIDAddress,
+                                                 CFSTR("org.videolan.vlc"));
+    
+    BGMMusicPlayers* players = [[BGMMusicPlayers alloc] initWithAudioDevices:devices
+                                                                userDefaults:defaults];
+    
+    XCTAssert(players.musicPlayers.count >= 6);
+    
+    XCTAssertEqualObjects(players.selectedMusicPlayer.musicPlayerID, vlcID);
+    XCTAssertEqualObjects(players.selectedMusicPlayer.name, @"VLC");
+}
+
+// TODO: Test setting the selectedMusicPlayer property
+
+- (void) resetDevice {
+    // Reset the mock BGMDevice.
+    [devices bgmDevice].SetPropertyData_CFString(kBGMMusicPlayerBundleIDAddress, NULL);
+}
+
+@end
+

BGMApp/BGMAppTests/UnitTests/Mock_CAHALAudioObject.cpp

@@ -0,0 +1,161 @@
+// This file is part of Background Music.
+//
+// Background Music is free software: you can redistribute it and/or
+// modify it under the terms of the GNU General Public License as
+// published by the Free Software Foundation, either version 2 of the
+// License, or (at your option) any later version.
+//
+// Background Music is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Background Music. If not, see <http://www.gnu.org/licenses/>.
+
+//
+//  Mock_CAHALAudioObject.cpp
+//  BGMAppUnitTests
+//
+//  Copyright © 2016 Kyle Neideck
+//
+
+// Self include
+#include "CAHALAudioObject.h"
+
+// BGM Includes
+#include "BGM_Types.h"
+
+// System includes
+#include <CoreAudio/AudioHardware.h>
+
+
+#pragma clang diagnostic ignored "-Wunused-parameter"
+
+// The value of the music player bundle ID property. Tests should set this back to NULL when they finish. (Has
+// to be static because we can't add to the real class's interface.)
+static CFStringRef __nullable playerBundleID = NULL;
+
+CAHALAudioObject::CAHALAudioObject(AudioObjectID inObjectID)
+:
+    mObjectID(inObjectID)
+{
+}
+
+CAHALAudioObject::~CAHALAudioObject()
+{
+}
+
+void	CAHALAudioObject::GetPropertyData(const AudioObjectPropertyAddress& inAddress, UInt32 inQualifierDataSize, const void* inQualifierData, UInt32& ioDataSize, void* outData) const
+{
+    if(inAddress.mSelector == kAudioDeviceCustomPropertyMusicPlayerBundleID)
+    {
+        *reinterpret_cast<CFStringRef*>(outData) = playerBundleID;
+    }
+}
+
+void	CAHALAudioObject::SetPropertyData(const AudioObjectPropertyAddress& inAddress, UInt32 inQualifierDataSize, const void* inQualifierData, UInt32 inDataSize, const void* inData)
+{
+    if(inAddress.mSelector == kAudioDeviceCustomPropertyMusicPlayerBundleID)
+    {
+        playerBundleID = *reinterpret_cast<const CFStringRef*>(inData);
+    }
+}
+
+#pragma mark Unimplemented methods
+
+AudioObjectID	CAHALAudioObject::GetObjectID() const
+{
+    return kAudioObjectUnknown;
+}
+
+void	CAHALAudioObject::SetObjectID(AudioObjectID inObjectID)
+{
+    Throw(new CAException(kAudio_UnimplementedError));
+}
+
+AudioClassID	CAHALAudioObject::GetClassID() const
+{
+    Throw(new CAException(kAudio_UnimplementedError));
+}
+
+AudioObjectID	CAHALAudioObject::GetOwnerObjectID() const
+{
+    Throw(new CAException(kAudio_UnimplementedError));
+}
+
+CFStringRef	CAHALAudioObject::CopyOwningPlugInBundleID() const
+{
+    Throw(new CAException(kAudio_UnimplementedError));
+}
+
+CFStringRef	CAHALAudioObject::CopyName() const
+{
+    Throw(new CAException(kAudio_UnimplementedError));
+}
+
+CFStringRef	CAHALAudioObject::CopyManufacturer() const
+{
+    Throw(new CAException(kAudio_UnimplementedError));
+}
+
+CFStringRef	CAHALAudioObject::CopyNameForElement(AudioObjectPropertyScope inScope, AudioObjectPropertyElement inElement) const
+{
+    Throw(new CAException(kAudio_UnimplementedError));
+}
+
+CFStringRef	CAHALAudioObject::CopyCategoryNameForElement(AudioObjectPropertyScope inScope, AudioObjectPropertyElement inElement) const
+{
+    Throw(new CAException(kAudio_UnimplementedError));
+}
+
+CFStringRef	CAHALAudioObject::CopyNumberNameForElement(AudioObjectPropertyScope inScope, AudioObjectPropertyElement inElement) const
+{
+    Throw(new CAException(kAudio_UnimplementedError));
+}
+
+bool	CAHALAudioObject::ObjectExists(AudioObjectID inObjectID)
+{
+    Throw(new CAException(kAudio_UnimplementedError));
+}
+
+UInt32	CAHALAudioObject::GetNumberOwnedObjects(AudioClassID inClass) const
+{
+    Throw(new CAException(kAudio_UnimplementedError));
+}
+
+void	CAHALAudioObject::GetAllOwnedObjects(AudioClassID inClass, UInt32& ioNumberObjects, AudioObjectID* ioObjectIDs) const
+{
+    Throw(new CAException(kAudio_UnimplementedError));
+}
+
+AudioObjectID	CAHALAudioObject::GetOwnedObjectByIndex(AudioClassID inClass, UInt32 inIndex)
+{
+    Throw(new CAException(kAudio_UnimplementedError));
+}
+
+bool	CAHALAudioObject::HasProperty(const AudioObjectPropertyAddress& inAddress) const
+{
+    Throw(new CAException(kAudio_UnimplementedError));
+}
+
+bool	CAHALAudioObject::IsPropertySettable(const AudioObjectPropertyAddress& inAddress) const
+{
+    Throw(new CAException(kAudio_UnimplementedError));
+}
+
+UInt32	CAHALAudioObject::GetPropertyDataSize(const AudioObjectPropertyAddress& inAddress, UInt32 inQualifierDataSize, const void* inQualifierData) const
+{
+    Throw(new CAException(kAudio_UnimplementedError));
+}
+
+void	CAHALAudioObject::AddPropertyListener(const AudioObjectPropertyAddress& inAddress, AudioObjectPropertyListenerProc inListenerProc, void* inClientData)
+{
+    Throw(new CAException(kAudio_UnimplementedError));
+}
+
+void	CAHALAudioObject::RemovePropertyListener(const AudioObjectPropertyAddress& inAddress, AudioObjectPropertyListenerProc inListenerProc, void* inClientData)
+{
+    Throw(new CAException(kAudio_UnimplementedError));
+}
+

BGMApp/BGMXPCHelper/BGMXPCHelperService.m

@@ -34,8 +34,8 @@
 
 #pragma clang assume_nonnull begin
 
-static NSXPCListenerEndpoint* sBGMAppEndpoint = nil;
-static NSXPCConnection* sBGMAppConnection = nil;
+static NSXPCListenerEndpoint* __nullable sBGMAppEndpoint = nil;
+static NSXPCConnection* __nullable sBGMAppConnection = nil;
 
 @implementation BGMXPCHelperService {
     NSXPCConnection* connection;
@@ -73,7 +73,7 @@ static NSXPCConnection* sBGMAppConnection = nil;
     if (!sBGMAppConnection && sBGMAppEndpoint) {
         // Create a new connection to BGMApp from the endpoint
         @synchronized(self) {
-            sBGMAppConnection = [[NSXPCConnection alloc] initWithListenerEndpoint:sBGMAppEndpoint];
+            sBGMAppConnection = [[NSXPCConnection alloc] initWithListenerEndpoint:(NSXPCListenerEndpoint* __nonnull)sBGMAppEndpoint];
             NSAssert(sBGMAppConnection, @"NSXPCConnection::initWithListenerEndpoint returned nil");
             
             [sBGMAppConnection setRemoteObjectInterface:[NSXPCInterface interfaceWithProtocol:@protocol(BGMAppXPCProtocol)]];
@@ -182,7 +182,7 @@ static NSXPCConnection* sBGMAppConnection = nil;
     }];
     
     // Wait for BGMApp's reply
-    long err = dispatch_semaphore_wait(bgmAppReplySemaphore, dispatch_time(DISPATCH_TIME_NOW, 30 * NSEC_PER_SEC));
+    long err = dispatch_semaphore_wait(bgmAppReplySemaphore, dispatch_time(DISPATCH_TIME_NOW, kStartIOTimeoutNsec));
     
     if (err != 0) {
         replyToBGMDriver = [BGMXPCHelperService errorWithCode:kBGMXPC_Timeout

BGMApp/BGMXPCHelper/main.m

@@ -58,14 +58,14 @@
 
 #pragma clang assume_nonnull begin
 
-int main(int argc, const char *argv[]) {
+int main(int argc, const char* __nullable argv[]) {
     #pragma unused (argc, argv)
     
     DebugMsg("BGMXPCHelper::main: Service starting up");
     
     // Set up the one NSXPCListener for this service. It will handle all incoming connections. This checks our service in with
     // the bootstrap service.
-    NSXPCListener *listener = [[NSXPCListener alloc] initWithMachServiceName:kBGMXPCHelperMachServiceName];
+    NSXPCListener* listener = [[NSXPCListener alloc] initWithMachServiceName:kBGMXPCHelperMachServiceName];
     BGMXPCListenerDelegate* delegate = [BGMXPCListenerDelegate new];
     listener.delegate = delegate;
     

BGMApp/BGMXPCHelper/post_install.sh

@@ -20,7 +20,7 @@
 # post_install.sh
 # BGMXPCHelper
 #
-# Copyright © 2016 Kyle Neideck
+# Copyright © 2016, 2017 Kyle Neideck
 #
 # Installs BGMXPCHelper's launchd plist file and "bootstraps" (registers/enables) it with launchd.
 #
@@ -28,30 +28,47 @@
 # runs as the final build phase.
 #
 
-# Check the environment variables we need from Xcode.
-if [[ -z ${EXECUTABLE_PATH} ]]; then
-    echo "Environment variable EXECUTABLE_PATH was not set." >&2
-    exit 1
+PATH=/bin:/sbin:/usr/bin:/usr/sbin; export PATH
+
+# Check we have the paths we need, either in environment variables from Xcode or from the args.
+if [[ -z $1 ]]; then
+    if [[ -z ${INSTALL_DIR} ]]; then
+        echo "Environment variable INSTALL_DIR was not set." >&2
+        exit 1
+    fi
+else
+    INSTALL_DIR="$1"
 fi
-if [[ -z ${INSTALL_DIR} ]]; then
-    echo "Environment variable INSTALL_DIR was not set." >&2
-    exit 1
+
+if [[ -z $2 ]]; then
+    if [[ -z ${EXECUTABLE_PATH} ]]; then
+        echo "Environment variable EXECUTABLE_PATH was not set." >&2
+        exit 1
+    fi
+else
+    EXECUTABLE_PATH="$2"
 fi
-if [[ -z ${TARGET_BUILD_DIR} ]]; then
-    echo "Environment variable TARGET_BUILD_DIR was not set." >&2
-    exit 1
-fi
-if [[ -z ${UNLOCALIZED_RESOURCES_FOLDER_PATH} ]]; then
-    echo "Environment variable UNLOCALIZED_RESOURCES_FOLDER_PATH was not set." >&2
-    exit 1
+
+if [[ -z $3 ]]; then
+    if [[ -z ${TARGET_BUILD_DIR} ]]; then
+        echo "Environment variable TARGET_BUILD_DIR was not set." >&2
+        exit 1
+    fi
+
+    if [[ -z ${UNLOCALIZED_RESOURCES_FOLDER_PATH} ]]; then
+        echo "Environment variable UNLOCALIZED_RESOURCES_FOLDER_PATH was not set." >&2
+        exit 1
+    fi
+
+    RESOURCES_PATH="${TARGET_BUILD_DIR}/${UNLOCALIZED_RESOURCES_FOLDER_PATH}"
+else
+    RESOURCES_PATH="$3"
 fi
 
 # Safe mode.
 set -euo pipefail
 IFS=$'\n\t'
 
-RESOURCES_PATH="${TARGET_BUILD_DIR}/${UNLOCALIZED_RESOURCES_FOLDER_PATH}"
-
 # Show a warning if INSTALL_DIR isn't set to a safe installation directory.
 if [[ $(bash "${RESOURCES_PATH}/safe_install_dir.sh" "${INSTALL_DIR}") != 1 ]]; then
     echo "$(tput setaf 11)WARNING$(tput sgr0): Installing to \"${INSTALL_DIR}\" may be" \

BGMApp/BGMXPCHelper/safe_install_dir.sh

@@ -20,7 +20,7 @@
 # safe_install_dir.sh
 # BGMXPCHelper
 #
-# Copyright © 2016 Kyle Neideck
+# Copyright © 2016, 2017 Kyle Neideck
 #
 # Prints the path to a directory the BGMXPCHelper bundle can safely be installed to. Intended to be
 # used as the INSTALL_DIR environment variable for xcodebuild commands. For example,
@@ -56,6 +56,8 @@
 # recommendation above, or "0" otherwise.
 #
 
+PATH=/bin:/sbin:/usr/bin:/usr/sbin; export PATH
+
 # Safe mode.
 set -euo pipefail
 IFS=$'\n\t'
@@ -96,13 +98,17 @@ check_dir() {
 # Used when we can't find a suitable installation directory. Prints an error message and exits.
 # (Reaching this point should be very uncommon.)
 fail() {
-    echo "$(tput setaf 11)WARNING$(tput sgr0): Installing BGMXPCHelper to its default location" \
-         "(${INSTALL_DIR} or, as a backup, ${BACKUP_INSTALL_DIR}) might not be secure on this" \
-         "system. It's recommended that each directory from the installation directory up to the" \
-         "root directory should be owned by root and not writable by any other user. See" \
-         "safe_install_dir.sh for more details." >&2
+    if [[ $ALLOW_UNSAFE_FALLBACK -eq 1 ]]; then
+        CONTINUE_ANYWAY="y"
+    else
+        echo "$(tput setaf 11)WARNING$(tput sgr0): Installing BGMXPCHelper to its default" \
+             "location (${INSTALL_DIR} or, as a backup, ${BACKUP_INSTALL_DIR}) might not be" \
+             "secure on this system. It's recommended that each directory from the installation" \
+             "directory up to the root directory should be owned by root and not writable by any" \
+             "other user. See safe_install_dir.sh for more details." >&2
 
-    read -e -p "Continue anyway? [y/N]" CONTINUE_ANYWAY
+        read -e -p "Continue anyway? [y/N]" CONTINUE_ANYWAY
+    fi
 
     if [[ "${CONTINUE_ANYWAY}" == "y" ]] || [[ "${CONTINUE_ANYWAY}" == "Y" ]]; then
         echo "${INSTALL_DIR}"
@@ -114,16 +120,26 @@ fail() {
     fi
 }
 
-# This script can be given a directory to check as an argument.
-# (Uses "${1+x}" instead of "$1" because having our "safe mode" enabled makes the script fail if you
-# reference an unset variable, even to check whether it's set or not.)
-if [[ ! -z "${1+x}" ]]; then
-    # Check the given path exists and is a directory.
-    if [[ ! -d "$1" ]]; then echo "$1 is not a directory." >&2; exit 1; fi
+ALLOW_UNSAFE_FALLBACK=0
 
-    check_dir "$1"
-    echo ${DIR_IS_SAFE}
-    exit 0
+# This script can be given a directory to check as an argument, or the -y option, which tells this
+# script to print the default dir if neither of the dirs are safe. The pkg installer uses -y so it
+# can install anyway and show the user instructions to fix the permissions, rather than just
+# failing.
+#
+# (This line uses "${1+x}" instead of "$1" because having our "safe mode" enabled makes the script
+# fail if you reference an unset variable, even to check whether it's set or not.)
+if [[ ! -z "${1+x}" ]]; then
+    if [[ "$1" == "-y" ]]; then
+        ALLOW_UNSAFE_FALLBACK=1
+    else
+        # Check the given path exists and is a directory.
+        if [[ ! -d "$1" ]]; then echo "$1 is not a directory." >&2; exit 1; fi
+
+        check_dir "$1"
+        echo ${DIR_IS_SAFE}
+        exit 0
+    fi
 fi
 
 # These are just for readability and to save keystrokes. If you change them, you'll have to change
@@ -143,7 +159,7 @@ if [[ ! -e "${INSTALL_DIR}" ]]; then
     sudo chmod go-w "${INSTALL_DIR}" 
 fi
 
-# Check the directory Xcode installed the build to.
+# Check the directory the build was installed to.
 check_dir "${INSTALL_DIR}"
 
 if [[ ${DIR_IS_SAFE} -eq 1 ]]; then

BGMApp/BGMXPCHelperTests/BGMXPCHelperTests.m

@@ -15,7 +15,7 @@
 
 //
 //  BGMXPCHelperTests.m
-//  BGMApp
+//  BGMXPCHelperTests
 //
 //  Copyright © 2016 Kyle Neideck
 //
@@ -69,7 +69,7 @@
         dispatch_semaphore_signal(replySemaphore);
     }];
     
-    if (0 != dispatch_semaphore_wait(replySemaphore, dispatch_time(DISPATCH_TIME_NOW, 30 * NSEC_PER_SEC))) {
+    if (0 != dispatch_semaphore_wait(replySemaphore, dispatch_time(DISPATCH_TIME_NOW, kStartIOTimeoutNsec))) {
         XCTFail(@"Timed out waiting for BGMXPCHelper");
     }
 }

BGMApp/PublicUtility/CADebugMacros.cpp

@@ -67,24 +67,50 @@ void	LogError(const char *fmt, ...)
 {
 	va_list args;
 	va_start(args, fmt);
+    // BGM edit: vprintf leaves args in an undefined state, which can cause a crash in
+    //           vsyslog. Also added CADebuggerStop(). Original code commented out below.
+//#if DEBUG
+//	vprintf(fmt, args);
+//#endif
+//#if TARGET_API_MAC_OSX
+//	vsyslog(LOG_ERR, fmt, args);
+//#endif
+#if (DEBUG || !TARGET_API_MAC_OSX) && !CoreAudio_UseSysLog
+    printf("[ERROR] ");
+    vprintf(fmt, args);
+    printf("\n");
+#else
+    vsyslog(LOG_ERR, fmt, args);
+#endif
 #if DEBUG
-	vprintf(fmt, args);
-#endif
-#if TARGET_API_MAC_OSX
-	vsyslog(LOG_ERR, fmt, args);
+    CADebuggerStop();
 #endif
+    // BGM edit end
 	va_end(args);
 }
 
 void	LogWarning(const char *fmt, ...)
 {
 	va_list args;
-	va_start(args, fmt);
+    va_start(args, fmt);
+    // BGM edit: vprintf leaves args in an undefined state, which can cause a crash in
+    //           vsyslog. Also added CADebuggerStop(). Original code commented out below.
+//#if DEBUG
+//	vprintf(fmt, args);
+//#endif
+//#if TARGET_API_MAC_OSX
+//	vsyslog(LOG_WARNING, fmt, args);
+//#endif
+#if (DEBUG || !TARGET_API_MAC_OSX) && !CoreAudio_UseSysLog
+    printf("[WARNING] ");
+    vprintf(fmt, args);
+    printf("\n");
+#else
+    vsyslog(LOG_WARNING, fmt, args);
+#endif
 #if DEBUG
-	vprintf(fmt, args);
-#endif
-#if TARGET_API_MAC_OSX
-	vsyslog(LOG_WARNING, fmt, args);
+    //CADebuggerStop(); // TODO: Add a toggle for this to the project file (under "Preprocessor Macros"). Default to off.
 #endif
+    // BGM edit end
 	va_end(args);
 }

BGMApp/PublicUtility/CADebugMacros.h

@@ -194,8 +194,9 @@
 #define DebugMessageN8(msg, N1, N2, N3, N4, N5, N6, N7, N8)		DebugMsg(msg, N1, N2, N3, N4, N5, N6, N7, N8)
 #define DebugMessageN9(msg, N1, N2, N3, N4, N5, N6, N7, N8, N9)	DebugMsg(msg, N1, N2, N3, N4, N5, N6, N7, N8, N9)
 
-void	LogError(const char *fmt, ...);			// writes to syslog (and stderr if debugging)
-void	LogWarning(const char *fmt, ...);		// writes to syslog (and stderr if debugging)
+// BGM edit: Added __printflike.
+void	LogError(const char *fmt, ...) __printflike(1, 2);			// writes to syslog (and stderr if debugging)
+void	LogWarning(const char *fmt, ...) __printflike(1, 2);		// writes to syslog (and stderr if debugging)
 
 #define	NO_ACTION	(void)0
 

BGMDriver/BGMDriver.xcodeproj/project.pbxproj

@@ -3,45 +3,53 @@
 	archiveVersion = 1;
 	classes = {
 	};
-	objectVersion = 46;
+	objectVersion = 47;
 	objects = {
 
 /* Begin PBXBuildFile section */
 		1C0CB6B91C642C600084C15A /* BGM_Client.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 1C0CB6B01C642C600084C15A /* BGM_Client.cpp */; };
 		1C0CB6BA1C642C600084C15A /* BGM_ClientMap.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 1C0CB6B21C642C600084C15A /* BGM_ClientMap.cpp */; };
 		1C0CB6BB1C642C600084C15A /* BGM_Clients.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 1C0CB6B41C642C600084C15A /* BGM_Clients.cpp */; };
-		1C305D9D1BE294B5004EBB91 /* CACFNumber.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 1C305D9B1BE294B5004EBB91 /* CACFNumber.cpp */; };
 		1C30A69F1C1E98F000C05AA5 /* CAMutex.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 1CB8B3841BBCEFE8000E2DD1 /* CAMutex.cpp */; };
 		1C38210E1C4A163A00A0C8C6 /* BGM_TaskQueue.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 1C38210C1C4A163A00A0C8C6 /* BGM_TaskQueue.cpp */; };
-		1C3821111C4A18DE00A0C8C6 /* CAPThread.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 1C38210F1C4A18DE00A0C8C6 /* CAPThread.cpp */; };
 		1C3DB4871BE063C500EC8160 /* BGM_DeviceTests.mm in Sources */ = {isa = PBXBuildFile; fileRef = 1C3DB4861BE063C500EC8160 /* BGM_DeviceTests.mm */; };
 		1C8034DD1BDD073B00668E00 /* BGM_ClientsTests.mm in Sources */ = {isa = PBXBuildFile; fileRef = 1C8034DC1BDD073B00668E00 /* BGM_ClientsTests.mm */; };
+		1CA2A9E21E8D1D08007A76A4 /* BGM_Stream.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 1CA2A9E01E8D1D08007A76A4 /* BGM_Stream.cpp */; };
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-		1CB8B3731BBBD8A4000E2DD1 /* CADebugMacros.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 1CB8B3701BBBD8A4000E2DD1 /* CADebugMacros.cpp */; };
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 		1CB8B3771BBBD924000E2DD1 /* CoreFoundation.framework in Frameworks */ = {isa = PBXBuildFile; fileRef = 1CB8B3751BBBD924000E2DD1 /* CoreFoundation.framework */; };
-		1CB8B37A1BBBDFA2000E2DD1 /* CADebugPrintf.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 1CB8B3781BBBDFA2000E2DD1 /* CADebugPrintf.cpp */; };
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 		1CB8B3801BBCCF87000E2DD1 /* BGM_Device.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 1CB8B37E1BBCCF87000E2DD1 /* BGM_Device.cpp */; };
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-		1CB8B3861BBCEFE8000E2DD1 /* CAMutex.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 1CB8B3841BBCEFE8000E2DD1 /* CAMutex.cpp */; };
-		1CB8B3891BBCF08A000E2DD1 /* CAHostTimeBase.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 1CB8B3871BBCF08A000E2DD1 /* CAHostTimeBase.cpp */; };
-		1CB8B38E1BBCF4A9000E2DD1 /* CACFString.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 1CB8B38A1BBCF4A9000E2DD1 /* CACFString.cpp */; };
-		1CB8B38F1BBCF4A9000E2DD1 /* CAVolumeCurve.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 1CB8B38C1BBCF4A9000E2DD1 /* CAVolumeCurve.cpp */; };
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-		1CB8B3951BBD2418000E2DD1 /* CADispatchQueue.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 1CB8B3931BBD2418000E2DD1 /* CADispatchQueue.cpp */; };
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-		1CC1DF891BE558B000FB8FE4 /* CADebugger.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 1CC1DF871BE558B000FB8FE4 /* CADebugger.cpp */; };
-		1CC1DF8A1BE5703B00FB8FE4 /* CACFArray.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 1CE3E68F1BE2683900167F5D /* CACFArray.cpp */; };
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 		1CC1DF9E1BE94AA200FB8FE4 /* DeviceIcon.icns in Resources */ = {isa = PBXBuildFile; fileRef = 1CC1DF9D1BE94AA200FB8FE4 /* DeviceIcon.icns */; };
+		1CD95B121E93AA5200EB8EF0 /* BGM_AbstractDevice.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 1CDF3ABD1E8644C20001E9B7 /* BGM_AbstractDevice.cpp */; };
+		1CD95B131E93AA5200EB8EF0 /* BGM_NullDevice.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 1CDF3ABA1E863B980001E9B7 /* BGM_NullDevice.cpp */; };
+		1CD95B141E93AA5200EB8EF0 /* BGM_Stream.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 1CA2A9E01E8D1D08007A76A4 /* BGM_Stream.cpp */; };
+		1CDF3ABC1E863B980001E9B7 /* BGM_NullDevice.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 1CDF3ABA1E863B980001E9B7 /* BGM_NullDevice.cpp */; };
+		1CDF3ABF1E8644C20001E9B7 /* BGM_AbstractDevice.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 1CDF3ABD1E8644C20001E9B7 /* BGM_AbstractDevice.cpp */; };
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+		2743C9E01D7EF8760089613B /* CAMutex.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 1CB8B3841BBCEFE8000E2DD1 /* CAMutex.cpp */; };
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+		2743C9E61D7EF8E00089613B /* libPublicUtility.a in Frameworks */ = {isa = PBXBuildFile; fileRef = 2743C9C61D7EF84B0089613B /* libPublicUtility.a */; };
+		275343BD1DE9B44900DF3858 /* BGM_Utils.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 275343BC1DE9B44900DF3858 /* BGM_Utils.cpp */; };
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@@ -59,6 +67,7 @@
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+		27E6B5F01E01966A00EC0AAB /* BGM_Utils.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 275343BC1DE9B44900DF3858 /* BGM_Utils.cpp */; };
 /* End PBXBuildFile section */
 
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+		1C37B3681E9B8D3C000DF98F /* CAPropertyAddress.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; name = CAPropertyAddress.h; path = PublicUtility/CAPropertyAddress.h; sourceTree = "<group>"; };
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@@ -82,6 +92,8 @@
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 		1C8034DE1BDD073B00668E00 /* Info.plist */ = {isa = PBXFileReference; lastKnownFileType = text.plist.xml; path = Info.plist; sourceTree = "<group>"; };
+		1CA2A9E01E8D1D08007A76A4 /* BGM_Stream.cpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; path = BGM_Stream.cpp; sourceTree = "<group>"; };
+		1CA2A9E11E8D1D08007A76A4 /* BGM_Stream.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = BGM_Stream.h; sourceTree = "<group>"; };
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@@ -114,12 +126,18 @@
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 		1CC1DF9D1BE94AA200FB8FE4 /* DeviceIcon.icns */ = {isa = PBXFileReference; lastKnownFileType = image.icns; path = DeviceIcon.icns; sourceTree = "<group>"; };
+		1CDF3ABA1E863B980001E9B7 /* BGM_NullDevice.cpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; path = BGM_NullDevice.cpp; sourceTree = "<group>"; };
+		1CDF3ABB1E863B980001E9B7 /* BGM_NullDevice.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = BGM_NullDevice.h; sourceTree = "<group>"; };
+		1CDF3ABD1E8644C20001E9B7 /* BGM_AbstractDevice.cpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; path = BGM_AbstractDevice.cpp; sourceTree = "<group>"; };
+		1CDF3ABE1E8644C20001E9B7 /* BGM_AbstractDevice.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = BGM_AbstractDevice.h; sourceTree = "<group>"; };
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@@ -141,16 +159,24 @@
 			isa = PBXFrameworksBuildPhase;
 			buildActionMask = 2147483647;
 			files = (
+				2743C9E61D7EF8E00089613B /* libPublicUtility.a in Frameworks */,
 				2795973E1C9847CF00A002FB /* Foundation.framework in Frameworks */,
 				1CB8B3761BBBD924000E2DD1 /* CoreAudio.framework in Frameworks */,
 				1CB8B3771BBBD924000E2DD1 /* CoreFoundation.framework in Frameworks */,
 			);
 			runOnlyForDeploymentPostprocessing = 0;
 		};
+		2743C9C31D7EF84B0089613B /* Frameworks */ = {
+			isa = PBXFrameworksBuildPhase;
+			buildActionMask = 2147483647;
+			files = (
+			);
+			runOnlyForDeploymentPostprocessing = 0;
+		};
 /* End PBXFrameworksBuildPhase section */
 
 /* Begin PBXGroup section */
-		1C0CB6AF1C642C600084C15A /* Device Clients */ = {
+		1C0CB6AF1C642C600084C15A /* DeviceClients */ = {
 			isa = PBXGroup;
 			children = (
 				1C0CB6B11C642C600084C15A /* BGM_Client.h */,
@@ -161,7 +187,6 @@
 				1C0CB6B41C642C600084C15A /* BGM_Clients.cpp */,
 				1C0CB6B81C642C600084C15A /* BGM_ClientTasks.h */,
 			);
-			name = "Device Clients";
 			path = DeviceClients;
 			sourceTree = "<group>";
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@@ -184,9 +209,7 @@
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 				1CB8B36F1BBBD7AE000E2DD1 /* PublicUtility */,
 				1CB8B3651BBBB78D000E2DD1 /* Products */,
-				2795973D1C9847CF00A002FB /* Foundation.framework */,
-				1CB8B3741BBBD924000E2DD1 /* CoreAudio.framework */,
-				1CB8B3751BBBD924000E2DD1 /* CoreFoundation.framework */,
+				2743CA241D86E2E80089613B /* Frameworks */,
 			);
 			sourceTree = "<group>";
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@@ -195,6 +218,7 @@
 			children = (
 				1CB8B3641BBBB78D000E2DD1 /* Background Music Device.driver */,
 				1C8034DA1BDD073B00668E00 /* BGMDriverTests.xctest */,
+				2743C9C61D7EF84B0089613B /* libPublicUtility.a */,
 			);
 			name = Products;
 			sourceTree = "<group>";
@@ -207,9 +231,15 @@
 				1CB8B37B1BBCCF62000E2DD1 /* BGM_PlugIn.cpp */,
 				1CB8B3821BBCE7B5000E2DD1 /* BGM_Object.h */,
 				1CB8B3811BBCE7B5000E2DD1 /* BGM_Object.cpp */,
+				1CDF3ABE1E8644C20001E9B7 /* BGM_AbstractDevice.h */,
+				1CDF3ABD1E8644C20001E9B7 /* BGM_AbstractDevice.cpp */,
 				1CB8B37F1BBCCF87000E2DD1 /* BGM_Device.h */,
 				1CB8B37E1BBCCF87000E2DD1 /* BGM_Device.cpp */,
-				1C0CB6AF1C642C600084C15A /* Device Clients */,
+				1CDF3ABB1E863B980001E9B7 /* BGM_NullDevice.h */,
+				1CDF3ABA1E863B980001E9B7 /* BGM_NullDevice.cpp */,
+				1CA2A9E11E8D1D08007A76A4 /* BGM_Stream.h */,
+				1CA2A9E01E8D1D08007A76A4 /* BGM_Stream.cpp */,
+				1C0CB6AF1C642C600084C15A /* DeviceClients */,
 				1C38210D1C4A163A00A0C8C6 /* BGM_TaskQueue.h */,
 				1C38210C1C4A163A00A0C8C6 /* BGM_TaskQueue.cpp */,
 				27381A151C8EF50F00DF167C /* BGM_XPCHelper.h */,
@@ -235,6 +265,7 @@
 			isa = PBXGroup;
 			children = (
 				1C0CB6A71C4E06F70084C15A /* CAAtomic.h */,
+				1C37B3681E9B8D3C000DF98F /* CAPropertyAddress.h */,
 				1C0CB6A61C4E06C00084C15A /* CAAtomicStack.h */,
 				1C0CB6A91C50A3AF0084C15A /* CAAutoDisposer.h */,
 				1CE3E68F1BE2683900167F5D /* CACFArray.cpp */,
@@ -266,11 +297,22 @@
 			name = PublicUtility;
 			sourceTree = "<group>";
 		};
+		2743CA241D86E2E80089613B /* Frameworks */ = {
+			isa = PBXGroup;
+			children = (
+				1CB8B3741BBBD924000E2DD1 /* CoreAudio.framework */,
+				1CB8B3751BBBD924000E2DD1 /* CoreFoundation.framework */,
+				2795973D1C9847CF00A002FB /* Foundation.framework */,
+			);
+			name = Frameworks;
+			sourceTree = "<group>";
+		};
 		27D643B61C9FABDE00737F6E /* SharedSource */ = {
 			isa = PBXGroup;
 			children = (
 				27D643B71C9FABF600737F6E /* BGM_Types.h */,
 				2771700E1CA0C16200AB34B4 /* BGM_Utils.h */,
+				275343BC1DE9B44900DF3858 /* BGM_Utils.cpp */,
 				27D643C21C9FBC5800737F6E /* BGM_TestUtils.h */,
 				27D643B81C9FABF600737F6E /* BGMXPCProtocols.h */,
 			);
@@ -279,6 +321,16 @@
 		};
 /* End PBXGroup section */
 
+/* Begin PBXHeadersBuildPhase section */
+		2743C9C41D7EF84B0089613B /* Headers */ = {
+			isa = PBXHeadersBuildPhase;
+			buildActionMask = 2147483647;
+			files = (
+			);
+			runOnlyForDeploymentPostprocessing = 0;
+		};
+/* End PBXHeadersBuildPhase section */
+
 /* Begin PBXNativeTarget section */
 		1C8034D91BDD073B00668E00 /* BGMDriverTests */ = {
 			isa = PBXNativeTarget;
@@ -314,6 +366,23 @@
 			productReference = 1CB8B3641BBBB78D000E2DD1 /* Background Music Device.driver */;
 			productType = "com.apple.product-type.bundle";
 		};
+		2743C9C51D7EF84B0089613B /* PublicUtility */ = {
+			isa = PBXNativeTarget;
+			buildConfigurationList = 2743C9C71D7EF84B0089613B /* Build configuration list for PBXNativeTarget "PublicUtility" */;
+			buildPhases = (
+				2743C9C21D7EF84B0089613B /* Sources */,
+				2743C9C31D7EF84B0089613B /* Frameworks */,
+				2743C9C41D7EF84B0089613B /* Headers */,
+			);
+			buildRules = (
+			);
+			dependencies = (
+			);
+			name = PublicUtility;
+			productName = PublicUtility;
+			productReference = 2743C9C61D7EF84B0089613B /* libPublicUtility.a */;
+			productType = "com.apple.product-type.library.static";
+		};
 /* End PBXNativeTarget section */
 
 /* Begin PBXProject section */
@@ -322,7 +391,7 @@
 			attributes = {
 				CLASSPREFIX = BGM_;
 				LastUpgradeCheck = 0700;
-				ORGANIZATIONNAME = "Kyle Neideck";
+				ORGANIZATIONNAME = "Background Music contributors";
 				TargetAttributes = {
 					1C8034D91BDD073B00668E00 = {
 						CreatedOnToolsVersion = 7.0.1;
@@ -330,10 +399,14 @@
 					1CB8B3631BBBB78D000E2DD1 = {
 						CreatedOnToolsVersion = 6.4;
 					};
+					2743C9C51D7EF84B0089613B = {
+						CreatedOnToolsVersion = 8.0;
+						ProvisioningStyle = Automatic;
+					};
 				};
 			};
 			buildConfigurationList = 1CB8B35D1BBBB69C000E2DD1 /* Build configuration list for PBXProject "BGMDriver" */;
-			compatibilityVersion = "Xcode 3.2";
+			compatibilityVersion = "Xcode 6.3";
 			developmentRegion = English;
 			hasScannedForEncodings = 0;
 			knownRegions = (
@@ -346,6 +419,7 @@
 			targets = (
 				1CB8B3631BBBB78D000E2DD1 /* Background Music Device */,
 				1C8034D91BDD073B00668E00 /* BGMDriverTests */,
+				2743C9C51D7EF84B0089613B /* PublicUtility */,
 			);
 		};
 /* End PBXProject section */
@@ -373,6 +447,10 @@
 			isa = PBXSourcesBuildPhase;
 			buildActionMask = 2147483647;
 			files = (
+				1CD95B121E93AA5200EB8EF0 /* BGM_AbstractDevice.cpp in Sources */,
+				1CD95B131E93AA5200EB8EF0 /* BGM_NullDevice.cpp in Sources */,
+				1CD95B141E93AA5200EB8EF0 /* BGM_Stream.cpp in Sources */,
+				27E6B5F01E01966A00EC0AAB /* BGM_Utils.cpp in Sources */,
 				277170101CA0CFC300AB34B4 /* BGM_PlugInInterface.cpp in Sources */,
 				277170111CA0CFC300AB34B4 /* CACFNumber.cpp in Sources */,
 				27D643C31C9FBE1600737F6E /* BGM_XPCHelper.m in Sources */,
@@ -405,28 +483,39 @@
 			isa = PBXSourcesBuildPhase;
 			buildActionMask = 2147483647;
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-				1CC1DF8A1BE5703B00FB8FE4 /* CACFArray.cpp in Sources */,
-				1CC1DF8B1BE5703B00FB8FE4 /* CACFDictionary.cpp in Sources */,
+				1CA2A9E21E8D1D08007A76A4 /* BGM_Stream.cpp in Sources */,
 				1CB8B3801BBCCF87000E2DD1 /* BGM_Device.cpp in Sources */,
-				1CB8B3951BBD2418000E2DD1 /* CADispatchQueue.cpp in Sources */,
-				1CB8B37A1BBBDFA2000E2DD1 /* CADebugPrintf.cpp in Sources */,
-				1C305D9D1BE294B5004EBB91 /* CACFNumber.cpp in Sources */,
-				1CB8B3731BBBD8A4000E2DD1 /* CADebugMacros.cpp in Sources */,
 				1C0CB6B91C642C600084C15A /* BGM_Client.cpp in Sources */,
-				1C3821111C4A18DE00A0C8C6 /* CAPThread.cpp in Sources */,
-				1CB8B38E1BBCF4A9000E2DD1 /* CACFString.cpp in Sources */,
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 				1CB8B37D1BBCCF62000E2DD1 /* BGM_PlugIn.cpp in Sources */,
 				27381A161C8EF50F00DF167C /* BGM_XPCHelper.m in Sources */,
+				1CDF3ABF1E8644C20001E9B7 /* BGM_AbstractDevice.cpp in Sources */,
 				1C0CB6BA1C642C600084C15A /* BGM_ClientMap.cpp in Sources */,
 				1CB8B3831BBCE7B5000E2DD1 /* BGM_Object.cpp in Sources */,
-				1CC1DF891BE558B000FB8FE4 /* CADebugger.cpp in Sources */,
-				1CB8B3861BBCEFE8000E2DD1 /* CAMutex.cpp in Sources */,
-				1CB8B3891BBCF08A000E2DD1 /* CAHostTimeBase.cpp in Sources */,
-				1CB8B38F1BBCF4A9000E2DD1 /* CAVolumeCurve.cpp in Sources */,
+				275343BD1DE9B44900DF3858 /* BGM_Utils.cpp in Sources */,
 				1C38210E1C4A163A00A0C8C6 /* BGM_TaskQueue.cpp in Sources */,
 				1C0CB6BB1C642C600084C15A /* BGM_Clients.cpp in Sources */,
+				1CDF3ABC1E863B980001E9B7 /* BGM_NullDevice.cpp in Sources */,
+			);
+			runOnlyForDeploymentPostprocessing = 0;
+		};
+		2743C9C21D7EF84B0089613B /* Sources */ = {
+			isa = PBXSourcesBuildPhase;
+			buildActionMask = 2147483647;
+			files = (
+				2743C9CD1D7EF8760089613B /* CACFArray.cpp in Sources */,
+				2743C9CF1D7EF8760089613B /* CACFDictionary.cpp in Sources */,
+				2743C9D11D7EF8760089613B /* CACFNumber.cpp in Sources */,
+				2743C9D31D7EF8760089613B /* CACFString.cpp in Sources */,
+				2743C9D51D7EF8760089613B /* CADebugger.cpp in Sources */,
+				2743C9D71D7EF8760089613B /* CADebugMacros.cpp in Sources */,
+				2743C9D91D7EF8760089613B /* CADebugPrintf.cpp in Sources */,
+				2743C9DB1D7EF8760089613B /* CADispatchQueue.cpp in Sources */,
+				2743C9DE1D7EF8760089613B /* CAHostTimeBase.cpp in Sources */,
+				2743C9E01D7EF8760089613B /* CAMutex.cpp in Sources */,
+				2743C9E21D7EF8760089613B /* CAPThread.cpp in Sources */,
+				2743C9E41D7EF8760089613B /* CAVolumeCurve.cpp in Sources */,
 			);
 			runOnlyForDeploymentPostprocessing = 0;
 		};
@@ -437,44 +526,21 @@
 			isa = XCBuildConfiguration;
 			buildSettings = {
 				ALWAYS_SEARCH_USER_PATHS = NO;
-				CLANG_CXX_LANGUAGE_STANDARD = "c++0x";
-				CLANG_CXX_LIBRARY = "libc++";
 				CLANG_ENABLE_MODULES = YES;
-				CLANG_ENABLE_OBJC_ARC = YES;
-				CLANG_WARN_BOOL_CONVERSION = YES;
-				CLANG_WARN_CONSTANT_CONVERSION = YES;
 				CLANG_WARN_DIRECT_OBJC_ISA_USAGE = YES_ERROR;
-				CLANG_WARN_EMPTY_BODY = YES;
-				CLANG_WARN_ENUM_CONVERSION = YES;
-				CLANG_WARN_INT_CONVERSION = YES;
+				CLANG_WARN_IMPLICIT_SIGN_CONVERSION = NO;
 				CLANG_WARN_OBJC_ROOT_CLASS = YES_ERROR;
-				CLANG_WARN_UNREACHABLE_CODE = YES;
-				CLANG_WARN__DUPLICATE_METHOD_MATCH = YES;
+				CLANG_WARN__EXIT_TIME_DESTRUCTORS = NO;
 				COMBINE_HIDPI_IMAGES = YES;
 				COPY_PHASE_STRIP = NO;
 				DEBUG_INFORMATION_FORMAT = dwarf;
-				ENABLE_STRICT_OBJC_MSGSEND = YES;
-				GCC_C_LANGUAGE_STANDARD = c11;
-				GCC_DYNAMIC_NO_PIC = NO;
-				GCC_NO_COMMON_BLOCKS = YES;
-				GCC_OPTIMIZATION_LEVEL = 0;
-				GCC_PREPROCESSOR_DEFINITIONS = (
-					"DEBUG=1",
-					"$(inherited)",
-				);
-				GCC_WARN_64_TO_32_BIT_CONVERSION = YES;
 				GCC_WARN_ABOUT_RETURN_TYPE = YES_ERROR;
-				GCC_WARN_UNDECLARED_SELECTOR = YES;
-				GCC_WARN_UNINITIALIZED_AUTOS = YES_AGGRESSIVE;
-				GCC_WARN_UNUSED_FUNCTION = YES;
-				GCC_WARN_UNUSED_VARIABLE = YES;
 				INFOPLIST_FILE = BGMDriverTests/Info.plist;
 				LD_RUNPATH_SEARCH_PATHS = "$(inherited) @executable_path/../Frameworks @loader_path/../Frameworks";
-				MACOSX_DEPLOYMENT_TARGET = 10.10;
 				MTL_ENABLE_DEBUG_INFO = YES;
-				PRODUCT_BUNDLE_IDENTIFIER = com.bearisdriving.BGMDriverTests;
+				PRODUCT_BUNDLE_IDENTIFIER = com.bearisdriving.BGM.DriverTests;
 				PRODUCT_NAME = "$(TARGET_NAME)";
-				SDKROOT = macosx;
+				WARNING_CFLAGS = "";
 			};
 			name = Debug;
 		};
@@ -482,52 +548,53 @@
 			isa = XCBuildConfiguration;
 			buildSettings = {
 				ALWAYS_SEARCH_USER_PATHS = NO;
-				CLANG_CXX_LANGUAGE_STANDARD = "c++0x";
-				CLANG_CXX_LIBRARY = "libc++";
 				CLANG_ENABLE_MODULES = YES;
-				CLANG_ENABLE_OBJC_ARC = YES;
-				CLANG_WARN_BOOL_CONVERSION = YES;
-				CLANG_WARN_CONSTANT_CONVERSION = YES;
 				CLANG_WARN_DIRECT_OBJC_ISA_USAGE = YES_ERROR;
-				CLANG_WARN_EMPTY_BODY = YES;
-				CLANG_WARN_ENUM_CONVERSION = YES;
-				CLANG_WARN_INT_CONVERSION = YES;
+				CLANG_WARN_IMPLICIT_SIGN_CONVERSION = NO;
 				CLANG_WARN_OBJC_ROOT_CLASS = YES_ERROR;
-				CLANG_WARN_UNREACHABLE_CODE = YES;
-				CLANG_WARN__DUPLICATE_METHOD_MATCH = YES;
+				CLANG_WARN__EXIT_TIME_DESTRUCTORS = NO;
 				COMBINE_HIDPI_IMAGES = YES;
 				COPY_PHASE_STRIP = NO;
 				DEBUG_INFORMATION_FORMAT = "dwarf-with-dsym";
-				ENABLE_NS_ASSERTIONS = NO;
-				ENABLE_STRICT_OBJC_MSGSEND = YES;
-				GCC_C_LANGUAGE_STANDARD = c11;
-				GCC_NO_COMMON_BLOCKS = YES;
-				GCC_WARN_64_TO_32_BIT_CONVERSION = YES;
+				ENABLE_NS_ASSERTIONS = YES;
 				GCC_WARN_ABOUT_RETURN_TYPE = YES_ERROR;
-				GCC_WARN_UNDECLARED_SELECTOR = YES;
-				GCC_WARN_UNINITIALIZED_AUTOS = YES_AGGRESSIVE;
-				GCC_WARN_UNUSED_FUNCTION = YES;
-				GCC_WARN_UNUSED_VARIABLE = YES;
 				INFOPLIST_FILE = BGMDriverTests/Info.plist;
 				LD_RUNPATH_SEARCH_PATHS = "$(inherited) @executable_path/../Frameworks @loader_path/../Frameworks";
-				MACOSX_DEPLOYMENT_TARGET = 10.10;
 				MTL_ENABLE_DEBUG_INFO = NO;
-				PRODUCT_BUNDLE_IDENTIFIER = com.bearisdriving.BGMDriverTests;
+				PRODUCT_BUNDLE_IDENTIFIER = com.bearisdriving.BGM.DriverTests;
 				PRODUCT_NAME = "$(TARGET_NAME)";
-				SDKROOT = macosx;
+				WARNING_CFLAGS = "";
 			};
 			name = Release;
 		};
 		1CB8B35E1BBBB69C000E2DD1 /* Debug */ = {
 			isa = XCBuildConfiguration;
 			buildSettings = {
+				ALWAYS_SEARCH_USER_PATHS = NO;
+				CLANG_ANALYZER_NONNULL = YES;
+				CLANG_ANALYZER_SECURITY_FLOATLOOPCOUNTER = YES;
+				CLANG_ANALYZER_SECURITY_INSECUREAPI_RAND = YES;
+				CLANG_ANALYZER_SECURITY_INSECUREAPI_STRCPY = YES;
+				CLANG_CXX_LANGUAGE_STANDARD = "c++0x";
+				CLANG_CXX_LIBRARY = "libc++";
 				CLANG_ENABLE_OBJC_ARC = YES;
 				CLANG_WARN_ASSIGN_ENUM = YES;
+				CLANG_WARN_DEPRECATED_OBJC_IMPLEMENTATIONS = YES;
 				CLANG_WARN_EMPTY_BODY = YES;
+				CLANG_WARN_IMPLICIT_SIGN_CONVERSION = YES;
+				CLANG_WARN_INFINITE_RECURSION = YES;
 				CLANG_WARN_NULLABLE_TO_NONNULL_CONVERSION = YES;
+				CLANG_WARN_OBJC_IMPLICIT_RETAIN_SELF = YES;
+				CLANG_WARN_OBJC_REPEATED_USE_OF_WEAK = YES;
 				CLANG_WARN_SUSPICIOUS_IMPLICIT_CONVERSION = YES;
+				CLANG_WARN_SUSPICIOUS_MOVE = YES;
+				CLANG_WARN_UNREACHABLE_CODE = YES;
+				CLANG_WARN__DUPLICATE_METHOD_MATCH = YES;
+				CLANG_WARN__EXIT_TIME_DESTRUCTORS = YES;
 				DEAD_CODE_STRIPPING = YES;
+				ENABLE_STRICT_OBJC_MSGSEND = YES;
 				ENABLE_TESTABILITY = YES;
+				GCC_C_LANGUAGE_STANDARD = c11;
 				GCC_NO_COMMON_BLOCKS = YES;
 				GCC_OPTIMIZATION_LEVEL = 0;
 				GCC_PREPROCESSOR_DEFINITIONS = (
@@ -535,13 +602,22 @@
 					"CoreAudio_Debug=1",
 					"CoreAudio_UseSysLog=1",
 					"CoreAudio_StopOnAssert=1",
+					"CoreAudio_ThreadStampMessages=0",
 				);
 				GCC_TREAT_WARNINGS_AS_ERRORS = YES;
 				GCC_WARN_64_TO_32_BIT_CONVERSION = YES;
 				GCC_WARN_ABOUT_MISSING_FIELD_INITIALIZERS = YES;
+				GCC_WARN_ABOUT_MISSING_NEWLINE = YES;
 				GCC_WARN_ABOUT_MISSING_PROTOTYPES = YES;
 				GCC_WARN_ABOUT_RETURN_TYPE = YES;
+				GCC_WARN_HIDDEN_VIRTUAL_FUNCTIONS = YES;
 				GCC_WARN_INITIALIZER_NOT_FULLY_BRACKETED = YES;
+				GCC_WARN_NON_VIRTUAL_DESTRUCTOR = YES;
+				GCC_WARN_SHADOW = YES;
+				GCC_WARN_SIGN_COMPARE = YES;
+				GCC_WARN_STRICT_SELECTOR_MATCH = YES;
+				GCC_WARN_UNDECLARED_SELECTOR = YES;
+				GCC_WARN_UNINITIALIZED_AUTOS = YES_AGGRESSIVE;
 				GCC_WARN_UNUSED_FUNCTION = YES;
 				GCC_WARN_UNUSED_LABEL = YES;
 				GCC_WARN_UNUSED_PARAMETER = YES;
@@ -549,38 +625,68 @@
 				MACOSX_DEPLOYMENT_TARGET = 10.9;
 				ONLY_ACTIVE_ARCH = YES;
 				RUN_CLANG_STATIC_ANALYZER = YES;
+				WARNING_CFLAGS = "-Wpartial-availability";
 			};
 			name = Debug;
 		};
 		1CB8B35F1BBBB69C000E2DD1 /* Release */ = {
 			isa = XCBuildConfiguration;
 			buildSettings = {
+				ALWAYS_SEARCH_USER_PATHS = NO;
+				CLANG_ANALYZER_NONNULL = YES;
+				CLANG_ANALYZER_SECURITY_FLOATLOOPCOUNTER = YES;
+				CLANG_ANALYZER_SECURITY_INSECUREAPI_RAND = YES;
+				CLANG_ANALYZER_SECURITY_INSECUREAPI_STRCPY = YES;
+				CLANG_CXX_LANGUAGE_STANDARD = "c++0x";
+				CLANG_CXX_LIBRARY = "libc++";
 				CLANG_ENABLE_OBJC_ARC = YES;
 				CLANG_WARN_ASSIGN_ENUM = YES;
+				CLANG_WARN_DEPRECATED_OBJC_IMPLEMENTATIONS = YES;
 				CLANG_WARN_EMPTY_BODY = YES;
+				CLANG_WARN_IMPLICIT_SIGN_CONVERSION = YES;
+				CLANG_WARN_INFINITE_RECURSION = YES;
 				CLANG_WARN_NULLABLE_TO_NONNULL_CONVERSION = YES;
+				CLANG_WARN_OBJC_IMPLICIT_RETAIN_SELF = YES;
+				CLANG_WARN_OBJC_REPEATED_USE_OF_WEAK = YES;
 				CLANG_WARN_SUSPICIOUS_IMPLICIT_CONVERSION = YES;
+				CLANG_WARN_SUSPICIOUS_MOVE = YES;
+				CLANG_WARN_UNREACHABLE_CODE = YES;
+				CLANG_WARN__DUPLICATE_METHOD_MATCH = YES;
+				CLANG_WARN__EXIT_TIME_DESTRUCTORS = YES;
 				DEAD_CODE_STRIPPING = YES;
+				ENABLE_NS_ASSERTIONS = NO;
+				ENABLE_STRICT_OBJC_MSGSEND = YES;
+				GCC_C_LANGUAGE_STANDARD = c11;
 				GCC_NO_COMMON_BLOCKS = YES;
-				GCC_OPTIMIZATION_LEVEL = s;
+				GCC_OPTIMIZATION_LEVEL = 3;
 				GCC_PREPROCESSOR_DEFINITIONS = (
 					"DEBUG=0",
 					"CoreAudio_Debug=0",
 					"CoreAudio_UseSysLog=1",
 					"CoreAudio_StopOnAssert=0",
+					"CoreAudio_ThreadStampMessages=0",
 				);
 				GCC_TREAT_WARNINGS_AS_ERRORS = YES;
 				GCC_WARN_64_TO_32_BIT_CONVERSION = YES;
 				GCC_WARN_ABOUT_MISSING_FIELD_INITIALIZERS = YES;
+				GCC_WARN_ABOUT_MISSING_NEWLINE = YES;
 				GCC_WARN_ABOUT_MISSING_PROTOTYPES = YES;
 				GCC_WARN_ABOUT_RETURN_TYPE = YES;
+				GCC_WARN_HIDDEN_VIRTUAL_FUNCTIONS = YES;
 				GCC_WARN_INITIALIZER_NOT_FULLY_BRACKETED = YES;
+				GCC_WARN_NON_VIRTUAL_DESTRUCTOR = YES;
+				GCC_WARN_SHADOW = YES;
+				GCC_WARN_SIGN_COMPARE = YES;
+				GCC_WARN_STRICT_SELECTOR_MATCH = YES;
+				GCC_WARN_UNDECLARED_SELECTOR = YES;
+				GCC_WARN_UNINITIALIZED_AUTOS = YES_AGGRESSIVE;
 				GCC_WARN_UNUSED_FUNCTION = YES;
 				GCC_WARN_UNUSED_LABEL = YES;
 				GCC_WARN_UNUSED_PARAMETER = YES;
 				GCC_WARN_UNUSED_VARIABLE = YES;
 				MACOSX_DEPLOYMENT_TARGET = 10.9;
 				RUN_CLANG_STATIC_ANALYZER = YES;
+				WARNING_CFLAGS = "-Wpartial-availability";
 			};
 			name = Release;
 		};
@@ -588,35 +694,26 @@
 			isa = XCBuildConfiguration;
 			buildSettings = {
 				ALWAYS_SEARCH_USER_PATHS = NO;
-				CLANG_CXX_LANGUAGE_STANDARD = "c++0x";
-				CLANG_CXX_LIBRARY = "libc++";
 				CLANG_ENABLE_MODULES = YES;
 				CLANG_ENABLE_OBJC_ARC = YES;
 				CLANG_WARN_BOOL_CONVERSION = YES;
 				CLANG_WARN_CONSTANT_CONVERSION = YES;
-				CLANG_WARN_DIRECT_OBJC_ISA_USAGE = YES_ERROR;
 				CLANG_WARN_EMPTY_BODY = YES;
 				CLANG_WARN_ENUM_CONVERSION = YES;
 				CLANG_WARN_INT_CONVERSION = YES;
-				CLANG_WARN_OBJC_ROOT_CLASS = YES_ERROR;
 				CLANG_WARN_UNREACHABLE_CODE = YES;
-				CLANG_WARN__DUPLICATE_METHOD_MATCH = YES;
 				COMBINE_HIDPI_IMAGES = YES;
 				DEBUG_INFORMATION_FORMAT = dwarf;
-				ENABLE_STRICT_OBJC_MSGSEND = YES;
 				GCC_C_LANGUAGE_STANDARD = "compiler-default";
 				GCC_DYNAMIC_NO_PIC = NO;
 				GCC_ENABLE_CPP_RTTI = NO;
-				GCC_PREPROCESSOR_DEFINITIONS = "$(inherited)";
 				GCC_WARN_64_TO_32_BIT_CONVERSION = YES;
 				GCC_WARN_ABOUT_RETURN_TYPE = YES_ERROR;
-				GCC_WARN_UNDECLARED_SELECTOR = YES;
 				GCC_WARN_UNINITIALIZED_AUTOS = YES_AGGRESSIVE;
 				GCC_WARN_UNUSED_FUNCTION = YES;
 				GCC_WARN_UNUSED_VARIABLE = YES;
 				INFOPLIST_FILE = BGMDriver/Info.plist;
 				INSTALL_PATH = "$(LOCAL_LIBRARY_DIR)/Audio/Plug-Ins/HAL";
-				MACOSX_DEPLOYMENT_TARGET = 10.9;
 				MTL_ENABLE_DEBUG_INFO = YES;
 				ONLY_ACTIVE_ARCH = YES;
 				PRODUCT_BUNDLE_IDENTIFIER = com.bearisdriving.BGM.Driver;
@@ -631,34 +728,26 @@
 			isa = XCBuildConfiguration;
 			buildSettings = {
 				ALWAYS_SEARCH_USER_PATHS = NO;
-				CLANG_CXX_LANGUAGE_STANDARD = "c++0x";
-				CLANG_CXX_LIBRARY = "libc++";
 				CLANG_ENABLE_MODULES = YES;
 				CLANG_ENABLE_OBJC_ARC = YES;
 				CLANG_WARN_BOOL_CONVERSION = YES;
 				CLANG_WARN_CONSTANT_CONVERSION = YES;
-				CLANG_WARN_DIRECT_OBJC_ISA_USAGE = YES_ERROR;
 				CLANG_WARN_EMPTY_BODY = YES;
 				CLANG_WARN_ENUM_CONVERSION = YES;
 				CLANG_WARN_INT_CONVERSION = YES;
-				CLANG_WARN_OBJC_ROOT_CLASS = YES_ERROR;
 				CLANG_WARN_UNREACHABLE_CODE = YES;
-				CLANG_WARN__DUPLICATE_METHOD_MATCH = YES;
 				COMBINE_HIDPI_IMAGES = YES;
 				DEBUG_INFORMATION_FORMAT = "dwarf-with-dsym";
 				ENABLE_NS_ASSERTIONS = NO;
-				ENABLE_STRICT_OBJC_MSGSEND = YES;
 				GCC_C_LANGUAGE_STANDARD = "compiler-default";
 				GCC_ENABLE_CPP_RTTI = NO;
 				GCC_WARN_64_TO_32_BIT_CONVERSION = YES;
 				GCC_WARN_ABOUT_RETURN_TYPE = YES_ERROR;
-				GCC_WARN_UNDECLARED_SELECTOR = YES;
 				GCC_WARN_UNINITIALIZED_AUTOS = YES_AGGRESSIVE;
 				GCC_WARN_UNUSED_FUNCTION = YES;
 				GCC_WARN_UNUSED_VARIABLE = YES;
 				INFOPLIST_FILE = BGMDriver/Info.plist;
 				INSTALL_PATH = "$(LOCAL_LIBRARY_DIR)/Audio/Plug-Ins/HAL";
-				MACOSX_DEPLOYMENT_TARGET = 10.9;
 				MTL_ENABLE_DEBUG_INFO = NO;
 				PRODUCT_BUNDLE_IDENTIFIER = com.bearisdriving.BGM.Driver;
 				PRODUCT_NAME = "$(TARGET_NAME)";
@@ -668,6 +757,57 @@
 			};
 			name = Release;
 		};
+		2743C9C81D7EF84B0089613B /* Debug */ = {
+			isa = XCBuildConfiguration;
+			buildSettings = {
+				CLANG_WARN_BOOL_CONVERSION = YES;
+				CLANG_WARN_CONSTANT_CONVERSION = YES;
+				CLANG_WARN_DIRECT_OBJC_ISA_USAGE = YES_ERROR;
+				CLANG_WARN_DOCUMENTATION_COMMENTS = YES;
+				CLANG_WARN_ENUM_CONVERSION = YES;
+				CLANG_WARN_IMPLICIT_SIGN_CONVERSION = NO;
+				CLANG_WARN_INT_CONVERSION = YES;
+				CLANG_WARN_OBJC_ROOT_CLASS = YES_ERROR;
+				CLANG_WARN_SUSPICIOUS_MOVES = YES;
+				CODE_SIGN_IDENTITY = "-";
+				COPY_PHASE_STRIP = NO;
+				DEBUG_INFORMATION_FORMAT = dwarf;
+				EXECUTABLE_PREFIX = lib;
+				GCC_DYNAMIC_NO_PIC = NO;
+				GCC_PREPROCESSOR_DEFINITIONS = (
+					"DEBUG=1",
+					"$(inherited)",
+				);
+				GCC_WARN_ABOUT_RETURN_TYPE = YES_ERROR;
+				MTL_ENABLE_DEBUG_INFO = YES;
+				PRODUCT_NAME = "$(TARGET_NAME)";
+				SDKROOT = macosx;
+			};
+			name = Debug;
+		};
+		2743C9C91D7EF84B0089613B /* Release */ = {
+			isa = XCBuildConfiguration;
+			buildSettings = {
+				CLANG_WARN_BOOL_CONVERSION = YES;
+				CLANG_WARN_CONSTANT_CONVERSION = YES;
+				CLANG_WARN_DIRECT_OBJC_ISA_USAGE = YES_ERROR;
+				CLANG_WARN_DOCUMENTATION_COMMENTS = YES;
+				CLANG_WARN_ENUM_CONVERSION = YES;
+				CLANG_WARN_IMPLICIT_SIGN_CONVERSION = NO;
+				CLANG_WARN_INT_CONVERSION = YES;
+				CLANG_WARN_OBJC_ROOT_CLASS = YES_ERROR;
+				CLANG_WARN_SUSPICIOUS_MOVES = YES;
+				CODE_SIGN_IDENTITY = "-";
+				COPY_PHASE_STRIP = NO;
+				DEBUG_INFORMATION_FORMAT = "dwarf-with-dsym";
+				EXECUTABLE_PREFIX = lib;
+				GCC_WARN_ABOUT_RETURN_TYPE = YES_ERROR;
+				MTL_ENABLE_DEBUG_INFO = NO;
+				PRODUCT_NAME = "$(TARGET_NAME)";
+				SDKROOT = macosx;
+			};
+			name = Release;
+		};
 /* End XCBuildConfiguration section */
 
 /* Begin XCConfigurationList section */
@@ -698,6 +838,15 @@
 			defaultConfigurationIsVisible = 0;
 			defaultConfigurationName = Release;
 		};
+		2743C9C71D7EF84B0089613B /* Build configuration list for PBXNativeTarget "PublicUtility" */ = {
+			isa = XCConfigurationList;
+			buildConfigurations = (
+				2743C9C81D7EF84B0089613B /* Debug */,
+				2743C9C91D7EF84B0089613B /* Release */,
+			);
+			defaultConfigurationIsVisible = 0;
+			defaultConfigurationName = Release;
+		};
 /* End XCConfigurationList section */
 	};
 	rootObject = 1CB8B35A1BBBB69C000E2DD1 /* Project object */;

BGMDriver/BGMDriver.xcodeproj/xcshareddata/xcschemes/Background Music Device.xcscheme

@@ -1,6 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <Scheme
-   LastUpgradeVersion = "0720"
+   LastUpgradeVersion = "0820"
    version = "1.3">
    <BuildAction
       parallelizeBuildables = "YES"

BGMDriver/BGMDriver.xcodeproj/xcshareddata/xcschemes/PublicUtility.xcscheme

@@ -0,0 +1,80 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<Scheme
+   LastUpgradeVersion = "0820"
+   version = "1.3">
+   <BuildAction
+      parallelizeBuildables = "YES"
+      buildImplicitDependencies = "YES">
+      <BuildActionEntries>
+         <BuildActionEntry
+            buildForTesting = "YES"
+            buildForRunning = "YES"
+            buildForProfiling = "YES"
+            buildForArchiving = "YES"
+            buildForAnalyzing = "YES">
+            <BuildableReference
+               BuildableIdentifier = "primary"
+               BlueprintIdentifier = "2743C9C51D7EF84B0089613B"
+               BuildableName = "libPublicUtility.a"
+               BlueprintName = "PublicUtility"
+               ReferencedContainer = "container:BGMDriver.xcodeproj">
+            </BuildableReference>
+         </BuildActionEntry>
+      </BuildActionEntries>
+   </BuildAction>
+   <TestAction
+      buildConfiguration = "Debug"
+      selectedDebuggerIdentifier = "Xcode.DebuggerFoundation.Debugger.LLDB"
+      selectedLauncherIdentifier = "Xcode.DebuggerFoundation.Launcher.LLDB"
+      shouldUseLaunchSchemeArgsEnv = "YES">
+      <Testables>
+      </Testables>
+      <AdditionalOptions>
+      </AdditionalOptions>
+   </TestAction>
+   <LaunchAction
+      buildConfiguration = "Debug"
+      selectedDebuggerIdentifier = "Xcode.DebuggerFoundation.Debugger.LLDB"
+      selectedLauncherIdentifier = "Xcode.DebuggerFoundation.Launcher.LLDB"
+      launchStyle = "0"
+      useCustomWorkingDirectory = "NO"
+      ignoresPersistentStateOnLaunch = "NO"
+      debugDocumentVersioning = "YES"
+      debugServiceExtension = "internal"
+      allowLocationSimulation = "YES">
+      <MacroExpansion>
+         <BuildableReference
+            BuildableIdentifier = "primary"
+            BlueprintIdentifier = "2743C9C51D7EF84B0089613B"
+            BuildableName = "libPublicUtility.a"
+            BlueprintName = "PublicUtility"
+            ReferencedContainer = "container:BGMDriver.xcodeproj">
+         </BuildableReference>
+      </MacroExpansion>
+      <AdditionalOptions>
+      </AdditionalOptions>
+   </LaunchAction>
+   <ProfileAction
+      buildConfiguration = "Release"
+      shouldUseLaunchSchemeArgsEnv = "YES"
+      savedToolIdentifier = ""
+      useCustomWorkingDirectory = "NO"
+      debugDocumentVersioning = "YES">
+      <MacroExpansion>
+         <BuildableReference
+            BuildableIdentifier = "primary"
+            BlueprintIdentifier = "2743C9C51D7EF84B0089613B"
+            BuildableName = "libPublicUtility.a"
+            BlueprintName = "PublicUtility"
+            ReferencedContainer = "container:BGMDriver.xcodeproj">
+         </BuildableReference>
+      </MacroExpansion>
+   </ProfileAction>
+   <AnalyzeAction
+      buildConfiguration = "Debug">
+   </AnalyzeAction>
+   <ArchiveAction
+      buildConfiguration = "Release"
+      revealArchiveInOrganizer = "YES">
+   </ArchiveAction>
+</Scheme>

BGMDriver/BGMDriver/BGM_AbstractDevice.cpp

@@ -0,0 +1,409 @@
+// This file is part of Background Music.
+//
+// Background Music is free software: you can redistribute it and/or
+// modify it under the terms of the GNU General Public License as
+// published by the Free Software Foundation, either version 2 of the
+// License, or (at your option) any later version.
+//
+// Background Music is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Background Music. If not, see <http://www.gnu.org/licenses/>.
+
+//
+//  BGM_AbstractDevice.cpp
+//  BGMDriver
+//
+//  Copyright © 2017 Kyle Neideck
+//  Portions copyright (C) 2013 Apple Inc. All Rights Reserved.
+//
+
+// Self Include
+#include "BGM_AbstractDevice.h"
+
+// Local Includes
+#include "BGM_Utils.h"
+
+// PublicUtility Includes
+#include "CAException.h"
+#include "CADebugMacros.h"
+
+
+#pragma clang assume_nonnull begin
+
+BGM_AbstractDevice::BGM_AbstractDevice(AudioObjectID inObjectID, AudioObjectID inOwnerObjectID)
+:
+    BGM_Object(inObjectID, kAudioDeviceClassID, kAudioObjectClassID, inOwnerObjectID)
+{
+}
+
+BGM_AbstractDevice::~BGM_AbstractDevice()
+{
+}
+
+#pragma mark Property Operations
+
+bool    BGM_AbstractDevice::HasProperty(AudioObjectID inObjectID,
+                                        pid_t inClientPID,
+                                        const AudioObjectPropertyAddress& inAddress) const
+{
+    bool theAnswer = false;
+    
+    switch(inAddress.mSelector)
+    {
+        case kAudioObjectPropertyName:
+        case kAudioObjectPropertyManufacturer:
+        case kAudioDevicePropertyDeviceUID:
+        case kAudioDevicePropertyModelUID:
+        case kAudioDevicePropertyTransportType:
+        case kAudioDevicePropertyRelatedDevices:
+        case kAudioDevicePropertyClockDomain:
+        case kAudioDevicePropertyDeviceIsAlive:
+        case kAudioDevicePropertyDeviceIsRunning:
+        case kAudioDevicePropertyDeviceCanBeDefaultDevice:
+        case kAudioDevicePropertyDeviceCanBeDefaultSystemDevice:
+        case kAudioDevicePropertyLatency:
+        case kAudioDevicePropertyStreams:
+        case kAudioObjectPropertyControlList:
+        case kAudioDevicePropertySafetyOffset:
+        case kAudioDevicePropertyNominalSampleRate:
+        case kAudioDevicePropertyAvailableNominalSampleRates:
+        case kAudioDevicePropertyIsHidden:
+        case kAudioDevicePropertyZeroTimeStampPeriod:
+            theAnswer = true;
+            break;
+            
+        default:
+            theAnswer = BGM_Object::HasProperty(inObjectID, inClientPID, inAddress);
+            break;
+    };
+
+    return theAnswer;
+}
+
+bool    BGM_AbstractDevice::IsPropertySettable(AudioObjectID inObjectID,
+                                               pid_t inClientPID,
+                                               const AudioObjectPropertyAddress& inAddress) const
+{
+    bool theAnswer = false;
+
+    switch(inAddress.mSelector)
+    {
+        case kAudioObjectPropertyName:
+        case kAudioObjectPropertyManufacturer:
+        case kAudioDevicePropertyDeviceUID:
+        case kAudioDevicePropertyModelUID:
+        case kAudioDevicePropertyTransportType:
+        case kAudioDevicePropertyRelatedDevices:
+        case kAudioDevicePropertyClockDomain:
+        case kAudioDevicePropertyDeviceIsAlive:
+        case kAudioDevicePropertyDeviceIsRunning:
+        case kAudioDevicePropertyDeviceCanBeDefaultDevice:
+        case kAudioDevicePropertyDeviceCanBeDefaultSystemDevice:
+        case kAudioDevicePropertyLatency:
+        case kAudioDevicePropertyStreams:
+        case kAudioObjectPropertyControlList:
+        case kAudioDevicePropertySafetyOffset:
+        case kAudioDevicePropertyNominalSampleRate:
+        case kAudioDevicePropertyAvailableNominalSampleRates:
+        case kAudioDevicePropertyIsHidden:
+        case kAudioDevicePropertyZeroTimeStampPeriod:
+            theAnswer = false;
+            break;
+            
+        default:
+            theAnswer = BGM_Object::IsPropertySettable(inObjectID, inClientPID, inAddress);
+            break;
+    };
+
+    return theAnswer;
+}
+
+UInt32    BGM_AbstractDevice::GetPropertyDataSize(AudioObjectID inObjectID,
+                                                  pid_t inClientPID,
+                                                  const AudioObjectPropertyAddress& inAddress,
+                                                  UInt32 inQualifierDataSize,
+                                                  const void* __nullable inQualifierData) const
+{
+    UInt32 theAnswer = 0;
+
+    switch(inAddress.mSelector)
+    {
+        case kAudioObjectPropertyName:
+            theAnswer = sizeof(CFStringRef);
+            break;
+
+        case kAudioObjectPropertyManufacturer:
+            theAnswer = sizeof(CFStringRef);
+            break;
+
+        case kAudioDevicePropertyDeviceUID:
+            theAnswer = sizeof(CFStringRef);
+            break;
+
+        case kAudioDevicePropertyModelUID:
+            theAnswer = sizeof(CFStringRef);
+            break;
+
+        case kAudioDevicePropertyTransportType:
+            theAnswer = sizeof(UInt32);
+            break;
+
+        case kAudioDevicePropertyRelatedDevices:
+            theAnswer = sizeof(AudioObjectID);
+            break;
+
+        case kAudioDevicePropertyClockDomain:
+            theAnswer = sizeof(UInt32);
+            break;
+
+        case kAudioDevicePropertyDeviceCanBeDefaultDevice:
+            theAnswer = sizeof(UInt32);
+            break;
+
+        case kAudioDevicePropertyDeviceCanBeDefaultSystemDevice:
+            theAnswer = sizeof(UInt32);
+            break;
+
+        case kAudioDevicePropertyDeviceIsAlive:
+            theAnswer = sizeof(AudioClassID);
+            break;
+
+        case kAudioDevicePropertyDeviceIsRunning:
+            theAnswer = sizeof(UInt32);
+            break;
+
+        case kAudioDevicePropertyLatency:
+            theAnswer = sizeof(UInt32);
+            break;
+
+        case kAudioDevicePropertyStreams:
+            theAnswer = 0;
+            break;
+
+        case kAudioObjectPropertyControlList:
+            theAnswer = 0;
+            break;
+
+        case kAudioDevicePropertySafetyOffset:
+            theAnswer = sizeof(UInt32);
+            break;
+
+        case kAudioDevicePropertyNominalSampleRate:
+            theAnswer = sizeof(Float64);
+            break;
+
+        case kAudioDevicePropertyAvailableNominalSampleRates:
+            theAnswer = 0;
+            break;
+
+        case kAudioDevicePropertyIsHidden:
+            theAnswer = sizeof(UInt32);
+            break;
+
+        case kAudioDevicePropertyZeroTimeStampPeriod:
+            theAnswer = sizeof(UInt32);
+            break;
+            
+        default:
+            theAnswer = BGM_Object::GetPropertyDataSize(inObjectID,
+                                                        inClientPID,
+                                                        inAddress,
+                                                        inQualifierDataSize,
+                                                        inQualifierData);
+            break;
+    };
+
+    return theAnswer;
+}
+
+void    BGM_AbstractDevice::GetPropertyData(AudioObjectID inObjectID,
+                                            pid_t inClientPID,
+                                            const AudioObjectPropertyAddress& inAddress,
+                                            UInt32 inQualifierDataSize,
+                                            const void* __nullable inQualifierData,
+                                            UInt32 inDataSize,
+                                            UInt32& outDataSize,
+                                            void* outData) const
+{
+    UInt32 theNumberItemsToFetch;
+
+    switch(inAddress.mSelector)
+    {
+        case kAudioObjectPropertyName:
+        case kAudioObjectPropertyManufacturer:
+        case kAudioDevicePropertyDeviceUID:
+        case kAudioDevicePropertyModelUID:
+        case kAudioDevicePropertyDeviceIsRunning:
+        case kAudioDevicePropertyZeroTimeStampPeriod:
+        case kAudioDevicePropertyNominalSampleRate:
+        case kAudioDevicePropertyAvailableNominalSampleRates:
+            // Crash debug builds if a concrete device delegates a required property that can't be
+            // handled here or in BGM_Object (the parent of this class).
+            //
+            // See BGM_Device for info about these properties.
+            //
+            // TODO: Write a test that checks all required properties for each subclass.
+            BGMAssert(false,
+                      "BGM_AbstractDevice::GetPropertyData: Property %u not handled in subclass",
+                      inAddress.mSelector);
+
+
+        case kAudioDevicePropertyTransportType:
+            // This value represents how the device is attached to the system. This can be
+            // any 32 bit integer, but common values for this property are defined in
+            // <CoreAudio/AudioHardwareBase.h>.
+            ThrowIf(inDataSize < sizeof(UInt32),
+                    CAException(kAudioHardwareBadPropertySizeError),
+                    "BGM_AbstractDevice::GetPropertyData: not enough space for the return value of "
+                    "kAudioDevicePropertyTransportType for the device");
+            // Default to virtual device.
+            *reinterpret_cast<UInt32*>(outData) = kAudioDeviceTransportTypeVirtual;
+            outDataSize = sizeof(UInt32);
+            break;
+
+        case kAudioDevicePropertyRelatedDevices:
+            // The related devices property identifies device objects that are very closely
+            // related. Generally, this is for relating devices that are packaged together
+            // in the hardware such as when the input side and the output side of a piece
+            // of hardware can be clocked separately and therefore need to be represented
+            // as separate AudioDevice objects. In such case, both devices would report
+            // that they are related to each other. Note that at minimum, a device is
+            // related to itself, so this list will always be at least one item long.
+
+            // Calculate the number of items that have been requested. Note that this
+            // number is allowed to be smaller than the actual size of the list. In such
+            // case, only that number of items will be returned
+            theNumberItemsToFetch = inDataSize / sizeof(AudioObjectID);
+
+            // Default to only have the one device.
+            if(theNumberItemsToFetch > 1)
+            {
+                theNumberItemsToFetch = 1;
+            }
+
+            // Write the devices' object IDs into the return value.
+            if(theNumberItemsToFetch > 0)
+            {
+                reinterpret_cast<AudioObjectID*>(outData)[0] = GetObjectID();
+            }
+            
+            // Report how much we wrote.
+            outDataSize = theNumberItemsToFetch * sizeof(AudioObjectID);
+            break;
+
+        case kAudioDevicePropertyClockDomain:
+            // This property allows the device to declare what other devices it is
+            // synchronized with in hardware. The way it works is that if two devices have
+            // the same value for this property and the value is not zero, then the two
+            // devices are synchronized in hardware. Note that a device that either can't
+            // be synchronized with others or doesn't know should return 0 for this
+            // property.
+            //
+            // Default to 0.
+            ThrowIf(inDataSize < sizeof(UInt32),
+                    CAException(kAudioHardwareBadPropertySizeError),
+                    "BGM_AbstractDevice::GetPropertyData: not enough space for the return value of "
+                    "kAudioDevicePropertyClockDomain for the device");
+            *reinterpret_cast<UInt32*>(outData) = 0;
+            outDataSize = sizeof(UInt32);
+            break;
+
+        case kAudioDevicePropertyDeviceIsAlive:
+            // Default to alive.
+            ThrowIf(inDataSize < sizeof(UInt32),
+                    CAException(kAudioHardwareBadPropertySizeError),
+                    "BGM_AbstractDevice::GetPropertyData: not enough space for the return value of "
+                    "kAudioDevicePropertyDeviceIsAlive for the device");
+            *reinterpret_cast<UInt32*>(outData) = 1;
+            outDataSize = sizeof(UInt32);
+            break;
+
+        case kAudioDevicePropertyDeviceCanBeDefaultDevice:
+            // This property returns whether or not the device wants to be able to be the
+            // default device for content. This is the device that iTunes and QuickTime
+            // will use to play their content on and FaceTime will use as it's microphone.
+            // Nearly all devices should allow for this.
+            //
+            // Default to true.
+            ThrowIf(inDataSize < sizeof(UInt32),
+                    CAException(kAudioHardwareBadPropertySizeError),
+                    "BGM_AbstractDevice::GetPropertyData: not enough space for the return value of "
+                    "kAudioDevicePropertyDeviceCanBeDefaultDevice for the device");
+            *reinterpret_cast<UInt32*>(outData) = 1;
+            outDataSize = sizeof(UInt32);
+            break;
+
+        case kAudioDevicePropertyDeviceCanBeDefaultSystemDevice:
+            // This property returns whether or not the device wants to be the system
+            // default device. This is the device that is used to play interface sounds and
+            // other incidental or UI-related sounds on. Most devices should allow this
+            // although devices with lots of latency may not want to.
+            //
+            // Default to true.
+            ThrowIf(inDataSize < sizeof(UInt32),
+                    CAException(kAudioHardwareBadPropertySizeError),
+                    "BGM_AbstractDevice::GetPropertyData: not enough space for the return value of "
+                    "kAudioDevicePropertyDeviceCanBeDefaultSystemDevice for the device");
+            *reinterpret_cast<UInt32*>(outData) = 1;
+            outDataSize = sizeof(UInt32);
+            break;
+
+        case kAudioDevicePropertyLatency:
+            // This property returns the presentation latency of the device. Default to 0.
+            ThrowIf(inDataSize < sizeof(UInt32),
+                    CAException(kAudioHardwareBadPropertySizeError),
+                    "BGM_AbstractDevice::GetPropertyData: not enough space for the return value of "
+                    "kAudioDevicePropertyLatency for the device");
+            *reinterpret_cast<UInt32*>(outData) = 0;
+            outDataSize = sizeof(UInt32);
+            break;
+
+        case kAudioDevicePropertyStreams:
+            // Default to not having any streams.
+            outDataSize = 0;
+            break;
+
+        case kAudioObjectPropertyControlList:
+            // Default to not having any controls.
+            outDataSize = 0;
+            break;
+
+        case kAudioDevicePropertySafetyOffset:
+            // This property returns the how close to now the HAL can read and write. Default to 0.
+            ThrowIf(inDataSize < sizeof(UInt32),
+                    CAException(kAudioHardwareBadPropertySizeError),
+                    "BGM_AbstractDevice::GetPropertyData: not enough space for the return value of "
+                    "kAudioDevicePropertySafetyOffset for the device");
+            *reinterpret_cast<UInt32*>(outData) = 0;
+            outDataSize = sizeof(UInt32);
+            break;
+
+        case kAudioDevicePropertyIsHidden:
+            // This returns whether or not the device is visible to clients. Default to not hidden.
+            ThrowIf(inDataSize < sizeof(UInt32),
+                    CAException(kAudioHardwareBadPropertySizeError),
+                    "BGM_AbstractDevice::GetPropertyData: not enough space for the return value of "
+                    "kAudioDevicePropertyIsHidden for the device");
+            *reinterpret_cast<UInt32*>(outData) = 0;
+            outDataSize = sizeof(UInt32);
+            break;
+
+        default:
+            BGM_Object::GetPropertyData(inObjectID,
+                                        inClientPID,
+                                        inAddress,
+                                        inQualifierDataSize,
+                                        inQualifierData,
+                                        inDataSize,
+                                        outDataSize,
+                                        outData);
+            break;
+    };
+}
+
+#pragma clang assume_nonnull end
+

BGMDriver/BGMDriver/BGM_AbstractDevice.h

@@ -0,0 +1,111 @@
+// This file is part of Background Music.
+//
+// Background Music is free software: you can redistribute it and/or
+// modify it under the terms of the GNU General Public License as
+// published by the Free Software Foundation, either version 2 of the
+// License, or (at your option) any later version.
+//
+// Background Music is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Background Music. If not, see <http://www.gnu.org/licenses/>.
+
+//
+//  BGM_AbstractDevice.h
+//  BGMDriver
+//
+//  Copyright © 2017 Kyle Neideck
+//
+
+#ifndef BGM_Driver__BGM_AbstractDevice
+#define BGM_Driver__BGM_AbstractDevice
+
+// SuperClass Includes
+#include "BGM_Object.h"
+
+
+#pragma clang assume_nonnull begin
+
+class BGM_AbstractDevice
+:
+    public BGM_Object
+{
+
+#pragma mark Construction/Destruction
+
+protected:
+                                BGM_AbstractDevice(AudioObjectID inObjectID,
+                                                   AudioObjectID inOwnerObjectID);
+    virtual                     ~BGM_AbstractDevice();
+
+#pragma mark Property Operations
+
+public:
+    virtual bool                HasProperty(AudioObjectID inObjectID,
+                                            pid_t inClientPID,
+                                            const AudioObjectPropertyAddress& inAddress) const;
+    virtual bool                IsPropertySettable(AudioObjectID inObjectID,
+                                                   pid_t inClientPID,
+                                                   const AudioObjectPropertyAddress& inAddress) const;
+    virtual UInt32              GetPropertyDataSize(AudioObjectID inObjectID,
+                                                    pid_t inClientPID,
+                                                    const AudioObjectPropertyAddress& inAddress,
+                                                    UInt32 inQualifierDataSize,
+                                                    const void* __nullable inQualifierData) const;
+    virtual void                GetPropertyData(AudioObjectID inObjectID,
+                                                pid_t inClientPID,
+                                                const AudioObjectPropertyAddress& inAddress,
+                                                UInt32 inQualifierDataSize,
+                                                const void* __nullable inQualifierData,
+                                                UInt32 inDataSize,
+                                                UInt32& outDataSize,
+                                                void* outData) const;
+
+#pragma mark IO Operations
+
+public:
+    virtual void                StartIO(UInt32 inClientID) = 0;
+    virtual void                StopIO(UInt32 inClientID) = 0;
+
+    virtual void                GetZeroTimeStamp(Float64& outSampleTime,
+                                                 UInt64& outHostTime,
+                                                 UInt64& outSeed) = 0;
+
+    virtual void                WillDoIOOperation(UInt32 inOperationID,
+                                                  bool& outWillDo,
+                                                  bool& outWillDoInPlace) const = 0;
+    virtual void                BeginIOOperation(UInt32 inOperationID,
+                                                 UInt32 inIOBufferFrameSize,
+                                                 const AudioServerPlugInIOCycleInfo& inIOCycleInfo,
+                                                 UInt32 inClientID) = 0;
+    virtual void                DoIOOperation(AudioObjectID inStreamObjectID,
+                                              UInt32 inClientID, UInt32 inOperationID,
+                                              UInt32 inIOBufferFrameSize,
+                                              const AudioServerPlugInIOCycleInfo& inIOCycleInfo,
+                                              void* ioMainBuffer,
+                                              void* __nullable ioSecondaryBuffer) = 0;
+    virtual void                EndIOOperation(UInt32 inOperationID,
+                                               UInt32 inIOBufferFrameSize,
+                                               const AudioServerPlugInIOCycleInfo& inIOCycleInfo,
+                                               UInt32 inClientID) = 0;
+
+#pragma mark Implementation
+
+public:
+    virtual CFStringRef         CopyDeviceUID() const = 0;
+    virtual void                AddClient(const AudioServerPlugInClientInfo* inClientInfo) = 0;
+    virtual void                RemoveClient(const AudioServerPlugInClientInfo* inClientInfo) = 0;
+    virtual void                PerformConfigChange(UInt64 inChangeAction,
+                                                    void* __nullable inChangeInfo) = 0;
+    virtual void                AbortConfigChange(UInt64 inChangeAction,
+                                                  void* __nullable inChangeInfo) = 0;
+    
+};
+
+#pragma clang assume_nonnull end
+
+#endif /* BGM_Driver__BGM_AbstractDevice */
+

BGMDriver/BGMDriver/BGM_Device.h

@@ -17,24 +17,25 @@
 //  BGM_Device.h
 //  BGMDriver
 //
-//  Copyright © 2016 Kyle Neideck
+//  Copyright © 2016, 2017 Kyle Neideck
 //  Portions copyright (C) 2013 Apple Inc. All Rights Reserved.
 //
-//  Based largely on SA_Device.h from Apple's SimpleAudioPlugin sample code.
+//  Based largely on SA_Device.h from Apple's SimpleAudioDriver Plug-In sample code.
 //  https://developer.apple.com/library/mac/samplecode/AudioDriverExamples
 //
 
-#ifndef __BGMDriver__BGM_Device__
-#define __BGMDriver__BGM_Device__
+#ifndef BGMDriver__BGM_Device
+#define BGMDriver__BGM_Device
 
 // SuperClass Includes
-#include "BGM_Object.h"
+#include "BGM_AbstractDevice.h"
 
 // Local Includes
 #include "BGM_Types.h"
 #include "BGM_WrappedAudioEngine.h"
 #include "BGM_Clients.h"
 #include "BGM_TaskQueue.h"
+#include "BGM_Stream.h"
 
 // PublicUtility Includes
 #include "CAMutex.h"
@@ -42,11 +43,12 @@
 
 // System Includes
 #include <CoreFoundation/CoreFoundation.h>
+#include <pthread.h>
 
 
 class BGM_Device
 :
-	public BGM_Object
+	public BGM_AbstractDevice
 {
 
 #pragma mark Construction/Destruction
@@ -85,15 +87,6 @@ private:
 	void						Device_GetPropertyData(AudioObjectID inObjectID, pid_t inClientPID, const AudioObjectPropertyAddress& inAddress, UInt32 inQualifierDataSize, const void* __nullable inQualifierData, UInt32 inDataSize, UInt32& outDataSize, void* __nonnull outData) const;
 	void						Device_SetPropertyData(AudioObjectID inObjectID, pid_t inClientPID, const AudioObjectPropertyAddress& inAddress, UInt32 inQualifierDataSize, const void* __nullable inQualifierData, UInt32 inDataSize, const void* __nonnull inData);
 
-#pragma mark Stream Property Operations
-    
-private:
-	bool						Stream_HasProperty(AudioObjectID inObjectID, pid_t inClientPID, const AudioObjectPropertyAddress& inAddress) const;
-	bool						Stream_IsPropertySettable(AudioObjectID inObjectID, pid_t inClientPID, const AudioObjectPropertyAddress& inAddress) const;
-	UInt32						Stream_GetPropertyDataSize(AudioObjectID inObjectID, pid_t inClientPID, const AudioObjectPropertyAddress& inAddress, UInt32 inQualifierDataSize, const void* __nullable inQualifierData) const;
-	void						Stream_GetPropertyData(AudioObjectID inObjectID, pid_t inClientPID, const AudioObjectPropertyAddress& inAddress, UInt32 inQualifierDataSize, const void* __nullable inQualifierData, UInt32 inDataSize, UInt32& outDataSize, void* __nonnull outData) const;
-	void						Stream_SetPropertyData(AudioObjectID inObjectID, pid_t inClientPID, const AudioObjectPropertyAddress& inAddress, UInt32 inQualifierDataSize, const void* __nullable inQualifierData, UInt32 inDataSize, const void* __nonnull inData);
-
 #pragma mark Control Property Operations
     
 private:
@@ -125,6 +118,50 @@ private:
     void                        UpdateAudibleStateSampleTimes_PostMix(UInt32 inIOBufferFrameSize, Float64 inOutputSampleTime, const void* __nonnull inBuffer);
     void                        UpdateDeviceAudibleState(UInt32 inIOBufferFrameSize, Float64 inOutputSampleTime);
 
+#pragma mark Accessors
+
+public:
+	/*!
+	 Enable or disable the device's volume and/or mute controls. This function is async because it
+	 has to ask the host to stop IO for the device before the controls can be enabled/disabled.
+
+	 See BGM_Device::PerformConfigChange and RequestDeviceConfigurationChange in AudioServerPlugIn.h.
+	 */
+    void                        RequestEnabledControls(bool inVolumeEnabled, bool inMuteEnabled);
+
+    Float64						GetSampleRate() const;
+    void                        RequestSampleRate(Float64 inRequestedSampleRate);
+
+private:
+    /*!
+     Enable or disable the device's volume and/or mute controls.
+
+     Private because (after initialisation) this can only be called after asking the host to stop IO
+     for the device. See BGM_Device::RequestEnabledControls, BGM_Device::PerformConfigChange and
+     RequestDeviceConfigurationChange in AudioServerPlugIn.h.
+     */
+    void                        SetEnabledControls(bool inVolumeEnabled, bool inMuteEnabled);
+    /*!
+     Set the device's sample rate.
+
+     Private because (after initialisation) this can only be called after asking the host to stop IO
+     for the device. See BGM_Device::RequestEnabledControls, BGM_Device::PerformConfigChange and
+     RequestDeviceConfigurationChange in AudioServerPlugIn.h.
+
+     @throws CAException if inNewSampleRate < 1 or if applying the sample rate to one of the streams
+             fails.
+     */
+    void                        SetSampleRate(Float64 inNewSampleRate);
+
+    /*! @return True if inObjectID is the ID of one of this device's streams. */
+    bool                        IsStreamID(AudioObjectID inObjectID) const noexcept;
+    /*! 
+     @return The stream that has the ID inObjectID and belongs to this device.
+     @throws CAException if there is no such stream (i.e. if inObjectID is neither
+             kObjectID_Stream_Input nor kObjectID_Stream_Output.)
+     */
+    const BGM_Stream&           GetStreamByID(AudioObjectID inObjectID) const;
+
 #pragma mark Hardware Accessors
     
 private:
@@ -135,8 +172,8 @@ private:
 	Float64						_HW_GetSampleRate() const;
 	kern_return_t				_HW_SetSampleRate(Float64 inNewSampleRate);
 	UInt32						_HW_GetRingBufferFrameSize() const;
-	SInt32						_HW_GetVolumeControlValue(int inObjectID) const;
-	kern_return_t				_HW_SetVolumeControlValue(int inObjectID, SInt32 inNewControlValue);
+	SInt32						_HW_GetVolumeControlValue(AudioObjectID inObjectID) const;
+	kern_return_t				_HW_SetVolumeControlValue(AudioObjectID inObjectID, SInt32 inNewControlValue);
     UInt32                      _HW_GetMuteControlValue(AudioObjectID inObjectID) const;
     kern_return_t               _HW_SetMuteControlValue(AudioObjectID inObjectID, UInt32 inValue);
 
@@ -146,7 +183,12 @@ public:
 	CFStringRef __nonnull		CopyDeviceUID() const { return CFSTR(kBGMDeviceUID); }
     void                        AddClient(const AudioServerPlugInClientInfo* __nonnull inClientInfo);
     void                        RemoveClient(const AudioServerPlugInClientInfo* __nonnull inClientInfo);
+    /*!
+     Apply a change requested with BGM_PlugIn::Host_RequestDeviceConfigurationChange. See
+     PerformDeviceConfigurationChange in AudioServerPlugIn.h.
+     */
 	void						PerformConfigChange(UInt64 inChangeAction, void* __nullable inChangeInfo);
+    /*! Cancel a change requested with BGM_PlugIn::Host_RequestDeviceConfigurationChange. */
 	void						AbortConfigChange(UInt64 inChangeAction, void* __nullable inChangeInfo);
 
 private:
@@ -164,17 +206,16 @@ private:
 								
 								kNumberOfStreams					= 2,
 								kNumberOfInputStreams				= 1,
-								kNumberOfOutputStreams				= 1,
-								
-								kNumberOfControls					= 2
+								kNumberOfOutputStreams				= 1
 	};
     
     CAMutex                     mStateMutex;
     CAMutex						mIOMutex;
     
-    UInt64						mSampleRateShadow;  // Currently unused
+    UInt64 __unused				mSampleRateShadow;  // Currently unused.
     const Float64               kSampleRateDefault = 44100.0;
-    // Before we can change sample rate, the host has to stop the device. The new sample rate is stored here while it does.
+    // Before we can change sample rate, the host has to stop the device. The new sample rate is
+    // stored here while it does.
     Float64                     mPendingSampleRate;
     
     BGM_WrappedAudioEngine* __nullable mWrappedAudioEngine;
@@ -193,8 +234,8 @@ private:
         UInt64					anchorHostTime    = 0;
     }                           mLoopbackTime;
 	
-	bool						mInputStreamIsActive;
-    bool						mOutputStreamIsActive;
+    BGM_Stream                  mInputStream;
+    BGM_Stream                  mOutputStream;
     
     SInt32                      mDeviceAudibleState;
     struct
@@ -204,13 +245,24 @@ private:
         Float64                 latestAudibleMusic;
         Float64                 latestSilentMusic;
     }                           mAudibleStateSampleTimes;
-    
+
+    enum class ChangeAction : UInt64
+    {
+        SetSampleRate,
+        SetEnabledControls
+    };
+
     // This volume range will be used when the BGMDevice isn't wrapping another device (or we fail to
     // get the range of the wrapped device for some reason).
     #define kDefaultMinRawVolumeValue   0
     #define kDefaultMaxRawVolumeValue	96
     #define kDefaultMinDbVolumeValue	-96.0f
     #define kDefaultMaxDbVolumeValue	0.0f
+
+    bool                        mOutputVolumeControlEnabled        = true;
+    bool                        mOutputMuteControlEnabled          = true;
+    bool                        mPendingOutputVolumeControlEnabled = true;
+    bool                        mPendingOutputMuteControlEnabled   = true;
 	
 	SInt32						mOutputMasterVolumeControlRawValueShadow;
     SInt32                      mOutputMasterMinRawVolumeShadow;
@@ -222,5 +274,5 @@ private:
 
 };
 
-#endif /* __BGMDriver__BGM_Device__ */
+#endif /* BGMDriver__BGM_Device */
 

BGMDriver/BGMDriver/BGM_NullDevice.cpp

@@ -0,0 +1,504 @@
+// This file is part of Background Music.
+//
+// Background Music is free software: you can redistribute it and/or
+// modify it under the terms of the GNU General Public License as
+// published by the Free Software Foundation, either version 2 of the
+// License, or (at your option) any later version.
+//
+// Background Music is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Background Music. If not, see <http://www.gnu.org/licenses/>.
+
+//
+//  BGM_NullDevice.cpp
+//  BGMDriver
+//
+//  Copyright © 2017 Kyle Neideck
+//
+
+// Self Include
+#include "BGM_NullDevice.h"
+
+// Local Includes
+#include "BGM_PlugIn.h"
+
+// PublicUtility Includes
+#include "CADebugMacros.h"
+#include "CAException.h"
+#include "CAPropertyAddress.h"
+#include "CADispatchQueue.h"
+
+// System Includes
+#include <mach/mach_time.h>  // For mach_absolute_time
+
+
+#pragma clang assume_nonnull begin
+
+static const Float64 kSampleRate = 44100.0;
+static const UInt32 kZeroTimeStampPeriod = 10000;  // Arbitrary.
+
+#pragma mark Construction/Destruction
+
+pthread_once_t     BGM_NullDevice::sStaticInitializer = PTHREAD_ONCE_INIT;
+BGM_NullDevice*    BGM_NullDevice::sInstance = nullptr;
+
+BGM_NullDevice&    BGM_NullDevice::GetInstance()
+{
+    pthread_once(&sStaticInitializer, StaticInitializer);
+    return *sInstance;
+}
+
+void    BGM_NullDevice::StaticInitializer()
+{
+    try
+    {
+        sInstance = new BGM_NullDevice;
+        // Note that we leave the device inactive initially. BGMApp will activate it when needed.
+    }
+    catch(...)
+    {
+        DebugMsg("BGM_NullDevice::StaticInitializer: Failed to create the device");
+        delete sInstance;
+        sInstance = nullptr;
+    }
+}
+
+BGM_NullDevice::BGM_NullDevice()
+:
+    BGM_AbstractDevice(kObjectID_Device_Null, kAudioObjectPlugInObject),
+    mStateMutex("Null Device State"),
+    mIOMutex("Null Device IO"),
+    mStream(kObjectID_Stream_Null, kObjectID_Device_Null, false, kSampleRate)
+{
+}
+
+BGM_NullDevice::~BGM_NullDevice()
+{
+}
+
+void    BGM_NullDevice::Activate()
+{
+    CAMutex::Locker theStateLocker(mStateMutex);
+
+    if(!IsActive())
+    {
+        // Call the super-class, which just marks the object as active.
+        BGM_AbstractDevice::Activate();
+
+        // Calculate the host ticks per frame for the clock.
+        struct mach_timebase_info theTimeBaseInfo;
+        mach_timebase_info(&theTimeBaseInfo);
+        Float64 theHostClockFrequency = theTimeBaseInfo.denom / theTimeBaseInfo.numer;
+        theHostClockFrequency *= 1000000000.0;
+        mHostTicksPerFrame = theHostClockFrequency / kSampleRate;
+
+        SendDeviceIsAlivePropertyNotifications();
+    }
+}
+
+void    BGM_NullDevice::Deactivate()
+{
+    CAMutex::Locker theStateLocker(mStateMutex);
+
+    if(IsActive())
+    {
+        CAMutex::Locker theIOLocker(mIOMutex);
+
+        // Mark the object inactive by calling the super-class.
+        BGM_AbstractDevice::Deactivate();
+
+        SendDeviceIsAlivePropertyNotifications();
+    }
+}
+
+void    BGM_NullDevice::SendDeviceIsAlivePropertyNotifications()
+{
+    CADispatchQueue::GetGlobalSerialQueue().Dispatch(false, ^{
+        AudioObjectPropertyAddress theChangedProperties[] = {
+            CAPropertyAddress(kAudioDevicePropertyDeviceIsAlive)
+        };
+
+        BGM_PlugIn::Host_PropertiesChanged(GetObjectID(), 1, theChangedProperties);
+    });
+}
+
+#pragma mark Property Operations
+
+bool    BGM_NullDevice::HasProperty(AudioObjectID inObjectID,
+                                    pid_t inClientPID,
+                                    const AudioObjectPropertyAddress& inAddress) const
+{
+    if(inObjectID == mStream.GetObjectID())
+    {
+        return mStream.HasProperty(inObjectID, inClientPID, inAddress);
+    }
+
+    bool theAnswer = false;
+    switch(inAddress.mSelector)
+    {
+        case kAudioDevicePropertyDeviceCanBeDefaultDevice:
+        case kAudioDevicePropertyDeviceCanBeDefaultSystemDevice:
+            theAnswer = true;
+            break;
+
+        default:
+            theAnswer = BGM_AbstractDevice::HasProperty(inObjectID, inClientPID, inAddress);
+            break;
+    };
+    return theAnswer;
+}
+
+bool    BGM_NullDevice::IsPropertySettable(AudioObjectID inObjectID,
+                                           pid_t inClientPID,
+                                           const AudioObjectPropertyAddress& inAddress) const
+{
+    // Forward stream properties.
+    if(inObjectID == mStream.GetObjectID())
+    {
+        return mStream.IsPropertySettable(inObjectID, inClientPID, inAddress);
+    }
+
+    bool theAnswer = false;
+
+    switch(inAddress.mSelector)
+    {
+        default:
+            theAnswer = BGM_AbstractDevice::IsPropertySettable(inObjectID, inClientPID, inAddress);
+            break;
+    };
+
+    return theAnswer;
+}
+
+UInt32    BGM_NullDevice::GetPropertyDataSize(AudioObjectID inObjectID,
+                                            pid_t inClientPID,
+                                            const AudioObjectPropertyAddress& inAddress,
+                                            UInt32 inQualifierDataSize,
+                                            const void* __nullable inQualifierData) const
+{
+    // Forward stream properties.
+    if(inObjectID == mStream.GetObjectID())
+    {
+        return mStream.GetPropertyDataSize(inObjectID,
+                                           inClientPID,
+                                           inAddress,
+                                           inQualifierDataSize,
+                                           inQualifierData);
+    }
+
+    UInt32 theAnswer = 0;
+
+    switch(inAddress.mSelector)
+    {
+        case kAudioDevicePropertyStreams:
+            theAnswer = 1 * sizeof(AudioObjectID);
+            break;
+
+        case kAudioDevicePropertyAvailableNominalSampleRates:
+            theAnswer = 1 * sizeof(AudioValueRange);
+            break;
+
+        default:
+            theAnswer = BGM_AbstractDevice::GetPropertyDataSize(inObjectID,
+                                                                inClientPID,
+                                                                inAddress,
+                                                                inQualifierDataSize,
+                                                                inQualifierData);
+            break;
+    };
+
+    return theAnswer;
+}
+
+void    BGM_NullDevice::GetPropertyData(AudioObjectID inObjectID,
+                                        pid_t inClientPID,
+                                        const AudioObjectPropertyAddress& inAddress,
+                                        UInt32 inQualifierDataSize,
+                                        const void* __nullable inQualifierData,
+                                        UInt32 inDataSize,
+                                        UInt32& outDataSize,
+                                        void* outData) const
+{
+    // Forward stream properties.
+    if(inObjectID == mStream.GetObjectID())
+    {
+        return mStream.GetPropertyData(inObjectID,
+                                       inClientPID,
+                                       inAddress,
+                                       inQualifierDataSize,
+                                       inQualifierData,
+                                       inDataSize,
+                                       outDataSize,
+                                       outData);
+    }
+
+    // See BGM_Device::Device_GetPropertyData for more information about these properties.
+
+    switch(inAddress.mSelector)
+    {
+        case kAudioObjectPropertyName:
+            ThrowIf(inDataSize < sizeof(AudioObjectID),
+                    CAException(kAudioHardwareBadPropertySizeError),
+                    "BGM_NullDevice::GetPropertyData: not enough space for the return value of "
+                    "kAudioObjectPropertyName for the device");
+            *reinterpret_cast<CFStringRef*>(outData) = CFSTR(kNullDeviceName);
+            outDataSize = sizeof(CFStringRef);
+            break;
+
+        case kAudioObjectPropertyManufacturer:
+            ThrowIf(inDataSize < sizeof(AudioObjectID),
+                    CAException(kAudioHardwareBadPropertySizeError),
+                    "BGM_NullDevice::GetPropertyData: not enough space for the return value of "
+                    "kAudioObjectPropertyManufacturer for the device");
+            *reinterpret_cast<CFStringRef*>(outData) = CFSTR(kNullDeviceManufacturerName);
+            outDataSize = sizeof(CFStringRef);
+            break;
+
+        case kAudioDevicePropertyDeviceUID:
+            ThrowIf(inDataSize < sizeof(AudioObjectID),
+                    CAException(kAudioHardwareBadPropertySizeError),
+                    "BGM_NullDevice::GetPropertyData: not enough space for the return value of "
+                    "kAudioDevicePropertyDeviceUID for the device");
+            *reinterpret_cast<CFStringRef*>(outData) = CFSTR(kBGMNullDeviceUID);
+            outDataSize = sizeof(CFStringRef);
+            break;
+
+        case kAudioDevicePropertyModelUID:
+            ThrowIf(inDataSize < sizeof(AudioObjectID),
+                    CAException(kAudioHardwareBadPropertySizeError),
+                    "BGM_NullDevice::GetPropertyData: not enough space for the return value of "
+                    "kAudioDevicePropertyModelUID for the device");
+            *reinterpret_cast<CFStringRef*>(outData) = CFSTR(kBGMNullDeviceModelUID);
+            outDataSize = sizeof(CFStringRef);
+            break;
+
+        case kAudioDevicePropertyDeviceIsAlive:
+            ThrowIf(inDataSize < sizeof(UInt32),
+                    CAException(kAudioHardwareBadPropertySizeError),
+                    "BGM_NullDevice::GetPropertyData: not enough space for the return value of "
+                    "kAudioDevicePropertyDeviceIsAlive for the device");
+            *reinterpret_cast<UInt32*>(outData) = IsActive() ? 1 : 0;
+            outDataSize = sizeof(UInt32);
+            break;
+
+        case kAudioDevicePropertyDeviceIsRunning:
+            {
+                ThrowIf(inDataSize < sizeof(UInt32),
+                        CAException(kAudioHardwareBadPropertySizeError),
+                        "BGM_NullDevice::GetPropertyData: not enough space for the return value of "
+                        "kAudioDevicePropertyDeviceIsRunning for the device");
+                CAMutex::Locker theStateLocker(mStateMutex);
+                // 1 means the device is running, i.e. doing IO.
+                *reinterpret_cast<UInt32*>(outData) = (mClientsDoingIO > 0) ? 1 : 0;
+                outDataSize = sizeof(UInt32);
+            }
+            break;
+
+        case kAudioDevicePropertyStreams:
+            if(inDataSize >= sizeof(AudioObjectID) &&
+               (inAddress.mScope == kAudioObjectPropertyScopeGlobal ||
+                inAddress.mScope == kAudioObjectPropertyScopeOutput))
+            {
+                // Return the ID of this device's stream.
+                reinterpret_cast<AudioObjectID*>(outData)[0] = kObjectID_Stream_Null;
+                // Report how much we wrote.
+                outDataSize = 1 * sizeof(AudioObjectID);
+            }
+            else
+            {
+                // Return nothing if we don't have a stream of the given scope or there's no room
+                // for the response.
+                outDataSize = 0;
+            }
+            break;
+
+        case kAudioDevicePropertyNominalSampleRate:
+            ThrowIf(inDataSize < sizeof(Float64),
+                    CAException(kAudioHardwareBadPropertySizeError),
+                    "BGM_NullDevice::GetPropertyData: not enough space for the return value of "
+                    "kAudioDevicePropertyNominalSampleRate for the device");
+            *reinterpret_cast<Float64*>(outData) = kSampleRate;
+            outDataSize = sizeof(Float64);
+            break;
+
+        case kAudioDevicePropertyAvailableNominalSampleRates:
+            // Check we were given space to return something.
+            if((inDataSize / sizeof(AudioValueRange)) >= 1)
+            {
+                // This device doesn't support changing the sample rate.
+                reinterpret_cast<AudioValueRange*>(outData)[0].mMinimum = kSampleRate;
+                reinterpret_cast<AudioValueRange*>(outData)[0].mMaximum = kSampleRate;
+                outDataSize = sizeof(AudioValueRange);
+            }
+            else
+            {
+                outDataSize = 0;
+            }
+            break;
+
+        case kAudioDevicePropertyZeroTimeStampPeriod:
+            ThrowIf(inDataSize < sizeof(UInt32),
+                    CAException(kAudioHardwareBadPropertySizeError),
+                    "BGM_NullDevice::GetPropertyData: not enough space for the return value of "
+                    "kAudioDevicePropertyZeroTimeStampPeriod for the device");
+            *reinterpret_cast<UInt32*>(outData) = kZeroTimeStampPeriod;
+            outDataSize = sizeof(UInt32);
+            break;
+
+        default:
+            BGM_AbstractDevice::GetPropertyData(inObjectID,
+                                                inClientPID,
+                                                inAddress,
+                                                inQualifierDataSize,
+                                                inQualifierData,
+                                                inDataSize,
+                                                outDataSize,
+                                                outData);
+            break;
+    };
+}
+
+void    BGM_NullDevice::SetPropertyData(AudioObjectID inObjectID,
+                                        pid_t inClientPID,
+                                        const AudioObjectPropertyAddress& inAddress,
+                                        UInt32 inQualifierDataSize,
+                                        const void* inQualifierData,
+                                        UInt32 inDataSize,
+                                        const void* inData)
+{
+    // This device doesn't have any settable properties, so just pass stream properties along.
+    if(inObjectID == mStream.GetObjectID())
+    {
+        mStream.SetPropertyData(inObjectID,
+                                inClientPID,
+                                inAddress,
+                                inQualifierDataSize,
+                                inQualifierData,
+                                inDataSize,
+                                inData);
+    }
+}
+
+#pragma mark IO Operations
+
+
+void    BGM_NullDevice::StartIO(UInt32 inClientID)
+{
+    #pragma unused (inClientID)
+
+    CAMutex::Locker theStateLocker(mStateMutex);
+
+    if(mClientsDoingIO == 0)
+    {
+        // Reset the clock.
+        mNumberTimeStamps = 0;
+        mAnchorHostTime = mach_absolute_time();
+
+        // Send notifications.
+        DebugMsg("BGM_NullDevice::StartIO: Sending kAudioDevicePropertyDeviceIsRunning");
+        CADispatchQueue::GetGlobalSerialQueue().Dispatch(false, ^{
+            AudioObjectPropertyAddress theChangedProperty[] = {
+                CAPropertyAddress(kAudioDevicePropertyDeviceIsRunning)
+            };
+            BGM_PlugIn::Host_PropertiesChanged(kObjectID_Device_Null, 1, theChangedProperty);
+        });
+    }
+
+    mClientsDoingIO++;
+}
+
+void    BGM_NullDevice::StopIO(UInt32 inClientID)
+{
+    #pragma unused (inClientID)
+
+    CAMutex::Locker theStateLocker(mStateMutex);
+
+    ThrowIf(mClientsDoingIO == 0,
+            CAException(kAudioHardwareIllegalOperationError),
+            "BGM_NullDevice::StopIO: Underflowed mClientsDoingIO");
+
+    mClientsDoingIO--;
+
+    if(mClientsDoingIO == 0)
+    {
+        // Send notifications.
+        DebugMsg("BGM_NullDevice::StopIO: Sending kAudioDevicePropertyDeviceIsRunning");
+        CADispatchQueue::GetGlobalSerialQueue().Dispatch(false, ^{
+            AudioObjectPropertyAddress theChangedProperty[] = {
+                CAPropertyAddress(kAudioDevicePropertyDeviceIsRunning)
+            };
+            BGM_PlugIn::Host_PropertiesChanged(kObjectID_Device_Null, 1, theChangedProperty);
+        });
+    }
+}
+
+void    BGM_NullDevice::GetZeroTimeStamp(Float64& outSampleTime,
+                                         UInt64& outHostTime,
+                                         UInt64& outSeed)
+{
+    CAMutex::Locker theIOLocker(mIOMutex);
+
+    // Not sure whether there's actually any point to implementing this. The documentation says that
+    // clockless devices don't need to, but if the device doesn't have
+    // kAudioDevicePropertyZeroTimeStampPeriod the HAL seems to reject it. So we give it a simple
+    // clock similar to the loopback clock in BGM_Device.
+    UInt64 theCurrentHostTime = mach_absolute_time();
+
+    // Calculate the next host time.
+    Float64 theHostTicksPerPeriod = mHostTicksPerFrame * static_cast<Float64>(kZeroTimeStampPeriod);
+    Float64 theHostTickOffset = static_cast<Float64>(mNumberTimeStamps + 1) * theHostTicksPerPeriod;
+    UInt64 theNextHostTime = mAnchorHostTime + static_cast<UInt64>(theHostTickOffset);
+
+    // Go to the next period if the next host time is less than the current time.
+    if(theNextHostTime <= theCurrentHostTime)
+    {
+        mNumberTimeStamps++;
+    }
+
+    Float64 theHostTicksSinceAnchor =
+        (static_cast<Float64>(mNumberTimeStamps) * theHostTicksPerPeriod);
+
+    // Set the return values.
+    outSampleTime = mNumberTimeStamps * kZeroTimeStampPeriod;
+    outHostTime = static_cast<UInt64>(mAnchorHostTime + theHostTicksSinceAnchor);
+    outSeed = 1;
+}
+
+void    BGM_NullDevice::WillDoIOOperation(UInt32 inOperationID,
+                                          bool& outWillDo,
+                                          bool& outWillDoInPlace) const
+{
+    switch(inOperationID)
+    {
+        case kAudioServerPlugInIOOperationWriteMix:
+            outWillDo = true;
+            outWillDoInPlace = true;
+            break;
+
+        default:
+            outWillDo = false;
+            outWillDoInPlace = true;
+            break;
+            
+    };
+}
+
+void    BGM_NullDevice::DoIOOperation(AudioObjectID inStreamObjectID,
+                                      UInt32 inClientID,
+                                      UInt32 inOperationID,
+                                      UInt32 inIOBufferFrameSize,
+                                      const AudioServerPlugInIOCycleInfo& inIOCycleInfo,
+                                      void* ioMainBuffer,
+                                      void* __nullable ioSecondaryBuffer)
+{
+    #pragma unused (inStreamObjectID, inClientID, inOperationID, inIOCycleInfo, inIOBufferFrameSize)
+    #pragma unused (ioMainBuffer, ioSecondaryBuffer)
+    // Ignore the audio data.
+}
+
+#pragma clang assume_nonnull end
+

BGMDriver/BGMDriver/BGM_NullDevice.h

@@ -0,0 +1,186 @@
+// This file is part of Background Music.
+//
+// Background Music is free software: you can redistribute it and/or
+// modify it under the terms of the GNU General Public License as
+// published by the Free Software Foundation, either version 2 of the
+// License, or (at your option) any later version.
+//
+// Background Music is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Background Music. If not, see <http://www.gnu.org/licenses/>.
+
+//
+//  BGM_NullDevice.h
+//  BGMDriver
+//
+//  Copyright © 2017 Kyle Neideck
+//
+//  A device with one output stream that ignores any audio played on that stream.
+//
+//  If we change BGMDevice's controls list, to match the output device set in BGMApp, we need to
+//  change the OS X default device so other programs (including the OS X audio UI) will update
+//  themselves. We could just change to the real output device and change back, but that could have
+//  side effects the user wouldn't expect. For example, an app the user had muted might be unmuted
+//  for a short period.
+//
+//  Instead, BGMApp temporarily enables this device and uses it to toggle the default device. This
+//  device is disabled at all other times so it can be hidden from the user. (We can't just use
+//  kAudioDevicePropertyIsHidden because hidden devices can't be default and the HAL doesn't seem to
+//  let devices change kAudioDevicePropertyIsHidden after setting it initially.)
+//
+//  It might be worth eventually having a virtual device for each real output device, but this is
+//  simpler and seems to work well enough for now.
+//
+
+#ifndef BGMDriver__BGM_NullDevice
+#define BGMDriver__BGM_NullDevice
+
+// SuperClass Includes
+#include "BGM_AbstractDevice.h"
+
+// Local Includes
+#include "BGM_Types.h"
+#include "BGM_Stream.h"
+
+// PublicUtility Includes
+#include "CAMutex.h"
+
+// System Includes
+#include <pthread.h>
+
+
+#pragma clang assume_nonnull begin
+
+class BGM_NullDevice
+:
+    public BGM_AbstractDevice
+{
+
+#pragma mark Construction/Destruction
+
+public:
+    static BGM_NullDevice&      GetInstance();
+
+private:
+    static void                 StaticInitializer();
+
+protected:
+                                BGM_NullDevice();
+    virtual                     ~BGM_NullDevice();
+
+public:
+    virtual void                Activate();
+    virtual void                Deactivate();
+
+private:
+    void                        SendDeviceIsAlivePropertyNotifications();
+
+#pragma mark Property Operations
+
+public:
+    bool                        HasProperty(AudioObjectID inObjectID,
+                                            pid_t inClientPID,
+                                            const AudioObjectPropertyAddress& inAddress) const;
+    bool                        IsPropertySettable(AudioObjectID inObjectID,
+                                                   pid_t inClientPID,
+                                                   const AudioObjectPropertyAddress& inAddress) const;
+    UInt32                      GetPropertyDataSize(AudioObjectID inObjectID,
+                                                    pid_t inClientPID,
+                                                    const AudioObjectPropertyAddress& inAddress,
+                                                    UInt32 inQualifierDataSize,
+                                                    const void* __nullable inQualifierData) const;
+    void                        GetPropertyData(AudioObjectID inObjectID,
+                                                pid_t inClientPID,
+                                                const AudioObjectPropertyAddress& inAddress,
+                                                UInt32 inQualifierDataSize,
+                                                const void* __nullable inQualifierData,
+                                                UInt32 inDataSize,
+                                                UInt32& outDataSize,
+                                                void* outData) const;
+    void                        SetPropertyData(AudioObjectID inObjectID,
+                                                pid_t inClientPID,
+                                                const AudioObjectPropertyAddress& inAddress,
+                                                UInt32 inQualifierDataSize,
+                                                const void* inQualifierData,
+                                                UInt32 inDataSize,
+                                                const void* inData);
+
+#pragma mark IO Operations
+
+public:
+    void                        StartIO(UInt32 inClientID);
+    void                        StopIO(UInt32 inClientID);
+
+    void                        GetZeroTimeStamp(Float64& outSampleTime,
+                                                 UInt64& outHostTime,
+                                                 UInt64& outSeed);
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wunused-parameter"
+    void                        WillDoIOOperation(UInt32 inOperationID,
+                                                  bool& outWillDo,
+                                                  bool& outWillDoInPlace) const;
+    void                        BeginIOOperation(UInt32 inOperationID,
+                                                 UInt32 inIOBufferFrameSize,
+                                                 const AudioServerPlugInIOCycleInfo& inIOCycleInfo,
+                                                 UInt32 inClientID)
+                                    { /* No-op */ };
+    void                        DoIOOperation(AudioObjectID inStreamObjectID,
+                                              UInt32 inClientID,
+                                              UInt32 inOperationID,
+                                              UInt32 inIOBufferFrameSize,
+                                              const AudioServerPlugInIOCycleInfo& inIOCycleInfo,
+                                              void* ioMainBuffer,
+                                              void* __nullable ioSecondaryBuffer);
+    void                        EndIOOperation(UInt32 inOperationID,
+                                               UInt32 inIOBufferFrameSize,
+                                               const AudioServerPlugInIOCycleInfo& inIOCycleInfo,
+                                               UInt32 inClientID)
+                                    { /* No-op */ };
+
+#pragma mark Implementation
+
+public:
+    CFStringRef                 CopyDeviceUID() const
+                                    { return CFSTR(kBGMNullDeviceUID); };
+
+    void                        AddClient(const AudioServerPlugInClientInfo* inClientInfo)
+                                    { /* No-op */ };
+    void                        RemoveClient(const AudioServerPlugInClientInfo* inClientInfo)
+                                    { /* No-op */ };
+    void                        PerformConfigChange(UInt64 inChangeAction,
+                                                    void* __nullable inChangeInfo)
+                                    { /* No-op */ };
+    void                        AbortConfigChange(UInt64 inChangeAction,
+                                                  void* __nullable inChangeInfo)
+                                    { /* No-op */ };
+#pragma clang diagnostic pop
+
+private:
+    static pthread_once_t       sStaticInitializer;
+    static BGM_NullDevice*      sInstance;
+
+    #define kNullDeviceName     "Background Music Null Device"
+    #define kNullDeviceManufacturerName \
+                                "Background Music contributors"
+
+    CAMutex                     mStateMutex;
+    CAMutex                     mIOMutex;
+
+    BGM_Stream                  mStream;
+
+    UInt32                      mClientsDoingIO    = 0;
+
+    Float64                     mHostTicksPerFrame = 0.0;
+    UInt64                      mNumberTimeStamps  = 0;
+    UInt64                      mAnchorHostTime    = 0;
+
+};
+
+#pragma clang assume_nonnull end
+
+#endif /* BGMDriver__BGM_NullDevice */
+

BGMDriver/BGMDriver/BGM_Object.cpp

@@ -20,7 +20,7 @@
 //  Copyright © 2016 Kyle Neideck
 //  Portions copyright (C) 2013 Apple Inc. All Rights Reserved.
 //
-//  Based largely on SA_Object.cpp from Apple's SimpleAudioPlugin sample code.
+//  Based largely on SA_Object.cpp from Apple's SimpleAudioDriver Plug-In sample code.
 //  https://developer.apple.com/library/mac/samplecode/AudioDriverExamples
 //
 //  Similarly to BGM_Object.h, this file hasn't been changed much from SA_Object.cpp, except to

BGMDriver/BGMDriver/BGM_Object.h

@@ -20,10 +20,10 @@
 //  Copyright © 2016 Kyle Neideck
 //  Portions copyright (C) 2013 Apple Inc. All Rights Reserved.
 //
-//  Based largely on SA_Object.h from Apple's SimpleAudioPlugin sample code.
+//  Based largely on SA_Object.h from Apple's SimpleAudioDriver Plug-In sample code.
 //  https://developer.apple.com/library/mac/samplecode/AudioDriverExamples
 //
-//  The base class for our classes that represent audio objects. (See AudioServerPlugin.h for a
+//  The base class for our classes that represent audio objects. (See AudioServerPlugIn.h for a
 //  quick explanation of audio objects.)
 // 
 //  This is a stripped down version of SA_Object.h. Unlike the sample code plugin that SA_Object.h