Improving README.

NSUserDefaults does not support KVO officially.

LICENSE

@@ -0,0 +1,22 @@
+Copyright (c) 2012-2013, Vadim Shpakovski
+All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are met:
+
+1. Redistributions of source code must retain the above copyright notice, this
+   list of conditions and the following disclaimer.
+2. Redistributions in binary form must reproduce the above copyright notice,
+   this list of conditions and the following disclaimer in the documentation
+   and/or other materials provided with the distribution.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
+ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
+ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

MASShortcut+Monitoring.m

@@ -2,8 +2,8 @@
 
 NSMutableDictionary *MASRegisteredHotKeys();
 BOOL InstallCommonEventHandler();
+BOOL InstallHotkeyWithShortcut(MASShortcut *shortcut, UInt32 *outCarbonHotKeyID, EventHotKeyRef *outCarbonHotKey);
 void UninstallEventHandler();
-void InstallHotkeyWithShortcut(MASShortcut *shortcut, UInt32 *outCarbonHotKeyID, EventHotKeyRef *outCarbonHotKey);
 
 #pragma mark -
 
@@ -24,8 +24,12 @@ void InstallHotkeyWithShortcut(MASShortcut *shortcut, UInt32 *outCarbonHotKeyID,
 
 + (id)addGlobalHotkeyMonitorWithShortcut:(MASShortcut *)shortcut handler:(void (^)())handler
 {
-    NSString *monitor = [NSString stringWithFormat:@"%p: %@", shortcut, shortcut.description];
+    NSString *monitor = [NSString stringWithFormat:@"%@", shortcut.description];
+    if ([MASRegisteredHotKeys() objectForKey:monitor]) return nil;
+
     MASShortcutHotKey *hotKey = [[MASShortcutHotKey alloc] initWithShortcut:shortcut handler:handler];
+    if (hotKey == nil) return nil;
+
     [MASRegisteredHotKeys() setObject:hotKey forKey:monitor];
     return monitor;
 }
@@ -59,7 +63,9 @@ void InstallHotkeyWithShortcut(MASShortcut *shortcut, UInt32 *outCarbonHotKeyID,
     if (self) {
         _shortcut = shortcut;
         _handler = [handler copy];
-        InstallHotkeyWithShortcut(shortcut, &_carbonHotKeyID, &_carbonHotKey);
+
+        if (!InstallHotkeyWithShortcut(shortcut, &_carbonHotKeyID, &_carbonHotKey))
+            self = nil;
     }
     return self;
 }
@@ -95,19 +101,20 @@ NSMutableDictionary *MASRegisteredHotKeys()
 
 FourCharCode const kMASShortcutSignature = 'MASS';
 
-void InstallHotkeyWithShortcut(MASShortcut *shortcut, UInt32 *outCarbonHotKeyID, EventHotKeyRef *outCarbonHotKey)
+BOOL InstallHotkeyWithShortcut(MASShortcut *shortcut, UInt32 *outCarbonHotKeyID, EventHotKeyRef *outCarbonHotKey)
 {
-    if ((shortcut == nil) || !InstallCommonEventHandler()) return;
+    if ((shortcut == nil) || !InstallCommonEventHandler()) return NO;
 
     static UInt32 sCarbonHotKeyID = 0;
 	EventHotKeyID hotKeyID = { .signature = kMASShortcutSignature, .id = ++ sCarbonHotKeyID };
     EventHotKeyRef carbonHotKey = NULL;
     if (RegisterEventHotKey(shortcut.carbonKeyCode, shortcut.carbonFlags, hotKeyID, GetEventDispatcherTarget(), kEventHotKeyExclusive, &carbonHotKey) != noErr) {
-        carbonHotKey = NULL;
+        return NO;
     }
 
     if (outCarbonHotKeyID) *outCarbonHotKeyID = hotKeyID.id;
     if (outCarbonHotKey) *outCarbonHotKey = carbonHotKey;
+    return YES;
 }
 
 static OSStatus CarbonCallback(EventHandlerCallRef inHandlerCallRef, EventRef inEvent, void *inUserData)

MASShortcut+UserDefaults.h

@@ -4,5 +4,6 @@
 
 + (void)registerGlobalShortcutWithUserDefaultsKey:(NSString *)userDefaultsKey handler:(void (^)())handler;
 + (void)unregisterGlobalShortcutWithUserDefaultsKey:(NSString *)userDefaultsKey;
++ (void)setGlobalShortcut:(MASShortcut *)shortcut forUserDefaultsKey:(NSString *)userDefaultsKey;
 
 @end

MASShortcut+UserDefaults.m

@@ -37,11 +37,22 @@
     [registeredHotKeys removeObjectForKey:userDefaultsKey];
 }
 
++ (void)setGlobalShortcut:(MASShortcut *)shortcut forUserDefaultsKey:(NSString *)userDefaultsKey
+{
+    NSData *shortcutData = shortcut.data;
+    if (shortcutData)
+        [[NSUserDefaults standardUserDefaults] setObject:shortcutData forKey:userDefaultsKey];
+    else
+        [[NSUserDefaults standardUserDefaults] removeObjectForKey:userDefaultsKey];
+}
+
 @end
 
 #pragma mark -
 
-@implementation MASShortcutUserDefaultsHotKey
+@implementation MASShortcutUserDefaultsHotKey {
+    NSString *_observableKeyPath;
+}
 
 @synthesize monitor = _monitor;
 @synthesize handler = _handler;
@@ -49,31 +60,37 @@
 
 #pragma mark -
 
+void *MASShortcutUserDefaultsContext = &MASShortcutUserDefaultsContext;
+
 - (id)initWithUserDefaultsKey:(NSString *)userDefaultsKey handler:(void (^)())handler
 {
     self = [super init];
     if (self) {
         _userDefaultsKey = userDefaultsKey.copy;
         _handler = [handler copy];
-        [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(userDefaultsDidChange:)
-                                                     name:NSUserDefaultsDidChangeNotification object:[NSUserDefaults standardUserDefaults]];
-        [self installHotKeyFromUserDefaults];
+        _observableKeyPath = [@"values." stringByAppendingString:_userDefaultsKey];
+        [[NSUserDefaultsController sharedUserDefaultsController] addObserver:self forKeyPath:_observableKeyPath options:NSKeyValueObservingOptionInitial context:MASShortcutUserDefaultsContext];
     }
     return self;
 }
 
 - (void)dealloc
 {
-    [[NSNotificationCenter defaultCenter] removeObserver:self name:NSUserDefaultsDidChangeNotification object:[NSUserDefaults standardUserDefaults]];
+    [[NSUserDefaultsController sharedUserDefaultsController] removeObserver:self forKeyPath:_observableKeyPath context:MASShortcutUserDefaultsContext];
     [MASShortcut removeGlobalHotkeyMonitor:self.monitor];
 }
 
 #pragma mark -
 
-- (void)userDefaultsDidChange:(NSNotification *)note
+- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context
 {
-    [MASShortcut removeGlobalHotkeyMonitor:self.monitor];
-    [self installHotKeyFromUserDefaults];
+    if (context == MASShortcutUserDefaultsContext) {
+        [MASShortcut removeGlobalHotkeyMonitor:self.monitor];
+        [self installHotKeyFromUserDefaults];
+    }
+    else {
+        [super observeValueForKeyPath:keyPath ofObject:object change:change context:context];
+    }
 }
 
 - (void)installHotKeyFromUserDefaults

MASShortcut.h

@@ -51,4 +51,9 @@ enum {
 
 - (BOOL)isTakenError:(NSError **)error;
 
+// The following API enable hotkeys with the Option key as the only modifier
+// For example, Option-G will not generate © and Option-R will not paste ®
++ (void)setAllowsAnyHotkeyWithOptionModifier:(BOOL)allow;
++ (BOOL)allowsAnyHotkeyWithOptionModifier;
+
 @end

MASShortcut.m

@@ -1,7 +1,7 @@
 #import "MASShortcut.h"
 
-NSString *const kMASShortcutKeyCode = @"KeyCode";
-NSString *const kMASShortcutModifierFlags = @"ModifierFlags";
+NSString *const MASShortcutKeyCode = @"KeyCode";
+NSString *const MASShortcutModifierFlags = @"ModifierFlags";
 
 @implementation MASShortcut {
     NSUInteger _keyCode; // NSNotFound if empty
@@ -15,17 +15,17 @@ NSString *const kMASShortcutModifierFlags = @"ModifierFlags";
 
 - (void)encodeWithCoder:(NSCoder *)coder
 {
-    [coder encodeInteger:(self.keyCode != NSNotFound ? (NSInteger)self.keyCode : - 1) forKey:kMASShortcutKeyCode];
-    [coder encodeInteger:(NSInteger)self.modifierFlags forKey:kMASShortcutModifierFlags];
+    [coder encodeInteger:(self.keyCode != NSNotFound ? (NSInteger)self.keyCode : - 1) forKey:MASShortcutKeyCode];
+    [coder encodeInteger:(NSInteger)self.modifierFlags forKey:MASShortcutModifierFlags];
 }
 
 - (id)initWithCoder:(NSCoder *)decoder
 {
     self = [super init];
     if (self) {
-        NSInteger code = [decoder decodeIntegerForKey:kMASShortcutKeyCode];
+        NSInteger code = [decoder decodeIntegerForKey:MASShortcutKeyCode];
         self.keyCode = (code < 0 ? NSNotFound : (NSUInteger)code);
-        self.modifierFlags = [decoder decodeIntegerForKey:kMASShortcutModifierFlags];
+        self.modifierFlags = [decoder decodeIntegerForKey:MASShortcutModifierFlags];
     }
     return self;
 }
@@ -105,6 +105,9 @@ NSString *const kMASShortcutModifierFlags = @"ModifierFlags";
             case kVK_F14: return MASShortcutChar(0xF711);
             case kVK_F15: return MASShortcutChar(0xF712);
             case kVK_F16: return MASShortcutChar(0xF713);
+            case kVK_F17: return MASShortcutChar(0xF714);
+            case kVK_F18: return MASShortcutChar(0xF715);
+            case kVK_F19: return MASShortcutChar(0xF716);
             case kVK_Space: return MASShortcutChar(0x20);
             default: return @"";
         }
@@ -133,6 +136,9 @@ NSString *const kMASShortcutModifierFlags = @"ModifierFlags";
         case kVK_F14: return @"F14";
         case kVK_F15: return @"F15";
         case kVK_F16: return @"F16";
+        case kVK_F17: return @"F17";
+        case kVK_F18: return @"F18";
+        case kVK_F19: return @"F19";
         case kVK_Space: return NSLocalizedString(@"Space", @"Shortcut glyph name for SPACE key");
         case kVK_Escape: return MASShortcutChar(kMASShortcutGlyphEscape);
         case kVK_Delete: return MASShortcutChar(kMASShortcutGlyphDeleteLeft);
@@ -232,19 +238,50 @@ NSString *const kMASShortcutModifierFlags = @"ModifierFlags";
     return (self.modifierFlags == NSCommandKeyMask) && ([codeString isEqualToString:@"W"] || [codeString isEqualToString:@"Q"]);
 }
 
+BOOL MASShortcutAllowsAnyHotkeyWithOptionModifier = NO;
+
++ (void)setAllowsAnyHotkeyWithOptionModifier:(BOOL)allow
+{
+    MASShortcutAllowsAnyHotkeyWithOptionModifier = allow;
+}
+
++ (BOOL)allowsAnyHotkeyWithOptionModifier
+{
+    return MASShortcutAllowsAnyHotkeyWithOptionModifier;
+}
+
 - (BOOL)isValid
 {
-    BOOL hasFlags = (_modifierFlags > 0);
-    BOOL hasCommand = ((_modifierFlags & NSCommandKeyMask) > 0);
-    BOOL hasControl = ((_modifierFlags & NSControlKeyMask) > 0);
-    BOOL hasOption = ((_modifierFlags & NSAlternateKeyMask) > 0);
-    BOOL isFunction = ((_keyCode == kVK_F1) || (_keyCode == kVK_F2) || (_keyCode == kVK_F3) || (_keyCode == kVK_F4) ||
-                       (_keyCode == kVK_F5) || (_keyCode == kVK_F6) || (_keyCode == kVK_F7) || (_keyCode == kVK_F8) ||
-                       (_keyCode == kVK_F9) || (_keyCode == kVK_F10) || (_keyCode == kVK_F11) || (_keyCode == kVK_F12) ||
-                       (_keyCode == kVK_F13) || (_keyCode == kVK_F14) || (_keyCode == kVK_F15) || (_keyCode == kVK_F16) ||
-                       (_keyCode == kVK_F17) || (_keyCode == kVK_F18) || (_keyCode == kVK_F19) || (_keyCode == kVK_F20));
-    BOOL isSpecial = ((_keyCode == kVK_Space) || (_keyCode == kVK_Escape) || (_keyCode == kVK_Return));
-    return ((hasFlags && (hasCommand || hasControl || (hasOption && isSpecial))) || isFunction);
+    // Allow any function key with any combination of modifiers
+    BOOL includesFunctionKey = ((_keyCode == kVK_F1) || (_keyCode == kVK_F2) || (_keyCode == kVK_F3) || (_keyCode == kVK_F4) ||
+                                (_keyCode == kVK_F5) || (_keyCode == kVK_F6) || (_keyCode == kVK_F7) || (_keyCode == kVK_F8) ||
+                                (_keyCode == kVK_F9) || (_keyCode == kVK_F10) || (_keyCode == kVK_F11) || (_keyCode == kVK_F12) ||
+                                (_keyCode == kVK_F13) || (_keyCode == kVK_F14) || (_keyCode == kVK_F15) || (_keyCode == kVK_F16) ||
+                                (_keyCode == kVK_F17) || (_keyCode == kVK_F18) || (_keyCode == kVK_F19) || (_keyCode == kVK_F20));
+    if (includesFunctionKey) return YES;
+
+    // Do not allow any other key without modifiers
+    BOOL hasModifierFlags = (_modifierFlags > 0);
+    if (!hasModifierFlags) return NO;
+
+    // Allow any hotkey containing Control or Command modifier
+    BOOL includesCommand = ((_modifierFlags & NSCommandKeyMask) > 0);
+    BOOL includesControl = ((_modifierFlags & NSControlKeyMask) > 0);
+    if (includesCommand || includesControl) return YES;
+
+    // Allow Option key only in selected cases
+    BOOL includesOption = ((_modifierFlags & NSAlternateKeyMask) > 0);
+    if (includesOption) {
+
+        // Always allow Option-Space and Option-Escape because they do not have any bind system commands
+        if ((_keyCode == kVK_Space) || (_keyCode == kVK_Escape)) return YES;
+
+        // Allow Option modifier with any key even if it will break the system binding
+        if ([[self class] allowsAnyHotkeyWithOptionModifier]) return YES;
+    }
+
+    // The hotkey does not have any modifiers or violates system bindings
+    return NO;
 }
 
 - (BOOL)isKeyEquivalent:(NSString *)keyEquivalent flags:(NSUInteger)flags takenInMenu:(NSMenu *)menu error:(NSError **)outError
@@ -263,7 +300,7 @@ NSString *const kMASShortcutModifierFlags = @"ModifierFlags";
         
         if (equalFlags && equalHotkeyLowercase) {
             if (outError) {
-                NSString *format = NSLocalizedString(@"This shortcut cannot be used used because it is already used by the menu item ‘%@’.",
+                NSString *format = NSLocalizedString(@"This shortcut cannot be used because it is already used by the menu item ‘%@’.",
                                                      @"Message for alert when shortcut is already used");
                 NSDictionary *info = [NSDictionary dictionaryWithObject:[NSString stringWithFormat:format, menuItem.title]
                                                                  forKey:NSLocalizedDescriptionKey];
@@ -290,7 +327,7 @@ NSString *const kMASShortcutModifierFlags = @"ModifierFlags";
                 ([(__bridge NSNumber *)flags unsignedIntegerValue] == self.carbonFlags)) {
 
                 if (outError) {
-                    NSString *description = NSLocalizedString(@"This combination cannot be used used because it is already used by a system-wide "
+                    NSString *description = NSLocalizedString(@"This combination cannot be used because it is already used by a system-wide "
                                                               @"keyboard shortcut.\nIf you really want to use this key combination, most shortcuts "
                                                               @"can be changed in the Keyboard & Mouse panel in System Preferences.",
                                                               @"Message for alert when shortcut is already used by the system");

MASShortcutView+UserDefaults.m

@@ -15,22 +15,24 @@
 
 @implementation MASShortcutView (UserDefaults)
 
-void *kDefaultsObserver = &kDefaultsObserver;
+void *MASAssociatedDefaultsObserver = &MASAssociatedDefaultsObserver;
 
 - (NSString *)associatedUserDefaultsKey
 {
-    MASShortcutDefaultsObserver *defaultsObserver = objc_getAssociatedObject(self, kDefaultsObserver);
+    MASShortcutDefaultsObserver *defaultsObserver = objc_getAssociatedObject(self, MASAssociatedDefaultsObserver);
     return defaultsObserver.userDefaultsKey;
 }
 
 - (void)setAssociatedUserDefaultsKey:(NSString *)associatedUserDefaultsKey
 {
     // First, stop observing previous shortcut view
-    objc_setAssociatedObject(self, kDefaultsObserver, nil, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
+    objc_setAssociatedObject(self, MASAssociatedDefaultsObserver, nil, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
+
+    if (associatedUserDefaultsKey.length == 0) return;
 
     // Next, start observing current shortcut view
     MASShortcutDefaultsObserver *defaultsObserver = [[MASShortcutDefaultsObserver alloc] initWithShortcutView:self userDefaultsKey:associatedUserDefaultsKey];
-    objc_setAssociatedObject(self, kDefaultsObserver, defaultsObserver, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
+    objc_setAssociatedObject(self, MASAssociatedDefaultsObserver, defaultsObserver, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
 }
 
 @end

MASShortcutView.m

@@ -169,7 +169,7 @@
         [self getShortcutRect:&shortcutRect hintRect:NULL];
         NSString *title = (self.recording
                            ? (_hinting
-                              ? NSLocalizedString(@"Use Old Shortuct", @"Cancel action button for non-empty shortcut in recording state")
+                              ? NSLocalizedString(@"Use Old Shortcut", @"Cancel action button for non-empty shortcut in recording state")
                               : (self.shortcutPlaceholder.length > 0
                                  ? self.shortcutPlaceholder
                                  : NSLocalizedString(@"Type New Shortcut", @"Non-empty shortcut button in recording state")))

README.md

@@ -8,23 +8,64 @@ The project MASShortcut introduces modern API and user interface for recording,
 
 I hope, it is really easy:
 
-	// Drop a custom view into XIB and set its class to MASShortcutView
-	@property (nonatomic, weak) IBOutlet MASShortcutView *shortcutView;
+```objective-c
+// Drop a custom view into XIB and set its class to MASShortcutView
+@property (nonatomic, weak) IBOutlet MASShortcutView *shortcutView;
 	
-	// Think up a preference key to store a global shortcut between launches
-	NSString *const kPreferenceGlobalShortcut = @"GlobalShortcut";
+// Think up a preference key to store a global shortcut between launches
+NSString *const kPreferenceGlobalShortcut = @"GlobalShortcut";
 
-	// Assign the preference key and the shortcut view will take care of persistence
-	self.shortcutView.associatedUserDefaultsKey = kPreferenceGlobalShortcut;
+// Assign the preference key and the shortcut view will take care of persistence
+self.shortcutView.associatedUserDefaultsKey = kPreferenceGlobalShortcut;
 
-	// Execute your block of code automatically when user triggers a shortcut from preferences
-	[MASShortcut registerGlobalShortcutWithUserDefaultsKey:kPreferenceGlobalShortcut handler:^{
-		
-		// Let me know if you find a better or more convenient API.
-	}];
+// Execute your block of code automatically when user triggers a shortcut from preferences
+[MASShortcut registerGlobalShortcutWithUserDefaultsKey:kPreferenceGlobalShortcut handler:^{
+    // Let me know if you find a better or more convenient API.
+}];
+```
 
 To set an example, I made a  demo project: [MASShortcutDemo](https://github.com/shpakovski/MASShortcutDemo). Enjoy!
 
+#Notifications
+By registering for KVO notifications from `NSUserDefaultsController`, you can get a callback whenever a user changes the shortcut, allowing you to perform any UI updates, or other code handling tasks.
+
+This is just as easy to implement:
+    
+```objective-c
+// Declare an ivar for key path in the user defaults controller
+NSString *_observableKeyPath;
+    
+// Make a global context reference
+void *kGlobalShortcutContext = &kGlobalShortcutContext;
+    
+// Implement when loading view
+_observableKeyPath = [@"values." stringByAppendingString:kPreferenceGlobalShortcut];
+[[NSUserDefaultsController sharedUserDefaultsController] addObserver:self forKeyPath:_observableKeyPath
+                                                             options:NSKeyValueObservingOptionInitial
+                                                             context:kGlobalShortcutContext];
+
+// Capture the KVO change and do something
+- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)obj
+                        change:(NSDictionary *)change context:(void *)ctx
+{
+    if (ctx == kGlobalShortcutContext) {
+        NSLog(@"Shortcut has changed");
+    }
+    else {
+        [super observeValueForKeyPath:keyPath ofObject:obj change:change context:ctx];
+    }
+}
+
+// Do not forget to remove the observer
+[[NSUserDefaultsController sharedUserDefaultsController] removeObserver:self
+                                                             forKeyPath:_observableKeyPath
+                                                                context:kGlobalShortcutContext];
+```
+
+# Non-ARC Version
+
+If you like retain/release, please check out these forks: [heardrwt/MASShortcut](https://github.com/heardrwt/MASShortcut) and [chendo/MASShortcut](https://github.com/chendo/MASShortcut). However, the preferred way is to enable the `-fobjc-arc` in Xcode source options.
+
 # Copyright
 
-MASShortcut is licensed under the BSD license.
+MASShortcut is licensed under the 2-clause BSD license.