Release v1.3.0

The crash happened on orientation change from landscape to portrait in
"Show Tab Bar" scene.

.travis.yml

@@ -2,6 +2,7 @@ language: swift
 branches:
   only:
     - master
+    - next
 cache:
   directories:
   - build

Examples/Maps/Maps/ViewController.swift

@@ -26,8 +26,8 @@ class ViewController: UIViewController, MKMapViewDelegate, UISearchBarDelegate,
 
         searchVC = storyboard?.instantiateViewController(withIdentifier: "SearchPanel") as? SearchPanelViewController
 
-        // Add a content view controller
-        fpc.show(searchVC, sender: self)
+        // Set a content view controller
+        fpc.set(contentViewController: searchVC)
         fpc.track(scrollView: searchVC.tableView)
 
         setupMapView()
@@ -234,6 +234,10 @@ public class SearchPanelLandscapeLayout: FloatingPanelLayout {
             ]
         }
     }
+
+    public func backdropAlphaFor(position: FloatingPanelPosition) -> CGFloat {
+        return 0.0
+    }
 }
 
 class SearchCell: UITableViewCell {

Examples/Samples/Sources/Base.lproj/Main.storyboard

@@ -1,11 +1,11 @@
 <?xml version="1.0" encoding="UTF-8"?>
-<document type="com.apple.InterfaceBuilder3.CocoaTouch.Storyboard.XIB" version="3.0" toolsVersion="14313.18" targetRuntime="iOS.CocoaTouch" propertyAccessControl="none" useAutolayout="YES" useTraitCollections="YES" useSafeAreas="YES" colorMatched="YES" initialViewController="RoN-h0-uBD">
-    <device id="retina4_7" orientation="portrait">
+<document type="com.apple.InterfaceBuilder3.CocoaTouch.Storyboard.XIB" version="3.0" toolsVersion="14460.31" targetRuntime="iOS.CocoaTouch" propertyAccessControl="none" useAutolayout="YES" useTraitCollections="YES" useSafeAreas="YES" colorMatched="YES" initialViewController="RoN-h0-uBD">
+    <device id="retina5_9" orientation="portrait">
         <adaptation id="fullscreen"/>
     </device>
     <dependencies>
         <deployment identifier="iOS"/>
-        <plugIn identifier="com.apple.InterfaceBuilder.IBCocoaTouchPlugin" version="14283.14"/>
+        <plugIn identifier="com.apple.InterfaceBuilder.IBCocoaTouchPlugin" version="14460.20"/>
         <capability name="Safe area layout guides" minToolsVersion="9.0"/>
         <capability name="documents saved in the Xcode 8 format" minToolsVersion="8.0"/>
     </dependencies>
@@ -15,7 +15,7 @@
             <objects>
                 <navigationController id="RoN-h0-uBD" sceneMemberID="viewController">
                     <navigationBar key="navigationBar" contentMode="scaleToFill" insetsLayoutMarginsFromSafeArea="NO" id="hNW-5m-Omi">
-                        <rect key="frame" x="0.0" y="20" width="375" height="44"/>
+                        <rect key="frame" x="0.0" y="44" width="375" height="44"/>
                         <autoresizingMask key="autoresizingMask"/>
                     </navigationBar>
                     <connections>
@@ -31,22 +31,22 @@
             <objects>
                 <viewController id="jF4-A0-Eq6" customClass="SampleListViewController" customModule="Samples" customModuleProvider="target" sceneMemberID="viewController">
                     <view key="view" contentMode="scaleToFill" id="Smh-Bd-AAc">
-                        <rect key="frame" x="0.0" y="0.0" width="375" height="667"/>
+                        <rect key="frame" x="0.0" y="0.0" width="375" height="812"/>
                         <autoresizingMask key="autoresizingMask" widthSizable="YES" heightSizable="YES"/>
                         <subviews>
                             <tableView clipsSubviews="YES" contentMode="scaleToFill" alwaysBounceVertical="YES" dataMode="prototypes" style="plain" separatorStyle="default" rowHeight="-1" estimatedRowHeight="-1" sectionHeaderHeight="28" sectionFooterHeight="28" translatesAutoresizingMaskIntoConstraints="NO" id="7IS-PU-x0P">
-                                <rect key="frame" x="0.0" y="0.0" width="375" height="667"/>
+                                <rect key="frame" x="0.0" y="0.0" width="375" height="778"/>
                                 <color key="backgroundColor" white="1" alpha="1" colorSpace="custom" customColorSpace="genericGamma22GrayColorSpace"/>
                                 <prototypes>
                                     <tableViewCell clipsSubviews="YES" contentMode="scaleToFill" preservesSuperviewLayoutMargins="YES" selectionStyle="default" indentationWidth="10" reuseIdentifier="Cell" textLabel="M0G-C8-hAO" style="IBUITableViewCellStyleDefault" id="ySY-oA-g81">
                                         <rect key="frame" x="0.0" y="28" width="375" height="44"/>
                                         <autoresizingMask key="autoresizingMask"/>
                                         <tableViewCellContentView key="contentView" opaque="NO" clipsSubviews="YES" multipleTouchEnabled="YES" contentMode="center" preservesSuperviewLayoutMargins="YES" insetsLayoutMarginsFromSafeArea="NO" tableViewCell="ySY-oA-g81" id="sXB-nH-2g2">
-                                            <rect key="frame" x="0.0" y="0.0" width="375" height="43.5"/>
+                                            <rect key="frame" x="0.0" y="0.0" width="375" height="43.666666666666664"/>
                                             <autoresizingMask key="autoresizingMask"/>
                                             <subviews>
                                                 <label opaque="NO" multipleTouchEnabled="YES" contentMode="left" insetsLayoutMarginsFromSafeArea="NO" text="Title" textAlignment="natural" lineBreakMode="tailTruncation" baselineAdjustment="alignBaselines" adjustsFontSizeToFit="NO" id="M0G-C8-hAO">
-                                                    <rect key="frame" x="15" y="0.0" width="345" height="43.5"/>
+                                                    <rect key="frame" x="15" y="0.0" width="345" height="43.666666666666664"/>
                                                     <autoresizingMask key="autoresizingMask"/>
                                                     <fontDescription key="fontDescription" type="system" pointSize="17"/>
                                                     <nil key="textColor"/>
@@ -81,17 +81,17 @@
             <objects>
                 <viewController id="RpE-lI-27a" customClass="TabBarContentViewController" customModule="Samples" customModuleProvider="target" sceneMemberID="viewController">
                     <view key="view" contentMode="scaleToFill" id="JER-jz-KSq">
-                        <rect key="frame" x="0.0" y="0.0" width="375" height="667"/>
+                        <rect key="frame" x="0.0" y="0.0" width="375" height="812"/>
                         <autoresizingMask key="autoresizingMask" widthSizable="YES" heightSizable="YES"/>
                         <subviews>
                             <label opaque="NO" userInteractionEnabled="NO" contentMode="left" horizontalHuggingPriority="251" verticalHuggingPriority="251" text="Item 2" textAlignment="natural" lineBreakMode="tailTruncation" baselineAdjustment="alignBaselines" adjustsFontSizeToFit="NO" translatesAutoresizingMaskIntoConstraints="NO" id="AiP-dx-mFn">
-                                <rect key="frame" x="163.5" y="323" width="48" height="21"/>
+                                <rect key="frame" x="163.66666666666666" y="395.66666666666669" width="48" height="21"/>
                                 <fontDescription key="fontDescription" type="system" pointSize="17"/>
                                 <nil key="textColor"/>
                                 <nil key="highlightedColor"/>
                             </label>
                             <button opaque="NO" contentMode="scaleToFill" contentHorizontalAlignment="center" contentVerticalAlignment="center" buttonType="roundedRect" lineBreakMode="middleTruncation" translatesAutoresizingMaskIntoConstraints="NO" id="IvG-yp-yzI">
-                                <rect key="frame" x="20" y="20" width="39" height="30"/>
+                                <rect key="frame" x="20" y="44" width="39" height="30"/>
                                 <state key="normal" title="Close"/>
                                 <connections>
                                     <action selector="closeWithSender:" destination="RpE-lI-27a" eventType="touchUpInside" id="hj3-Xv-6Gq"/>
@@ -119,17 +119,17 @@
             <objects>
                 <viewController id="lto-Zc-Vtp" customClass="TabBarContentViewController" customModule="Samples" customModuleProvider="target" sceneMemberID="viewController">
                     <view key="view" contentMode="scaleToFill" id="ji9-Ez-N7i">
-                        <rect key="frame" x="0.0" y="0.0" width="375" height="667"/>
+                        <rect key="frame" x="0.0" y="0.0" width="375" height="812"/>
                         <autoresizingMask key="autoresizingMask" widthSizable="YES" heightSizable="YES"/>
                         <subviews>
                             <label opaque="NO" userInteractionEnabled="NO" contentMode="left" horizontalHuggingPriority="251" verticalHuggingPriority="251" text="Item 1" textAlignment="natural" lineBreakMode="tailTruncation" baselineAdjustment="alignBaselines" adjustsFontSizeToFit="NO" translatesAutoresizingMaskIntoConstraints="NO" id="uoW-c8-9wx">
-                                <rect key="frame" x="164.5" y="323" width="46" height="21"/>
+                                <rect key="frame" x="164.66666666666666" y="395.66666666666669" width="46" height="21"/>
                                 <fontDescription key="fontDescription" type="system" pointSize="17"/>
                                 <nil key="textColor"/>
                                 <nil key="highlightedColor"/>
                             </label>
                             <button opaque="NO" contentMode="scaleToFill" contentHorizontalAlignment="center" contentVerticalAlignment="center" buttonType="roundedRect" lineBreakMode="middleTruncation" translatesAutoresizingMaskIntoConstraints="NO" id="eFN-tN-4Ct">
-                                <rect key="frame" x="20" y="20" width="39" height="30"/>
+                                <rect key="frame" x="20" y="44" width="39" height="30"/>
                                 <state key="normal" title="Close"/>
                                 <connections>
                                     <action selector="closeWithSender:" destination="bYI-y3-Rzb" eventType="touchUpInside" id="YL4-GP-ZEZ"/>
@@ -152,6 +152,35 @@
             </objects>
             <point key="canvasLocation" x="-380" y="1576"/>
         </scene>
+        <!--Intrinsic View Controller-->
+        <scene sceneID="wtJ-qZ-aCl">
+            <objects>
+                <viewController storyboardIdentifier="IntrinsicViewController" title="Intrinsic View Controller" id="aK0-kv-mTu" sceneMemberID="viewController">
+                    <view key="view" contentMode="scaleToFill" id="eLM-xc-d9e">
+                        <rect key="frame" x="0.0" y="0.0" width="375" height="812"/>
+                        <autoresizingMask key="autoresizingMask" widthSizable="YES" heightSizable="YES"/>
+                        <subviews>
+                            <label opaque="NO" userInteractionEnabled="NO" contentMode="left" horizontalHuggingPriority="1000" verticalHuggingPriority="1000" horizontalCompressionResistancePriority="1000" verticalCompressionResistancePriority="1000" text="Change this text" textAlignment="center" lineBreakMode="tailTruncation" numberOfLines="0" baselineAdjustment="alignBaselines" adjustsFontSizeToFit="NO" translatesAutoresizingMaskIntoConstraints="NO" id="ge4-RW-Gmz">
+                                <rect key="frame" x="24" y="68" width="327" height="20.333333333333329"/>
+                                <fontDescription key="fontDescription" type="system" pointSize="17"/>
+                                <nil key="textColor"/>
+                                <nil key="highlightedColor"/>
+                            </label>
+                        </subviews>
+                        <color key="backgroundColor" white="1" alpha="1" colorSpace="custom" customColorSpace="genericGamma22GrayColorSpace"/>
+                        <constraints>
+                            <constraint firstItem="vtu-Jb-oOn" firstAttribute="trailing" secondItem="ge4-RW-Gmz" secondAttribute="trailing" constant="24" id="V59-MD-Lcg"/>
+                            <constraint firstItem="ge4-RW-Gmz" firstAttribute="leading" secondItem="eLM-xc-d9e" secondAttribute="leading" constant="24" id="hAO-P0-7Kw"/>
+                            <constraint firstItem="ge4-RW-Gmz" firstAttribute="top" secondItem="vtu-Jb-oOn" secondAttribute="top" constant="24" id="j0s-fd-MYj"/>
+                            <constraint firstAttribute="bottom" relation="greaterThanOrEqual" secondItem="ge4-RW-Gmz" secondAttribute="bottom" constant="24" id="tEn-PO-nVD"/>
+                        </constraints>
+                        <viewLayoutGuide key="safeArea" id="vtu-Jb-oOn"/>
+                    </view>
+                </viewController>
+                <placeholder placeholderIdentifier="IBFirstResponder" id="DfE-fL-zy5" userLabel="First Responder" sceneMemberID="firstResponder"/>
+            </objects>
+            <point key="canvasLocation" x="-940" y="805"/>
+        </scene>
         <!--Tab Bar View Controller-->
         <scene sceneID="nQ5-PV-qFw">
             <objects>
@@ -175,22 +204,22 @@
             <objects>
                 <viewController storyboardIdentifier="ModalViewController" id="bYI-y3-Rzb" customClass="ModalViewController" customModule="Samples" customModuleProvider="target" sceneMemberID="viewController">
                     <view key="view" contentMode="scaleToFill" id="qwo-GK-p1U">
-                        <rect key="frame" x="0.0" y="0.0" width="375" height="667"/>
+                        <rect key="frame" x="0.0" y="0.0" width="375" height="812"/>
                         <autoresizingMask key="autoresizingMask" widthSizable="YES" heightSizable="YES"/>
                         <subviews>
                             <view contentMode="scaleToFill" translatesAutoresizingMaskIntoConstraints="NO" id="vut-mK-Y4t" customClass="SafeAreaView" customModule="Samples" customModuleProvider="target">
-                                <rect key="frame" x="0.0" y="667" width="375" height="0.0"/>
+                                <rect key="frame" x="0.0" y="778" width="375" height="34"/>
                                 <color key="backgroundColor" white="0.66666666666666663" alpha="1" colorSpace="custom" customColorSpace="genericGamma22GrayColorSpace"/>
                             </view>
                             <button opaque="NO" contentMode="scaleToFill" contentHorizontalAlignment="center" contentVerticalAlignment="center" buttonType="roundedRect" lineBreakMode="middleTruncation" translatesAutoresizingMaskIntoConstraints="NO" id="sbF-Az-7sy">
-                                <rect key="frame" x="20" y="20" width="39" height="30"/>
+                                <rect key="frame" x="20" y="44" width="39" height="30"/>
                                 <state key="normal" title="Close"/>
                                 <connections>
                                     <action selector="closeWithSender:" destination="bYI-y3-Rzb" eventType="touchUpInside" id="MSC-ch-YJK"/>
                                 </connections>
                             </button>
                             <stackView opaque="NO" contentMode="scaleToFill" axis="vertical" alignment="top" spacing="44" translatesAutoresizingMaskIntoConstraints="NO" id="9p4-06-y2T">
-                                <rect key="frame" x="145" y="108" width="85" height="178"/>
+                                <rect key="frame" x="139.66666666666666" y="132" width="96" height="252"/>
                                 <subviews>
                                     <button opaque="NO" contentMode="scaleToFill" contentHorizontalAlignment="center" contentVerticalAlignment="center" buttonType="roundedRect" lineBreakMode="middleTruncation" translatesAutoresizingMaskIntoConstraints="NO" id="i9x-x5-n1q">
                                         <rect key="frame" x="0.0" y="0.0" width="80" height="30"/>
@@ -213,6 +242,13 @@
                                             <action selector="moveToTipWithSender:" destination="bYI-y3-Rzb" eventType="touchUpInside" id="BmL-91-9ai"/>
                                         </connections>
                                     </button>
+                                    <button opaque="NO" contentMode="scaleToFill" contentHorizontalAlignment="center" contentVerticalAlignment="center" buttonType="roundedRect" lineBreakMode="middleTruncation" translatesAutoresizingMaskIntoConstraints="NO" id="szf-HE-QTk">
+                                        <rect key="frame" x="0.0" y="222" width="96" height="30"/>
+                                        <state key="normal" title="Update layout"/>
+                                        <connections>
+                                            <action selector="updateLayout:" destination="bYI-y3-Rzb" eventType="touchUpInside" id="Woz-a7-YMJ"/>
+                                        </connections>
+                                    </button>
                                 </subviews>
                             </stackView>
                         </subviews>
@@ -356,7 +392,7 @@
                     </connections>
                 </swipeGestureRecognizer>
             </objects>
-            <point key="canvasLocation" x="1239" y="806"/>
+            <point key="canvasLocation" x="1311" y="806"/>
         </scene>
         <!--Detail View Controller-->
         <scene sceneID="b6k-zi-3wn">
@@ -384,24 +420,47 @@
                                 </constraints>
                             </view>
                             <view contentMode="scaleToFill" translatesAutoresizingMaskIntoConstraints="NO" id="Kva-Z7-0qY" customClass="OnSafeAreaView" customModule="Samples" customModuleProvider="target">
-                                <rect key="frame" x="0.0" y="734" width="375" height="44"/>
+                                <rect key="frame" x="0.0" y="700" width="375" height="44"/>
                                 <color key="backgroundColor" red="0.0078431372550000003" green="0.72156862749999995" blue="0.45882352939999999" alpha="1" colorSpace="calibratedRGB"/>
                                 <constraints>
                                     <constraint firstAttribute="height" constant="44" id="DQJ-cY-cKx"/>
                                 </constraints>
                             </view>
+                            <stackView opaque="NO" contentMode="scaleToFill" axis="vertical" spacing="22" translatesAutoresizingMaskIntoConstraints="NO" id="tP3-oJ-4EB">
+                                <rect key="frame" x="130.66666666666666" y="132" width="114" height="82"/>
+                                <subviews>
+                                    <button opaque="NO" contentMode="scaleToFill" contentHorizontalAlignment="center" contentVerticalAlignment="center" buttonType="roundedRect" lineBreakMode="middleTruncation" translatesAutoresizingMaskIntoConstraints="NO" id="c5r-jU-haj">
+                                        <rect key="frame" x="0.0" y="0.0" width="114" height="30"/>
+                                        <state key="normal" title="Show"/>
+                                        <connections>
+                                            <action selector="buttonPressed:" destination="YC8-ae-15L" eventType="touchUpInside" id="Mi1-o6-TWt"/>
+                                        </connections>
+                                    </button>
+                                    <button opaque="NO" contentMode="scaleToFill" contentHorizontalAlignment="center" contentVerticalAlignment="center" buttonType="roundedRect" lineBreakMode="middleTruncation" translatesAutoresizingMaskIntoConstraints="NO" id="wmd-ab-Nz3">
+                                        <rect key="frame" x="0.0" y="52" width="114" height="30"/>
+                                        <state key="normal" title="Present Modallly"/>
+                                        <connections>
+                                            <action selector="buttonPressed:" destination="YC8-ae-15L" eventType="touchUpInside" id="tjH-Ev-kpx"/>
+                                            <segue destination="bYI-y3-Rzb" kind="presentation" identifier="PresentModallySegue" id="3yq-HE-Tgn"/>
+                                        </connections>
+                                    </button>
+                                </subviews>
+                            </stackView>
                         </subviews>
-                        <color key="backgroundColor" white="1" alpha="1" colorSpace="custom" customColorSpace="genericGamma22GrayColorSpace"/>
+                        <color key="backgroundColor" red="1" green="0.83234566450000003" blue="0.47320586440000001" alpha="1" colorSpace="custom" customColorSpace="sRGB"/>
                         <gestureRecognizers/>
                         <constraints>
                             <constraint firstItem="noi-1a-5bZ" firstAttribute="top" secondItem="g7l-kO-y7q" secondAttribute="top" constant="12" id="EQy-cr-F2Y"/>
+                            <constraint firstItem="tP3-oJ-4EB" firstAttribute="centerX" secondItem="g7l-kO-y7q" secondAttribute="centerX" id="EsD-Vf-dNZ"/>
                             <constraint firstItem="8yw-OC-Ubk" firstAttribute="bottom" secondItem="g7l-kO-y7q" secondAttribute="bottom" id="JOL-wC-w74"/>
                             <constraint firstItem="8yw-OC-Ubk" firstAttribute="leading" secondItem="tAi-nk-rDB" secondAttribute="leading" id="RiJ-Hb-OOZ"/>
                             <constraint firstItem="8yw-OC-Ubk" firstAttribute="trailing" secondItem="tAi-nk-rDB" secondAttribute="trailing" id="Sof-yL-mwK"/>
+                            <constraint firstItem="tP3-oJ-4EB" firstAttribute="top" secondItem="tAi-nk-rDB" secondAttribute="top" constant="88" id="Zhb-Ss-epe"/>
                             <constraint firstItem="Kva-Z7-0qY" firstAttribute="trailing" secondItem="tAi-nk-rDB" secondAttribute="trailing" id="kkp-Yo-FQW"/>
                             <constraint firstItem="tAi-nk-rDB" firstAttribute="trailing" secondItem="noi-1a-5bZ" secondAttribute="trailing" constant="12" id="lv9-Nf-HNB"/>
                             <constraint firstItem="Kva-Z7-0qY" firstAttribute="leading" secondItem="tAi-nk-rDB" secondAttribute="leading" id="oVC-i1-TwS"/>
                             <constraint firstItem="tAi-nk-rDB" firstAttribute="bottom" secondItem="Kva-Z7-0qY" secondAttribute="bottom" id="rW2-mF-5DR"/>
+                            <constraint firstItem="8yw-OC-Ubk" firstAttribute="top" relation="greaterThanOrEqual" secondItem="tP3-oJ-4EB" secondAttribute="bottom" constant="8" symbolic="YES" id="vKQ-h9-uKt"/>
                         </constraints>
                         <viewLayoutGuide key="safeArea" id="tAi-nk-rDB"/>
                         <connections>
@@ -413,6 +472,7 @@
                     <size key="freeformSize" width="375" height="778"/>
                     <connections>
                         <outlet property="closeButton" destination="noi-1a-5bZ" id="eWQ-ha-8y7"/>
+                        <segue destination="bYI-y3-Rzb" kind="show" identifier="ShowSegue" id="r1P-2i-NDe"/>
                     </connections>
                 </viewController>
                 <placeholder placeholderIdentifier="IBFirstResponder" id="Wqk-xl-O3I" userLabel="First Responder" sceneMemberID="firstResponder"/>
@@ -432,7 +492,7 @@
                     </connections>
                 </pongPressGestureRecognizer>
             </objects>
-            <point key="canvasLocation" x="1442" y="-23"/>
+            <point key="canvasLocation" x="1440.8" y="-23.388305847076463"/>
         </scene>
         <!--Debug Text View Controller-->
         <scene sceneID="Bkq-O7-q4A">
@@ -507,4 +567,7 @@ Section 1.10.33 of "de Finibus Bonorum et Malorum", written by Cicero in 45 BC
             <point key="canvasLocation" x="729" y="-23"/>
         </scene>
     </scenes>
+    <inferredMetricsTieBreakers>
+        <segue reference="3yq-HE-Tgn"/>
+    </inferredMetricsTieBreakers>
 </document>

Examples/Samples/Sources/ViewController.swift

@@ -9,7 +9,7 @@
 import UIKit
 import FloatingPanel
 
-class SampleListViewController: UIViewController, UITableViewDataSource, UITableViewDelegate {
+class SampleListViewController: UIViewController, UITableViewDataSource, UITableViewDelegate, FloatingPanelControllerDelegate, FloatingPanelLayout {
     @IBOutlet weak var tableView: UITableView!
 
     enum Menu: Int, CaseIterable {
@@ -17,17 +17,23 @@ class SampleListViewController: UIViewController, UITableViewDataSource, UITable
         case trackingTextView
         case showDetail
         case showModal
+        case showFloatingPanelModal
         case showTabBar
         case showNestedScrollView
+        case showRemovablePanel
+        case showIntrinsicView
 
         var name: String {
             switch self {
-            case .trackingTableView: return "Scroll tracking (UITableView)"
-            case .trackingTextView: return "Scroll tracking (UITextView)"
+            case .trackingTableView: return "Scroll tracking(TableView)"
+            case .trackingTextView: return "Scroll tracking(TextView)"
             case .showDetail: return "Show Detail Panel"
             case .showModal: return "Show Modal"
+            case .showFloatingPanelModal: return "Show Floating Panel Modal"
             case .showTabBar: return "Show Tab Bar"
             case .showNestedScrollView: return "Show Nested ScrollView"
+            case .showRemovablePanel: return "Show Removable Panel"
+            case .showIntrinsicView: return "Show Intrinsic View"
             }
         }
 
@@ -37,14 +43,18 @@ class SampleListViewController: UIViewController, UITableViewDataSource, UITable
             case .trackingTextView: return "ConsoleViewController"
             case .showDetail: return "DetailViewController"
             case .showModal: return "ModalViewController"
+            case .showFloatingPanelModal: return nil
             case .showTabBar: return "TabBarViewController"
             case .showNestedScrollView: return "NestedScrollViewController"
+            case .showRemovablePanel: return "DetailViewController"
+            case .showIntrinsicView: return "IntrinsicViewController"
             }
         }
     }
 
     var mainPanelVC: FloatingPanelController!
     var detailPanelVC: FloatingPanelController!
+    var currentMenu: Menu = .trackingTableView
 
     override func viewDidLoad() {
         super.viewDidLoad()
@@ -52,21 +62,38 @@ class SampleListViewController: UIViewController, UITableViewDataSource, UITable
         tableView.delegate = self
         tableView.register(UITableViewCell.self, forCellReuseIdentifier: "Cell")
 
-        let contentVC = DebugTableViewController(style: .plain)
+        let contentVC = DebugTableViewController()
         addMainPanel(with: contentVC)
     }
 
+    override func viewDidAppear(_ animated: Bool) {
+        super.viewDidAppear(animated)
+    }
+
     func addMainPanel(with contentVC: UIViewController) {
         // Initialize FloatingPanelController
         mainPanelVC = FloatingPanelController()
+        mainPanelVC.delegate = self
 
         // Initialize FloatingPanelController and add the view
         mainPanelVC.surfaceView.cornerRadius = 6.0
         mainPanelVC.surfaceView.shadowHidden = false
 
-        // Add a content view controller and connect with the scroll view
-        mainPanelVC.show(contentVC, sender: self)
+        // Set a content view controller
+        mainPanelVC.set(contentViewController: contentVC)
 
+        // Enable tap-to-hide and removal interaction
+        switch currentMenu {
+        case .showRemovablePanel, .showIntrinsicView:
+            mainPanelVC.isRemovalInteractionEnabled = true
+
+            let backdropTapGesture = UITapGestureRecognizer(target: self, action: #selector(handleBackdrop(tapGesture:)))
+            mainPanelVC.backdropView.addGestureRecognizer(backdropTapGesture)
+        default:
+            break
+        }
+
+        // Track a scroll view
         switch contentVC {
         case let consoleVC as DebugTextViewController:
             mainPanelVC.track(scrollView: consoleVC.textView)
@@ -78,6 +105,7 @@ class SampleListViewController: UIViewController, UITableViewDataSource, UITable
         default:
             break
         }
+
         //  Add FloatingPanel to self.view
         mainPanelVC.addPanel(toParent: self, belowView: nil, animated: true)
     }
@@ -86,6 +114,10 @@ class SampleListViewController: UIViewController, UITableViewDataSource, UITable
         detailPanelVC.removePanelFromParent(animated: true, completion: nil)
     }
 
+    @objc func handleBackdrop(tapGesture: UITapGestureRecognizer) {
+        mainPanelVC.hide(animated: true, completion: nil)
+    }
+
     // MARK:- TableViewDatasource
 
     func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
@@ -104,15 +136,17 @@ class SampleListViewController: UIViewController, UITableViewDataSource, UITable
     func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
         let menu = Menu.allCases[indexPath.row]
         let contentVC: UIViewController = {
-            guard let storyboardID = menu.storyboardID else { return DebugTableViewController(style: .plain) }
+            guard let storyboardID = menu.storyboardID else { return DebugTableViewController() }
             guard let vc = self.storyboard?.instantiateViewController(withIdentifier: storyboardID) else { fatalError() }
             return vc
         }()
 
+        self.currentMenu = menu
+
         switch menu {
         case .showDetail:
-            detailPanelVC?.removeFromParent()
-
+            detailPanelVC?.removePanelFromParent(animated: false)
+            
             // Initialize FloatingPanelController
             detailPanelVC = FloatingPanelController()
 
@@ -120,16 +154,26 @@ class SampleListViewController: UIViewController, UITableViewDataSource, UITable
             detailPanelVC.surfaceView.cornerRadius = 6.0
             detailPanelVC.surfaceView.shadowHidden = false
 
-            // Add a content view controller and connect with the scroll view
-            detailPanelVC.show(contentVC, sender: self)
-
-            // (contentVC as? DetailViewController)?.closeButton?.addTarget(self, action: #selector(dismissDetailPanelVC), for: .touchUpInside)
+            // Set a content view controller
+            detailPanelVC.set(contentViewController: contentVC)
 
             //  Add FloatingPanel to self.view
             detailPanelVC.addPanel(toParent: self, belowView: nil, animated: true)
         case .showModal, .showTabBar:
             let modalVC = contentVC
             present(modalVC, animated: true, completion: nil)
+        case .showFloatingPanelModal:
+            let fpc = FloatingPanelController()
+            let contentVC = self.storyboard!.instantiateViewController(withIdentifier: "DetailViewController")
+            fpc.set(contentViewController: contentVC)
+            fpc.delegate = self
+
+            fpc.surfaceView.cornerRadius = 38.5
+            fpc.surfaceView.shadowHidden = false
+
+            fpc.isRemovalInteractionEnabled = true
+
+            self.present(fpc, animated: true, completion: nil)
         default:
             detailPanelVC?.removePanelFromParent(animated: true, completion: nil)
             mainPanelVC?.removePanelFromParent(animated: true) {
@@ -137,6 +181,86 @@ class SampleListViewController: UIViewController, UITableViewDataSource, UITable
             }
         }
     }
+
+    func floatingPanel(_ vc: FloatingPanelController, layoutFor newCollection: UITraitCollection) -> FloatingPanelLayout? {
+        switch currentMenu {
+        case .showRemovablePanel:
+            return newCollection.verticalSizeClass == .compact ? RemovablePanelLandscapeLayout() :  RemovablePanelLayout()
+        case .showIntrinsicView:
+            return IntrinsicPanelLayout()
+        case .showFloatingPanelModal:
+            if vc != mainPanelVC && vc != detailPanelVC {
+                return ModalPanelLayout()
+            }
+            fallthrough
+        default:
+            return (newCollection.verticalSizeClass == .compact) ? nil  : self
+        }
+    }
+
+    var initialPosition: FloatingPanelPosition {
+        return .half
+    }
+
+    func insetFor(position: FloatingPanelPosition) -> CGFloat? {
+        switch position {
+        case .full: return UIScreen.main.bounds.height == 667.0 ? 18.0 : 16.0
+        case .half: return 262.0
+        case .tip: return 69.0
+        case .hidden: return nil
+        }
+    }
+}
+
+class IntrinsicPanelLayout: FloatingPanelIntrinsicLayout { }
+
+class RemovablePanelLayout: FloatingPanelIntrinsicLayout {
+    var supportedPositions: Set<FloatingPanelPosition> {
+        return [.full, .half]
+    }
+    var topInteractionBuffer: CGFloat {
+        return 200.0
+    }
+    var bottomInteractionBuffer: CGFloat {
+        return 261.0 - 22.0
+    }
+
+    func insetFor(position: FloatingPanelPosition) -> CGFloat? {
+        switch position {
+        case .half: return 130.0
+        default: return nil
+        }
+    }
+    func backdropAlphaFor(position: FloatingPanelPosition) -> CGFloat {
+        return 0.3
+    }
+}
+
+class RemovablePanelLandscapeLayout: FloatingPanelIntrinsicLayout {
+    var supportedPositions: Set<FloatingPanelPosition> {
+        return [.full, .half]
+    }
+    var bottomInteractionBuffer: CGFloat {
+        return 261.0 - 22.0
+    }
+    func insetFor(position: FloatingPanelPosition) -> CGFloat? {
+        switch position {
+        case .half: return 261.0
+        default: return nil
+        }
+    }
+    func backdropAlphaFor(position: FloatingPanelPosition) -> CGFloat {
+        return 0.3
+    }
+}
+
+class ModalPanelLayout: FloatingPanelIntrinsicLayout {
+    var topInteractionBuffer: CGFloat {
+        return 100.0
+    }
+    func backdropAlphaFor(position: FloatingPanelPosition) -> CGFloat {
+        return 0.3
+    }
 }
 
 class NestedScrollViewController: UIViewController {
@@ -173,22 +297,103 @@ class DebugTextViewController: UIViewController, UITextViewDelegate {
     }
 
     @IBAction func close(sender: UIButton) {
-        // Now impossible
-        // dismiss(animated: true, completion: nil)
-        (self.parent as? FloatingPanelController)?.removePanelFromParent(animated: true, completion: nil)
+        // (self.parent as? FloatingPanelController)?.removePanelFromParent(animated: true, completion: nil)
+        dismiss(animated: true, completion: nil)
     }
 }
 
-class DebugTableViewController: UITableViewController {
+class DebugTableViewController: UIViewController, UITableViewDataSource, UITableViewDelegate {
+    weak var tableView: UITableView!
     var items: [String] = []
+    var itemHeight: CGFloat = 66.0
     override func viewDidLoad() {
         super.viewDidLoad()
+
+        let tableView = UITableView(frame: .zero,
+                                    style: .plain)
+        view.addSubview(tableView)
+        tableView.translatesAutoresizingMaskIntoConstraints = false
+        NSLayoutConstraint.activate([
+            tableView.topAnchor.constraint(equalTo: view.topAnchor),
+            tableView.bottomAnchor.constraint(equalTo: view.bottomAnchor),
+            tableView.leftAnchor.constraint(equalTo: view.leftAnchor),
+            tableView.rightAnchor.constraint(equalTo: view.rightAnchor)
+            ])
+        tableView.dataSource = self
+        tableView.delegate = self
+        self.tableView = tableView
+
+        let stackView = UIStackView()
+        view.addSubview(stackView)
+        stackView.axis = .vertical
+        stackView.distribution = .fillEqually
+        stackView.alignment = .trailing
+        stackView.spacing = 10.0
+        stackView.translatesAutoresizingMaskIntoConstraints = false
+        NSLayoutConstraint.activate([
+            stackView.topAnchor.constraint(equalTo: view.topAnchor, constant: 22.0),
+            stackView.rightAnchor.constraint(equalTo: view.rightAnchor, constant: -22.0),
+            ])
+
+        let button = UIButton()
+        button.setTitle("Animate Scroll", for: .normal)
+        button.setTitleColor(view.tintColor, for: .normal)
+        button.addTarget(self, action: #selector(animateScroll), for: .touchUpInside)
+        stackView.addArrangedSubview(button)
+
+        let button2 = UIButton()
+        button2.setTitle("Change content size", for: .normal)
+        button2.setTitleColor(view.tintColor, for: .normal)
+        button2.addTarget(self, action: #selector(changeContentSize), for: .touchUpInside)
+        stackView.addArrangedSubview(button2)
+
         for i in 0...100 {
             items.append("Items \(i)")
         }
         tableView.register(UITableViewCell.self, forCellReuseIdentifier: "Cell")
     }
 
+    @objc func animateScroll() {
+        tableView.scrollToRow(at: IndexPath(row: lround(Double(items.count) / 2.0),
+                                            section: 0),
+                              at: .top, animated: true)
+    }
+
+    @objc func changeContentSize() {
+        let actionSheet = UIAlertController(title: "Change content size", message: "", preferredStyle: .actionSheet)
+        actionSheet.addAction(UIAlertAction(title: "Large", style: .default, handler: { (_) in
+            self.itemHeight = 66.0
+            self.changeItems(100)
+        }))
+        actionSheet.addAction(UIAlertAction(title: "Match", style: .default, handler: { (_) in
+            switch self.tableView.bounds.height {
+            case 585: // iPhone 6,7,8
+                self.itemHeight = self.tableView.bounds.height / 13.0
+                self.changeItems(13)
+            case 656: // iPhone {6,7,8} Plus
+                self.itemHeight = self.tableView.bounds.height / 16.0
+                self.changeItems(16)
+            default: // iPhone X family
+                self.itemHeight = self.tableView.bounds.height / 12.0
+                self.changeItems(12)
+            }
+        }))
+        actionSheet.addAction(UIAlertAction(title: "Short", style: .default, handler: { (_) in
+            self.itemHeight = 66.0
+            self.changeItems(3)
+        }))
+
+        self.present(actionSheet, animated: true, completion: nil)
+    }
+
+    func changeItems(_ count: Int) {
+        items.removeAll()
+        for i in 0..<count {
+            items.append("Items \(i)")
+        }
+        tableView.reloadData()
+    }
+
     @objc func close(sender: UIButton) {
         //  Remove FloatingPanel from a view
         (self.parent as! FloatingPanelController).removePanelFromParent(animated: true, completion: nil)
@@ -238,28 +443,48 @@ class DebugTableViewController: UITableViewController {
         print("Content View: willTransition(to: \(newCollection), with: \(coordinator))")
     }
 
-    override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
+    func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
         return items.count
     }
 
-    override func tableView(_ tableView: UITableView, heightForRowAt indexPath: IndexPath) -> CGFloat {
-        return 66.0
+    func tableView(_ tableView: UITableView, heightForRowAt indexPath: IndexPath) -> CGFloat {
+        return itemHeight
     }
 
-    override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
+    func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
         let cell = tableView.dequeueReusableCell(withIdentifier: "Cell", for: indexPath)
         cell.textLabel?.text = items[indexPath.row]
         return cell
     }
+
+    func tableView(_ tableView: UITableView, editActionsForRowAt indexPath: IndexPath) -> [UITableViewRowAction]? {
+        return [
+            UITableViewRowAction(style: .destructive, title: "Delete", handler: { (action, path) in
+                self.items.remove(at: path.row)
+                tableView.deleteRows(at: [path], with: .automatic)
+            }),
+        ]
+    }
 }
 
 class DetailViewController: UIViewController {
     @IBOutlet weak var closeButton: UIButton!
     @IBAction func close(sender: UIButton) {
-        // Now impossible
-        // dismiss(animated: true, completion: nil)
-        (self.parent as? FloatingPanelController)?.removePanelFromParent(animated: true, completion: nil)
+        // (self.parent as? FloatingPanelController)?.removePanelFromParent(animated: true, completion: nil)
+        dismiss(animated: true, completion: nil)
     }
+
+    @IBAction func buttonPressed(_ sender: UIButton) {
+        switch sender.titleLabel?.text {
+        case "Show":
+            performSegue(withIdentifier: "ShowSegue", sender: self)
+        case "Present Modally":
+            performSegue(withIdentifier: "PresentModallySegue", sender: self)
+        default:
+            break
+        }
+    }
+
     @IBAction func tapped(_ sender: Any) {
         print("Detail panel is tapped!")
     }
@@ -271,25 +496,31 @@ class DetailViewController: UIViewController {
     }
 }
 
-class ModalViewController: UIViewController {
+class ModalViewController: UIViewController, FloatingPanelControllerDelegate {
     var fpc: FloatingPanelController!
     var consoleVC: DebugTextViewController!
+
     @IBOutlet weak var safeAreaView: UIView!
+
+    var isNewlayout: Bool = false
+
     override func viewWillAppear(_ animated: Bool) {
         super.viewWillAppear(animated)
         // Initialize FloatingPanelController
         fpc = FloatingPanelController()
+        fpc.delegate = self
 
         // Initialize FloatingPanelController and add the view
         fpc.surfaceView.cornerRadius = 6.0
         fpc.surfaceView.shadowHidden = false
 
-        // Add a content view controller and connect with the scroll view
+        // Set a content view controller and track the scroll view
         let consoleVC = storyboard?.instantiateViewController(withIdentifier: "ConsoleViewController") as! DebugTextViewController
-        fpc.show(consoleVC, sender: self)
-        self.consoleVC = consoleVC
+        fpc.set(contentViewController: consoleVC)
         fpc.track(scrollView: consoleVC.textView)
 
+        self.consoleVC = consoleVC
+
         //  Add FloatingPanel to self.view
         fpc.addPanel(toParent: self, belowView: safeAreaView)
     }
@@ -313,6 +544,32 @@ class ModalViewController: UIViewController {
     @IBAction func moveToTip(sender: UIButton) {
         fpc.move(to: .tip, animated: true)
     }
+
+    @IBAction func updateLayout(_ sender: Any) {
+        isNewlayout = !isNewlayout
+        UIView.animate(withDuration: 0.5) {
+            self.fpc.updateLayout()
+        }
+    }
+
+    func floatingPanel(_ vc: FloatingPanelController, layoutFor newCollection: UITraitCollection) -> FloatingPanelLayout? {
+        return (isNewlayout) ? ModalSecondLayout() : nil
+    }
+}
+
+class ModalSecondLayout: FloatingPanelLayout {
+    var initialPosition: FloatingPanelPosition {
+        return .half
+    }
+
+    func insetFor(position: FloatingPanelPosition) -> CGFloat? {
+        switch position {
+        case .full: return 18.0
+        case .half: return 262.0
+        case .tip: return 44.0
+        case .hidden: return nil
+        }
+    }
 }
 
 class TabBarViewController: UITabBarController {}
@@ -331,11 +588,11 @@ class TabBarContentViewController: UIViewController, FloatingPanelControllerDele
         fpc.surfaceView.cornerRadius = 6.0
         fpc.surfaceView.shadowHidden = false
 
-        // Add a content view controller and connect with the scroll view
+        // Set a content view controller and track the scroll view
         let consoleVC = storyboard?.instantiateViewController(withIdentifier: "ConsoleViewController") as! DebugTextViewController
-        fpc.show(consoleVC, sender: self)
-        self.consoleVC = consoleVC
+        fpc.set(contentViewController: consoleVC)
         fpc.track(scrollView: consoleVC.textView)
+        self.consoleVC = consoleVC
 
         //  Add FloatingPanel to self.view
         fpc.addPanel(toParent: self)

Examples/Stocks/Stocks/Base.lproj/Main.storyboard

@@ -1,6 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <document type="com.apple.InterfaceBuilder3.CocoaTouch.Storyboard.XIB" version="3.0" toolsVersion="14313.18" targetRuntime="iOS.CocoaTouch" propertyAccessControl="none" useAutolayout="YES" useTraitCollections="YES" useSafeAreas="YES" colorMatched="YES" initialViewController="BYZ-38-t0r">
-    <device id="retina5_9" orientation="portrait">
+    <device id="retina4_7" orientation="portrait">
         <adaptation id="fullscreen"/>
     </device>
     <dependencies>
@@ -15,11 +15,11 @@
             <objects>
                 <viewController id="BYZ-38-t0r" customClass="ViewController" customModule="Stocks" customModuleProvider="target" sceneMemberID="viewController">
                     <view key="view" contentMode="scaleToFill" id="8bC-Xf-vdC">
-                        <rect key="frame" x="0.0" y="0.0" width="375" height="812"/>
+                        <rect key="frame" x="0.0" y="0.0" width="375" height="667"/>
                         <autoresizingMask key="autoresizingMask" widthSizable="YES" heightSizable="YES"/>
                         <subviews>
                             <scrollView clipsSubviews="YES" multipleTouchEnabled="YES" contentMode="scaleToFill" translatesAutoresizingMaskIntoConstraints="NO" id="Uop-sw-I6p">
-                                <rect key="frame" x="0.0" y="109" width="375" height="624.66666666666663"/>
+                                <rect key="frame" x="0.0" y="85" width="375" height="537.5"/>
                                 <subviews>
                                     <imageView userInteractionEnabled="NO" contentMode="scaleToFill" horizontalHuggingPriority="251" verticalHuggingPriority="251" placeholderIntrinsicWidth="375" placeholderIntrinsicHeight="625" image="stocks_list" translatesAutoresizingMaskIntoConstraints="NO" id="XJR-iK-fem">
                                         <rect key="frame" x="0.0" y="0.0" width="375" height="625"/>
@@ -34,10 +34,10 @@
                                 </constraints>
                             </scrollView>
                             <view contentMode="scaleToFill" translatesAutoresizingMaskIntoConstraints="NO" id="dFl-81-6ok">
-                                <rect key="frame" x="0.0" y="733.66666666666663" width="375" height="78.333333333333371"/>
+                                <rect key="frame" x="0.0" y="622.5" width="375" height="44.5"/>
                                 <subviews>
                                     <imageView userInteractionEnabled="NO" contentMode="scaleToFill" horizontalHuggingPriority="251" verticalHuggingPriority="251" image="yahoo_bottom_bar" translatesAutoresizingMaskIntoConstraints="NO" id="NKr-gS-mpx">
-                                        <rect key="frame" x="0.0" y="0.0" width="375" height="44.333333333333336"/>
+                                        <rect key="frame" x="0.0" y="0.0" width="375" height="44.5"/>
                                         <color key="backgroundColor" white="0.0" alpha="0.0" colorSpace="custom" customColorSpace="genericGamma22GrayColorSpace"/>
                                         <constraints>
                                             <constraint firstAttribute="height" relation="greaterThanOrEqual" constant="44.5" id="B5t-ZF-qUj"/>
@@ -52,18 +52,17 @@
                                     <constraint firstItem="NKr-gS-mpx" firstAttribute="leading" secondItem="dFl-81-6ok" secondAttribute="leading" id="T2r-kY-JYy"/>
                                 </constraints>
                             </view>
-                            <stackView opaque="NO" contentMode="scaleToFill" fixedFrame="YES" axis="vertical" alignment="top" spacing="-8" translatesAutoresizingMaskIntoConstraints="NO" id="f7r-Al-pIN">
-                                <rect key="frame" x="16" y="44.000000000000014" width="153.33333333333334" height="56.666666666666664"/>
-                                <autoresizingMask key="autoresizingMask" flexibleMaxX="YES" flexibleMaxY="YES"/>
+                            <stackView opaque="NO" contentMode="scaleToFill" axis="vertical" alignment="top" spacing="-8" translatesAutoresizingMaskIntoConstraints="NO" id="f7r-Al-pIN">
+                                <rect key="frame" x="16" y="20" width="153.5" height="57"/>
                                 <subviews>
                                     <label opaque="NO" userInteractionEnabled="NO" contentMode="left" horizontalHuggingPriority="251" verticalHuggingPriority="251" text="STOCKS" textAlignment="natural" lineBreakMode="tailTruncation" baselineAdjustment="alignBaselines" adjustsFontSizeToFit="NO" translatesAutoresizingMaskIntoConstraints="NO" id="PCG-Wl-fXa">
-                                        <rect key="frame" x="0.0" y="0.0" width="111.66666666666667" height="32.333333333333336"/>
+                                        <rect key="frame" x="0.0" y="0.0" width="111.5" height="32.5"/>
                                         <fontDescription key="fontDescription" type="system" weight="heavy" pointSize="27"/>
                                         <color key="textColor" white="1" alpha="1" colorSpace="custom" customColorSpace="genericGamma22GrayColorSpace"/>
                                         <nil key="highlightedColor"/>
                                     </label>
                                     <label opaque="NO" userInteractionEnabled="NO" contentMode="left" horizontalHuggingPriority="251" verticalHuggingPriority="251" text="OCTOBER 5" textAlignment="natural" lineBreakMode="tailTruncation" baselineAdjustment="alignBaselines" adjustsFontSizeToFit="NO" translatesAutoresizingMaskIntoConstraints="NO" id="XmK-pu-9g4">
-                                        <rect key="frame" x="0.0" y="24.333333333333332" width="153.33333333333334" height="32.333333333333343"/>
+                                        <rect key="frame" x="0.0" y="24.5" width="153.5" height="32.5"/>
                                         <fontDescription key="fontDescription" type="system" weight="heavy" pointSize="27"/>
                                         <color key="textColor" red="0.55308091640472412" green="0.55657511949539185" blue="0.57255202531814575" alpha="1" colorSpace="custom" customColorSpace="displayP3"/>
                                         <nil key="highlightedColor"/>
@@ -75,10 +74,12 @@
                         <constraints>
                             <constraint firstItem="6Tk-OE-BBY" firstAttribute="trailing" secondItem="dFl-81-6ok" secondAttribute="trailing" id="20i-yz-AaQ"/>
                             <constraint firstItem="Uop-sw-I6p" firstAttribute="leading" secondItem="6Tk-OE-BBY" secondAttribute="leading" id="44w-r8-vYl"/>
+                            <constraint firstItem="f7r-Al-pIN" firstAttribute="leading" secondItem="6Tk-OE-BBY" secondAttribute="leading" constant="16" id="4Bq-Km-eET"/>
                             <constraint firstItem="Uop-sw-I6p" firstAttribute="top" secondItem="6Tk-OE-BBY" secondAttribute="top" constant="65" id="CXL-Dk-8MM"/>
                             <constraint firstItem="Uop-sw-I6p" firstAttribute="trailing" secondItem="6Tk-OE-BBY" secondAttribute="trailing" id="CsO-WF-T8L"/>
                             <constraint firstItem="dFl-81-6ok" firstAttribute="top" secondItem="Uop-sw-I6p" secondAttribute="bottom" id="Cz0-dW-r9H"/>
                             <constraint firstAttribute="bottom" secondItem="dFl-81-6ok" secondAttribute="bottom" id="KGl-8W-5ja"/>
+                            <constraint firstItem="f7r-Al-pIN" firstAttribute="top" secondItem="6Tk-OE-BBY" secondAttribute="top" constant="1.4210854715202004e-14" id="Qvt-vQ-PpT"/>
                             <constraint firstItem="dFl-81-6ok" firstAttribute="leading" secondItem="6Tk-OE-BBY" secondAttribute="leading" id="nlX-Ab-1aI"/>
                             <constraint firstItem="6Tk-OE-BBY" firstAttribute="bottom" secondItem="NKr-gS-mpx" secondAttribute="bottom" id="yeu-NH-Pmp"/>
                         </constraints>

Examples/Stocks/Stocks/ViewController.swift

@@ -34,8 +34,8 @@ class ViewController: UIViewController, FloatingPanelControllerDelegate {
 
         newsVC = storyboard?.instantiateViewController(withIdentifier: "News") as? NewsViewController
 
-        // Add a content view controller
-        fpc.show(newsVC, sender: self)
+        // Set a content view controller
+        fpc.set(contentViewController: newsVC)
         fpc.track(scrollView: newsVC.scrollView)
 
         fpc.addPanel(toParent: self, belowView: bottomToolView, animated: false)
@@ -114,10 +114,13 @@ class FloatingPanelStocksLayout: FloatingPanelLayout {
         case .full: return 56.0
         case .half: return 262.0
         case .tip: return 85.0 + 44.0 // Visible + ToolView
+        default: return nil
         }
     }
 
-    var backdropAlpha: CGFloat = 0.0
+    func backdropAlphaFor(position: FloatingPanelPosition) -> CGFloat {
+        return 0.0
+    }
 }
 
 // MARK: My custom behavior

FloatingPanel.podspec

@@ -1,10 +1,10 @@
 Pod::Spec.new do |s|
 
   s.name                = "FloatingPanel"
-  s.version             = "1.1.0"
-  s.summary             = "FloatingPanel is a simple and easy-to-use UI component of a floating panel interface"
+  s.version             = "1.3.0"
+  s.summary             = "FloatingPanel is a clean and easy-to-use UI component of a floating panel interface."
   s.description         = <<-DESC
-FloatingPanel is a simple and easy-to-use UI component for a new interface introduced in Apple Maps, Shortcuts and Stocks app.
+FloatingPanel is a clean and easy-to-use UI component for a new interface introduced in Apple Maps, Shortcuts and Stocks app.
 The new interface displays the related contents and utilities in parallel as a user wants.
                    DESC
   s.homepage            = "https://github.com/SCENEE/FloatingPanel"

Framework/FloatingPanel.xcodeproj/project.pbxproj

@@ -7,6 +7,8 @@
 	objects = {
 
 /* Begin PBXBuildFile section */
+		54352E9821A521CA00CBCA08 /* FloatingPanelView.swift in Sources */ = {isa = PBXBuildFile; fileRef = 54352E9721A521CA00CBCA08 /* FloatingPanelView.swift */; };
+		54352E9621A51A2500CBCA08 /* FloatingPanelTransitioning.swift in Sources */ = {isa = PBXBuildFile; fileRef = 54352E9521A51A2500CBCA08 /* FloatingPanelTransitioning.swift */; };
 		5450EEE421646DF500135936 /* FloatingPanelBehavior.swift in Sources */ = {isa = PBXBuildFile; fileRef = 5450EEE321646DF500135936 /* FloatingPanelBehavior.swift */; };
 		545DB9CB2151169500CA77B8 /* FloatingPanel.framework in Frameworks */ = {isa = PBXBuildFile; fileRef = 545DB9C12151169500CA77B8 /* FloatingPanel.framework */; };
 		545DB9D02151169500CA77B8 /* ViewTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = 545DB9CF2151169500CA77B8 /* ViewTests.swift */; };
@@ -32,6 +34,8 @@
 /* End PBXContainerItemProxy section */
 
 /* Begin PBXFileReference section */
+		54352E9721A521CA00CBCA08 /* FloatingPanelView.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = FloatingPanelView.swift; sourceTree = "<group>"; };
+		54352E9521A51A2500CBCA08 /* FloatingPanelTransitioning.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = FloatingPanelTransitioning.swift; sourceTree = "<group>"; };
 		5450EEE321646DF500135936 /* FloatingPanelBehavior.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = FloatingPanelBehavior.swift; sourceTree = "<group>"; };
 		545DB9C12151169500CA77B8 /* FloatingPanel.framework */ = {isa = PBXFileReference; explicitFileType = wrapper.framework; includeInIndex = 0; path = FloatingPanel.framework; sourceTree = BUILT_PRODUCTS_DIR; };
 		545DB9C42151169500CA77B8 /* FloatingPanelController.h */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.h; path = FloatingPanelController.h; sourceTree = "<group>"; };
@@ -92,9 +96,11 @@
 				545DB9C52151169500CA77B8 /* Info.plist */,
 				545DB9C42151169500CA77B8 /* FloatingPanelController.h */,
 				545DB9DF21511AC100CA77B8 /* FloatingPanelController.swift */,
+				54352E9521A51A2500CBCA08 /* FloatingPanelTransitioning.swift */,
 				54CFBFC4215CD09C006B5735 /* FloatingPanel.swift */,
 				54CFBFC2215CD045006B5735 /* FloatingPanelLayout.swift */,
 				5450EEE321646DF500135936 /* FloatingPanelBehavior.swift */,
+				54352E9721A521CA00CBCA08 /* FloatingPanelView.swift */,
 				54CDC5D2215B6D5A007D205C /* FloatingPanelSurfaceView.swift */,
 				54CDC5D4215B6D8D007D205C /* FloatingPanelBackdropView.swift */,
 				545DBA2A2152383100CA77B8 /* GrabberHandleView.swift */,
@@ -225,11 +231,13 @@
 				54CDC5D3215B6D5A007D205C /* FloatingPanelSurfaceView.swift in Sources */,
 				54CFBFC3215CD045006B5735 /* FloatingPanelLayout.swift in Sources */,
 				54CDC5D5215B6D8D007D205C /* FloatingPanelBackdropView.swift in Sources */,
+				54352E9821A521CA00CBCA08 /* FloatingPanelView.swift in Sources */,
 				54CFBFC5215CD09C006B5735 /* FloatingPanel.swift in Sources */,
 				54ABD7AF216CCFF7002E6C13 /* Logger.swift in Sources */,
 				545DB9E021511AC100CA77B8 /* FloatingPanelController.swift in Sources */,
 				5450EEE421646DF500135936 /* FloatingPanelBehavior.swift in Sources */,
 				545DBA2B2152383100CA77B8 /* GrabberHandleView.swift in Sources */,
+				54352E9621A51A2500CBCA08 /* FloatingPanelTransitioning.swift in Sources */,
 				545DB9DE215118C800CA77B8 /* UIExtensions.swift in Sources */,
 			);
 			runOnlyForDeploymentPostprocessing = 0;

Framework/Sources/FloatingPanel.swift

@@ -33,12 +33,21 @@ class FloatingPanel: NSObject, UIGestureRecognizerDelegate, UIScrollViewDelegate
 
     unowned let viewcontroller: FloatingPanelController
 
-    private(set) var state: FloatingPanelPosition = .tip
+    private(set) var state: FloatingPanelPosition = .hidden {
+        didSet { viewcontroller.delegate?.floatingPanelDidChangePosition(viewcontroller) }
+    }
+
+    private var isBottomState: Bool {
+        let remains = layoutAdapter.supportedPositions.filter { $0.rawValue > state.rawValue }
+        return remains.count == 0
+    }
 
     let panGesture: FloatingPanelPanGestureRecognizer
+    var isRemovalInteractionEnabled: Bool = false
 
     private var animator: UIViewPropertyAnimator?
     private var initialFrame: CGRect = .zero
+    private var initialScrollOffset: CGPoint = .zero
     private var transOffsetY: CGFloat = 0
     private var interactionInProgress: Bool = false
 
@@ -51,7 +60,10 @@ class FloatingPanel: NSObject, UIGestureRecognizerDelegate, UIScrollViewDelegate
 
     init(_ vc: FloatingPanelController, layout: FloatingPanelLayout, behavior: FloatingPanelBehavior) {
         viewcontroller = vc
-        surfaceView = vc.view as! FloatingPanelSurfaceView
+
+        surfaceView = FloatingPanelSurfaceView()
+        surfaceView.backgroundColor = .white
+
         backdropView = FloatingPanelBackdropView()
         backdropView.backgroundColor = .black
         backdropView.alpha = 0.0
@@ -74,29 +86,36 @@ class FloatingPanel: NSObject, UIGestureRecognizerDelegate, UIScrollViewDelegate
         panGesture.delegate = self
     }
 
-    func layoutViews(in vc: UIViewController) {
+    func setUpViews(in vc: UIViewController) {
         unowned let view = vc.view!
 
-        view.insertSubview(backdropView, belowSubview: surfaceView)
-        backdropView.frame = view.bounds
+        // FloatingPanelSurfaceWrapperView is needed to update the surface's height
+        // without animation and prevent the backdrop's cut-off on orientation change.
+        let surfaceWrapperView = FloatingPanelSurfaceWrapperView()
+        surfaceWrapperView.frame = view.bounds
+        surfaceWrapperView.backgroundColor = .clear
 
-        layoutAdapter.prepareLayout(toParent: vc)
+        view.addSubview(surfaceWrapperView)
+
+        surfaceWrapperView.translatesAutoresizingMaskIntoConstraints = false
+        NSLayoutConstraint.activate([
+            surfaceWrapperView.topAnchor.constraint(equalTo: view.topAnchor, constant: 0.0),
+            surfaceWrapperView.leftAnchor.constraint(equalTo: view.leftAnchor, constant: 0.0),
+            surfaceWrapperView.rightAnchor.constraint(equalTo: view.rightAnchor, constant: 0.0),
+            surfaceWrapperView.bottomAnchor.constraint(equalTo: view.bottomAnchor, constant: 0.0),
+            ])
+
+        surfaceWrapperView.addSubview(surfaceView)
+
+        view.insertSubview(backdropView, belowSubview: surfaceWrapperView)
+        backdropView.frame = view.bounds
     }
 
     func move(to: FloatingPanelPosition, animated: Bool, completion: (() -> Void)? = nil) {
         move(from: state, to: to, animated: animated, completion: completion)
     }
 
-    func present(animated: Bool, completion: (() -> Void)? = nil) {
-        self.layoutAdapter.activateLayout(of: nil)
-        move(from: nil, to: layoutAdapter.layout.initialPosition, animated: animated, completion: completion)
-    }
-
-    func dismiss(animated: Bool, completion: (() -> Void)? = nil) {
-        move(from: state, to: nil, animated: animated, completion: completion)
-    }
-
-    private func move(from: FloatingPanelPosition?, to: FloatingPanelPosition?, animated: Bool, completion: (() -> Void)? = nil) {
+    private func move(from: FloatingPanelPosition, to: FloatingPanelPosition, animated: Bool, completion: (() -> Void)? = nil) {
         if to != .full {
             lockScrollView()
         }
@@ -104,23 +123,19 @@ class FloatingPanel: NSObject, UIGestureRecognizerDelegate, UIScrollViewDelegate
         if animated {
             let animator: UIViewPropertyAnimator
             switch (from, to) {
-            case (nil, let to?):
+            case (.hidden, let to):
                 animator = behavior.addAnimator(self.viewcontroller, to: to)
-            case (let from?, let to?):
-                animator = behavior.moveAnimator(self.viewcontroller, from: from, to: to)
-            case (let from?, nil):
+            case (let from, .hidden):
                 animator = behavior.removeAnimator(self.viewcontroller, from: from)
-            case (nil, nil):
-                fatalError()
+            case (let from, let to):
+                animator = behavior.moveAnimator(self.viewcontroller, from: from, to: to)
             }
 
             animator.addAnimations { [weak self] in
                 guard let self = self else { return }
 
                 self.updateLayout(to: to)
-                if let to = to {
-                    self.state = to
-                }
+                self.state = to
             }
             animator.addCompletion { _ in
                 completion?()
@@ -128,34 +143,33 @@ class FloatingPanel: NSObject, UIGestureRecognizerDelegate, UIScrollViewDelegate
             animator.startAnimation()
         } else {
             self.updateLayout(to: to)
-            if let to = to {
-                self.state = to
-            }
+            self.state = to
             completion?()
         }
     }
 
     // MARK: - Layout update
 
-    private func updateLayout(to target: FloatingPanelPosition?) {
+    private func updateLayout(to target: FloatingPanelPosition) {
         self.layoutAdapter.activateLayout(of: target)
-        self.setBackdropAlpha(of: target)
-    }
-
-    private func setBackdropAlpha(of target: FloatingPanelPosition?) {
-        switch target {
-        case .full?:
-            self.backdropView.alpha = layoutAdapter.layout.backdropAlpha
-        default:
-            self.backdropView.alpha = 0.0
-        }
     }
 
     private func getBackdropAlpha(with translation: CGPoint) -> CGFloat {
-        let topY = layoutAdapter.topY
-        let middleY = layoutAdapter.middleY
         let currentY = getCurrentY(from: initialFrame, with: translation)
-        return (1 - (currentY - topY) / (middleY - topY)) * layoutAdapter.layout.backdropAlpha
+
+        let next = directionalPosition(with: translation)
+        let pre = redirectionalPosition(with: translation)
+        let nextY = layoutAdapter.positionY(for: next)
+        let preY = layoutAdapter.positionY(for: pre)
+
+        let nextAlpha = layoutAdapter.layout.backdropAlphaFor(position: next)
+        let preAlpha = layoutAdapter.layout.backdropAlphaFor(position: pre)
+
+        if preY == nextY {
+            return preAlpha
+        } else {
+            return preAlpha + max(min(1.0, 1.0 - (nextY - currentY) / (nextY - preY) ), 0.0) * (nextAlpha - preAlpha)
+        }
     }
 
     // MARK: - UIGestureRecognizerDelegate
@@ -164,77 +178,157 @@ class FloatingPanel: NSObject, UIGestureRecognizerDelegate, UIScrollViewDelegate
                                   shouldRecognizeSimultaneouslyWith otherGestureRecognizer: UIGestureRecognizer) -> Bool {
         guard gestureRecognizer == panGesture else { return false }
 
-        log.debug("shouldRecognizeSimultaneouslyWith", otherGestureRecognizer)
+        /* log.debug("shouldRecognizeSimultaneouslyWith", otherGestureRecognizer) */
 
-        return otherGestureRecognizer == scrollView?.panGestureRecognizer
+        // all gestures of the tracking scroll view should be recognized in parallel
+        // and handle them in self.handle(panGesture:)
+        return scrollView?.gestureRecognizers?.contains(otherGestureRecognizer) ?? false
     }
 
     public func gestureRecognizer(_ gestureRecognizer: UIGestureRecognizer, shouldBeRequiredToFailBy otherGestureRecognizer: UIGestureRecognizer) -> Bool {
         guard gestureRecognizer == panGesture else { return false }
 
-        // Do not begin any gestures excluding the tracking scrollView's pan gesture until the pan gesture fails
-        if otherGestureRecognizer == scrollView?.panGestureRecognizer {
+        /* log.debug("shouldBeRequiredToFailBy", otherGestureRecognizer) */
+
+        // The tracking scroll view's gestures should begin without waiting for the pan gesture failure.
+        // `scrollView.gestureRecognizers` can contains the following gestures
+        // * UIScrollViewDelayedTouchesBeganGestureRecognizer
+        // * UIScrollViewPanGestureRecognizer (scrollView.panGestureRecognizer)
+        // * _UIDragAutoScrollGestureRecognizer
+        // * _UISwipeActionPanGestureRecognizer
+        // * UISwipeDismissalGestureRecognizer
+        if let scrollView = scrollView,
+            let scrollGestureRecognizers = scrollView.gestureRecognizers,
+            scrollGestureRecognizers.contains(otherGestureRecognizer) {
             return false
-        } else {
-            return true
         }
+
+        // Long press gesture should begin without waiting for the pan gesture failure.
+        if otherGestureRecognizer is UILongPressGestureRecognizer {
+            return false
+        }
+
+        // Do not begin any other gestures until the pan gesture fails.
+        return true
     }
 
     public func gestureRecognizer(_ gestureRecognizer: UIGestureRecognizer, shouldRequireFailureOf otherGestureRecognizer: UIGestureRecognizer) -> Bool {
         guard gestureRecognizer == panGesture else { return false }
 
-        // Do not begin the pan gesture until any other gestures fail except fo the tracking scrollView's pan gesture.
+        log.debug("shouldRequireFailureOf", otherGestureRecognizer)
+
+        // Should begin the pan gesture without waiting for the tracking scroll view's gestures.
+        // `scrollView.gestureRecognizers` can contains the following gestures
+        // * UIScrollViewDelayedTouchesBeganGestureRecognizer
+        // * UIScrollViewPanGestureRecognizer (scrollView.panGestureRecognizer)
+        // * _UIDragAutoScrollGestureRecognizer
+        // * _UISwipeActionPanGestureRecognizer
+        // * UISwipeDismissalGestureRecognizer
+        if let scrollView = scrollView {
+            // On short contents scroll, `_UISwipeActionPanGestureRecognizer` blocks
+            // the panel's pan gesture if not returns false
+            if let scrollGestureRecognizers = scrollView.gestureRecognizers,
+                scrollGestureRecognizers.contains(otherGestureRecognizer) {
+                return false
+            }
+        }
+
         switch otherGestureRecognizer {
-        case scrollView?.panGestureRecognizer:
-            return false
         case is UIPanGestureRecognizer,
              is UISwipeGestureRecognizer,
              is UIRotationGestureRecognizer,
              is UIScreenEdgePanGestureRecognizer,
              is UIPinchGestureRecognizer:
+            // Do not begin the pan gesture until these gestures fail
             return true
         default:
+            // Should begin the pan gesture witout waiting tap/long press gestures fail
             return false
         }
     }
 
-    // MARK: - Gesture handling
+    var grabberAreaFrame: CGRect {
+        let grabberAreaFrame = CGRect(x: surfaceView.bounds.origin.x,
+                                     y: surfaceView.bounds.origin.y,
+                                     width: surfaceView.bounds.width,
+                                     height: FloatingPanelSurfaceView.topGrabberBarHeight * 2)
+        return grabberAreaFrame
+    }
 
+    // MARK: - Gesture handling
+    private let offsetThreshold: CGFloat = 5.0 // Optimal value from testing
     @objc func handle(panGesture: UIPanGestureRecognizer) {
         log.debug("Gesture >>>>", panGesture)
+        let velocity = panGesture.velocity(in: panGesture.view)
 
         switch panGesture {
         case scrollView?.panGestureRecognizer:
             guard let scrollView = scrollView else { return }
+
+            log.debug("SrollPanGesture ScrollView.contentOffset >>>", scrollView.contentOffset.y, scrollView.contentSize, scrollView.bounds.size)
+
+            // Prevent scoll slip by the top bounce when the scroll view's height is
+            // less than the content's height
+            if scrollView.isDecelerating == false, scrollView.contentSize.height > scrollView.bounds.height {
+                scrollView.bounces = (scrollView.contentOffset.y > offsetThreshold)
+            }
+
             if surfaceView.frame.minY > layoutAdapter.topY {
-                scrollView.contentOffset.y = scrollView.contentOffsetZero.y
+                switch state {
+                case .full:
+                    let point = panGesture.location(in: surfaceView)
+                    if grabberAreaFrame.contains(point) {
+                        // Preserve the current content offset in moving from full.
+                        scrollView.contentOffset.y = initialScrollOffset.y
+                    } else {
+                        // Prevent over scrolling in moving from full.
+                        scrollView.contentOffset.y = scrollView.contentOffsetZero.y
+                    }
+                case .half, .tip:
+                    guard scrollView.isDecelerating == false else {
+                        // Don't fix the scroll offset in animating the panel to half and tip.
+                        // It causes a buggy scrolling deceleration because `state` becomes
+                        // a target position in animating the panel on the interaction from full.
+                        return
+                    }
+                    // Fix the scroll offset in moving the panel from half and tip.
+                    scrollView.contentOffset.y = initialScrollOffset.y
+                case .hidden:
+                    fatalError("A floating panel hidden must not be used by a user")
+                }
+
+                // Always hide a scroll indicator at the non-top.
+                if interactionInProgress {
+                    lockScrollView()
+                }
+            } else {
+                // Always show a scroll indicator at the top.
+                if interactionInProgress {
+                    unlockScrollView()
+                }
             }
         case panGesture:
             let translation = panGesture.translation(in: panGesture.view!.superview)
-            let velocity = panGesture.velocity(in: panGesture.view)
             let location = panGesture.location(in: panGesture.view)
 
-            log.debug(panGesture.state, ">>>", "{ translation: \(translation), velocity: \(velocity) }")
+            log.debug(panGesture.state, ">>>", "translation: \(translation.y), velocity: \(velocity.y)")
 
-            if let scrollView = scrollView, scrollView.frame.contains(location) {
-                log.debug("ScrollView.contentOffset >>>", scrollView.contentOffset)
-                if state == .full {
-                    if scrollView.contentOffset.y - scrollView.contentOffsetZero.y > 0 {
-                        return
-                    }
-                    if scrollView.isDecelerating {
-                        return
-                    }
-                    if interactionInProgress == false, velocity.y < 0 || velocity.y > 2500.0 {
-                        return
-                    }
-                }
+            if shouldScrollViewHandleTouch(scrollView, point: location, velocity: velocity) {
+                return
+            }
+
+            if let animator = self.animator {
+                animator.stopAnimation(true)
+                self.animator = nil
             }
 
             switch panGesture.state {
             case .began:
                 panningBegan()
             case .changed:
+                if interactionInProgress == false {
+                    startInteraction(with: translation)
+                }
                 panningChange(with: translation)
             case .ended, .cancelled, .failed:
                 panningEnd(with: translation, velocity: velocity)
@@ -246,18 +340,56 @@ class FloatingPanel: NSObject, UIGestureRecognizerDelegate, UIScrollViewDelegate
         }
     }
 
+    private func shouldScrollViewHandleTouch(_ scrollView: UIScrollView?, point: CGPoint, velocity: CGPoint) -> Bool {
+        // When no scrollView, nothing to handle.
+        guard let scrollView = scrollView else { return false }
+
+        // For _UISwipeActionPanGestureRecognizer
+        if let scrollGestureRecognizers = scrollView.gestureRecognizers {
+            for gesture in scrollGestureRecognizers {
+                guard gesture.state == .began || gesture.state == .changed
+                else { continue }
+
+                if gesture !=  scrollView.panGestureRecognizer {
+                    return true
+                }
+            }
+        }
+
+        guard
+            state == .full,                   // When not .full, don't scroll.
+            interactionInProgress == false,   // When interaction already in progress, don't scroll.
+            scrollView.frame.contains(point), // When point not in scrollView, don't scroll.
+            !grabberAreaFrame.contains(point) // When point within grabber area, don't scroll.
+        else {
+            return false
+        }
+
+        log.debug("ScrollView.contentOffset >>>", scrollView.contentOffset.y)
+
+        let offset = scrollView.contentOffset.y - scrollView.contentOffsetZero.y
+        if  abs(offset) > offsetThreshold {
+            return true
+        }
+        if scrollView.isDecelerating {
+            return true
+        }
+        if velocity.y < 0 {
+            return true
+        }
+
+        return false
+    }
+
     private func panningBegan() {
         // A user interaction does not always start from Began state of the pan gesture
         // because it can be recognized in scrolling a content in a content view controller.
-        // So I do nothing here.
-        log.debug("panningBegan \(initialFrame)")
+        // So do nothing here.
+        log.debug("panningBegan")
     }
 
     private func panningChange(with translation: CGPoint) {
         log.debug("panningChange")
-        if interactionInProgress == false {
-            startInteraction(with: translation)
-        }
 
         let currentY = getCurrentY(from: initialFrame, with: translation)
 
@@ -275,36 +407,111 @@ class FloatingPanel: NSObject, UIGestureRecognizerDelegate, UIScrollViewDelegate
             initialFrame = surfaceView.frame
         }
 
-        stopScrollDeceleration = (surfaceView.frame.minY > layoutAdapter.topY) // Projecting the dragging to the scroll dragging
+        stopScrollDeceleration = (surfaceView.frame.minY > layoutAdapter.topY) // Projecting the dragging to the scroll dragging or not
 
         let targetPosition = self.targetPosition(with: translation, velocity: velocity)
         let distance = self.distance(to: targetPosition, with: translation)
 
         endInteraction(for: targetPosition)
 
+        if isRemovalInteractionEnabled, isBottomState {
+            let velocityVector = (distance != 0) ? CGVector(dx: 0,
+                                                            dy: max(min(velocity.y/distance, behavior.removalVelocity), 0.0)) : .zero
+
+            if shouldStartRemovalAnimation(with: translation, velocityVector: velocityVector) {
+
+                viewcontroller.delegate?.floatingPanelDidEndDraggingToRemove(viewcontroller, withVelocity: velocity)
+                self.startRemovalAnimation(with: velocityVector) { [weak self] in
+                    guard let self = self else { return }
+                    self.viewcontroller.dismiss(animated: false)
+                    self.viewcontroller.delegate?.floatingPanelDidEndRemove(self.viewcontroller)
+                }
+                return
+            }
+        }
+
         viewcontroller.delegate?.floatingPanelDidEndDragging(viewcontroller, withVelocity: velocity, targetPosition: targetPosition)
         viewcontroller.delegate?.floatingPanelWillBeginDecelerating(viewcontroller)
 
         startAnimation(to: targetPosition, at: distance, with: velocity)
     }
 
+    private func shouldStartRemovalAnimation(with translation: CGPoint, velocityVector: CGVector) -> Bool {
+        let posY = layoutAdapter.positionY(for: state)
+        let currentY = getCurrentY(from: initialFrame, with: translation)
+        let safeAreaBottomY = layoutAdapter.safeAreaBottomY
+        let vth = behavior.removalVelocity
+        let pth = max(min(behavior.removalProgress, 1.0), 0.0)
+
+        let num = (currentY - posY)
+        let den = (safeAreaBottomY - posY)
+
+        guard num >= 0, den != 0, (num / den >= pth || velocityVector.dy == vth)
+        else { return false }
+
+        return true
+    }
+
+    private func startRemovalAnimation(with velocityVector: CGVector, completion: (() -> Void)?) {
+        let animator = self.behavior.removalInteractionAnimator(self.viewcontroller, with: velocityVector)
+
+        animator.addAnimations { [weak self] in
+            self?.updateLayout(to: .hidden)
+        }
+        animator.addCompletion({ _ in
+            completion?()
+        })
+        animator.startAnimation()
+    }
+
     private func startInteraction(with translation: CGPoint) {
+        /* Don't lock a scroll view to show a scroll indicator after hitting the top */
         log.debug("startInteraction")
         initialFrame = surfaceView.frame
+        if let scrollView = scrollView {
+            initialScrollOffset = scrollView.contentOffset
+        }
         transOffsetY = translation.y
+
         viewcontroller.delegate?.floatingPanelWillBeginDragging(viewcontroller)
 
-        lockScrollView()
+        if layoutAdapter.layout is FloatingPanelIntrinsicLayout {
+            viewcontroller.contentViewController?.view?.constraints.forEach({ (const) in
+                switch viewcontroller.contentViewController?.layoutGuide.bottomAnchor {
+                case const.firstAnchor:
+                    (const.secondItem as? UIView)?.disableAutoLayout()
+                case const.secondAnchor:
+                    (const.firstItem as? UIView)?.disableAutoLayout()
+                default:
+                    break
+                }
+            })
+        }
 
         interactionInProgress = true
     }
 
     private func endInteraction(for targetPosition: FloatingPanelPosition) {
         log.debug("endInteraction for \(targetPosition)")
-        if targetPosition != .full {
-            lockScrollView(withBounce: true)
-        }
         interactionInProgress = false
+
+        // Prevent to keep a scoll view indicator visible at the half/tip position
+        if targetPosition != .full {
+            lockScrollView()
+        }
+
+        if layoutAdapter.layout is FloatingPanelIntrinsicLayout {
+            viewcontroller.contentViewController?.view?.constraints.forEach({ (const) in
+                switch viewcontroller.contentViewController?.layoutGuide.bottomAnchor {
+                case const.firstAnchor:
+                    (const.secondItem as? UIView)?.enableAutoLayout()
+                case const.secondAnchor:
+                    (const.firstItem as? UIView)?.enableAutoLayout()
+                default:
+                    break
+                }
+            })
+        }
     }
 
     private func getCurrentY(from rect: CGRect, with translation: CGPoint) -> CGFloat {
@@ -322,19 +529,20 @@ class FloatingPanel: NSObject, UIGestureRecognizerDelegate, UIScrollViewDelegate
                 return max(topY, min(bottomY, y))
             }
         }
-        return max(topY - topBuffer, min(bottomY + bottomBuffer, y))
+        let topMax = layoutAdapter.topMaxY
+        let bottomMax = layoutAdapter.bottomMaxY
+        return max(max(topY - topBuffer, topMax), min(min(bottomY + bottomBuffer, bottomMax), y))
     }
 
     private func startAnimation(to targetPosition: FloatingPanelPosition, at distance: CGFloat, with velocity: CGPoint) {
         let targetY = layoutAdapter.positionY(for: targetPosition)
         let velocityVector = (distance != 0) ? CGVector(dx: 0, dy: max(min(velocity.y/distance, 30.0), -30.0)) : .zero
         let animator = behavior.interactionAnimator(self.viewcontroller, to: targetPosition, with: velocityVector)
-        animator.isInterruptible = false // To prevent a backdrop color's punk
         animator.addAnimations { [weak self] in
             guard let self = self else { return }
             if self.state == targetPosition {
                 self.surfaceView.frame.origin.y = targetY
-                self.setBackdropAlpha(of: targetPosition)
+                self.layoutAdapter.setBackdropAlpha(of: targetPosition)
             } else {
                 self.updateLayout(to: targetPosition)
             }
@@ -358,8 +566,11 @@ class FloatingPanel: NSObject, UIGestureRecognizerDelegate, UIScrollViewDelegate
         self.animator = nil
         self.viewcontroller.delegate?.floatingPanelDidEndDecelerating(self.viewcontroller)
 
+        stopScrollDeceleration = false
         // Don't unlock scroll view in animating view when presentation layer != model layer
-        unlockScrollView()
+        if targetPosition == .full {
+            unlockScrollView()
+        }
     }
 
     private func distance(to targetPosition: FloatingPanelPosition, with translation: CGPoint) -> CGFloat {
@@ -367,6 +578,7 @@ class FloatingPanel: NSObject, UIGestureRecognizerDelegate, UIScrollViewDelegate
         let middleY = layoutAdapter.middleY
         let bottomY = layoutAdapter.bottomY
         let currentY = getCurrentY(from: initialFrame, with: translation)
+
         switch targetPosition {
         case .full:
             return CGFloat(fabs(Double(currentY - topY)))
@@ -374,6 +586,72 @@ class FloatingPanel: NSObject, UIGestureRecognizerDelegate, UIScrollViewDelegate
             return CGFloat(fabs(Double(currentY - middleY)))
         case .tip:
             return CGFloat(fabs(Double(currentY - bottomY)))
+        case .hidden:
+            fatalError("A floating panel hidden must not be used by a user")
+        }
+    }
+
+    private func directionalPosition(with translation: CGPoint) -> FloatingPanelPosition {
+        let currentY = getCurrentY(from: initialFrame, with: translation)
+
+        let supportedPositions = layoutAdapter.supportedPositions
+
+        if supportedPositions.count == 1 {
+            return state
+        }
+
+        switch supportedPositions {
+        case [.full, .half]: return translation.y >= 0 ? .half : .full
+        case [.half, .tip]: return translation.y >= 0 ? .tip : .half
+        case [.full, .tip]: return translation.y >= 0 ? .tip : .full
+        default:
+            let middleY = layoutAdapter.middleY
+
+            switch state {
+            case .full:
+                if translation.y <= 0 {
+                    return .full
+                }
+                return currentY > middleY ? .tip : .half
+            case .half:
+                return translation.y >= 0 ? .tip : .full
+            case .tip:
+                if translation.y >= 0 {
+                    return .tip
+                }
+                return currentY > middleY ? .half : .full
+            case .hidden:
+                fatalError("A floating panel hidden must not be used by a user")
+            }
+        }
+    }
+
+    private func redirectionalPosition(with translation: CGPoint) -> FloatingPanelPosition {
+        let currentY = getCurrentY(from: initialFrame, with: translation)
+
+        let supportedPositions = layoutAdapter.supportedPositions
+
+        if supportedPositions.count == 1 {
+            return state
+        }
+
+        switch supportedPositions {
+        case [.full, .half]: return translation.y >= 0 ? .full : .half
+        case [.half, .tip]: return translation.y >= 0 ? .half : .tip
+        case [.full, .tip]: return translation.y >= 0 ? .full : .tip
+        default:
+            let middleY = layoutAdapter.middleY
+
+            switch state {
+            case .full:
+                return currentY > middleY ? .half : .full
+            case .half:
+                return .half
+            case .tip:
+                return currentY > middleY ? .tip : .half
+            case .hidden:
+                fatalError("A floating panel hidden must not be used by a user")
+            }
         }
     }
 
@@ -386,9 +664,11 @@ class FloatingPanel: NSObject, UIGestureRecognizerDelegate, UIScrollViewDelegate
 
     private func targetPosition(with translation: CGPoint, velocity: CGPoint) -> (FloatingPanelPosition) {
         let currentY = getCurrentY(from: initialFrame, with: translation)
-        let supportedPositions: Set = layoutAdapter.layout.supportedPositions
+        let supportedPositions = layoutAdapter.supportedPositions
 
-        assert(supportedPositions.count > 1)
+        if supportedPositions.count == 1 {
+            return state
+        }
 
         switch supportedPositions {
         case [.full, .half]:
@@ -399,14 +679,46 @@ class FloatingPanel: NSObject, UIGestureRecognizerDelegate, UIScrollViewDelegate
             return targetPosition(from: [.full, .tip], at: currentY, velocity: velocity)
         default:
             /*
-             [topY|full]---[th1]---[middleY|default]---[th2]---[bottomY|collapsed]
+             [topY|full]---[th1]---[middleY|half]---[th2]---[bottomY|tip]
              */
             let topY = layoutAdapter.topY
             let middleY = layoutAdapter.middleY
             let bottomY = layoutAdapter.bottomY
 
-            let th1 = (topY + middleY) / 2
-            let th2 = (middleY + bottomY) / 2
+            let target: FloatingPanelPosition
+            let forwardYDirection: Bool
+
+            switch state {
+            case .full:
+                target = .half
+                forwardYDirection = true
+            case .half:
+                if (currentY < middleY) {
+                    target = .full
+                    forwardYDirection = false
+                } else {
+                    target = .tip
+                    forwardYDirection = true
+                }
+            case .tip:
+                target = .half
+                forwardYDirection = false
+            case .hidden:
+                fatalError("A floating panel hidden must not be used by a user")
+            }
+
+            let redirectionalProgress = max(min(behavior.redirectionalProgress(viewcontroller, from: state, to: target), 1.0), 0.0)
+
+            let th1: CGFloat
+            let th2: CGFloat
+
+            if forwardYDirection {
+                th1 = topY + (middleY - topY) * redirectionalProgress
+                th2 = middleY + (bottomY - middleY) * redirectionalProgress
+            } else {
+                th1 = middleY - (middleY - topY) * redirectionalProgress
+                th2 = bottomY - (bottomY - middleY) * redirectionalProgress
+            }
 
             switch currentY {
             case ..<th1:
@@ -446,7 +758,10 @@ class FloatingPanel: NSObject, UIGestureRecognizerDelegate, UIScrollViewDelegate
         let topY = layoutAdapter.positionY(for: top)
         let bottomY = layoutAdapter.positionY(for: bottom)
 
-        let th = (topY + bottomY) / 2
+        let target = top == state ? bottom : top
+        let redirectionalProgress = max(min(behavior.redirectionalProgress(viewcontroller, from: state, to: target), 1.0), 0.0)
+
+        let th = topY + (bottomY - topY) * redirectionalProgress
 
         switch currentY {
         case ..<th:
@@ -466,17 +781,15 @@ class FloatingPanel: NSObject, UIGestureRecognizerDelegate, UIScrollViewDelegate
 
     // MARK: - ScrollView handling
 
-    func lockScrollView(withBounce bounce: Bool = false) {
+    private func lockScrollView() {
         guard let scrollView = scrollView else { return }
 
         scrollView.isDirectionalLockEnabled = true
-        if bounce {
-            scrollView.bounces = false
-        }
+        scrollView.bounces = false
         scrollView.showsVerticalScrollIndicator = false
     }
 
-    func unlockScrollView() {
+    private func unlockScrollView() {
         guard let scrollView = scrollView else { return }
 
         scrollView.isDirectionalLockEnabled = false
@@ -498,6 +811,13 @@ class FloatingPanel: NSObject, UIGestureRecognizerDelegate, UIScrollViewDelegate
         }
     }
 
+    func scrollViewDidEndScrollingAnimation(_ scrollView: UIScrollView) {
+        if state != .full {
+            initialScrollOffset = scrollView.contentOffset
+        }
+        userScrollViewDelegate?.scrollViewDidEndScrollingAnimation?(scrollView)
+    }
+
     func scrollViewWillEndDragging(_ scrollView: UIScrollView, withVelocity velocity: CGPoint, targetContentOffset: UnsafeMutablePointer<CGPoint>) {
         if stopScrollDeceleration {
             targetContentOffset.pointee = scrollView.contentOffset

Framework/Sources/FloatingPanelBehavior.swift

@@ -6,7 +6,12 @@
 import UIKit
 
 public protocol FloatingPanelBehavior {
-    /// Returns a UIViewPropertyAnimator object for interacting with a floating panel by a user pan gesture
+    /// Returns the progress to redirect to the previous position
+    ///
+    /// The progress is represented by a floating-point value between 0.0 and 1.0, inclusive, where 1.0 indicates the floating panel is impossible to move to the next posiiton. The default value is 0.5. Values less than 0.0 and greater than 1.0 are pinned to those limits.
+    func redirectionalProgress(_ fpc: FloatingPanelController, from: FloatingPanelPosition, to: FloatingPanelPosition) -> CGFloat
+
+    /// Returns a UIViewPropertyAnimator object to project a floating panel to a position on finger up if the user dragged.
     func interactionAnimator(_ fpc: FloatingPanelController, to targetPosition: FloatingPanelPosition, with velocity: CGVector) -> UIViewPropertyAnimator
 
     /// Returns a UIViewPropertyAnimator object to add a floating panel to a position.
@@ -26,9 +31,28 @@ public protocol FloatingPanelBehavior {
     /// Its animator instance will be used to animate the surface view in `FloatingPanelController.move(to:animated:completion:)`.
     /// Default is an animator with ease-in-out curve and 0.25 sec duration.
     func moveAnimator(_ fpc: FloatingPanelController, from: FloatingPanelPosition, to: FloatingPanelPosition) -> UIViewPropertyAnimator
+
+    /// Returns a y-axis velocity to invoke a removal interaction at the bottom position.
+    ///
+    /// Default is 10.0. This method is called when FloatingPanelController.isRemovalInteractionEnabled is true.
+    var removalVelocity: CGFloat { get }
+
+    /// Returns the threshold of the transition to invoke a removal interaction at the bottom position.
+    ///
+    /// The progress is represented by a floating-point value between 0.0 and 1.0, inclusive, where 1.0 indicates the floating panel is impossible to invoke the removal interaction. The default value is 0.5. Values less than 0.0 and greater than 1.0 are pinned to those limits. This method is called when FloatingPanelController.isRemovalInteractionEnabled is true.
+    var removalProgress: CGFloat { get }
+
+    /// Returns a UIViewPropertyAnimator object to remove a floating panel with a velocity interactively at the bottom position.
+    ///
+    /// Default is a spring animator with 1.0 damping ratio. This method is called when FloatingPanelController.isRemovalInteractionEnabled is true.
+    func removalInteractionAnimator(_ fpc: FloatingPanelController, with velocity: CGVector) -> UIViewPropertyAnimator
 }
 
 public extension FloatingPanelBehavior {
+    func redirectionalProgress(_ fpc: FloatingPanelController, from: FloatingPanelPosition, to: FloatingPanelPosition) -> CGFloat {
+        return 0.5
+    }
+
     func addAnimator(_ fpc: FloatingPanelController, to: FloatingPanelPosition) -> UIViewPropertyAnimator {
         return UIViewPropertyAnimator(duration: 0.25, curve: .easeInOut)
     }
@@ -40,15 +64,31 @@ public extension FloatingPanelBehavior {
     func moveAnimator(_ fpc: FloatingPanelController, from: FloatingPanelPosition, to: FloatingPanelPosition) -> UIViewPropertyAnimator {
         return UIViewPropertyAnimator(duration: 0.25, curve: .easeInOut)
     }
+
+    var removalVelocity: CGFloat {
+        return 10.0
+    }
+
+    var removalProgress: CGFloat {
+        return 0.5
+    }
+
+    func removalInteractionAnimator(_ fpc: FloatingPanelController, with velocity: CGVector) -> UIViewPropertyAnimator {
+        log.debug("velocity", velocity)
+        let timing = UISpringTimingParameters(dampingRatio: 1.0,
+                                        frequencyResponse: 0.3,
+                                        initialVelocity: velocity)
+        return UIViewPropertyAnimator(duration: 0, timingParameters: timing)
+    }
 }
 
 class FloatingPanelDefaultBehavior: FloatingPanelBehavior {
     func interactionAnimator(_ fpc: FloatingPanelController, to targetPosition: FloatingPanelPosition, with velocity: CGVector) -> UIViewPropertyAnimator {
-        let timing = timeingCurve(to: targetPosition, with: velocity)
+        let timing = timeingCurve(with: velocity)
         return UIViewPropertyAnimator(duration: 0, timingParameters: timing)
     }
 
-    private func timeingCurve(to: FloatingPanelPosition, with velocity: CGVector) -> UITimingCurveProvider {
+    private func timeingCurve(with velocity: CGVector) -> UITimingCurveProvider {
         log.debug("velocity", velocity)
         let damping = self.getDamping(with: velocity)
         return UISpringTimingParameters(dampingRatio: damping,

Framework/Sources/FloatingPanelController.swift

@@ -12,6 +12,8 @@ public protocol FloatingPanelControllerDelegate: class {
     // if it returns nil, FloatingPanelController uses the default behavior
     func floatingPanel(_ vc: FloatingPanelController, behaviorFor newCollection: UITraitCollection) -> FloatingPanelBehavior?
 
+    func floatingPanelDidChangePosition(_ vc: FloatingPanelController) // changed the settled position in the model layer
+
     func floatingPanelDidMove(_ vc: FloatingPanelController) // any offset changes
 
     // called on start of dragging (may require some time and or distance to move)
@@ -20,6 +22,11 @@ public protocol FloatingPanelControllerDelegate: class {
     func floatingPanelDidEndDragging(_ vc: FloatingPanelController, withVelocity velocity: CGPoint, targetPosition: FloatingPanelPosition)
     func floatingPanelWillBeginDecelerating(_ vc: FloatingPanelController) // called on finger up as we are moving
     func floatingPanelDidEndDecelerating(_ vc: FloatingPanelController) // called when scroll view grinds to a halt
+
+    // called on start of dragging to remove its views from a parent view controller
+    func floatingPanelDidEndDraggingToRemove(_ vc: FloatingPanelController, withVelocity velocity: CGPoint)
+    // called when its views are removed from a parent view controller
+    func floatingPanelDidEndRemove(_ vc: FloatingPanelController)
 }
 
 public extension FloatingPanelControllerDelegate {
@@ -29,24 +36,28 @@ public extension FloatingPanelControllerDelegate {
     func floatingPanel(_ vc: FloatingPanelController, behaviorFor newCollection: UITraitCollection) -> FloatingPanelBehavior? {
         return nil
     }
+    func floatingPanelDidChangePosition(_ vc: FloatingPanelController) {}
     func floatingPanelDidMove(_ vc: FloatingPanelController) {}
     func floatingPanelWillBeginDragging(_ vc: FloatingPanelController) {}
     func floatingPanelDidEndDragging(_ vc: FloatingPanelController, withVelocity velocity: CGPoint, targetPosition: FloatingPanelPosition) {}
     func floatingPanelWillBeginDecelerating(_ vc: FloatingPanelController) {}
     func floatingPanelDidEndDecelerating(_ vc: FloatingPanelController) {}
+
+    func floatingPanelDidEndDraggingToRemove(_ vc: FloatingPanelController, withVelocity velocity: CGPoint) {}
+    func floatingPanelDidEndRemove(_ vc: FloatingPanelController) {}
 }
 
 public enum FloatingPanelPosition: Int, CaseIterable {
     case full
     case half
     case tip
+    case hidden
 }
 
 ///
 /// A container view controller to display a floating panel to present contents in parallel as a user wants.
 ///
 public class FloatingPanelController: UIViewController, UIScrollViewDelegate, UIGestureRecognizerDelegate {
-
     /// Constants indicating how safe area insets are added to the adjusted content inset.
     public enum ContentInsetAdjustmentBehavior: Int {
         case always
@@ -58,7 +69,7 @@ public class FloatingPanelController: UIViewController, UIScrollViewDelegate, UI
 
     /// Returns the surface view managed by the controller object. It's the same as `self.view`.
     public var surfaceView: FloatingPanelSurfaceView! {
-        return view as? FloatingPanelSurfaceView
+        return floatingPanel.surfaceView
     }
 
     /// Returns the backdrop view managed by the controller object.
@@ -81,7 +92,17 @@ public class FloatingPanelController: UIViewController, UIScrollViewDelegate, UI
         return floatingPanel.state
     }
 
-    /// The content insets of the tracking scroll view derived from the safe area of the parent view
+    /// The layout object managed by the controller
+    public var layout: FloatingPanelLayout {
+        return floatingPanel.layoutAdapter.layout
+    }
+
+    /// The behavior object managed by the controller
+    public var behavior: FloatingPanelBehavior {
+        return floatingPanel.behavior
+    }
+
+    /// The content insets of the tracking scroll view derived from this safe area
     public var adjustedContentInsets: UIEdgeInsets {
         return floatingPanel.layoutAdapter.adjustedContentInsets
     }
@@ -91,69 +112,114 @@ public class FloatingPanelController: UIViewController, UIScrollViewDelegate, UI
     /// This property specifies how the content area of the tracking scroll view is modified using `adjustedContentInsets`. The default value of this property is FloatingPanelController.ContentInsetAdjustmentBehavior.always.
     public var contentInsetAdjustmentBehavior: ContentInsetAdjustmentBehavior = .always
 
+    /// A Boolean value that determines whether the removal interaction is enabled.
+    public var isRemovalInteractionEnabled: Bool {
+        set { floatingPanel.isRemovalInteractionEnabled = newValue }
+        get { return floatingPanel.isRemovalInteractionEnabled }
+    }
+
+    /// The view controller responsible for the content portion of the floating panel.
+    public var contentViewController: UIViewController? {
+        set { set(contentViewController: newValue) }
+        get { return _contentViewController }
+    }
+    private var _contentViewController: UIViewController?
+
     private var floatingPanel: FloatingPanel!
+    private var safeAreaInsetsObservation: NSKeyValueObservation?
+    private let modalTransition = FloatingPanelModalTransition()
 
     required init?(coder aDecoder: NSCoder) {
         super.init(coder: aDecoder)
-
-        floatingPanel = FloatingPanel(self,
-                                      layout: fetchLayout(for: self.traitCollection),
-                                      behavior: fetchBehavior(for: self.traitCollection))
+        setUp()
     }
 
     /// Initialize a newly created floating panel controller.
     public init() {
         super.init(nibName: nil, bundle: nil)
+        setUp()
+    }
+
+    private func setUp() {
+        _ = FloatingPanelController.dismissSwizzling
+
+        modalPresentationStyle = .custom
+        transitioningDelegate = modalTransition
 
         floatingPanel = FloatingPanel(self,
                                       layout: fetchLayout(for: self.traitCollection),
                                       behavior: fetchBehavior(for: self.traitCollection))
     }
 
+    // MARK:- Overrides
+
     /// Creates the view that the controller manages.
     override public func loadView() {
         assert(self.storyboard == nil, "Storyboard isn't supported")
 
-        let view = FloatingPanelSurfaceView()
-        view.backgroundColor = .white
+        let view = FloatingPanelPassThroughView()
+        view.backgroundColor = .clear
 
         self.view = view as UIView
     }
 
+    public override func viewDidLoad() {
+        super.viewDidLoad()
+        floatingPanel.setUpViews(in: self)
+    }
+
+    public override func viewWillTransition(to size: CGSize, with coordinator: UIViewControllerTransitionCoordinator) {
+        super.viewWillTransition(to: size, with: coordinator)
+
+        view.frame.size = size
+        view.layoutIfNeeded()
+
+        floatingPanel.layoutAdapter.checkLayoutConsistance()
+    }
+
     public override func willTransition(to newCollection: UITraitCollection, with coordinator: UIViewControllerTransitionCoordinator) {
         super.willTransition(to: newCollection, with: coordinator)
 
         // Change layout for a new trait collection
-        floatingPanel.layoutAdapter.layout = fetchLayout(for: newCollection)
+        updateLayout(for: newCollection)
+
         floatingPanel.behavior = fetchBehavior(for: newCollection)
-
-        guard let parent = parent else { fatalError() }
-
-        floatingPanel.layoutAdapter.prepareLayout(toParent: parent)
-        floatingPanel.layoutAdapter.activateLayout(of: floatingPanel.state)
     }
 
     public override func traitCollectionDidChange(_ previousTraitCollection: UITraitCollection?) {
         super.traitCollectionDidChange(previousTraitCollection)
         guard previousTraitCollection != traitCollection else { return }
 
-        if let parent = parent {
-            self.update(safeAreaInsets: parent.layoutInsets)
-        }
-        floatingPanel.backdropView.isHidden = (traitCollection.verticalSizeClass == .compact)
+        self.update(safeAreaInsets: layoutInsets)
     }
 
     public override func viewDidAppear(_ animated: Bool) {
         super.viewDidAppear(animated)
-
-        // Need to update safeAreaInsets here to ensure that the `adjustedContentInsets` has a correct value.
-        // Because the parent VC does not call viewSafeAreaInsetsDidChange() expectedly and
-        // `view.safeAreaInsets` has a correct value of the bottom inset here.
-        if let parent = parent {
-            self.update(safeAreaInsets: parent.layoutInsets)
+        // Must track safeAreaInsets/{top,bottom}LayoutGuide of the `self.view`
+        // to update floatingPanel.safeAreaInsets`. There are 2 reasons.
+        // 1. This or the parent VC doesn't call viewSafeAreaInsetsDidChange() on the bottom
+        // inset's update expectedly.
+        // 2. The safe area top inset can be variable on the large title navigation bar(iOS11+).
+        // That's why it needs the observation to keep `adjustedContentInsets` correct.
+        if #available(iOS 11.0, *) {
+            safeAreaInsetsObservation = self.observe(\.view.safeAreaInsets) { [weak self] (vc, chaneg) in
+                guard let self = self else { return }
+                self.update(safeAreaInsets: vc.layoutInsets)
+            }
+        } else {
+            // KVOs for topLayoutGuide & bottomLayoutGuide are not effective.
+            // Instead, safeAreaInsets is updated here
+            self.update(safeAreaInsets: layoutInsets)
         }
     }
 
+    public override func viewWillDisappear(_ animated: Bool) {
+        super.viewWillDisappear(animated)
+        safeAreaInsetsObservation = nil
+    }
+
+    // MARK:- Privates
+
     private func fetchLayout(for traitCollection: UITraitCollection) -> FloatingPanelLayout {
         switch traitCollection.verticalSizeClass {
         case .compact:
@@ -168,7 +234,13 @@ public class FloatingPanelController: UIViewController, UIScrollViewDelegate, UI
     }
 
     private func update(safeAreaInsets: UIEdgeInsets) {
+        // preserve the current content offset
+        let contentOffset = scrollView?.contentOffset
+
         floatingPanel.safeAreaInsets = safeAreaInsets
+
+        scrollView?.contentOffset = contentOffset ?? .zero
+
         switch contentInsetAdjustmentBehavior {
         case .always:
             scrollView?.contentInset = adjustedContentInsets
@@ -178,8 +250,30 @@ public class FloatingPanelController: UIViewController, UIScrollViewDelegate, UI
         }
     }
 
+    private func updateLayout(for traitCollection: UITraitCollection) {
+        floatingPanel.layoutAdapter.layout = fetchLayout(for: traitCollection)
+        floatingPanel.layoutAdapter.prepareLayout(in: self)
+        floatingPanel.layoutAdapter.activateLayout(of: floatingPanel.state)
+    }
+
     // MARK: - Container view controller interface
 
+    /// Shows the surface view at the initial position defined by the current layout
+    public func show(animated: Bool = false, completion: (() -> Void)? = nil) {
+        // Must apply the current layout here
+        updateLayout(for: traitCollection)
+        move(to: floatingPanel.layoutAdapter.layout.initialPosition,
+             animated: animated,
+             completion: completion)
+    }
+
+    /// Hides the surface view to the hidden position
+    public func hide(animated: Bool = false, completion: (() -> Void)? = nil) {
+        move(to: .hidden,
+             animated: animated,
+             completion: completion)
+    }
+
     /// Adds the view managed by the controller as a child of the specified view controller.
     /// - Parameters:
     ///     - parent: A parent view controller object that displays FloatingPanelController's view. A container view controller object isn't applicable.
@@ -191,22 +285,22 @@ public class FloatingPanelController: UIViewController, UIScrollViewDelegate, UI
             return
         }
         precondition((parent is UINavigationController) == false, "UINavigationController displays only one child view controller at a time.")
-        precondition((parent is UITableViewController) == false, "UITableViewController should not be the parent because the view hierarchy will be break in reusing cells.")
-        precondition((parent is UICollectionViewController) == false, "UICollectionViewController should not be the parent because the view hierarchy will be break in reusing cells.")
+        precondition((parent is UITabBarController) == false, "UITabBarController displays child view controllers with a radio-style selection interface")
+        precondition((parent is UISplitViewController) == false, "UISplitViewController manages two child view controllers in a master-detail interface")
+        precondition((parent is UITableViewController) == false, "UITableViewController should not be the parent because the view is a table view so that a floating panel doens't work well")
+        precondition((parent is UICollectionViewController) == false, "UICollectionViewController should not be the parent because the view is a collection view so that a floating panel doens't work well")
 
-        view.frame = parent.view.bounds
         if let belowView = belowView {
             parent.view.insertSubview(self.view, belowSubview: belowView)
         } else {
             parent.view.addSubview(self.view)
         }
 
+        view.frame = parent.view.bounds // MUST
+
         parent.addChild(self)
 
-        // Must set a layout again here because `self.traitCollection` is applied correctly once it's added to a parent VC
-        floatingPanel.layoutAdapter.layout = fetchLayout(for: traitCollection)
-        floatingPanel.layoutViews(in: parent)
-        floatingPanel.present(animated: animated) { [weak self] in
+        show(animated: true) { [weak self] in
             guard let self = self else { return }
             self.didMove(toParent: parent)
         }
@@ -222,9 +316,8 @@ public class FloatingPanelController: UIViewController, UIScrollViewDelegate, UI
             return
         }
 
-        floatingPanel.dismiss(animated: animated) { [weak self] in
+        hide(animated: animated) { [weak self] in
             guard let self = self else { return }
-
             self.willMove(toParent: nil)
             self.view.removeFromSuperview()
             self.removeFromParent()
@@ -238,23 +331,40 @@ public class FloatingPanelController: UIViewController, UIScrollViewDelegate, UI
     ///     - animated: Pass true to animate the presentation; otherwise, pass false.
     ///     - completion: The block to execute after the view controller has finished moving. This block has no return value and takes no parameters. You may specify nil for this parameter.
     public func move(to: FloatingPanelPosition, animated: Bool, completion: (() -> Void)? = nil) {
+        precondition(floatingPanel.layoutAdapter.vc != nil, "Use show(animated:completion)")
         floatingPanel.move(to: to, animated: animated, completion: completion)
     }
 
-    /// Presents the specified view controller as the content view controller in the surface view interface.
+    /// Sets the view controller responsible for the content portion of the floating panel..
+    public func set(contentViewController: UIViewController?) {
+        if let vc = _contentViewController {
+            vc.willMove(toParent: nil)
+            vc.view.removeFromSuperview()
+            vc.removeFromParent()
+        }
+
+        if let vc = contentViewController {
+            let surfaceView = floatingPanel.surfaceView
+            surfaceView.add(childView: vc.view)
+            addChild(vc)
+            vc.didMove(toParent: self)
+        }
+
+        _contentViewController = contentViewController
+    }
+    
+    @available(*, unavailable, renamed: "set(contentViewController:)")
     public override func show(_ vc: UIViewController, sender: Any?) {
-        let surfaceView = self.view as! FloatingPanelSurfaceView
-        surfaceView.contentView.addSubview(vc.view)
-        vc.view.frame = surfaceView.contentView.bounds
-        vc.view.translatesAutoresizingMaskIntoConstraints = false
-        NSLayoutConstraint.activate([
-            vc.view.topAnchor.constraint(equalTo: surfaceView.contentView.topAnchor, constant: 0.0),
-            vc.view.leftAnchor.constraint(equalTo: surfaceView.contentView.leftAnchor, constant: 0.0),
-            vc.view.rightAnchor.constraint(equalTo: surfaceView.contentView.rightAnchor, constant: 0.0),
-            vc.view.bottomAnchor.constraint(equalTo: surfaceView.contentView.bottomAnchor, constant: 0.0),
-            ])
-        addChild(vc)
-        vc.didMove(toParent: self)
+        if let target = self.parent?.targetViewController(forAction: #selector(UIViewController.show(_:sender:)), sender: sender) {
+            target.show(vc, sender: sender)
+        }
+    }
+
+    @available(*, unavailable, renamed: "set(contentViewController:)")
+    public override func showDetailViewController(_ vc: UIViewController, sender: Any?) {
+        if let target = self.parent?.targetViewController(forAction: #selector(UIViewController.showDetailViewController(_:sender:)), sender: sender) {
+            target.showDetailViewController(vc, sender: sender)
+        }
     }
 
     // MARK: - Scroll view tracking
@@ -266,8 +376,10 @@ public class FloatingPanelController: UIViewController, UIScrollViewDelegate, UI
     ///
     public func track(scrollView: UIScrollView) {
         floatingPanel.scrollView = scrollView
-        floatingPanel.userScrollViewDelegate = scrollView.delegate
-        scrollView.delegate = floatingPanel
+        if scrollView.delegate !== floatingPanel {
+            floatingPanel.userScrollViewDelegate = scrollView.delegate
+            scrollView.delegate = floatingPanel
+        }
         switch contentInsetAdjustmentBehavior {
         case .always:
             if #available(iOS 11.0, *) {
@@ -282,7 +394,19 @@ public class FloatingPanelController: UIViewController, UIScrollViewDelegate, UI
         }
     }
 
-    // MARK: - Helpers
+    // MARK: - Utilities
+
+    /// Updates the layout object from the delegate and lays out the views managed
+    /// by the controller immediately.
+    ///
+    /// This method updates the `FloatingPanelLayout` object from the delegate and
+    /// then it calls `layoutIfNeeded()` of the root view to force the view
+    /// to update the floating panel's layout immediately. It can be called in an
+    /// animation block.
+    public func updateLayout() {
+        updateLayout(for: view.traitCollection)
+        floatingPanel.layoutAdapter.checkLayoutConsistance()
+    }
 
     /// Returns the y-coordinate of the point at the origin of the surface view
     public func originYOfSurface(for pos: FloatingPanelPosition) -> CGFloat {
@@ -293,6 +417,38 @@ public class FloatingPanelController: UIViewController, UIScrollViewDelegate, UI
             return floatingPanel.layoutAdapter.middleY
         case .tip:
             return floatingPanel.layoutAdapter.bottomY
+        case .hidden:
+            return floatingPanel.layoutAdapter.hiddenY
+        }
+    }
+}
+
+extension FloatingPanelController {
+    private static let dismissSwizzling: Any? = {
+        let aClass: AnyClass! = UIViewController.self //object_getClass(vc)
+        if let imp = class_getMethodImplementation(aClass, #selector(dismiss(animated:completion:))),
+            let originalAltMethod = class_getInstanceMethod(aClass, #selector(fp_original_dismiss(animated:completion:))) {
+            method_setImplementation(originalAltMethod, imp)
+        }
+        let originalMethod = class_getInstanceMethod(aClass, #selector(dismiss(animated:completion:)))
+        let swizzledMethod = class_getInstanceMethod(aClass, #selector(fp_dismiss(animated:completion:)))
+        if let originalMethod = originalMethod, let swizzledMethod = swizzledMethod {
+            // switch implementation..
+            method_exchangeImplementations(originalMethod, swizzledMethod)
+        }
+        return nil
+    }()
+}
+
+public extension UIViewController {
+    @objc public func fp_original_dismiss(animated flag: Bool, completion: (() -> Void)? = nil) {
+        // Implementation will be replaced by IMP of self.dismiss(animated:completion:)
+    }
+    @objc public func fp_dismiss(animated flag: Bool, completion: (() -> Void)? = nil) {
+        if let fpc = parent as? FloatingPanelController, fpc.parent != nil {
+            fpc.removePanelFromParent(animated: flag, completion: completion)
+        } else {
+            self.fp_original_dismiss(animated: flag, completion: completion)
         }
     }
 }

Framework/Sources/FloatingPanelLayout.swift

@@ -5,11 +5,37 @@
 
 import UIKit
 
+/// FloatingPanelIntrinsicLayout
+///
+/// - Attention:
+///     `insetFor(position:)` must return `nil` for full position because the inset is determined automatically.
+///     You can customize insets only for half, tip and hidden positions
+///     on FloatingPanelIntrinsicLayout.
+public protocol FloatingPanelIntrinsicLayout: FloatingPanelLayout { }
+
+public extension FloatingPanelIntrinsicLayout {
+    var initialPosition: FloatingPanelPosition {
+        return .full
+    }
+
+    var supportedPositions: Set<FloatingPanelPosition> {
+        return [.full]
+    }
+
+    func insetFor(position: FloatingPanelPosition) -> CGFloat? {
+        return nil
+    }
+}
+
 public protocol FloatingPanelLayout: class {
     /// Returns the initial position of a floating panel.
     var initialPosition: FloatingPanelPosition { get }
 
-    /// Returns a set of FloatingPanelPosition objects to tell the applicable positions of the floating panel controller. Default is all of them.
+    /// Returns a set of FloatingPanelPosition objects to tell the applicable
+    /// positions of the floating panel controller.
+    ///
+    /// By default, it returns all position exepct for `hidden` position. Because
+    /// it's always supported by `FloatingPanelController` so you don't need to return it.
     var supportedPositions: Set<FloatingPanelPosition> { get }
 
     /// Return the interaction buffer to the top from the top position. Default is 6.0.
@@ -18,10 +44,13 @@ public protocol FloatingPanelLayout: class {
     /// Return the interaction buffer to the bottom from the bottom position. Default is 6.0.
     var bottomInteractionBuffer: CGFloat { get }
 
-    /// Returns a CGFloat value to determine a floating panel height for each position(full, half and tip).
-    /// A value for full position indicates a top inset from a safe area.
-    /// On the other hand, values for half and tip positions indicate bottom insets from a safe area.
-    /// If a position doesn't contain the supported positions, return nil.
+    /// Returns a CGFloat value to determine a Y coordinate of a floating panel for each position(full, half, tip and hidden).
+    ///
+    /// Its returning value indicates a different inset for each positiion.
+    /// For full position, a top inset from a safe area in `FloatingPanelController.view`.
+    /// For half or tip position, a bottom inset from the safe area.
+    /// For hidden position, a bottom inset from `FloatingPanelController.view`.
+    /// If a position isn't supported or the default value is used, return nil.
     func insetFor(position: FloatingPanelPosition) -> CGFloat?
 
     /// Returns X-axis and width layout constraints of the surface view of a floating panel.
@@ -30,17 +59,18 @@ public protocol FloatingPanelLayout: class {
     /// By default, the width of a surface view fits a safe area.
     func prepareLayout(surfaceView: UIView, in view: UIView) -> [NSLayoutConstraint]
 
-    /// Return the backdrop alpha of black color in full position. Default is 0.3.
-    var backdropAlpha: CGFloat { get }
+    /// Returns a CGFloat value to determine the backdrop view's alpha for a position.
+    ///
+    /// Default is 0.3 at full position, otherwise 0.0.
+    func backdropAlphaFor(position: FloatingPanelPosition) -> CGFloat
 }
 
 public extension FloatingPanelLayout {
-    var backdropAlpha: CGFloat { return 0.3 }
     var topInteractionBuffer: CGFloat { return 6.0 }
     var bottomInteractionBuffer: CGFloat { return 6.0 }
 
-    public var supportedPositions: Set<FloatingPanelPosition> {
-        return Set(FloatingPanelPosition.allCases)
+    var supportedPositions: Set<FloatingPanelPosition> {
+        return Set([.full, .half, .tip])
     }
     
     func prepareLayout(surfaceView: UIView, in view: UIView) -> [NSLayoutConstraint] {
@@ -49,9 +79,15 @@ public extension FloatingPanelLayout {
             surfaceView.rightAnchor.constraint(equalTo: view.sideLayoutGuide.rightAnchor, constant: 0.0),
         ]
     }
+
+    func backdropAlphaFor(position: FloatingPanelPosition) -> CGFloat {
+        return position == .full ? 0.3 : 0.0
+    }
 }
 
 public class FloatingPanelDefaultLayout: FloatingPanelLayout {
+    public var contentViewController: UIViewController?
+    
     public var initialPosition: FloatingPanelPosition {
         return .half
     }
@@ -61,11 +97,14 @@ public class FloatingPanelDefaultLayout: FloatingPanelLayout {
         case .full: return 18.0
         case .half: return 262.0
         case .tip: return 69.0
+        case .hidden: return nil
         }
     }
 }
 
 public class FloatingPanelDefaultLandscapeLayout: FloatingPanelLayout {
+    public var contentViewController: UIViewController?
+    
     public var initialPosition: FloatingPanelPosition {
         return .tip
     }
@@ -80,27 +119,21 @@ public class FloatingPanelDefaultLandscapeLayout: FloatingPanelLayout {
         default: return nil
         }
     }
-
-    public func prepareLayout(surfaceView: UIView, in view: UIView) -> [NSLayoutConstraint] {
-        return [
-            surfaceView.leftAnchor.constraint(equalTo: view.sideLayoutGuide.leftAnchor, constant: 0.0),
-            surfaceView.rightAnchor.constraint(equalTo: view.sideLayoutGuide.rightAnchor, constant: 0.0),
-        ]
-    }
 }
 
 
 class FloatingPanelLayoutAdapter {
+    weak var vc: UIViewController!
     private weak var surfaceView: FloatingPanelSurfaceView!
-    private weak var backdropVIew: FloatingPanelBackdropView!
+    private weak var backdropView: FloatingPanelBackdropView!
 
-    var layout: FloatingPanelLayout {
-        didSet { checkConsistance(of: layout) }
-    }
+    var layout: FloatingPanelLayout
 
     var safeAreaInsets: UIEdgeInsets = .zero {
         didSet {
-            updateHeight()
+            if oldValue != safeAreaInsets {
+                updateHeight()
+            }
         }
     }
 
@@ -110,10 +143,14 @@ class FloatingPanelLayoutAdapter {
     private var halfConstraints: [NSLayoutConstraint] = []
     private var tipConstraints: [NSLayoutConstraint] = []
     private var offConstraints: [NSLayoutConstraint] = []
-    private var heightConstraints: NSLayoutConstraint? = nil
+    private var heightConstraints: [NSLayoutConstraint] = []
 
     private var fullInset: CGFloat {
-        return layout.insetFor(position: .full) ?? 0.0
+        if layout is FloatingPanelIntrinsicLayout {
+            return intrinsicHeight
+        } else {
+            return layout.insetFor(position: .full) ?? 0.0
+        }
     }
     private var halfInset: CGFloat {
         return layout.insetFor(position: .half) ?? 0.0
@@ -121,10 +158,23 @@ class FloatingPanelLayoutAdapter {
     private var tipInset: CGFloat {
         return layout.insetFor(position: .tip) ?? 0.0
     }
+    private var hiddenInset: CGFloat {
+        return layout.insetFor(position: .hidden) ?? 0.0
+    }
+
+    var supportedPositions: Set<FloatingPanelPosition> {
+        var supportedPositions = layout.supportedPositions
+        supportedPositions.remove(.hidden)
+        return supportedPositions
+    }
 
     var topY: CGFloat {
-        if layout.supportedPositions.contains(.full) {
-            return (safeAreaInsets.top + fullInset)
+        if supportedPositions.contains(.full) {
+            if layout is FloatingPanelIntrinsicLayout {
+                return surfaceView.superview!.bounds.height - (safeAreaInsets.bottom + fullInset)
+            } else {
+                return (safeAreaInsets.top + fullInset)
+            }
         } else {
             return middleY
         }
@@ -135,13 +185,24 @@ class FloatingPanelLayoutAdapter {
     }
 
     var bottomY: CGFloat {
-        if layout.supportedPositions.contains(.tip) {
+        if supportedPositions.contains(.tip) {
             return surfaceView.superview!.bounds.height - (safeAreaInsets.bottom + tipInset)
         } else {
             return middleY
         }
     }
 
+    var hiddenY: CGFloat {
+        return surfaceView.superview!.bounds.height
+    }
+
+    var safeAreaBottomY: CGFloat {
+        return surfaceView.superview!.bounds.height - (safeAreaInsets.bottom + hiddenInset)
+    }
+
+    var topMaxY: CGFloat { return -safeAreaInsets.top }
+    var bottomMaxY: CGFloat { return safeAreaBottomY }
+
     var adjustedContentInsets: UIEdgeInsets {
         return UIEdgeInsets(top: 0.0,
                             left: 0.0,
@@ -157,88 +218,122 @@ class FloatingPanelLayoutAdapter {
             return middleY
         case .tip:
             return bottomY
+        case .hidden:
+            return hiddenY
         }
     }
 
+    var intrinsicHeight: CGFloat = 0.0
+
     init(surfaceView: FloatingPanelSurfaceView, backdropView: FloatingPanelBackdropView, layout: FloatingPanelLayout) {
         self.layout = layout
         self.surfaceView = surfaceView
-        self.backdropVIew = backdropView
+        self.backdropView = backdropView
     }
 
-    func prepareLayout(toParent parent: UIViewController) {
+    func updateIntrinsicHeight() {
+        let fittingSize = UIView.layoutFittingCompressedSize
+        intrinsicHeight = surfaceView.contentView.systemLayoutSizeFitting(fittingSize).height
+    }
+
+    func prepareLayout(in vc: UIViewController) {
+        self.vc = vc
+
         surfaceView.translatesAutoresizingMaskIntoConstraints = false
-        backdropVIew.translatesAutoresizingMaskIntoConstraints = false
+        backdropView.translatesAutoresizingMaskIntoConstraints = false
 
         NSLayoutConstraint.deactivate(fixedConstraints + fullConstraints + halfConstraints + tipConstraints + offConstraints)
 
         // Fixed constraints of surface and backdrop views
-        let surfaceConstraints = layout.prepareLayout(surfaceView: surfaceView, in: parent.view!)
-        let backdroptConstraints = [
-            backdropVIew.topAnchor.constraint(equalTo: parent.view.topAnchor,
-                                              constant: 0.0),
-            backdropVIew.leftAnchor.constraint(equalTo: parent.view.leftAnchor,
-                                               constant: 0.0),
-            backdropVIew.rightAnchor.constraint(equalTo: parent.view.rightAnchor,
-                                                constant: 0.0),
-            backdropVIew.bottomAnchor.constraint(equalTo: parent.view.bottomAnchor,
-                                                 constant: 0.0),
+        let surfaceConstraints = layout.prepareLayout(surfaceView: surfaceView, in: vc.view!)
+        let backdropConstraints = [
+            backdropView.topAnchor.constraint(equalTo: vc.view.topAnchor, constant: 0.0),
+            backdropView.leftAnchor.constraint(equalTo: vc.view.leftAnchor,constant: 0.0),
+            backdropView.rightAnchor.constraint(equalTo: vc.view.rightAnchor, constant: 0.0),
+            backdropView.bottomAnchor.constraint(equalTo: vc.view.bottomAnchor, constant: 0.0),
             ]
-        fixedConstraints = surfaceConstraints + backdroptConstraints
+
+        fixedConstraints = surfaceConstraints + backdropConstraints
 
         // Flexible surface constarints for full, half, tip and off
-        fullConstraints = [
-            surfaceView.topAnchor.constraint(equalTo: parent.layoutGuide.topAnchor,
-                                             constant: fullInset),
-        ]
+        if layout is FloatingPanelIntrinsicLayout {
+            updateIntrinsicHeight()
+            fullConstraints = [
+                surfaceView.topAnchor.constraint(equalTo: vc.layoutGuide.bottomAnchor,
+                                                 constant: -fullInset),
+            ]
+        } else {
+            fullConstraints = [
+                surfaceView.topAnchor.constraint(equalTo: vc.layoutGuide.topAnchor,
+                                                 constant: fullInset),
+            ]
+        }
         halfConstraints = [
-            surfaceView.topAnchor.constraint(equalTo: parent.layoutGuide.bottomAnchor,
+            surfaceView.topAnchor.constraint(equalTo: vc.layoutGuide.bottomAnchor,
                                              constant: -halfInset),
         ]
         tipConstraints = [
-            surfaceView.topAnchor.constraint(equalTo: parent.layoutGuide.bottomAnchor,
+            surfaceView.topAnchor.constraint(equalTo: vc.layoutGuide.bottomAnchor,
                                              constant: -tipInset),
         ]
         offConstraints = [
-            surfaceView.topAnchor.constraint(equalTo: parent.layoutGuide.bottomAnchor, constant: 0.0),
+            surfaceView.topAnchor.constraint(equalTo: vc.view.bottomAnchor,
+                                             constant: -hiddenInset),
         ]
     }
 
     // The method is separated from prepareLayout(to:) for the rotation support
     // It must be called in FloatingPanelController.traitCollectionDidChange(_:)
     func updateHeight() {
+        guard let vc = vc else { return }
         defer {
             UIView.performWithoutAnimation {
                 surfaceView.superview!.layoutIfNeeded()
             }
         }
 
-        if let consts = self.heightConstraints {
-            NSLayoutConstraint.deactivate([consts])
+        NSLayoutConstraint.deactivate(heightConstraints)
+
+        let height: CGFloat
+        if layout is FloatingPanelIntrinsicLayout {
+            updateIntrinsicHeight()
+            height = intrinsicHeight + safeAreaInsets.bottom
+        } else {
+            // Must use the`vc` height, not the screen height because safe area insets
+            // of `vc` are relative values. For example, a view controller in
+            // Navigation controller's safe area insets and frame can be changed whether
+            // the navigation bar is translucent or not.
+            height = vc.view.bounds.height - (safeAreaInsets.top + fullInset)
         }
 
-        let height = UIScreen.main.bounds.height - (safeAreaInsets.top + fullInset)
-        let consts = surfaceView.heightAnchor.constraint(equalToConstant: height)
+        heightConstraints = [
+            surfaceView.heightAnchor.constraint(equalToConstant: height)
+        ]
+        NSLayoutConstraint.activate(heightConstraints)
+        surfaceView.set(bottomOverflow: heightBuffer + layout.topInteractionBuffer)
 
-        NSLayoutConstraint.activate([consts])
-        heightConstraints = consts
-        surfaceView.bottomOverflow = heightBuffer
+        if layout is FloatingPanelIntrinsicLayout {
+            NSLayoutConstraint.deactivate(fullConstraints)
+            fullConstraints = [
+                surfaceView.topAnchor.constraint(equalTo: vc.layoutGuide.bottomAnchor,
+                                                 constant: -fullInset),
+            ]
+            NSLayoutConstraint.activate(fullConstraints)
+        }
     }
 
-    func activateLayout(of state: FloatingPanelPosition?) {
+    func activateLayout(of state: FloatingPanelPosition) {
         defer {
             surfaceView.superview!.layoutIfNeeded()
         }
 
+        var state = state
+
+        setBackdropAlpha(of: state)
+
         NSLayoutConstraint.activate(fixedConstraints)
 
-        guard var state = state else {
-            NSLayoutConstraint.deactivate(fullConstraints + halfConstraints + tipConstraints)
-            NSLayoutConstraint.activate(offConstraints)
-            return
-        }
-
-        if layout.supportedPositions.contains(state) == false {
+        if supportedPositions.union([.hidden]).contains(state) == false {
             state = layout.initialPosition
         }
 
@@ -253,24 +348,36 @@ class FloatingPanelLayoutAdapter {
         case .tip:
             NSLayoutConstraint.deactivate(fullConstraints + halfConstraints + offConstraints)
             NSLayoutConstraint.activate(tipConstraints)
+        case .hidden:
+            NSLayoutConstraint.deactivate(fullConstraints + halfConstraints + tipConstraints)
+            NSLayoutConstraint.activate(offConstraints)
         }
     }
 
-    private func checkConsistance(of layout: FloatingPanelLayout) {
-        // Verify layout configurations
-        assert(layout.supportedPositions.count > 1)
-        assert(layout.supportedPositions.contains(layout.initialPosition),
-               "Does not include an initial potision(\(layout.initialPosition)) in supportedPositions(\(layout.supportedPositions))")
-        layout.supportedPositions.forEach { (pos) in
-            assert(layout.insetFor(position: pos) != nil,
-                   "Undefined an inset for a pos(\(pos))")
+    func setBackdropAlpha(of target: FloatingPanelPosition) {
+        if target == .hidden {
+            self.backdropView.alpha = 0.0
+        } else {
+            self.backdropView.alpha = layout.backdropAlphaFor(position: target)
         }
+    }
+
+    func checkLayoutConsistance() {
+        // Verify layout configurations
+        assert(supportedPositions.count > 0)
+        assert(supportedPositions.contains(layout.initialPosition),
+               "Does not include an initial potision(\(layout.initialPosition)) in supportedPositions(\(supportedPositions))")
+
+        if layout is FloatingPanelIntrinsicLayout {
+            assert(layout.insetFor(position: .full) == nil, "Return `nil` for full position on FloatingPanelIntrinsicLayout")
+        }
+
         if halfInset > 0 {
             assert(halfInset > tipInset, "Invalid half and tip insets")
         }
         if fullInset > 0 {
-            assert(middleY > topY, "Invalid insets")
-            assert(bottomY > topY, "Invalid insets")
+            assert(middleY > topY, "Invalid insets { topY: \(topY), middleY: \(middleY) }")
+            assert(bottomY > topY, "Invalid insets { topY: \(topY), bottomY: \(bottomY) }")
         }
     }
 }

Framework/Sources/FloatingPanelSurfaceView.swift

@@ -10,7 +10,10 @@ class FloatingPanelSurfaceContentView: UIView {}
 /// A view that presents a surface interface in a floating panel.
 public class FloatingPanelSurfaceView: UIView {
 
-    /// A GrabberHandleView object displayed at the top of the surface view
+    /// A GrabberHandleView object displayed at the top of the surface view.
+    ///
+    /// To use a custom grabber handle, hide this and then add the custom one
+    /// to the surface view at appropirate coordinates.
     public var grabberHandle: GrabberHandleView!
 
     /// The height of the grabber bar area
@@ -21,15 +24,12 @@ public class FloatingPanelSurfaceView: UIView {
     /// A UIView object that can have the surface view added to it.
     public var contentView: UIView!
 
-    private var color: UIColor? = .white { didSet { setNeedsDisplay() } }
-    var bottomOverflow: CGFloat = 0.0 { didSet { setNeedsDisplay() }}
+    private var color: UIColor? = .white { didSet { setNeedsLayout() } }
+    private var bottomOverflow: CGFloat = 0.0 // Must not call setNeedsLayout()
 
     public override var backgroundColor: UIColor? {
         get { return color }
-        set {
-            color = newValue
-            setNeedsDisplay()
-        }
+        set { color = newValue }
     }
 
     /// The radius to use when drawing top rounded corners.
@@ -59,7 +59,7 @@ public class FloatingPanelSurfaceView: UIView {
     /// The color of the surface border.
     public var borderWidth: CGFloat = 0.0  { didSet { setNeedsLayout() } }
 
-    private var shadowLayer: CAShapeLayer!  { didSet { setNeedsLayout() } }
+    private var backgroundLayer: CAShapeLayer!  { didSet { setNeedsLayout() } }
 
     private struct Default {
         public static let grabberTopPadding: CGFloat = 6.0
@@ -79,10 +79,14 @@ public class FloatingPanelSurfaceView: UIView {
         super.backgroundColor = .clear
         self.clipsToBounds = false
 
+        let backgroundLayer = CAShapeLayer()
+        layer.insertSublayer(backgroundLayer, at: 0)
+        self.backgroundLayer = backgroundLayer
+
         let contentView = FloatingPanelSurfaceContentView()
         addSubview(contentView)
         self.contentView = contentView as UIView
-        // contentView.backgroundColor = .lightGray
+        contentView.backgroundColor = color
         contentView.translatesAutoresizingMaskIntoConstraints = false
         NSLayoutConstraint.activate([
             contentView.topAnchor.constraint(equalTo: topAnchor, constant: 0.0),
@@ -102,17 +106,39 @@ public class FloatingPanelSurfaceView: UIView {
             grabberHandle.heightAnchor.constraint(equalToConstant: grabberHandle.frame.height),
             grabberHandle.centerXAnchor.constraint(equalTo: centerXAnchor),
             ])
-
-        let shadowLayer = CAShapeLayer()
-        layer.insertSublayer(shadowLayer, at: 0)
-        self.shadowLayer = shadowLayer
     }
 
     public override func layoutSubviews() {
         super.layoutSubviews()
 
-        updateShadowLayer()
+        updateLayers()
+        updateContentViewMask()
 
+        contentView.layer.borderColor = borderColor?.cgColor
+        contentView.layer.borderWidth = borderWidth
+        contentView.backgroundColor = color
+    }
+
+    private func updateLayers() {
+        log.debug("SurfaceView bounds", bounds)
+        
+        var rect = bounds
+        rect.size.height += bottomOverflow // Expand the height for overflow buffer
+        let path = UIBezierPath(roundedRect: rect,
+                                byRoundingCorners: [.topLeft, .topRight],
+                                cornerRadii: CGSize(width: cornerRadius, height: cornerRadius))
+        backgroundLayer.path = path.cgPath
+        backgroundLayer.fillColor = color?.cgColor
+		
+        if shadowHidden == false {
+            layer.shadowColor = shadowColor.cgColor
+            layer.shadowOffset = shadowOffset
+            layer.shadowOpacity = shadowOpacity
+            layer.shadowRadius = shadowRadius
+        }
+    }
+
+    private func updateContentViewMask() {
         if #available(iOS 11, *) {
             // Don't use `contentView.clipToBounds` because it prevents content view from expanding the height of a subview of it
             // for the bottom overflow like Auto Layout settings of UIVisualEffectView in Main.storyborad of Example/Maps.
@@ -129,26 +155,24 @@ public class FloatingPanelSurfaceView: UIView {
             // Don't use `contentView.layer.mask` because of a UIVisualEffectView issue in iOS 10, https://forums.developer.apple.com/thread/50854
             // Instead, a user can mask the content view manually in an application.
         }
-
-        contentView.layer.borderColor = borderColor?.cgColor
-        contentView.layer.borderWidth = borderWidth
     }
 
-    private func updateShadowLayer() {
-        log.debug("SurfaceView bounds", bounds)
-        var rect = bounds
-        rect.size.height += bottomOverflow // Expand the height for overflow buffer
-        let path = UIBezierPath(roundedRect: rect,
-                                byRoundingCorners: [.topLeft, .topRight],
-                                cornerRadii: CGSize(width: cornerRadius, height: cornerRadius))
-        shadowLayer.path = path.cgPath
-        shadowLayer.fillColor = color?.cgColor
-        if shadowHidden == false {
-            shadowLayer.shadowPath = shadowLayer.path
-            shadowLayer.shadowColor = shadowColor.cgColor
-            shadowLayer.shadowOffset = shadowOffset
-            shadowLayer.shadowOpacity = shadowOpacity
-            shadowLayer.shadowRadius = shadowRadius
-        }
+    func set(bottomOverflow: CGFloat) {
+        self.bottomOverflow = bottomOverflow
+        updateLayers()
+        updateContentViewMask()
+    }
+
+
+    func add(childView: UIView) {
+        contentView.addSubview(childView)
+        childView.frame = contentView.bounds
+        childView.translatesAutoresizingMaskIntoConstraints = false
+        NSLayoutConstraint.activate([
+            childView.topAnchor.constraint(equalTo: contentView.topAnchor, constant: 0.0),
+            childView.leftAnchor.constraint(equalTo: contentView.leftAnchor, constant: 0.0),
+            childView.rightAnchor.constraint(equalTo: contentView.rightAnchor, constant: 0.0),
+            childView.bottomAnchor.constraint(equalTo: contentView.bottomAnchor, constant: 0.0),
+            ])
     }
 }

Framework/Sources/FloatingPanelTransitioning.swift

@@ -0,0 +1,99 @@
+//
+//  Created by Shin Yamamoto on 2018/11/21.
+//  Copyright © 2018 Shin Yamamoto. All rights reserved.
+//
+
+import UIKit
+
+class FloatingPanelModalTransition: NSObject, UIViewControllerTransitioningDelegate {
+    func animationController(forPresented presented: UIViewController,
+                             presenting: UIViewController,
+                             source: UIViewController) -> UIViewControllerAnimatedTransitioning? {
+        return FloatingPanelModalPresentTransition()
+    }
+
+    func animationController(forDismissed dismissed: UIViewController) -> UIViewControllerAnimatedTransitioning? {
+        return FloatingPanelModalDismissTransition()
+    }
+
+    func presentationController(forPresented presented: UIViewController, presenting: UIViewController?, source: UIViewController) -> UIPresentationController? {
+        return FloatingPanelPresentationController(presentedViewController: presented, presenting: presenting)
+    }
+}
+
+class FloatingPanelPresentationController: UIPresentationController {
+    override func presentationTransitionDidEnd(_ completed: Bool) {
+        // For non-animated presentation
+        if let fpc = presentedViewController as? FloatingPanelController, fpc.position == .hidden {
+            fpc.show(animated: false, completion: nil)
+        }
+    }
+
+    override func dismissalTransitionDidEnd(_ completed: Bool) {
+        // For non-animated dismissal
+        if let fpc = presentedViewController as? FloatingPanelController, fpc.position != .hidden {
+            fpc.hide(animated: false, completion: nil)
+        }
+    }
+
+    override func containerViewWillLayoutSubviews() {
+        guard
+            let containerView = self.containerView,
+            let fpc = presentedViewController as? FloatingPanelController,
+            let fpView = fpc.view
+            else { fatalError() }
+
+        let tapGesture = UITapGestureRecognizer(target: self, action: #selector(handleBackdrop(tapGesture:)))
+        fpc.backdropView.addGestureRecognizer(tapGesture)
+
+        containerView.addSubview(fpView)
+        fpView.frame = containerView.bounds //MUST
+    }
+
+    @objc func handleBackdrop(tapGesture: UITapGestureRecognizer) {
+        presentedViewController.dismiss(animated: true, completion: nil)
+    }
+}
+
+class FloatingPanelModalPresentTransition: NSObject, UIViewControllerAnimatedTransitioning {
+    func transitionDuration(using transitionContext: UIViewControllerContextTransitioning?) -> TimeInterval {
+        guard
+            let fpc = transitionContext?.viewController(forKey: .to) as? FloatingPanelController
+        else { fatalError()}
+
+        let animator = fpc.behavior.addAnimator(fpc, to: fpc.layout.initialPosition)
+        return TimeInterval(animator.duration)
+    }
+
+    func animateTransition(using transitionContext: UIViewControllerContextTransitioning) {
+        guard
+            let fpc = transitionContext.viewController(forKey: .to) as? FloatingPanelController
+        else { fatalError() }
+
+        fpc.show(animated: true) {
+            transitionContext.completeTransition(!transitionContext.transitionWasCancelled)
+        }
+    }
+}
+
+class FloatingPanelModalDismissTransition: NSObject, UIViewControllerAnimatedTransitioning {
+    func transitionDuration(using transitionContext: UIViewControllerContextTransitioning?) -> TimeInterval {
+        guard
+            let fpc = transitionContext?.viewController(forKey: .from) as? FloatingPanelController
+        else { fatalError()}
+
+        let animator = fpc.behavior.removeAnimator(fpc, from: fpc.position)
+        return TimeInterval(animator.duration)
+    }
+
+    func animateTransition(using transitionContext: UIViewControllerContextTransitioning) {
+        guard
+            let fpc = transitionContext.viewController(forKey: .from) as? FloatingPanelController
+        else { fatalError() }
+
+        fpc.hide(animated: true) {
+            transitionContext.completeTransition(!transitionContext.transitionWasCancelled)
+        }
+    }
+}
+

Framework/Sources/FloatingPanelView.swift

@@ -0,0 +1,30 @@
+//
+//  Created by Shin Yamamoto on 2018/11/21.
+//  Copyright © 2018 Shin Yamamoto. All rights reserved.
+//
+
+import UIKit
+
+class FloatingPanelPassThroughView: UIView {
+    public override func hitTest(_ point: CGPoint, with event: UIEvent?) -> UIView? {
+        let view = super.hitTest(point, with: event)
+        switch view {
+        case is FloatingPanelPassThroughView:
+            return nil
+        default:
+            return view
+        }
+    }
+}
+
+class FloatingPanelSurfaceWrapperView: UIView {
+    public override func hitTest(_ point: CGPoint, with event: UIEvent?) -> UIView? {
+        let view = super.hitTest(point, with: event)
+        switch view {
+        case is FloatingPanelSurfaceWrapperView:
+            return nil
+        default:
+            return view
+        }
+    }
+}

Framework/Sources/GrabberHandleView.swift

@@ -24,8 +24,14 @@ public class GrabberHandleView: UIView {
         self.backgroundColor = Default.barColor
         render()
     }
+
     private func render() {
         self.layer.masksToBounds = true
         self.layer.cornerRadius = frame.size.height * 0.5
     }
+
+    public override func hitTest(_ point: CGPoint, with event: UIEvent?) -> UIView? {
+        let view = super.hitTest(point, with: event)
+        return view == self ? nil : view
+    }
 }

Framework/Sources/UIExtensions.swift

@@ -50,6 +50,8 @@ protocol SideLayoutGuideProvider {
 extension UIView: SideLayoutGuideProvider {}
 extension UILayoutGuide: SideLayoutGuideProvider {}
 
+// The reason why UIView has no extensions of safe area insets and top/bottom guides
+// is for iOS10 compat.
 extension UIView {
     var sideLayoutGuide: SideLayoutGuideProvider {
         if #available(iOS 11.0, *) {
@@ -60,6 +62,17 @@ extension UIView {
     }
 }
 
+extension UIView {
+    func disableAutoLayout() {
+        let frame = self.frame
+        translatesAutoresizingMaskIntoConstraints = true
+        self.frame = frame
+    }
+    func enableAutoLayout() {
+        translatesAutoresizingMaskIntoConstraints = false
+    }
+}
+
 extension UIGestureRecognizer.State: CustomDebugStringConvertible {
     public var debugDescription: String {
         switch self {

README.md

@@ -23,16 +23,23 @@ The new interface displays the related contents and utilities in parallel as a u
   - [CocoaPods](#cocoapods)
   - [Carthage](#carthage)
 - [Getting Started](#getting-started)
+  - [Add a floating panel as a child view controller](#add-a-floating-panel-as-a-child-view-controller)
+  - [Present a floating panel as a modality](#present-a-floating-panel-as-a-modality)
 - [Usage](#usage)
-  - [Customize the layout of a floating panel with  `FloatingPanelLayout` protocol](#customize-the-layout-of-a-floating-panel-with--floatingpanellayout-protocol)
-    - [Change the initial position, supported positions and height](#change-the-initial-position-supported-positions-and-height)
+  - [Show/Hide a floating panel in a view with your view hierarchy](#showhide-a-floating-panel-in-a-view-with-your-view-hierarchy)
+  - [Customize the layout with `FloatingPanelLayout` protocol](#customize-the-layout-with-floatingpanellayout-protocol)
+    - [Change the initial position and height](#change-the-initial-position-and-height)
     - [Support your landscape layout](#support-your-landscape-layout)
+    - [Use Intrinsic height layout](#use-intrinsic-height-layout)
   - [Customize the behavior with `FloatingPanelBehavior` protocol](#customize-the-behavior-with-floatingpanelbehavior-protocol)
     - [Modify your floating panel's interaction](#modify-your-floating-panels-interaction)
+  - [Use a custom grabber handle](#use-a-custom-grabber-handle)
+  - [Add tap gestures to the surface or backdrop views](#add-tap-gestures-to-the-surface-or-backdrop-views)
   - [Create an additional floating panel for a detail](#create-an-additional-floating-panel-for-a-detail)
   - [Move a position with an animation](#move-a-position-with-an-animation)
-  - [Make your contents correspond with a floating panel behavior](#make-your-contents-correspond-with-a-floating-panel-behavior)
+  - [Work your contents together with a floating panel behavior](#work-your-contents-together-with-a-floating-panel-behavior)
 - [Notes](#notes)
+  - ['Show' or 'Show Detail' Segues from `FloatingPanelController`'s content view controller](#show-or-show-detail-segues-from-floatingpanelcontrollers-content-view-controller)
   - [FloatingPanelSurfaceView's issue on iOS 10](#floatingpanelsurfaceviews-issue-on-ios-10)
 - [Author](#author)
 - [License](#license)
@@ -45,10 +52,11 @@ The new interface displays the related contents and utilities in parallel as a u
 - [x] Fluid animation and gesture handling
 - [x] Scroll view tracking
 - [x] Common UI elements: Grabber handle, Backdrop and Surface rounding corners
-- [x] 2 or 3 anchor positions(full, half, tip)
+- [x] 1~3 anchor positions(full, half, tip)
 - [x] Layout customization for all trait environments(i.e. Landscape orientation support)
 - [x] Behavior customization
 - [x] Free from common issues of Auto Layout and gesture handling
+- [x] Modal presentation
 
 Examples are here.
 
@@ -81,6 +89,8 @@ github "scenee/FloatingPanel"
 
 ## Getting Started
 
+### Add a floating panel as a child view controller
+
 ```swift
 import UIKit
 import FloatingPanel
@@ -96,29 +106,75 @@ class ViewController: UIViewController, FloatingPanelControllerDelegate {
         // Assign self as the delegate of the controller.
         fpc.delegate = self // Optional
 
-        // Add a content view controller.
+        // Set a content view controller.
         let contentVC = ContentViewController()
-        fpc.show(contentVC, sender: nil)
+        fpc.set(contentViewController: contentVC)
 
         // Track a scroll view(or the siblings) in the content view controller.
         fpc.track(scrollView: contentVC.tableView)
 
-        // Add the views managed by the `FloatingPanelController` object to self.view.
+        // Add and show the views managed by the `FloatingPanelController` object to self.view.
         fpc.addPanel(toParent: self)
     }
 
     override func viewWillDisappear(_ animated: Bool) {
         super.viewWillDisappear(animated)
+
         // Remove the views managed by the `FloatingPanelController` object from self.view.
         fpc.removePanelFromParent()
     }
-    ...
 }
 ```
 
+### Present a floating panel as a modality
+
+```swift
+let fpc = FloatingPanelController()
+let contentVC = ...
+fpc.set(contentViewController: contentVC)
+
+fpc.isRemovalInteractionEnabled = true // Optional: Let it removable by a swipe-down
+
+self.present(fpc, animated: true, completion: nil)
+```
+
+You can show a floating panel over UINavigationController from the containnee view controllers as a modality of `.overCurrentContext` style.
+
+NOTE: FloatingPanelController has the custom presentation controller. If you would like to customize the presentation/dismissal, please see [FloatingPanelTransitioning](https://github.com/SCENEE/FloatingPanel/blob/feat-modality/Framework/Sources/FloatingPanelTransitioning.swift).
+
 ## Usage
 
-### Customize the layout of a floating panel with  `FloatingPanelLayout` protocol
+### Show/Hide a floating panel in a view with your view hierarchy
+
+```swift
+// Add the controller and the managed views to a view controller.
+// From the second time, just call `show(animated:completion)`.
+view.addSubview(fpc.view)
+fpc.view.frame = view.bounds // MUST
+parent.addChild(fpc)
+
+// Show a floating panel to the initial position defined in your `FloatingPanelLayout` object.
+fpc.show(animated: true) {
+
+    // Only for the first time
+    self.didMove(toParent: self)
+}
+
+...
+
+// Hide it
+fpc.hide(animated: true) {
+
+    // Remove it if needed
+    self.willMove(toParent: nil)
+    self.view.removeFromSuperview()
+    self.removeFromParent()
+}
+```
+
+NOTE: `FloatingPanelController` wraps `show`/`hide` with `addPanel`/`removePanelFromParent` for easy-to-use. But `show`/`hide` are more convenience for your app.
+
+### Customize the layout with `FloatingPanelLayout` protocol
 
 #### Change the initial position and height
 
@@ -128,7 +184,6 @@ class ViewController: UIViewController, FloatingPanelControllerDelegate {
     func floatingPanel(_ vc: FloatingPanelController, layoutFor newCollection: UITraitCollection) -> FloatingPanelLayout? {
         return MyFloatingPanelLayout()
     }
-    ...
 }
 
 class MyFloatingPanelLayout: FloatingPanelLayout {
@@ -141,6 +196,7 @@ class MyFloatingPanelLayout: FloatingPanelLayout {
             case .full: return 16.0 // A top inset from safe area
             case .half: return 216.0 // A bottom inset from the safe area
             case .tip: return 44.0 // A bottom inset from the safe area
+            default: return nil // Or `case .hidden: return nil`
         }
     }
 }
@@ -154,7 +210,6 @@ class ViewController: UIViewController, FloatingPanelControllerDelegate {
     func floatingPanel(_ vc: FloatingPanelController, layoutFor newCollection: UITraitCollection) -> FloatingPanelLayout? {
         return (newCollection.verticalSizeClass == .compact) ? FloatingPanelLandscapeLayout() : nil // Returning nil indicates to use the default layout
     }
-    ...
 }
 
 class FloatingPanelLandscapeLayout: FloatingPanelLayout {
@@ -182,6 +237,33 @@ class FloatingPanelLandscapeLayout: FloatingPanelLayout {
 }
 ```
 
+#### Use Intrinsic height layout
+
+1. Lay out your content View with the intrinsic height size. For example, see "Detail View Controller scene"/"Intrinsic View Controller scene" of [Main.storyboard](https://github.com/SCENEE/FloatingPanel/blob/master/Examples/Samples/Sources/Base.lproj/Main.storyboard). The 'Stack View.bottom' constraint determines the intrinsic height.
+2. Create a layout that adopts and conforms to `FloatingPanelIntrinsicLayout` and use it.
+
+```swift
+class ViewController: UIViewController, FloatingPanelControllerDelegate {
+    ...
+    func floatingPanel(_ vc: FloatingPanelController, layoutFor newCollection: UITraitCollection) -> FloatingPanelLayout? {
+        return RemovablePanelLayout()
+    }
+}
+
+class RemovablePanelLayout: FloatingPanelIntrinsicLayout {
+    var supportedPositions: Set<FloatingPanelPosition> {
+        return [.full, .half]
+    }
+    func insetFor(position: FloatingPanelPosition) -> CGFloat? {
+        switch position {
+        case .half: return 130.0
+        default: return nil  // Must return nil for .full
+        }
+    }
+    ...
+}
+```
+
 ### Customize the behavior with `FloatingPanelBehavior` protocol
 
 #### Modify your floating panel's interaction
@@ -192,51 +274,67 @@ class ViewController: UIViewController, FloatingPanelControllerDelegate {
     func floatingPanel(_ vc: FloatingPanelController, behaviorFor newCollection: UITraitCollection) -> FloatingPanelBehavior? {
         return FloatingPanelStocksBehavior()
     }
-    ...
 }
-...
 
 class FloatingPanelStocksBehavior: FloatingPanelBehavior {
-    var velocityThreshold: CGFloat {
-        return 15.0
-    }
-
+    ...
     func interactionAnimator(_ fpc: FloatingPanelController, to targetPosition: FloatingPanelPosition, with velocity: CGVector) -> UIViewPropertyAnimator {
         let damping = self.damping(with: velocity)
         let springTiming = UISpringTimingParameters(dampingRatio: damping, initialVelocity: velocity)
         return UIViewPropertyAnimator(duration: 0.5, timingParameters: springTiming)
     }
+}
+```
+
+### Use a custom grabber handle
+
+```swift
+let myGrabberHandleView = MyGrabberHandleView()
+fpc.surfaceView.grabberHandle.isHidden = true
+fpc.surfaceView.addSubview(myGrabberHandleView)
+```
+
+### Add tap gestures to the surface or backdrop views
+
+```swift
+override func viewDidLoad() {
     ...
+    surfaceTapGesture = UITapGestureRecognizer(target: self, action: #selector(handleSurface(tapGesture:)))
+    fpc.surfaceView.addGestureRecognizer(surfaceTapGesture)
+
+    backdropTapGesture = UITapGestureRecognizer(target: self, action: #selector(handleBackdrop(tapGesture:)))
+    fpc.backdropView.addGestureRecognizer(backdropTapGesture)
+
+    surfaceTapGesture.isEnabled = (fpc.position == .tip)
+}
+
+// Enable `surfaceTapGesture` only at `tip` position
+func floatingPanelDidChangePosition(_ vc: FloatingPanelController) {
+    surfaceTapGesture.isEnabled = (vc.position == .tip)
 }
 ```
 
 ### Create an additional floating panel for a detail
 
 ```swift
-class ViewController: UIViewController, FloatingPanelControllerDelegate {
-    var searchPanelVC: FloatingPanelController!
-    var detailPanelVC: FloatingPanelController!
+override func viewDidLoad() {
+    // Setup Search panel
+    self.searchPanelVC = FloatingPanelController()
 
-    override func viewDidLoad() {
-        // Setup Search panel
-        self.searchPanelVC = FloatingPanelController()
+    let searchVC = SearchViewController()
+    self.searchPanelVC.set(contentViewController: searchVC)
+    self.searchPanelVC.track(scrollView: contentVC.tableView)
 
-        let searchVC = SearchViewController()
-        self.searchPanelVC.show(searchVC, sender: nil)
-        self.searchPanelVC.track(scrollView: contentVC.tableView)
+    self.searchPanelVC.addPanel(toParent: self)
 
-        self.searchPanelVC.addPanel(toParent: self)
+    // Setup Detail panel
+    self.detailPanelVC = FloatingPanelController()
 
-        // Setup Detail panel
-        self.detailPanelVC = FloatingPanelController()
+    let contentVC = ContentViewController()
+    self.detailPanelVC.set(contentViewController: contentVC)
+    self.detailPanelVC.track(scrollView: contentVC.scrollView)
 
-        let contentVC = ContentViewController()
-        self.detailPanelVC.show(contentVC, sender: nil)
-        self.detailPanelVC.track(scrollView: contentVC.scrollView)
-
-        self.detailPanelVC.addPanel(toParent: self)
-    }
-    ...
+    self.detailPanelVC.addPanel(toParent: self)
 }
 ```
 
@@ -245,18 +343,18 @@ class ViewController: UIViewController, FloatingPanelControllerDelegate {
 In the following example, I move a floating panel to full or half position while opening or closing a search bar like Apple Maps.
 
 ```swift
-    func searchBarCancelButtonClicked(_ searchBar: UISearchBar) {
-        ...
-        fpc.move(to: .half, animated: true)
-    }
+func searchBarCancelButtonClicked(_ searchBar: UISearchBar) {
+    ...
+    fpc.move(to: .half, animated: true)
+}
 
-    func searchBarTextDidBeginEditing(_ searchBar: UISearchBar) {
-        ...
-        fpc.move(to: .full, animated: true)
-    }
+func searchBarTextDidBeginEditing(_ searchBar: UISearchBar) {
+    ...
+    fpc.move(to: .full, animated: true)
+}
 ```
 
-### Make your contents correspond with a floating panel behavior
+### Work your contents together with a floating panel behavior
 
 ```swift
 class ViewController: UIViewController, FloatingPanelControllerDelegate {
@@ -273,15 +371,46 @@ class ViewController: UIViewController, FloatingPanelControllerDelegate {
             searchVC.hideHeader()
         }
     }
-    ...
 }
 ```
 
 ## Notes
 
-###  FloatingPanelSurfaceView's issue on iOS 10
+### 'Show' or 'Show Detail' Segues from `FloatingPanelController`'s content view controller
 
-* On iOS 10,   `FloatingPanelSurfaceView.cornerRadius` isn't not automatically masked with the top rounded corners  because of UIVisualEffectView issue. See https://forums.developer.apple.com/thread/50854. 
+'Show' or 'Show Detail' segues from a content view controller will be managed by a view controller(hereinafter called 'master VC') adding a floating panel. Because a floating panel is just a subview of the master VC(except for modality).
+
+`FloatingPanelController` has no way to manage a stack of view controllers like `UINavigationController`. If so, it would be so complicated and the interface will become `UINavigationController`. This component should not have the responsibility to manage the stack.
+
+By the way, a content view controller can present a view controller modally with `present(_:animated:completion:)` or 'Present Modally' segue.
+
+However, sometimes you want to show a destination view controller of 'Show' or 'Show Detail' segue with another floating panel. It's possible to override `show(_:sender)` of the master VC!
+
+Here is an example.
+
+```swift
+class ViewController: UIViewController {
+    var fpc: FloatingPanelController!
+    var secondFpc: FloatingPanelController!
+
+    ...
+    override func show(_ vc: UIViewController, sender: Any?) {
+        secondFpc = FloatingPanelController()
+
+        secondFpc.set(contentViewController: vc)
+
+        secondFpc.addPanel(toParent: self)
+    }
+}
+```
+
+A `FloatingPanelController` object proxies an action for `show(_:sender)` to the master VC. That's why the master VC can handle a destination view controller of a 'Show' or 'Show Detail' segue and you can hook `show(_:sender)` to show a secondary floating panel set the destination view controller to the content.
+
+It's a great way to decouple between a floating panel and the content VC.
+
+### FloatingPanelSurfaceView's issue on iOS 10
+
+* On iOS 10, `FloatingPanelSurfaceView.cornerRadius` isn't not automatically masked with the top rounded corners  because of `UIVisualEffectView` issue. See https://forums.developer.apple.com/thread/50854. 
 So you need to draw top rounding corners of your content.  Here is an example in Examples/Maps.
 ```swift
 override func viewDidLayoutSubviews() {
@@ -292,11 +421,11 @@ override func viewDidLayoutSubviews() {
     }
 }
 ```
-* If you sets clear color to `FloatingPanelSurfaceView.backgroundColor`, please note the bottom overflow of your content on bouncing at full position. To prevent it, you need to expand your content. For example, See Example/Maps's Auto Layout settings of UIVisualEffectView in Main.storyborad.
+* If you sets clear color to `FloatingPanelSurfaceView.backgroundColor`, please note the bottom overflow of your content on bouncing at full position. To prevent it, you need to expand your content. For example, See Example/Maps App's Auto Layout settings of `UIVisualEffectView` in Main.storyboard.
 
 ## Author
 
-Shin Yamamoto <shin@scenee.com>
+Shin Yamamoto <shin@scenee.com> | [@scenee](https://twitter.com/scenee)
 
 ## License