Release v1.6.3

CocoaPods stage can be failed at `pod spec lint` job if the git tag hasn't
existing yet. We can restart the job after the tag is pushed so it's
best to run it as the last job to ensure other builds are passed.

It's helpful on the release workflow.

.travis.yml

@@ -36,6 +36,17 @@ jobs:
     osx_image: xcode10.2
     name: "iPhone X (iOS 12.2)"
 
+  - stage: Build examples
+    osx_image: xcode10.2
+    script: xcodebuild -scheme Maps -sdk iphonesimulator clean build
+    name: "Maps"
+  - script: xcodebuild -scheme Stocks -sdk iphonesimulator clean build
+    osx_image: xcode10.2
+    name: "Stocks"
+  - script: xcodebuild -scheme Samples -sdk iphonesimulator clean build
+    osx_image: xcode10.2
+    name: "Samples"
+
   - stage: Carthage
     osx_image: xcode10.2
     before_install:
@@ -47,16 +58,5 @@ jobs:
   - stage: CocoaPods
     osx_image: xcode10.2
     script:
-    - pod spec lint
-    - pod lib lint
-
-  - stage: Build examples
-    osx_image: xcode10.2
-    script: xcodebuild -scheme Maps -sdk iphonesimulator clean build
-    name: "Maps"
-  - script: xcodebuild -scheme Stocks -sdk iphonesimulator clean build
-    osx_image: xcode10.2
-    name: "Stocks"
-  - script: xcodebuild -scheme Samples -sdk iphonesimulator clean build
-    osx_image: xcode10.2
-    name: "Samples"
+    - pod spec lint --allow-warnings
+    - pod lib lint --allow-warnings

Examples/Samples/Sources/ViewController.swift

@@ -677,6 +677,10 @@ class DebugTableViewController: InspectableViewController {
         //  Remove FloatingPanel from a view
         (self.parent as! FloatingPanelController).removePanelFromParent(animated: true, completion: nil)
     }
+
+    func scrollViewDidScroll(_ scrollView: UIScrollView) {
+        print("TableView --- ", scrollView.contentOffset, scrollView.contentInset)
+    }
 }
 
 extension DebugTableViewController: UITableViewDataSource {
@@ -933,7 +937,7 @@ extension TabBarContentViewController: UITextViewDelegate {
         // Using KVO of `scrollView.contentOffset`). Because it can lead to an
         // infinite loop if a user also resets a content offset as below and,
         // in the situation, a user has to modify the library.
-        if fpc.position != .full, fpc.surfaceView.frame.minY < fpc.originYOfSurface(for: .full) {
+        if fpc.position != .full, fpc.surfaceView.frame.minY > fpc.originYOfSurface(for: .full) {
             scrollView.contentOffset = .zero
         }
     }

FloatingPanel.podspec

@@ -1,7 +1,7 @@
 Pod::Spec.new do |s|
 
   s.name                = "FloatingPanel"
-  s.version             = "1.6.0"
+  s.version             = "1.6.3"
   s.summary             = "FloatingPanel is a clean and easy-to-use UI component of a floating panel interface."
   s.description         = <<-DESC
 FloatingPanel is a clean and easy-to-use UI component for a new interface introduced in Apple Maps, Shortcuts and Stocks app.

Framework/FloatingPanel.xcodeproj/project.pbxproj

@@ -7,6 +7,8 @@
 	objects = {
 
 /* Begin PBXBuildFile section */
+		542753C622C49A6E00D17955 /* FloatingPanelLayoutTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = 542753C522C49A6E00D17955 /* FloatingPanelLayoutTests.swift */; };
+		542753C822C49A8F00D17955 /* Utils.swift in Sources */ = {isa = PBXBuildFile; fileRef = 542753C722C49A8F00D17955 /* Utils.swift */; };
 		54352E9621A51A2500CBCA08 /* FloatingPanelTransitioning.swift in Sources */ = {isa = PBXBuildFile; fileRef = 54352E9521A51A2500CBCA08 /* FloatingPanelTransitioning.swift */; };
 		54352E9821A521CA00CBCA08 /* FloatingPanelView.swift in Sources */ = {isa = PBXBuildFile; fileRef = 54352E9721A521CA00CBCA08 /* FloatingPanelView.swift */; };
 		5450EEE421646DF500135936 /* FloatingPanelBehavior.swift in Sources */ = {isa = PBXBuildFile; fileRef = 5450EEE321646DF500135936 /* FloatingPanelBehavior.swift */; };
@@ -16,9 +18,10 @@
 		545DB9DE215118C800CA77B8 /* UIExtensions.swift in Sources */ = {isa = PBXBuildFile; fileRef = 545DB9DD215118C800CA77B8 /* UIExtensions.swift */; };
 		545DB9E021511AC100CA77B8 /* FloatingPanelController.swift in Sources */ = {isa = PBXBuildFile; fileRef = 545DB9DF21511AC100CA77B8 /* FloatingPanelController.swift */; };
 		545DBA2B2152383100CA77B8 /* GrabberHandleView.swift in Sources */ = {isa = PBXBuildFile; fileRef = 545DBA2A2152383100CA77B8 /* GrabberHandleView.swift */; };
+		549E944522CF295D0050AECF /* FloatingPanelPositionTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = 549E944422CF295D0050AECF /* FloatingPanelPositionTests.swift */; };
 		54A6B6B122968B530077F348 /* FloatingPanelTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = 54A6B6B022968B530077F348 /* FloatingPanelTests.swift */; };
 		54A6B6B622968F710077F348 /* LaunchScreen.storyboard in Resources */ = {isa = PBXBuildFile; fileRef = 54A6B6B522968F710077F348 /* LaunchScreen.storyboard */; };
-		54A6B6B82296A8520077F348 /* FloatingPanelViewTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = 54A6B6B72296A8520077F348 /* FloatingPanelViewTests.swift */; };
+		54A6B6B82296A8520077F348 /* FloatingPanelSurfaceViewTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = 54A6B6B72296A8520077F348 /* FloatingPanelSurfaceViewTests.swift */; };
 		54ABD7AF216CCFF7002E6C13 /* Logger.swift in Sources */ = {isa = PBXBuildFile; fileRef = 54ABD7AE216CCFF7002E6C13 /* Logger.swift */; };
 		54CDC5D3215B6D5A007D205C /* FloatingPanelSurfaceView.swift in Sources */ = {isa = PBXBuildFile; fileRef = 54CDC5D2215B6D5A007D205C /* FloatingPanelSurfaceView.swift */; };
 		54CDC5D5215B6D8D007D205C /* FloatingPanelBackdropView.swift in Sources */ = {isa = PBXBuildFile; fileRef = 54CDC5D4215B6D8D007D205C /* FloatingPanelBackdropView.swift */; };
@@ -45,6 +48,8 @@
 /* End PBXContainerItemProxy section */
 
 /* Begin PBXFileReference section */
+		542753C522C49A6E00D17955 /* FloatingPanelLayoutTests.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = FloatingPanelLayoutTests.swift; sourceTree = "<group>"; };
+		542753C722C49A8F00D17955 /* Utils.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = Utils.swift; sourceTree = "<group>"; };
 		54352E9521A51A2500CBCA08 /* FloatingPanelTransitioning.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = FloatingPanelTransitioning.swift; sourceTree = "<group>"; };
 		54352E9721A521CA00CBCA08 /* FloatingPanelView.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = FloatingPanelView.swift; sourceTree = "<group>"; };
 		5450EEE321646DF500135936 /* FloatingPanelBehavior.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = FloatingPanelBehavior.swift; sourceTree = "<group>"; };
@@ -57,9 +62,10 @@
 		545DB9DD215118C800CA77B8 /* UIExtensions.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = UIExtensions.swift; sourceTree = "<group>"; };
 		545DB9DF21511AC100CA77B8 /* FloatingPanelController.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = FloatingPanelController.swift; sourceTree = "<group>"; };
 		545DBA2A2152383100CA77B8 /* GrabberHandleView.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = GrabberHandleView.swift; sourceTree = "<group>"; };
+		549E944422CF295D0050AECF /* FloatingPanelPositionTests.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = FloatingPanelPositionTests.swift; sourceTree = "<group>"; };
 		54A6B6B022968B530077F348 /* FloatingPanelTests.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = FloatingPanelTests.swift; sourceTree = "<group>"; };
 		54A6B6B522968F710077F348 /* LaunchScreen.storyboard */ = {isa = PBXFileReference; lastKnownFileType = file.storyboard; path = LaunchScreen.storyboard; sourceTree = "<group>"; };
-		54A6B6B72296A8520077F348 /* FloatingPanelViewTests.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = FloatingPanelViewTests.swift; sourceTree = "<group>"; };
+		54A6B6B72296A8520077F348 /* FloatingPanelSurfaceViewTests.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = FloatingPanelSurfaceViewTests.swift; sourceTree = "<group>"; };
 		54ABD7AE216CCFF7002E6C13 /* Logger.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = Logger.swift; sourceTree = "<group>"; };
 		54CDC5D2215B6D5A007D205C /* FloatingPanelSurfaceView.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = FloatingPanelSurfaceView.swift; sourceTree = "<group>"; };
 		54CDC5D4215B6D8D007D205C /* FloatingPanelBackdropView.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = FloatingPanelBackdropView.swift; sourceTree = "<group>"; };
@@ -140,8 +146,11 @@
 			isa = PBXGroup;
 			children = (
 				54A6B6B022968B530077F348 /* FloatingPanelTests.swift */,
-				54A6B6B72296A8520077F348 /* FloatingPanelViewTests.swift */,
 				545DB9CF2151169500CA77B8 /* FloatingPanelControllerTests.swift */,
+				542753C522C49A6E00D17955 /* FloatingPanelLayoutTests.swift */,
+				54A6B6B72296A8520077F348 /* FloatingPanelSurfaceViewTests.swift */,
+				549E944422CF295D0050AECF /* FloatingPanelPositionTests.swift */,
+				542753C722C49A8F00D17955 /* Utils.swift */,
 				545DB9D12151169500CA77B8 /* Info.plist */,
 			);
 			path = Tests;
@@ -309,6 +318,7 @@
 				545DBA2B2152383100CA77B8 /* GrabberHandleView.swift in Sources */,
 				54352E9621A51A2500CBCA08 /* FloatingPanelTransitioning.swift in Sources */,
 				545DB9DE215118C800CA77B8 /* UIExtensions.swift in Sources */,
+				542753C822C49A8F00D17955 /* Utils.swift in Sources */,
 			);
 			runOnlyForDeploymentPostprocessing = 0;
 		};
@@ -318,7 +328,9 @@
 			files = (
 				54A6B6B122968B530077F348 /* FloatingPanelTests.swift in Sources */,
 				545DB9D02151169500CA77B8 /* FloatingPanelControllerTests.swift in Sources */,
-				54A6B6B82296A8520077F348 /* FloatingPanelViewTests.swift in Sources */,
+				549E944522CF295D0050AECF /* FloatingPanelPositionTests.swift in Sources */,
+				542753C622C49A6E00D17955 /* FloatingPanelLayoutTests.swift in Sources */,
+				54A6B6B82296A8520077F348 /* FloatingPanelSurfaceViewTests.swift in Sources */,
 			);
 			runOnlyForDeploymentPostprocessing = 0;
 		};

Framework/FloatingPanel.xcodeproj/xcshareddata/xcschemes/FloatingPanel.xcscheme

@@ -29,7 +29,9 @@
       shouldUseLaunchSchemeArgsEnv = "YES">
       <Testables>
          <TestableReference
-            skipped = "NO">
+            skipped = "NO"
+            parallelizable = "YES"
+            testExecutionOrdering = "random">
             <BuildableReference
                BuildableIdentifier = "primary"
                BlueprintIdentifier = "545DB9C92151169500CA77B8"

Framework/Sources/FloatingPanel.swift

@@ -8,9 +8,9 @@ import UIKit.UIGestureRecognizerSubclass // For Xcode 9.4.1
 ///
 /// FloatingPanel presentation model
 ///
-class FloatingPanel: NSObject, UIGestureRecognizerDelegate, UIScrollViewDelegate {
+class FloatingPanel: NSObject, UIGestureRecognizerDelegate {
     // MUST be a weak reference to prevent UI freeze on the presentation modally
-    weak var viewcontroller: FloatingPanelController!
+    weak var viewcontroller: FloatingPanelController?
 
     let surfaceView: FloatingPanelSurfaceView
     let backdropView: FloatingPanelBackdropView
@@ -25,7 +25,11 @@ class FloatingPanel: NSObject, UIGestureRecognizerDelegate, UIScrollViewDelegate
     }
 
     private(set) var state: FloatingPanelPosition = .hidden {
-        didSet { viewcontroller.delegate?.floatingPanelDidChangePosition(viewcontroller) }
+        didSet {
+            if let vc = viewcontroller {
+                vc.delegate?.floatingPanelDidChangePosition(vc)
+            }
+        }
     }
 
     private var isBottomState: Bool {
@@ -36,15 +40,7 @@ class FloatingPanel: NSObject, UIGestureRecognizerDelegate, UIScrollViewDelegate
     let panGestureRecognizer: FloatingPanelPanGestureRecognizer
     var isRemovalInteractionEnabled: Bool = false
 
-    fileprivate var animator: UIViewPropertyAnimator? {
-        didSet {
-            // This intends to avoid `tableView(_:didSelectRowAt:)` not being
-            // called on first tap after the moving animation, but it doesn't
-            // seem to be enough. The same issue happens on Apple Maps so it
-            // might be an issue in `UITableView`.
-            scrollView?.isUserInteractionEnabled = (animator == nil)
-        }
-    }
+    fileprivate var animator: UIViewPropertyAnimator?
 
     private var initialFrame: CGRect = .zero
     private var initialTranslationY: CGFloat = 0
@@ -55,13 +51,10 @@ class FloatingPanel: NSObject, UIGestureRecognizerDelegate, UIScrollViewDelegate
 
     // Scroll handling
     private var initialScrollOffset: CGPoint = .zero
-    private var initialScrollFrame: CGRect = .zero
     private var stopScrollDeceleration: Bool = false
     private var scrollBouncable = false
     private var scrollIndictorVisible = false
 
-    private var isScrollLocked: Bool = false
-
     // MARK: - Interface
 
     init(_ vc: FloatingPanelController, layout: FloatingPanelLayout, behavior: FloatingPanelBehavior) {
@@ -99,6 +92,11 @@ class FloatingPanel: NSObject, UIGestureRecognizerDelegate, UIScrollViewDelegate
     }
 
     private func move(from: FloatingPanelPosition, to: FloatingPanelPosition, animated: Bool, completion: (() -> Void)? = nil) {
+        assert(layoutAdapter.isValid(to), "Can't move to '\(to)' position because it's not valid in the layout")
+        guard let vc = viewcontroller else {
+            completion?()
+            return
+        }
         if state != layoutAdapter.topMostState {
             lockScrollView()
         }
@@ -108,11 +106,11 @@ class FloatingPanel: NSObject, UIGestureRecognizerDelegate, UIScrollViewDelegate
             let animator: UIViewPropertyAnimator
             switch (from, to) {
             case (.hidden, let to):
-                animator = behavior.addAnimator(self.viewcontroller, to: to)
+                animator = behavior.addAnimator(vc, to: to)
             case (let from, .hidden):
-                animator = behavior.removeAnimator(self.viewcontroller, from: from)
+                animator = behavior.removeAnimator(vc, from: from)
             case (let from, let to):
-                animator = behavior.moveAnimator(self.viewcontroller, from: from, to: to)
+                animator = behavior.moveAnimator(vc, from: from, to: to)
             }
 
             animator.addAnimations { [weak self] in
@@ -124,7 +122,11 @@ class FloatingPanel: NSObject, UIGestureRecognizerDelegate, UIScrollViewDelegate
             animator.addCompletion { [weak self] _ in
                 guard let `self` = self else { return }
                 self.animator = nil
-                self.unlockScrollView()
+                if self.state == self.layoutAdapter.topMostState {
+                    self.unlockScrollView()
+                } else {
+                    self.lockScrollView()
+                }
                 completion?()
             }
             self.animator = animator
@@ -132,7 +134,11 @@ class FloatingPanel: NSObject, UIGestureRecognizerDelegate, UIScrollViewDelegate
         } else {
             self.state = to
             self.updateLayout(to: to)
-            self.unlockScrollView()
+            if self.state == self.layoutAdapter.topMostState {
+                self.unlockScrollView()
+            } else {
+                self.lockScrollView()
+            }
             completion?()
         }
     }
@@ -143,11 +149,15 @@ class FloatingPanel: NSObject, UIGestureRecognizerDelegate, UIScrollViewDelegate
         self.layoutAdapter.activateLayout(of: target)
     }
 
-    private func getBackdropAlpha(with translation: CGPoint) -> CGFloat {
-        let currentY = surfaceView.frame.minY
+    func getBackdropAlpha(at currentY: CGFloat, with translation: CGPoint) -> CGFloat {
+        let forwardY = (translation.y >= 0)
+        let segment = layoutAdapter.segument(at: currentY, forward: forwardY)
+        let lowerPos = segment.lower ?? layoutAdapter.topMostState
+        let upperPos = segment.upper ?? layoutAdapter.bottomMostState
+
+        let pre = forwardY ? lowerPos : upperPos
+        let next = forwardY ? upperPos : lowerPos
 
-        let next = directionalPosition(at: currentY, with: translation)
-        let pre = redirectionalPosition(at: currentY, with: translation)
         let nextY = layoutAdapter.positionY(for: next)
         let preY = layoutAdapter.positionY(for: pre)
 
@@ -169,7 +179,8 @@ class FloatingPanel: NSObject, UIGestureRecognizerDelegate, UIScrollViewDelegate
 
         /* log.debug("shouldRecognizeSimultaneouslyWith", otherGestureRecognizer) */
 
-        if viewcontroller.delegate?.floatingPanel(viewcontroller, shouldRecognizeSimultaneouslyWith: otherGestureRecognizer) ?? false {
+        if let vc = viewcontroller,
+            vc.delegate?.floatingPanel(vc, shouldRecognizeSimultaneouslyWith: otherGestureRecognizer) ?? false {
             return true
         }
 
@@ -216,11 +227,11 @@ class FloatingPanel: NSObject, UIGestureRecognizerDelegate, UIScrollViewDelegate
             }
         }
 
-        if viewcontroller.delegate?.floatingPanel(viewcontroller, shouldRecognizeSimultaneouslyWith: otherGestureRecognizer) ?? false {
+        if let vc = viewcontroller,
+            vc.delegate?.floatingPanel(vc, shouldRecognizeSimultaneouslyWith: otherGestureRecognizer) ?? false {
             return false
         }
 
-
         switch otherGestureRecognizer {
         case is UIPanGestureRecognizer,
              is UISwipeGestureRecognizer,
@@ -253,14 +264,16 @@ class FloatingPanel: NSObject, UIGestureRecognizerDelegate, UIScrollViewDelegate
 
             let location = panGesture.location(in: surfaceView)
 
-            let belowTop = surfaceView.frame.minY > layoutAdapter.topY
+            let belowTop = surfaceView.presentationFrame.minY > layoutAdapter.topY
+            let offset = scrollView.contentOffset.y - scrollView.contentOffsetZero.y
 
             log.debug("scroll gesture(\(state):\(panGesture.state)) --",
                 "belowTop = \(belowTop),",
                 "interactionInProgress = \(interactionInProgress),",
-                "scroll offset = \(scrollView.contentOffset.y),",
+                "scroll offset = \(offset),",
                 "location = \(location.y), velocity = \(velocity.y)")
 
+
             if belowTop {
                 // Scroll offset pinning
                 if state == layoutAdapter.topMostState {
@@ -271,33 +284,49 @@ class FloatingPanel: NSObject, UIGestureRecognizerDelegate, UIScrollViewDelegate
                         if grabberAreaFrame.contains(location) {
                             // Preserve the current content offset in moving from full.
                             scrollView.setContentOffset(initialScrollOffset, animated: false)
-                        } else {
-                            let offset = scrollView.contentOffset.y - scrollView.contentOffsetZero.y
-                            if offset < 0 {
-                                fitToBounds(scrollView: scrollView)
-                                let translation = panGesture.translation(in: panGestureRecognizer.view!.superview)
-                                startInteraction(with: translation, at: location)
-                            }
                         }
                     }
                 } else {
                     scrollView.setContentOffset(initialScrollOffset, animated: false)
                 }
 
-                // Always hide a scroll indicator at the non-top.
+                // Hide a scroll indicator at the non-top in dragging.
                 if interactionInProgress {
                     lockScrollView()
+                } else {
+                    if state == layoutAdapter.topMostState, self.animator == nil,
+                        offset > 0, velocity.y < 0 {
+                        unlockScrollView()
+                    }
                 }
             } else {
-                // Always show a scroll indicator at the top.
                 if interactionInProgress {
-                    unlockScrollView()
+                    // Show a scroll indicator at the top in dragging.
+                    if offset >= 0, velocity.y <= 0 {
+                        unlockScrollView()
+                    } else {
+                        if state == layoutAdapter.topMostState {
+                            // Adjust a small gap of the scroll offset just after swiping down starts in the grabber area.
+                            if grabberAreaFrame.contains(location), grabberAreaFrame.contains(initialLocation) {
+                                scrollView.setContentOffset(initialScrollOffset, animated: false)
+                            }
+                        }
+                    }
                 } else {
-                    let offset = scrollView.contentOffset.y - scrollView.contentOffsetZero.y
-                    if state == layoutAdapter.topMostState, offset < 0, velocity.y > 0 {
-                        fitToBounds(scrollView: scrollView)
-                        let translation = panGesture.translation(in: panGestureRecognizer.view!.superview)
-                        startInteraction(with: translation, at: location)
+                    if state == layoutAdapter.topMostState {
+                        // Hide a scroll indicator just before starting an interaction by swiping a panel down.
+                        if offset < 0, velocity.y > 0 {
+                            lockScrollView()
+                        }
+                        // Show a scroll indicator when an animation is interrupted at the top and content is scrolled up
+                        if offset > 0, velocity.y < 0 {
+                            unlockScrollView()
+                        }
+
+                        // Adjust a small gap of the scroll offset just before swiping down starts in the grabber area,
+                        if grabberAreaFrame.contains(location), grabberAreaFrame.contains(initialLocation) {
+                            scrollView.setContentOffset(initialScrollOffset, animated: false)
+                        }
                     }
                 }
             }
@@ -309,21 +338,25 @@ class FloatingPanel: NSObject, UIGestureRecognizerDelegate, UIScrollViewDelegate
                 "translation =  \(translation.y), location = \(location.y), velocity = \(velocity.y)")
 
             if let animator = self.animator {
+                guard surfaceView.presentationFrame.minY >= layoutAdapter.topMaxY else { return }
                 log.debug("panel animation interrupted!!!")
                 if animator.isInterruptible {
                     animator.stopAnimation(false)
+                    // A user can stop a panel at the nearest Y of a target position so this fine-tunes
+                    // the a small gap between the presentation layer frame and model layer frame
+                    // to unlock scroll view properly at finishAnimation(at:)
+                    if abs(surfaceView.frame.minY - layoutAdapter.topY) <= 1.0 {
+                        surfaceView.frame.origin.y = layoutAdapter.topY
+                    }
                     animator.finishAnimation(at: .current)
-                }
-                self.animator = nil
-
-                // A user can stop a panel at the nearest Y of a target position
-                if abs(surfaceView.frame.minY - layoutAdapter.topY) < 1.0 {
-                    surfaceView.frame.origin.y = layoutAdapter.topY
+                } else {
+                    self.animator = nil
                 }
             }
 
             if interactionInProgress == false,
-                viewcontroller.delegate?.floatingPanelShouldBeginDragging(viewcontroller) == false {
+                let vc = viewcontroller,
+                vc.delegate?.floatingPanelShouldBeginDragging(vc) == false {
                 return
             }
 
@@ -410,33 +443,36 @@ class FloatingPanel: NSObject, UIGestureRecognizerDelegate, UIScrollViewDelegate
         // So here just preserve the current state if needed.
         log.debug("panningBegan -- location = \(location.y)")
         initialLocation = location
+
+        guard let scrollView = scrollView else { return }
         if state == layoutAdapter.topMostState {
-            if let scrollView = scrollView {
-                initialScrollFrame = scrollView.frame
-            }
-        } else {
-            if let scrollView = scrollView {
+            if grabberAreaFrame.contains(location) {
                 initialScrollOffset = scrollView.contentOffset
             }
+        } else {
+            initialScrollOffset = scrollView.contentOffset
         }
     }
 
     private func panningChange(with translation: CGPoint) {
         log.debug("panningChange -- translation = \(translation.y)")
-        let pre = surfaceView.frame.minY
+        let preY = surfaceView.frame.minY
         let dy = translation.y - initialTranslationY
 
         layoutAdapter.updateInteractiveTopConstraint(diff: dy,
                                                      allowsTopBuffer: allowsTopBuffer(for: dy),
                                                      with: behavior)
 
-        backdropView.alpha = getBackdropAlpha(with: translation)
+        let currentY = surfaceView.frame.minY
+        backdropView.alpha = getBackdropAlpha(at: currentY, with: translation)
         preserveContentVCLayoutIfNeeded()
 
-        let didMove = (pre != surfaceView.frame.minY)
+        let didMove = (preY != currentY)
         guard didMove else { return }
 
-        viewcontroller.delegate?.floatingPanelDidMove(viewcontroller)
+        if let vc = viewcontroller {
+            vc.delegate?.floatingPanelDidMove(vc)
+        }
     }
 
     private func allowsTopBuffer(for translationY: CGFloat) -> Bool {
@@ -451,20 +487,25 @@ class FloatingPanel: NSObject, UIGestureRecognizerDelegate, UIScrollViewDelegate
     }
 
     private var disabledBottomAutoLayout = false
+    private var disabledAutoLayoutItems: Set<NSLayoutConstraint> = []
     // Prevent stretching a view having a constraint to SafeArea.bottom in an overflow
     // from the full position because SafeArea is global in a screen.
     private func preserveContentVCLayoutIfNeeded() {
+        guard let vc = viewcontroller else { return }
         // Must include topY
         if (surfaceView.frame.minY <= layoutAdapter.topY) {
             if !disabledBottomAutoLayout {
-                viewcontroller.contentViewController?.view?.constraints.forEach({ (const) in
-                    switch viewcontroller.contentViewController?.layoutGuide.bottomAnchor {
+                disabledAutoLayoutItems.removeAll()
+                vc.contentViewController?.view?.constraints.forEach({ (const) in
+                    switch vc.contentViewController?.layoutGuide.bottomAnchor {
                     case const.firstAnchor:
                         (const.secondItem as? UIView)?.disableAutoLayout()
                         const.isActive = false
+                        disabledAutoLayoutItems.insert(const)
                     case const.secondAnchor:
                         (const.firstItem as? UIView)?.disableAutoLayout()
                         const.isActive = false
+                        disabledAutoLayoutItems.insert(const)
                     default:
                         break
                     }
@@ -473,8 +514,8 @@ class FloatingPanel: NSObject, UIGestureRecognizerDelegate, UIScrollViewDelegate
             disabledBottomAutoLayout = true
         } else {
             if disabledBottomAutoLayout {
-                viewcontroller.contentViewController?.view?.constraints.forEach({ (const) in
-                    switch viewcontroller.contentViewController?.layoutGuide.bottomAnchor {
+                disabledAutoLayoutItems.forEach({ (const) in
+                    switch vc.contentViewController?.layoutGuide.bottomAnchor {
                     case const.firstAnchor:
                         (const.secondItem as? UIView)?.enableAutoLayout()
                         const.isActive = true
@@ -485,6 +526,7 @@ class FloatingPanel: NSObject, UIGestureRecognizerDelegate, UIScrollViewDelegate
                         break
                     }
                 })
+                disabledAutoLayoutItems.removeAll()
             }
             disabledBottomAutoLayout = false
         }
@@ -506,30 +548,37 @@ class FloatingPanel: NSObject, UIGestureRecognizerDelegate, UIScrollViewDelegate
             }
         }
 
-        let targetPosition = self.targetPosition(with: velocity)
+        let currentY = surfaceView.frame.minY
+        let targetPosition = self.targetPosition(from: currentY, with: velocity)
         let distance = self.distance(to: targetPosition)
 
         endInteraction(for: targetPosition)
 
         if isRemovalInteractionEnabled, isBottomState {
-            let velocityVector = (distance != 0) ? CGVector(dx: 0,
-                                                            dy: min(abs(velocity.y)/distance, behavior.removalVelocity)) : .zero
-
-            if shouldStartRemovalAnimation(with: 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, completion: { [weak self] in
-                        guard let `self` = self else { return }
-                        self.viewcontroller.delegate?.floatingPanelDidEndRemove(self.viewcontroller)
-                    })
+            let velocityVector = (distance != 0) ? CGVector(dx: 0, dy: min(velocity.y/distance, behavior.removalVelocity)) : .zero
+            // `velocityVector` will be replaced by just a velocity(not vector) when FloatingPanelRemovalInteraction will be added.
+            if shouldStartRemovalAnimation(with: velocityVector), let vc = viewcontroller {
+                vc.delegate?.floatingPanelDidEndDraggingToRemove(vc, withVelocity: velocity)
+                let animationVector = CGVector(dx: abs(velocityVector.dx), dy: abs(velocityVector.dy))
+                startRemovalAnimation(vc, with: animationVector) { [weak self] in
+                    self?.finishRemovalAnimation()
                 }
                 return
             }
         }
 
-        viewcontroller.delegate?.floatingPanelDidEndDragging(viewcontroller, withVelocity: velocity, targetPosition: targetPosition)
+        if let vc = viewcontroller {
+            vc.delegate?.floatingPanelDidEndDragging(vc, withVelocity: velocity, targetPosition: targetPosition)
+        }
+
+        if scrollView != nil, !stopScrollDeceleration,
+            surfaceView.frame.minY == layoutAdapter.topY,
+            targetPosition == layoutAdapter.topMostState {
+            self.state = targetPosition
+            self.updateLayout(to: targetPosition)
+            self.unlockScrollView()
+            return
+        }
 
         // Workaround: Disable a tracking scroll to prevent bouncing a scroll content in a panel animating
         let isScrollEnabled = scrollView?.isScrollEnabled
@@ -549,12 +598,12 @@ class FloatingPanel: NSObject, UIGestureRecognizerDelegate, UIScrollViewDelegate
     private func shouldStartRemovalAnimation(with velocityVector: CGVector) -> Bool {
         let posY = layoutAdapter.positionY(for: state)
         let currentY = surfaceView.frame.minY
-        let bottomMaxY = layoutAdapter.bottomMaxY
+        let hiddenY = layoutAdapter.positionY(for: .hidden)
         let vth = behavior.removalVelocity
         let pth = max(min(behavior.removalProgress, 1.0), 0.0)
 
         let num = (currentY - posY)
-        let den = (bottomMaxY - posY)
+        let den = (hiddenY - posY)
 
         guard num >= 0, den != 0, (num / den >= pth || velocityVector.dy == vth)
         else { return false }
@@ -562,8 +611,8 @@ class FloatingPanel: NSObject, UIGestureRecognizerDelegate, UIScrollViewDelegate
         return true
     }
 
-    private func startRemovalAnimation(with velocityVector: CGVector, completion: (() -> Void)?) {
-        let animator = self.behavior.removalInteractionAnimator(self.viewcontroller, with: velocityVector)
+    private func startRemovalAnimation(_ vc: FloatingPanelController, with velocityVector: CGVector, completion: (() -> Void)?) {
+        let animator = behavior.removalInteractionAnimator(vc, with: velocityVector)
 
         animator.addAnimations { [weak self] in
             self?.updateLayout(to: .hidden)
@@ -576,17 +625,27 @@ class FloatingPanel: NSObject, UIGestureRecognizerDelegate, UIScrollViewDelegate
         animator.startAnimation()
     }
 
+    private func finishRemovalAnimation() {
+        viewcontroller?.dismiss(animated: false) { [weak self] in
+            guard let vc = self?.viewcontroller else { return }
+            vc.delegate?.floatingPanelDidEndRemove(vc)
+        }
+    }
+
     private func startInteraction(with translation: CGPoint, at location: CGPoint) {
         /* Don't lock a scroll view to show a scroll indicator after hitting the top */
         log.debug("startInteraction  -- translation = \(translation.y), location = \(location.y)")
         guard interactionInProgress == false else { return }
 
+        var offset: CGPoint = .zero
+
         initialFrame = surfaceView.frame
         if state == layoutAdapter.topMostState, let scrollView = scrollView {
             if grabberAreaFrame.contains(location) {
                 initialScrollOffset = scrollView.contentOffset
             } else {
-                settle(scrollView: scrollView)
+                // Fit the surface bounds to a scroll offset content by startInteraction(at:offset:)
+                offset = CGPoint(x: -scrollView.contentOffset.x, y: -scrollView.contentOffset.y)
                 initialScrollOffset = scrollView.contentOffsetZero
             }
             log.debug("initial scroll offset --", initialScrollOffset)
@@ -594,11 +653,15 @@ class FloatingPanel: NSObject, UIGestureRecognizerDelegate, UIScrollViewDelegate
 
         initialTranslationY = translation.y
 
-        viewcontroller.delegate?.floatingPanelWillBeginDragging(viewcontroller)
+        if let vc = viewcontroller {
+            vc.delegate?.floatingPanelWillBeginDragging(vc)
+        }
 
-        layoutAdapter.startInteraction(at: state)
+        layoutAdapter.startInteraction(at: state, offset: offset)
 
         interactionInProgress = true
+
+        lockScrollView()
     }
 
     private func endInteraction(for targetPosition: FloatingPanelPosition) {
@@ -611,7 +674,7 @@ class FloatingPanel: NSObject, UIGestureRecognizerDelegate, UIScrollViewDelegate
         interactionInProgress = false
 
         // Prevent to keep a scroll view indicator visible at the half/tip position
-        if state != layoutAdapter.topMostState {
+        if targetPosition != layoutAdapter.topMostState {
             lockScrollView()
         }
 
@@ -626,19 +689,23 @@ class FloatingPanel: NSObject, UIGestureRecognizerDelegate, UIScrollViewDelegate
 
     private func startAnimation(to targetPosition: FloatingPanelPosition, at distance: CGFloat, with velocity: CGPoint) {
         log.debug("startAnimation to \(targetPosition) -- distance = \(distance), velocity = \(velocity.y)")
+        guard let vc = viewcontroller else { return }
 
         isDecelerating = true
-        viewcontroller.delegate?.floatingPanelWillBeginDecelerating(viewcontroller)
 
-        let velocityVector = (distance != 0) ? CGVector(dx: 0, dy: min(abs(velocity.y)/distance, 30.0)) : .zero
-        let animator = behavior.interactionAnimator(self.viewcontroller, to: targetPosition, with: velocityVector)
+        vc.delegate?.floatingPanelWillBeginDecelerating(vc)
+
+        let velocityVector = (distance != 0) ? CGVector(dx: 0, dy: abs(velocity.y)/distance) : .zero
+        let animator = behavior.interactionAnimator(vc, to: targetPosition, with: velocityVector)
         animator.addAnimations { [weak self] in
             guard let `self` = self else { return }
             self.state = targetPosition
             self.updateLayout(to: targetPosition)
         }
         animator.addCompletion { [weak self] pos in
-            guard let `self` = self else { return }
+            // Prevent calling `finishAnimation(at:)` by the old animator whose `isInterruptive` is false
+            // when a new animator has been started after the old one is interrupted.
+            guard let `self` = self, self.animator == animator else { return }
             self.finishAnimation(at: targetPosition)
         }
         self.animator = animator
@@ -651,66 +718,26 @@ class FloatingPanel: NSObject, UIGestureRecognizerDelegate, UIScrollViewDelegate
         self.isDecelerating = false
         self.animator = nil
 
-        self.viewcontroller.delegate?.floatingPanelDidEndDecelerating(self.viewcontroller)
+        if let vc = viewcontroller {
+            vc.delegate?.floatingPanelDidEndDecelerating(vc)
+        }
 
         if let scrollView = scrollView {
             log.debug("finishAnimation -- scroll offset = \(scrollView.contentOffset)")
         }
 
         stopScrollDeceleration = false
-        // Don't unlock scroll view in animating view when presentation layer != model layer
-        if state == layoutAdapter.topMostState {
+
+        log.debug("finishAnimation -- state = \(state) surface.minY = \(surfaceView.presentationFrame.minY) topY = \(layoutAdapter.topY)")
+        if state == layoutAdapter.topMostState, abs(surfaceView.presentationFrame.minY - layoutAdapter.topY) <= 1.0 {
             unlockScrollView()
         }
     }
 
     private func distance(to targetPosition: FloatingPanelPosition) -> CGFloat {
-        let topY = layoutAdapter.topY
-        let middleY = layoutAdapter.middleY
-        let bottomY = layoutAdapter.bottomY
         let currentY = surfaceView.frame.minY
-
-        switch targetPosition {
-        case .full:
-            return CGFloat(abs(currentY - topY))
-        case .half:
-            return CGFloat(abs(currentY - middleY))
-        case .tip:
-            return CGFloat(abs(currentY - bottomY))
-        case .hidden:
-            fatalError("Now .hidden must not be used for a user interaction")
-        }
-    }
-
-    private func directionalPosition(at currentY: CGFloat, with translation: CGPoint) -> FloatingPanelPosition {
-        return getPosition(at: currentY, with: translation, directional: true)
-    }
-
-    private func redirectionalPosition(at currentY: CGFloat, with translation: CGPoint) -> FloatingPanelPosition {
-        return getPosition(at: currentY, with: translation, directional: false)
-    }
-
-    private func getPosition(at currentY: CGFloat, with translation: CGPoint, directional: Bool) -> FloatingPanelPosition {
-        let supportedPositions: Set = layoutAdapter.supportedPositions
-        if supportedPositions.count == 1 {
-            return state
-        }
-        let isForwardYAxis = (translation.y >= 0)
-        switch supportedPositions {
-        case [.full, .half]:
-            return (isForwardYAxis == directional) ? .half : .full
-        case [.half, .tip]:
-            return (isForwardYAxis == directional) ? .tip : .half
-        case [.full, .tip]:
-            return (isForwardYAxis == directional) ? .tip : .full
-        default:
-            let middleY = layoutAdapter.middleY
-            if currentY > middleY {
-                return (isForwardYAxis == directional) ? .tip : .half
-            } else {
-                return (isForwardYAxis == directional) ? .half : .full
-            }
-        }
+        let targetY = layoutAdapter.positionY(for: targetPosition)
+        return CGFloat(abs(currentY - targetY))
     }
 
     // Distance travelled after decelerating to zero velocity at a constant rate.
@@ -719,148 +746,57 @@ class FloatingPanel: NSObject, UIGestureRecognizerDelegate, UIScrollViewDelegate
         return (initialVelocity / 1000.0) * decelerationRate / (1.0 - decelerationRate)
     }
 
-    private func targetPosition(with velocity: CGPoint) -> (FloatingPanelPosition) {
-        let currentY = surfaceView.frame.minY
+    func targetPosition(from currentY: CGFloat, with velocity: CGPoint) -> (FloatingPanelPosition) {
+        guard let vc = viewcontroller else { return state }
         let supportedPositions = layoutAdapter.supportedPositions
 
-        if supportedPositions.count == 1 {
+        guard supportedPositions.count > 1 else {
             return state
         }
 
-        switch supportedPositions {
-        case [.full, .half]:
-            return targetPosition(from: [.full, .half], at: currentY, velocity: velocity)
-        case [.half, .tip]:
-            return targetPosition(from: [.half, .tip], at: currentY, velocity: velocity)
-        case [.full, .tip]:
-            return targetPosition(from: [.full, .tip], at: currentY, velocity: velocity)
-        default:
-            /*
-             [topY|full]---[th1]---[middleY|half]---[th2]---[bottomY|tip]
-             */
-            let topY = layoutAdapter.topY
-            let middleY = layoutAdapter.middleY
-            let bottomY = layoutAdapter.bottomY
+        let sortedPositions = Array(supportedPositions).sorted(by: { $0.rawValue < $1.rawValue })
 
-            let nextState: FloatingPanelPosition
-            let forwardYDirection: Bool
+        // Projection
+        let decelerationRate = behavior.momentumProjectionRate(vc)
+        let baseY = abs(layoutAdapter.positionY(for: layoutAdapter.bottomMostState) - layoutAdapter.positionY(for: layoutAdapter.topMostState))
+        let vecY = velocity.y / baseY
+        var pY = project(initialVelocity: vecY, decelerationRate: decelerationRate) * baseY + currentY
 
-            /*
-             full <-> half <-> tip
-             */
-            switch state {
-            case .full:
-                nextState = .half
-                forwardYDirection = true
-            case .half:
-                nextState = (currentY > middleY) ? .tip : .full
-                forwardYDirection = (currentY > middleY)
-            case .tip:
-                nextState = .half
-                forwardYDirection = false
-            case .hidden:
-                fatalError("Now .hidden must not be used for a user interaction")
+        let forwardY = velocity.y == 0 ? (currentY - layoutAdapter.positionY(for: state) > 0) : velocity.y > 0
+
+        let segment = layoutAdapter.segument(at: pY, forward: forwardY)
+
+        var fromPos: FloatingPanelPosition
+        var toPos: FloatingPanelPosition
+
+        let (lowerPos, upperPos) = (segment.lower ?? sortedPositions.first!, segment.upper ?? sortedPositions.last!)
+        (fromPos, toPos) = forwardY ? (lowerPos, upperPos) : (upperPos, lowerPos)
+
+        if behavior.shouldProjectMomentum(vc, for: toPos) == false {
+            let segment = layoutAdapter.segument(at: currentY, forward: forwardY)
+            var (lowerPos, upperPos) = (segment.lower ?? sortedPositions.first!, segment.upper ?? sortedPositions.last!)
+            // Equate the segment out of {top,bottom} most state to the {top,bottom} most segment
+            if lowerPos == upperPos {
+                if forwardY {
+                    upperPos = lowerPos.next(in: sortedPositions)
+                } else {
+                    lowerPos = upperPos.pre(in: sortedPositions)
+                }
             }
-
-            let redirectionalProgress = max(min(behavior.redirectionalProgress(viewcontroller, from: state, to: nextState), 1.0), 0.0)
-
-            let th1: CGFloat
-            let th2: CGFloat
-
-            if forwardYDirection {
-                th1 = topY + (middleY - topY) * redirectionalProgress
-                th2 = middleY + (bottomY - middleY) * redirectionalProgress
+            (fromPos, toPos) = forwardY ? (lowerPos, upperPos) : (upperPos, lowerPos)
+            // Block a projection to a segment over the next from the current segment
+            // (= Trim pY with the current segment)
+            if forwardY {
+                pY = max(min(pY, layoutAdapter.positionY(for: toPos.next(in: sortedPositions))), layoutAdapter.positionY(for: fromPos))
             } else {
-                th1 = middleY - (middleY - topY) * redirectionalProgress
-                th2 = bottomY - (bottomY - middleY) * redirectionalProgress
-            }
-
-            let decelerationRate = behavior.momentumProjectionRate(viewcontroller)
-
-            let baseY = abs(bottomY - topY)
-            let vecY = velocity.y / baseY
-            let pY = project(initialVelocity: vecY, decelerationRate: decelerationRate) * baseY + currentY
-
-            switch currentY {
-            case ..<th1:
-                switch pY {
-                case bottomY...:
-                    return behavior.shouldProjectMomentum(viewcontroller, for: .tip) ? .tip : .half
-                case middleY...:
-                    return .half
-                case topY...:
-                    return .full
-                default:
-                    return .full
-                }
-            case ...middleY:
-                switch pY {
-                case bottomY...:
-                    return behavior.shouldProjectMomentum(viewcontroller, for: .tip) ? .tip : .half
-                case middleY...:
-                    return .half
-                case topY...:
-                    return .half
-                default:
-                    return .full
-                }
-            case ..<th2:
-                switch pY {
-                case bottomY...:
-                    return .tip
-                case middleY...:
-                    return .half
-                case topY...:
-                    return .half
-                default:
-                    return behavior.shouldProjectMomentum(viewcontroller, for: .full) ? .full : .half
-                }
-            default:
-                switch pY {
-                case bottomY...:
-                    return .tip
-                case middleY...:
-                    return .tip
-                case topY...:
-                    return .half
-                default:
-                    return behavior.shouldProjectMomentum(viewcontroller, for: .full) ? .full : .half
-                }
+                pY = max(min(pY, layoutAdapter.positionY(for: fromPos)), layoutAdapter.positionY(for: toPos.pre(in: sortedPositions)))
             }
         }
-    }
 
-    private func targetPosition(from positions: [FloatingPanelPosition], at currentY: CGFloat, velocity: CGPoint) -> FloatingPanelPosition {
-        assert(positions.count == 2)
-
-        let top = positions[0]
-        let bottom = positions[1]
-
-        let topY = layoutAdapter.positionY(for: top)
-        let bottomY = layoutAdapter.positionY(for: bottom)
-
-        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
-
-        let decelerationRate = behavior.momentumProjectionRate(viewcontroller)
-        let pY = project(initialVelocity: velocity.y, decelerationRate: decelerationRate) + currentY
-
-        switch currentY {
-        case ..<th:
-            if pY >= bottomY {
-                return bottom
-            } else {
-                return top
-            }
-        default:
-            if pY <= topY {
-                return top
-            } else {
-                return bottom
-            }
-        }
+        // Redirection
+        let redirectionalProgress = max(min(behavior.redirectionalProgress(vc, from: fromPos, to: toPos), 1.0), 0.0)
+        let progress = abs(pY - layoutAdapter.positionY(for: fromPos)) / abs(layoutAdapter.positionY(for: fromPos) - layoutAdapter.positionY(for: toPos))
+        return progress > redirectionalProgress ? toPos : fromPos
     }
 
     // MARK: - ScrollView handling
@@ -868,11 +804,11 @@ class FloatingPanel: NSObject, UIGestureRecognizerDelegate, UIScrollViewDelegate
     private func lockScrollView() {
         guard let scrollView = scrollView else { return }
 
-        if isScrollLocked {
+        if scrollView.isLocked {
             log.debug("Already scroll locked.")
             return
         }
-        isScrollLocked = true
+        log.debug("lock scroll view")
 
         scrollBouncable = scrollView.bounces
         scrollIndictorVisible = scrollView.showsVerticalScrollIndicator
@@ -883,39 +819,14 @@ class FloatingPanel: NSObject, UIGestureRecognizerDelegate, UIScrollViewDelegate
     }
 
     private func unlockScrollView() {
-        guard let scrollView = scrollView, isScrollLocked else { return }
-
-        isScrollLocked = false
+        guard let scrollView = scrollView, scrollView.isLocked else { return }
+        log.debug("unlock scroll view")
 
         scrollView.isDirectionalLockEnabled = false
         scrollView.bounces = scrollBouncable
         scrollView.showsVerticalScrollIndicator = scrollIndictorVisible
     }
 
-    private func fitToBounds(scrollView: UIScrollView) {
-        log.debug("fit scroll view to bounds -- scroll offset =", scrollView.contentOffset.y)
-
-        surfaceView.frame.origin.y = layoutAdapter.topY - scrollView.contentOffset.y
-        scrollView.transform = CGAffineTransform.identity.translatedBy(x: 0.0,
-                                                                       y: scrollView.contentOffset.y)
-        scrollView.scrollIndicatorInsets = UIEdgeInsets(top: -scrollView.contentOffset.y,
-                                                        left: 0.0,
-                                                        bottom: 0.0,
-                                                        right: 0.0)
-    }
-
-    private func settle(scrollView: UIScrollView) {
-        log.debug("settle scroll view")
-        let frame = surfaceView.layer.presentation()?.frame ?? surfaceView.frame
-        surfaceView.transform = .identity
-        surfaceView.frame = frame
-        scrollView.transform = .identity
-        scrollView.frame = initialScrollFrame
-        scrollView.contentOffset = scrollView.contentOffsetZero
-        scrollView.scrollIndicatorInsets = .zero
-    }
-
-
     private func stopScrollingWithDeceleration(at contentOffset: CGPoint) {
         // Must use setContentOffset(_:animated) to force-stop deceleration
         scrollView?.setContentOffset(contentOffset, animated: false)

Framework/Sources/FloatingPanelBehavior.swift

@@ -23,6 +23,11 @@ public protocol FloatingPanelBehavior {
     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.
+    ///
+    /// - Attention:
+    /// By default, it returns a non-interruptible animator to prevent a propagation of the animation to a content view.
+    /// However returning an interruptible animator is working well depending on a content view and it can be better
+    /// than using a non-interruptible one.
     func interactionAnimator(_ fpc: FloatingPanelController, to targetPosition: FloatingPanelPosition, with velocity: CGVector) -> UIViewPropertyAnimator
 
     /// Returns a UIViewPropertyAnimator object to add a floating panel to a position.
@@ -67,14 +72,7 @@ public protocol FloatingPanelBehavior {
 
 public extension FloatingPanelBehavior {
     func shouldProjectMomentum(_ fpc: FloatingPanelController, for proposedTargetPosition: FloatingPanelPosition) -> Bool {
-        switch (fpc.position, proposedTargetPosition) {
-        case (.full, .tip):
-            return false
-        case (.tip,  .full):
-            return false
-        default:
-            return true
-        }
+        return false
     }
 
     func momentumProjectionRate(_ fpc: FloatingPanelController) -> CGFloat {
@@ -134,7 +132,7 @@ public class FloatingPanelDefaultBehavior: FloatingPanelBehavior {
     public func interactionAnimator(_ fpc: FloatingPanelController, to targetPosition: FloatingPanelPosition, with velocity: CGVector) -> UIViewPropertyAnimator {
         let timing = timeingCurve(with: velocity)
         let animator = UIViewPropertyAnimator(duration: 0, timingParameters: timing)
-        animator.isInterruptible = false
+        animator.isInterruptible = false // Prevent a propagation of the animation(spring etc) to a content view
         return animator
     }
 

Framework/Sources/FloatingPanelController.swift

@@ -68,6 +68,40 @@ public enum FloatingPanelPosition: Int {
     case half
     case tip
     case hidden
+
+    static var allCases: [FloatingPanelPosition] {
+        return [.full, .half, .tip, .hidden]
+    }
+
+    func next(in positions: [FloatingPanelPosition]) -> FloatingPanelPosition {
+        #if swift(>=4.2)
+        guard
+            let index = positions.firstIndex(of: self),
+            positions.indices.contains(index + 1)
+            else { return self }
+        #else
+        guard
+            let index = positions.index(of: self),
+            positions.indices.contains(index + 1)
+            else { return self }
+        #endif
+        return positions[index + 1]
+    }
+
+    func pre(in positions: [FloatingPanelPosition]) -> FloatingPanelPosition {
+        #if swift(>=4.2)
+        guard
+            let index = positions.firstIndex(of: self),
+            positions.indices.contains(index - 1)
+            else { return self }
+        #else
+        guard
+            let index = positions.index(of: self),
+            positions.indices.contains(index - 1)
+            else { return self }
+        #endif
+        return positions[index - 1]
+    }
 }
 
 ///
@@ -145,7 +179,7 @@ open class FloatingPanelController: UIViewController, UIScrollViewDelegate, UIGe
     }
     private var _contentViewController: UIViewController?
 
-    private var floatingPanel: FloatingPanel!
+    private(set) var floatingPanel: FloatingPanel!
     private var preSafeAreaInsets: UIEdgeInsets = .zero // Capture the latest one
     private var safeAreaInsetsObservation: NSKeyValueObservation?
     private let modalTransition = FloatingPanelModalTransition()
@@ -196,18 +230,19 @@ open class FloatingPanelController: UIViewController, UIScrollViewDelegate, UIGe
         self.view = view as UIView
     }
 
-    open  override func viewDidLayoutSubviews() {
+    open override func viewDidLayoutSubviews() {
         super.viewDidLayoutSubviews()
         if #available(iOS 11.0, *) {}
         else {
             // Because {top,bottom}LayoutGuide is managed as a view
-            if preSafeAreaInsets != layoutInsets {
+            if preSafeAreaInsets != layoutInsets,
+                floatingPanel.isDecelerating == false {
                 self.update(safeAreaInsets: layoutInsets)
             }
         }
     }
 
-    open  override func viewWillTransition(to size: CGSize, with coordinator: UIViewControllerTransitionCoordinator) {
+    open override func viewWillTransition(to size: CGSize, with coordinator: UIViewControllerTransitionCoordinator) {
         super.viewWillTransition(to: size, with: coordinator)
 
         if view.translatesAutoresizingMaskIntoConstraints {
@@ -216,14 +251,9 @@ open class FloatingPanelController: UIViewController, UIScrollViewDelegate, UIGe
         }
     }
 
-    open  override func willTransition(to newCollection: UITraitCollection, with coordinator: UIViewControllerTransitionCoordinator) {
+    open override func willTransition(to newCollection: UITraitCollection, with coordinator: UIViewControllerTransitionCoordinator) {
         super.willTransition(to: newCollection, with: coordinator)
-
-        // Change layout for a new trait collection
-        reloadLayout(for: newCollection)
-        setUpLayout()
-
-        floatingPanel.behavior = fetchBehavior(for: newCollection)
+        self.prepare(for: newCollection)
     }
 
     open override func viewWillDisappear(_ animated: Bool) {
@@ -231,6 +261,15 @@ open class FloatingPanelController: UIViewController, UIScrollViewDelegate, UIGe
         safeAreaInsetsObservation = nil
     }
 
+    // MARK:- Internals
+    func prepare(for newCollection: UITraitCollection) {
+        guard newCollection.shouldUpdateLayout(from: traitCollection) else { return }
+        // Change a layout & behavior for a new trait collection
+        reloadLayout(for: newCollection)
+        activateLayout()
+        floatingPanel.behavior = fetchBehavior(for: newCollection)
+    }
+
     // MARK:- Privates
 
     private func fetchLayout(for traitCollection: UITraitCollection) -> FloatingPanelLayout {
@@ -248,8 +287,7 @@ open class FloatingPanelController: UIViewController, UIScrollViewDelegate, UIGe
 
     private func update(safeAreaInsets: UIEdgeInsets) {
         guard
-            preSafeAreaInsets != safeAreaInsets,
-            self.floatingPanel.isDecelerating == false
+            preSafeAreaInsets != safeAreaInsets
             else { return }
 
         log.debug("Update safeAreaInsets", safeAreaInsets)
@@ -257,7 +295,7 @@ open class FloatingPanelController: UIViewController, UIScrollViewDelegate, UIGe
         // Prevent an infinite loop on iOS 10: setUpLayout() -> viewDidLayoutSubviews() -> setUpLayout()
         preSafeAreaInsets = safeAreaInsets
 
-        setUpLayout()
+        activateLayout()
 
         switch contentInsetAdjustmentBehavior {
         case .always:
@@ -282,7 +320,7 @@ open class FloatingPanelController: UIViewController, UIScrollViewDelegate, UIGe
         }
     }
 
-    private func setUpLayout() {
+    private func activateLayout() {
         // preserve the current content offset
         let contentOffset = scrollView?.contentOffset
 
@@ -298,7 +336,7 @@ open class FloatingPanelController: UIViewController, UIScrollViewDelegate, UIGe
     public func show(animated: Bool = false, completion: (() -> Void)? = nil) {
         // Must apply the current layout here
         reloadLayout(for: traitCollection)
-        setUpLayout()
+        activateLayout()
 
         if #available(iOS 11.0, *) {
             // Must track the safeAreaInsets of `self.view` to update the layout.
@@ -513,21 +551,12 @@ open class FloatingPanelController: UIViewController, UIScrollViewDelegate, UIGe
     /// animation block.
     public func updateLayout() {
         reloadLayout(for: traitCollection)
-        setUpLayout()
+        activateLayout()
     }
 
     /// Returns the y-coordinate of the point at the origin of the surface view.
     public func originYOfSurface(for pos: FloatingPanelPosition) -> CGFloat {
-        switch pos {
-        case .full:
-            return floatingPanel.layoutAdapter.topY
-        case .half:
-            return floatingPanel.layoutAdapter.middleY
-        case .tip:
-            return floatingPanel.layoutAdapter.bottomY
-        case .hidden:
-            return floatingPanel.layoutAdapter.hiddenY
-        }
+        return floatingPanel.layoutAdapter.positionY(for: pos)
     }
 }
 

Framework/Sources/FloatingPanelLayout.swift

@@ -43,14 +43,16 @@ public protocol FloatingPanelLayout: class {
     /// Returns a set of FloatingPanelPosition objects to tell the applicable
     /// positions of the floating panel controller.
     ///
-    /// By default, it returns all position except for `hidden` position. Because
-    /// it's always supported by `FloatingPanelController` so you don't need to return it.
+    /// By default, it returns full, half and tip positions.
     var supportedPositions: Set<FloatingPanelPosition> { get }
 
     /// Return the interaction buffer to the top from the top position. Default is 6.0.
     var topInteractionBuffer: CGFloat { get }
 
     /// Return the interaction buffer to the bottom from the bottom position. Default is 6.0.
+    ///
+    /// - Important:
+    /// The specified buffer is ignored when `FloatingPanelController.isRemovalInteractionEnabled` is set to true.
     var bottomInteractionBuffer: CGFloat { get }
 
     /// Returns a CGFloat value to determine a Y coordinate of a floating panel for each position(full, half, tip and hidden).
@@ -130,9 +132,13 @@ public class FloatingPanelDefaultLandscapeLayout: FloatingPanelLayout {
     }
 }
 
+struct LayoutSegment {
+    let lower: FloatingPanelPosition?
+    let upper: FloatingPanelPosition?
+}
 
 class FloatingPanelLayoutAdapter {
-    weak var vc: UIViewController!
+    weak var vc: FloatingPanelController!
     private weak var surfaceView: FloatingPanelSurfaceView!
     private weak var backdropView: FloatingPanelBackdropView!
 
@@ -175,70 +181,31 @@ class FloatingPanelLayoutAdapter {
     }
 
     var supportedPositions: Set<FloatingPanelPosition> {
-        var supportedPositions = layout.supportedPositions
-        supportedPositions.remove(.hidden)
-        return supportedPositions
+        return layout.supportedPositions
     }
 
     var topMostState: FloatingPanelPosition {
-        if supportedPositions.contains(.full) {
-            return .full
-        }
-        if supportedPositions.contains(.half) {
-            return .half
-        }
-        return .tip
+        return supportedPositions.sorted(by: { $0.rawValue < $1.rawValue }).first ?? .hidden
+    }
+
+    var bottomMostState: FloatingPanelPosition {
+        return supportedPositions.sorted(by: { $0.rawValue < $1.rawValue }).last ?? .hidden
     }
 
     var topY: CGFloat {
-        if supportedPositions.contains(.full) {
-            switch layout {
-            case is FloatingPanelIntrinsicLayout:
-                return surfaceView.superview!.bounds.height - surfaceView.bounds.height
-            case is FloatingPanelFullScreenLayout:
-                return fullInset
-            default:
-                return (safeAreaInsets.top + fullInset)
-            }
-        } else {
-            return middleY
-        }
-    }
-
-    var middleY: CGFloat {
-        if layout is FloatingPanelFullScreenLayout {
-            return surfaceView.superview!.bounds.height - halfInset
-        } else{
-            return surfaceView.superview!.bounds.height - (safeAreaInsets.bottom + halfInset)
-        }
+        return positionY(for: topMostState)
     }
 
     var bottomY: CGFloat {
-        if supportedPositions.contains(.tip) {
-            if layout is FloatingPanelFullScreenLayout {
-                return surfaceView.superview!.bounds.height - tipInset
-            } else{
-                return surfaceView.superview!.bounds.height - (safeAreaInsets.bottom + tipInset)
-            }
-        } else {
-            return middleY
-        }
-    }
-
-    var hiddenY: CGFloat {
-        return surfaceView.superview!.bounds.height
+        return positionY(for: bottomMostState)
     }
 
     var topMaxY: CGFloat {
-        return layout is FloatingPanelFullScreenLayout ? 0.0 : safeAreaInsets.top
+        return topY - layout.topInteractionBuffer
     }
 
     var bottomMaxY: CGFloat {
-        if layout is FloatingPanelFullScreenLayout{
-            return surfaceView.superview!.bounds.height - hiddenInset
-        } else {
-            return surfaceView.superview!.bounds.height - (safeAreaInsets.bottom + hiddenInset)
-        }
+        return bottomY + layout.bottomInteractionBuffer
     }
 
     var adjustedContentInsets: UIEdgeInsets {
@@ -251,13 +218,30 @@ class FloatingPanelLayoutAdapter {
     func positionY(for pos: FloatingPanelPosition) -> CGFloat {
         switch pos {
         case .full:
-            return topY
+            switch layout {
+            case is FloatingPanelIntrinsicLayout:
+                return surfaceView.superview!.bounds.height - surfaceView.bounds.height
+            case is FloatingPanelFullScreenLayout:
+                return fullInset
+            default:
+                return (safeAreaInsets.top + fullInset)
+            }
         case .half:
-            return middleY
+            switch layout {
+            case is FloatingPanelFullScreenLayout:
+                return surfaceView.superview!.bounds.height - halfInset
+            default:
+                return surfaceView.superview!.bounds.height - (safeAreaInsets.bottom + halfInset)
+            }
         case .tip:
-            return bottomY
+            switch layout {
+            case is FloatingPanelFullScreenLayout:
+                return surfaceView.superview!.bounds.height - tipInset
+            default:
+                return surfaceView.superview!.bounds.height - (safeAreaInsets.bottom + tipInset)
+            }
         case .hidden:
-            return hiddenY
+            return surfaceView.superview!.bounds.height - hiddenInset
         }
     }
 
@@ -291,7 +275,7 @@ class FloatingPanelLayoutAdapter {
                   ", content safe area(bottom) =", safeAreaBottom)
     }
 
-    func prepareLayout(in vc: UIViewController) {
+    func prepareLayout(in vc: FloatingPanelController) {
         self.vc = vc
 
         NSLayoutConstraint.deactivate(fixedConstraints + fullConstraints + halfConstraints + tipConstraints + offConstraints)
@@ -353,18 +337,19 @@ class FloatingPanelLayoutAdapter {
         ]
     }
 
-    func startInteraction(at state: FloatingPanelPosition) {
+    func startInteraction(at state: FloatingPanelPosition, offset: CGPoint = .zero) {
+        guard self.interactiveTopConstraint == nil else { return }
         NSLayoutConstraint.deactivate(fullConstraints + halfConstraints + tipConstraints + offConstraints)
 
         let interactiveTopConstraint: NSLayoutConstraint
         switch layout {
         case is FloatingPanelIntrinsicLayout,
              is FloatingPanelFullScreenLayout:
-            initialConst = surfaceView.frame.minY
+            initialConst = surfaceView.frame.minY + offset.y
             interactiveTopConstraint = surfaceView.topAnchor.constraint(equalTo: vc.view.topAnchor,
                                                                         constant: initialConst)
         default:
-            initialConst = surfaceView.frame.minY - safeAreaInsets.top
+            initialConst = surfaceView.frame.minY - safeAreaInsets.top + offset.y
             interactiveTopConstraint = surfaceView.topAnchor.constraint(equalTo: vc.layoutGuide.topAnchor,
                                                                         constant: initialConst)
         }
@@ -429,13 +414,14 @@ class FloatingPanelLayoutAdapter {
         }()
         let bottomMostConst: CGFloat = {
             var ret: CGFloat = 0.0
+            let _bottomY = vc.isRemovalInteractionEnabled ? positionY(for: .hidden) : bottomY
             switch layout {
             case is FloatingPanelIntrinsicLayout, is FloatingPanelFullScreenLayout:
-                ret = bottomY
+                ret = _bottomY
             default:
-                ret = bottomY - safeAreaInsets.top
+                ret = _bottomY - safeAreaInsets.top
             }
-            return min(ret, bottomMaxY)
+            return min(ret, surfaceView.superview!.bounds.height)
         }()
         let minConst = allowsTopBuffer ? topMostConst - layout.topInteractionBuffer : topMostConst
         let maxConst = bottomMostConst + layout.bottomInteractionBuffer
@@ -481,7 +467,7 @@ class FloatingPanelLayoutAdapter {
         }
         NSLayoutConstraint.activate(fixedConstraints)
 
-        if supportedPositions.union([.hidden]).contains(state) == false {
+        if isValid(state) == false {
             state = layout.initialPosition
         }
 
@@ -498,6 +484,10 @@ class FloatingPanelLayoutAdapter {
         }
     }
 
+    func isValid(_ state: FloatingPanelPosition) -> Bool {
+        return supportedPositions.union([.hidden]).contains(state)
+    }
+
     private func setBackdropAlpha(of target: FloatingPanelPosition) {
         if target == .hidden {
             self.backdropView.alpha = 0.0
@@ -509,7 +499,7 @@ class FloatingPanelLayoutAdapter {
     private func checkLayoutConsistance() {
         // Verify layout configurations
         assert(supportedPositions.count > 0)
-        assert(supportedPositions.union([.hidden]).contains(layout.initialPosition),
+        assert(supportedPositions.contains(layout.initialPosition),
                "Does not include an initial position (\(layout.initialPosition)) in supportedPositions (\(supportedPositions))")
 
         if layout is FloatingPanelIntrinsicLayout {
@@ -528,4 +518,38 @@ class FloatingPanelLayoutAdapter {
             assert(bottomY > topY, "Invalid insets { topY: \(topY), bottomY: \(bottomY) }")
          }*/
     }
+
+    func segument(at posY: CGFloat, forward: Bool) -> LayoutSegment {
+        /// ----------------------->Y
+        /// --> forward                <-- backward
+        /// |-------|===o===|-------|  |-------|-------|===o===|
+        /// |-------|-------x=======|  |-------|=======x-------|
+        /// |-------|-------|===o===|  |-------|===o===|-------|
+        /// pos: o/x, seguement: =
+        let sortedPositions = supportedPositions.sorted(by: { $0.rawValue < $1.rawValue })
+
+        let upperIndex: Int?
+        if forward {
+            #if swift(>=4.2)
+            upperIndex = sortedPositions.firstIndex(where: { posY < positionY(for: $0) })
+            #else
+            upperIndex = sortedPositions.index(where: { posY < positionY(for: $0) })
+            #endif
+        } else {
+            #if swift(>=4.2)
+            upperIndex = sortedPositions.firstIndex(where: { posY <= positionY(for: $0) })
+            #else
+            upperIndex = sortedPositions.index(where: { posY <= positionY(for: $0) })
+            #endif
+        }
+
+        switch upperIndex {
+        case 0:
+            return LayoutSegment(lower: nil, upper: sortedPositions.first)
+        case let upperIndex?:
+            return LayoutSegment(lower: sortedPositions[upperIndex - 1], upper: sortedPositions[upperIndex])
+        default:
+            return LayoutSegment(lower: sortedPositions[sortedPositions.endIndex - 1], upper: nil)
+        }
+    }
 }

Framework/Sources/Info.plist

@@ -15,7 +15,7 @@
 	<key>CFBundlePackageType</key>
 	<string>FMWK</string>
 	<key>CFBundleShortVersionString</key>
-	<string>1.6.0</string>
+	<string>1.6.3</string>
 	<key>CFBundleVersion</key>
 	<string>$(CURRENT_PROJECT_VERSION)</string>
 </dict>

Framework/Sources/UIExtensions.swift

@@ -60,6 +60,10 @@ extension UIView {
             return self
         }
     }
+
+    var presentationFrame: CGRect {
+        return layer.presentation()?.frame ?? frame
+    }
 }
 
 extension UIView {
@@ -107,6 +111,9 @@ extension UIScrollView {
     var contentOffsetZero: CGPoint {
         return CGPoint(x: 0.0, y: 0.0 - contentInset.top)
     }
+    var isLocked: Bool {
+        return !showsVerticalScrollIndicator && !bounces &&  isDirectionalLockEnabled
+    }
 }
 
 extension UISpringTimingParameters {
@@ -124,3 +131,12 @@ extension CGPoint {
                        y: CGFloat.nan)
     }
 }
+
+extension UITraitCollection {
+    func shouldUpdateLayout(from previous: UITraitCollection) -> Bool {
+        return previous.horizontalSizeClass != horizontalSizeClass
+            || previous.verticalSizeClass != verticalSizeClass
+            || previous.preferredContentSizeCategory != preferredContentSizeCategory
+            || previous.layoutDirection != layoutDirection
+    }
+}

Framework/Tests/FloatingPanelControllerTests.swift

@@ -7,9 +7,7 @@ import XCTest
 @testable import FloatingPanel
 
 class FloatingPanelControllerTests: XCTestCase {
-
     override func setUp() {}
-
     override func tearDown() {}
 
     func test_warningRetainCycle() {
@@ -28,24 +26,90 @@ class FloatingPanelControllerTests: XCTestCase {
 
     func test_addPanel() {
         guard let rootVC = UIApplication.shared.keyWindow?.rootViewController else { fatalError() }
-
         let fpc = FloatingPanelController()
         fpc.addPanel(toParent: rootVC)
-
-        waitRunLoop(secs: 1.0)
         XCTAssert(fpc.surfaceView.frame.minY ==  (fpc.view.bounds.height - fpc.layoutInsets.bottom) - fpc.layout.insetFor(position: .half)!)
+        fpc.move(to: .tip, animated: false)
+        XCTAssert(fpc.surfaceView.frame.minY == (fpc.view.bounds.height - fpc.layoutInsets.bottom) - fpc.layout.insetFor(position: .tip)!)
+    }
+
+    @available(iOS 12.0, *)
+    func test_updateLayout_willTransition() {
+        class MyDelegate: FloatingPanelControllerDelegate {
+            func floatingPanel(_ vc: FloatingPanelController, layoutFor newCollection: UITraitCollection) -> FloatingPanelLayout? {
+                if newCollection.userInterfaceStyle == .dark {
+                    XCTFail()
+                }
+                return nil
+            }
+        }
+        let myDelegate = MyDelegate()
+        let fpc = FloatingPanelController(delegate: myDelegate)
+        let traitCollection = UITraitCollection(traitsFrom: [fpc.traitCollection,
+                                                             UITraitCollection(userInterfaceStyle: .dark)])
+        XCTAssertEqual(traitCollection.userInterfaceStyle, .dark)
+        fpc.prepare(for: traitCollection)
+    }
+
+    func test_moveTo() {
+        let fpc = FloatingPanelController(delegate: nil)
+        fpc.showForTest()
+        fpc.move(to: .full, animated: false)
+        XCTAssertEqual(fpc.position, .full)
+        XCTAssertEqual(fpc.surfaceView.frame.minY, fpc.originYOfSurface(for: .full))
+
+        fpc.move(to: .half, animated: false)
+        XCTAssertEqual(fpc.position, .half)
+        XCTAssertEqual(fpc.surfaceView.frame.minY, fpc.originYOfSurface(for: .half))
+
+        fpc.move(to: .tip, animated: false)
+        XCTAssertEqual(fpc.position, .tip)
+        XCTAssertEqual(fpc.surfaceView.frame.minY, fpc.originYOfSurface(for: .tip))
+
+        fpc.move(to: .hidden, animated: false)
+        XCTAssertEqual(fpc.position, .hidden)
+        XCTAssertEqual(fpc.surfaceView.frame.minY, fpc.originYOfSurface(for: .hidden))
+
+        fpc.move(to: .full, animated: true)
+        waitRunLoop(secs: 0.3)
+        XCTAssertEqual(fpc.position, .full)
+        XCTAssertEqual(fpc.surfaceView.frame.minY, fpc.originYOfSurface(for: .full))
+
+        fpc.move(to: .half, animated: true)
+        waitRunLoop(secs: 0.3)
+        XCTAssertEqual(fpc.position, .half)
+        XCTAssertEqual(fpc.surfaceView.frame.minY, fpc.originYOfSurface(for: .half))
 
         fpc.move(to: .tip, animated: true)
-        waitRunLoop(secs: 1.0)
-        XCTAssert(fpc.surfaceView.frame.minY == (fpc.view.bounds.height - fpc.layoutInsets.bottom) - fpc.layout.insetFor(position: .tip)!)
+        waitRunLoop(secs: 0.3)
+        XCTAssertEqual(fpc.position, .tip)
+        XCTAssertEqual(fpc.surfaceView.frame.minY, fpc.originYOfSurface(for: .tip))
+
+        fpc.move(to: .hidden, animated: true)
+        waitRunLoop(secs: 0.3)
+        XCTAssertEqual(fpc.position, .hidden)
+        XCTAssertEqual(fpc.surfaceView.frame.minY, fpc.originYOfSurface(for: .hidden))
+
+    }
+
+    func test_originSurfaceY() {
+        let fpc = FloatingPanelController(delegate: nil)
+        fpc.loadViewIfNeeded()
+        fpc.view.frame = CGRect(x: 0, y: 0, width: 375, height: 667)
+        fpc.show(animated: false, completion: nil)
+
+        fpc.move(to: .full, animated: false)
+        XCTAssertEqual(fpc.surfaceView.frame.minY, fpc.originYOfSurface(for: .full))
+        fpc.move(to: .half, animated: false)
+        XCTAssertEqual(fpc.surfaceView.frame.minY, fpc.originYOfSurface(for: .half))
+        fpc.move(to: .tip, animated: false)
+        XCTAssertEqual(fpc.surfaceView.frame.minY, fpc.originYOfSurface(for: .tip))
+        fpc.move(to: .hidden, animated: false)
+        XCTAssertEqual(fpc.surfaceView.frame.minY, fpc.originYOfSurface(for: .hidden))
     }
 }
 
-func waitRunLoop(secs: TimeInterval = 0) {
-    RunLoop.main.run(until: Date(timeIntervalSinceNow: secs))
-}
-
-class MyZombieViewController: UIViewController, FloatingPanelLayout, FloatingPanelBehavior, FloatingPanelControllerDelegate {
+private class MyZombieViewController: UIViewController, FloatingPanelLayout, FloatingPanelBehavior, FloatingPanelControllerDelegate {
     var fpc: FloatingPanelController?
     override func viewDidLoad() {
         fpc = FloatingPanelController(delegate: self)

Framework/Tests/FloatingPanelLayoutTests.swift

@@ -0,0 +1,206 @@
+//
+//  Created by Shin Yamamoto on 2019/06/27.
+//  Copyright © 2019 scenee. All rights reserved.
+//
+
+import XCTest
+@testable import FloatingPanel
+
+class FloatingPanelLayoutTests: XCTestCase {
+    var fpc: FloatingPanelController!
+    override func setUp() {
+        fpc = FloatingPanelController(delegate: nil)
+        fpc.loadViewIfNeeded()
+        fpc.view.frame = CGRect(x: 0, y: 0, width: 375, height: 667)
+    }
+    override func tearDown() {}
+
+    func test_layoutAdapter_topAndBottomMostState() {
+        XCTAssertEqual(fpc.floatingPanel.layoutAdapter.topMostState, .full)
+        XCTAssertEqual(fpc.floatingPanel.layoutAdapter.bottomMostState, .tip)
+
+        class FloatingPanelLayoutWithHidden: FloatingPanelLayout {
+            func insetFor(position: FloatingPanelPosition) -> CGFloat? { return nil }
+            let initialPosition: FloatingPanelPosition = .hidden
+            let supportedPositions: Set<FloatingPanelPosition> = [.hidden, .half, .full]
+        }
+        class FloatingPanelLayout2Positions: FloatingPanelLayout {
+            func insetFor(position: FloatingPanelPosition) -> CGFloat? { return nil }
+            let initialPosition: FloatingPanelPosition = .tip
+            let supportedPositions: Set<FloatingPanelPosition> = [.tip, .half]
+        }
+        let delegate = FloatingPanelTestDelegate()
+        delegate.layout = FloatingPanelLayoutWithHidden()
+        fpc.delegate = delegate
+        XCTAssertEqual(fpc.floatingPanel.layoutAdapter.topMostState, .full)
+        XCTAssertEqual(fpc.floatingPanel.layoutAdapter.bottomMostState, .hidden)
+
+        delegate.layout = FloatingPanelLayout2Positions()
+        fpc.delegate = delegate
+        XCTAssertEqual(fpc.floatingPanel.layoutAdapter.topMostState, .half)
+        XCTAssertEqual(fpc.floatingPanel.layoutAdapter.bottomMostState, .tip)
+    }
+
+    func test_layoutSegment_3position() {
+        class FloatingPanelLayout3Positions: FloatingPanelTestLayout {
+            let initialPosition: FloatingPanelPosition = .half
+            let supportedPositions: Set<FloatingPanelPosition> = [.tip, .half, .full]
+        }
+
+        let delegate = FloatingPanelTestDelegate()
+        delegate.layout = FloatingPanelLayout3Positions()
+        fpc.delegate = delegate
+
+        let fullPos = fpc.originYOfSurface(for: .full)
+        let halfPos = fpc.originYOfSurface(for: .half)
+        let tipPos = fpc.originYOfSurface(for: .tip)
+
+        let minPos = CGFloat.leastNormalMagnitude
+        let maxPos = CGFloat.greatestFiniteMagnitude
+
+        assertLayoutSegment(fpc.floatingPanel, with: [
+            (#line, pos: minPos, forwardY: true, lower: nil, upper: .full),
+            (#line, pos: minPos, forwardY: false, lower: nil, upper: .full),
+            (#line, pos: fullPos, forwardY: true, lower: .full, upper: .half),
+            (#line, pos: fullPos, forwardY: false, lower: nil,  upper: .full),
+            (#line, pos: halfPos, forwardY: true, lower: .half, upper: .tip),
+            (#line, pos: halfPos, forwardY: false, lower: .full,  upper: .half),
+            (#line, pos: tipPos, forwardY: true, lower: .tip, upper: nil),
+            (#line, pos: tipPos, forwardY: false, lower: .half,  upper: .tip),
+            (#line, pos: maxPos, forwardY: true, lower: .tip, upper: nil),
+            (#line, pos: maxPos, forwardY: false, lower: .tip, upper: nil),
+            ])
+    }
+
+    func test_layoutSegment_2positions() {
+        class FloatingPanelLayout2Positions: FloatingPanelTestLayout {
+            let initialPosition: FloatingPanelPosition = .half
+            let supportedPositions: Set<FloatingPanelPosition> = [.half, .full]
+        }
+
+        let delegate = FloatingPanelTestDelegate()
+        delegate.layout = FloatingPanelLayout2Positions()
+        fpc.delegate = delegate
+
+        let fullPos = fpc.originYOfSurface(for: .full)
+        let halfPos = fpc.originYOfSurface(for: .half)
+
+        let minPos = CGFloat.leastNormalMagnitude
+        let maxPos = CGFloat.greatestFiniteMagnitude
+
+        assertLayoutSegment(fpc.floatingPanel, with: [
+            (#line, pos: minPos, forwardY: true, lower: nil, upper: .full),
+            (#line, pos: minPos, forwardY: false, lower: nil, upper: .full),
+            (#line, pos: fullPos, forwardY: true, lower: .full, upper: .half),
+            (#line, pos: fullPos, forwardY: false, lower: nil,  upper: .full),
+            (#line, pos: halfPos, forwardY: true, lower: .half, upper: nil),
+            (#line, pos: halfPos, forwardY: false, lower: .full,  upper: .half),
+            (#line, pos: maxPos, forwardY: true, lower: .half, upper: nil),
+            (#line, pos: maxPos, forwardY: false, lower: .half, upper: nil),
+            ])
+    }
+
+    func test_layoutSegment_1positions() {
+        class FloatingPanelLayout1Positions: FloatingPanelTestLayout {
+            let initialPosition: FloatingPanelPosition = .full
+            let supportedPositions: Set<FloatingPanelPosition> = [.full]
+        }
+
+        let delegate = FloatingPanelTestDelegate()
+        delegate.layout = FloatingPanelLayout1Positions()
+        fpc.delegate = delegate
+
+        let fullPos = fpc.originYOfSurface(for: .full)
+
+        let minPos = CGFloat.leastNormalMagnitude
+        let maxPos = CGFloat.greatestFiniteMagnitude
+
+        assertLayoutSegment(fpc.floatingPanel, with: [
+            (#line, pos: minPos, forwardY: true, lower: nil, upper: .full),
+            (#line, pos: minPos, forwardY: false, lower: nil, upper: .full),
+            (#line, pos: fullPos, forwardY: true, lower: .full, upper: nil),
+            (#line, pos: fullPos, forwardY: false, lower: nil,  upper: .full),
+            (#line, pos: maxPos, forwardY: true, lower: .full, upper: nil),
+            (#line, pos: maxPos, forwardY: false, lower: .full, upper: nil),
+            ])
+    }
+
+    func test_updateInteractiveTopConstraint() {
+        fpc.showForTest()
+        fpc.move(to: .full, animated: false)
+
+        fpc.floatingPanel.layoutAdapter.startInteraction(at: fpc.position)
+        fpc.floatingPanel.layoutAdapter.startInteraction(at: fpc.position) // Should be ignore
+
+        let fullPos = fpc.originYOfSurface(for: .full)
+        let tipPos = fpc.originYOfSurface(for: .tip)
+
+        var pre: CGFloat
+        var next: CGFloat
+        pre = fpc.surfaceView.frame.minY
+        fpc.floatingPanel.layoutAdapter.updateInteractiveTopConstraint(diff: -100.0, allowsTopBuffer: false, with: fpc.behavior)
+        next = fpc.surfaceView.frame.minY
+        XCTAssertEqual(next, pre)
+
+        fpc.floatingPanel.layoutAdapter.updateInteractiveTopConstraint(diff: -100.0, allowsTopBuffer: true, with: fpc.behavior)
+        next = fpc.surfaceView.frame.minY
+        XCTAssertEqual(next, fullPos - fpc.layout.topInteractionBuffer)
+
+        fpc.floatingPanel.layoutAdapter.updateInteractiveTopConstraint(diff: 100.0, allowsTopBuffer: true, with: fpc.behavior)
+        next = fpc.surfaceView.frame.minY
+        XCTAssertEqual(next, fullPos + 100.0)
+
+        fpc.floatingPanel.layoutAdapter.updateInteractiveTopConstraint(diff: tipPos - fullPos, allowsTopBuffer: true, with: fpc.behavior)
+        next = fpc.surfaceView.frame.minY
+        XCTAssertEqual(next, tipPos)
+
+        fpc.floatingPanel.layoutAdapter.updateInteractiveTopConstraint(diff: tipPos - fullPos + 100.0, allowsTopBuffer: true, with: fpc.behavior)
+        next = fpc.surfaceView.frame.minY
+        XCTAssertEqual(next, tipPos + fpc.layout.bottomInteractionBuffer)
+
+        fpc.floatingPanel.layoutAdapter.endInteraction(at: fpc.position)
+    }
+
+    func test_updateInteractiveTopConstraintWithHidden() {
+        class FloatingPanelLayout2Positions: FloatingPanelTestLayout {
+            let initialPosition: FloatingPanelPosition = .hidden
+            let supportedPositions: Set<FloatingPanelPosition> = [.hidden, .full]
+        }
+        let delegate = FloatingPanelTestDelegate()
+        delegate.layout = FloatingPanelLayout2Positions()
+        fpc.delegate = delegate
+        fpc.showForTest()
+        fpc.move(to: .full, animated: false)
+
+        fpc.floatingPanel.layoutAdapter.startInteraction(at: fpc.position)
+
+        let fullPos = fpc.originYOfSurface(for: .full)
+        let hiddenPos = fpc.originYOfSurface(for: .hidden)
+
+        var pre: CGFloat
+        var next: CGFloat
+        pre = fpc.surfaceView.frame.minY
+        fpc.floatingPanel.layoutAdapter.updateInteractiveTopConstraint(diff: -100.0, allowsTopBuffer: false, with: fpc.behavior)
+        next = fpc.surfaceView.frame.minY
+        XCTAssertEqual(next, pre)
+
+        fpc.floatingPanel.layoutAdapter.updateInteractiveTopConstraint(diff: -100.0, allowsTopBuffer: true, with: fpc.behavior)
+        next = fpc.surfaceView.frame.minY
+        XCTAssertEqual(next, fullPos - fpc.layout.topInteractionBuffer)
+
+        fpc.floatingPanel.layoutAdapter.updateInteractiveTopConstraint(diff: hiddenPos - fullPos + 100.0, allowsTopBuffer: true, with: fpc.behavior)
+        next = fpc.surfaceView.frame.minY
+        XCTAssertEqual(next, hiddenPos + fpc.layout.bottomInteractionBuffer)
+
+        fpc.floatingPanel.layoutAdapter.endInteraction(at: fpc.position)
+    }
+}
+
+private typealias LayoutSegmentTestParameter = (UInt, pos: CGFloat, forwardY: Bool, lower: FloatingPanelPosition?, upper: FloatingPanelPosition?)
+private func assertLayoutSegment(_ floatingPanel: FloatingPanel, with params: [LayoutSegmentTestParameter]) {
+    params.forEach { (line, pos, forwardY, lowr, upper) in
+        let segument = floatingPanel.layoutAdapter.segument(at: pos, forward: forwardY)
+        XCTAssertEqual(segument.lower, lowr, line: line)
+        XCTAssertEqual(segument.upper, upper, line: line)
+    }
+}

Framework/Tests/FloatingPanelPositionTests.swift

@@ -0,0 +1,27 @@
+//
+//  Created by Shin Yamamoto on 2019/07/05.
+//  Copyright © 2019 scenee. All rights reserved.
+//
+
+import XCTest
+@testable import FloatingPanel
+
+class FloatingPanelPositionTests: XCTestCase {
+    override func setUp() { }
+    override func tearDown() { }
+
+    func test_nextAndPre() {
+        var positions: [FloatingPanelPosition]
+        positions = [.full, .half, .tip, .hidden]
+        XCTAssertEqual(FloatingPanelPosition.full.next(in: positions),  .half)
+        XCTAssertEqual(FloatingPanelPosition.full.pre(in: positions),  .full)
+        XCTAssertEqual(FloatingPanelPosition.hidden.next(in: positions), .hidden)
+        XCTAssertEqual(FloatingPanelPosition.hidden.pre(in: positions), .tip)
+
+        positions = [.full, .hidden]
+        XCTAssertEqual(FloatingPanelPosition.full.next(in: positions),  .hidden)
+        XCTAssertEqual(FloatingPanelPosition.full.pre(in: positions),  .full)
+        XCTAssertEqual(FloatingPanelPosition.hidden.next(in: positions), .hidden)
+        XCTAssertEqual(FloatingPanelPosition.hidden.pre(in: positions), .full)
+    }
+}

Framework/Tests/FloatingPanelSurfaceViewTests.swift

@@ -6,10 +6,8 @@
 import XCTest
 @testable import FloatingPanel
 
-class FloatingPanelViewTests: XCTestCase {
-
+class FloatingPanelSurfaceViewTests: XCTestCase {
     override func setUp() {}
-
     override func tearDown() {}
 
     func test_surfaceView() {
@@ -24,6 +22,26 @@ class FloatingPanelViewTests: XCTestCase {
         XCTAssert(surface.backgroundColor == surface.containerView.backgroundColor)
     }
 
+    func test_surfaceView_constraintsUpdate() {
+        let window = UIWindow()
+        let surface = FloatingPanelSurfaceView(frame: CGRect(x: 0.0, y: 0.0, width: 320.0, height: 480.0))
+        window.addSubview(surface)
+        window.makeKeyAndVisible()
+        XCTAssert(surface.contentView == nil)
+        surface.layoutIfNeeded()
+        XCTAssert(surface.grabberHandle.frame.minY == 6.0)
+        XCTAssert(surface.grabberHandle.frame.width == surface.grabberHandleWidth)
+        XCTAssert(surface.grabberHandle.frame.height == surface.grabberHandleHeight)
+
+        surface.grabberHandleWidth = 44.0
+        surface.grabberHandleHeight = 12.0
+        surface.layoutIfNeeded()
+        waitRunLoop(secs: 0.000_001)
+        XCTAssert(surface.grabberHandle.frame.width == surface.grabberHandleWidth, "\(surface.grabberHandle.frame.width) == \(surface.grabberHandleWidth)")
+        XCTAssert(surface.grabberHandle.frame.height == surface.grabberHandleHeight, "\(surface.grabberHandle.frame.height) == \(surface.grabberHandleHeight)")
+        window.resignKey()
+    }
+
     func test_surfaceView_cornderRaduis() {
         let surface = FloatingPanelSurfaceView(frame: CGRect(x: 0.0, y: 0.0, width: 320.0, height: 480.0))
         XCTAssert(surface.cornerRadius == 0.0)

Framework/Tests/FloatingPanelTests.swift

@@ -4,11 +4,534 @@
 //
 
 import XCTest
+@testable import FloatingPanel
 
 class FloatingPanelTests: XCTestCase {
-
     override func setUp() {}
-
     override func tearDown() {}
 
+    func test_scrolllock() {
+        let fpc = FloatingPanelController()
+
+        let contentVC1 = UITableViewController(nibName: nil, bundle: nil)
+        XCTAssertEqual(contentVC1.tableView.showsVerticalScrollIndicator, true)
+        XCTAssertEqual(contentVC1.tableView.bounces, true)
+        fpc.set(contentViewController: contentVC1)
+        fpc.track(scrollView: contentVC1.tableView)
+        fpc.showForTest()
+
+        XCTAssertEqual(fpc.position, .half)
+        XCTAssertEqual(contentVC1.tableView.showsVerticalScrollIndicator, false)
+        XCTAssertEqual(contentVC1.tableView.bounces, false)
+
+        fpc.move(to: .full, animated: false)
+        XCTAssertEqual(contentVC1.tableView.showsVerticalScrollIndicator, true)
+        XCTAssertEqual(contentVC1.tableView.bounces, true)
+
+        fpc.move(to: .tip, animated: false)
+        XCTAssertEqual(contentVC1.tableView.showsVerticalScrollIndicator, false)
+        XCTAssertEqual(contentVC1.tableView.bounces, false)
+
+        let exp1 = expectation(description: "move to full with animation")
+        fpc.move(to: .full, animated: true) {
+            XCTAssertEqual(contentVC1.tableView.showsVerticalScrollIndicator, true)
+            XCTAssertEqual(contentVC1.tableView.bounces, true)
+            exp1.fulfill()
+        }
+        wait(for: [exp1], timeout: 1.0)
+
+        let exp2 = expectation(description: "move to tip with animation")
+        fpc.move(to: .tip, animated: false) {
+            XCTAssertEqual(contentVC1.tableView.showsVerticalScrollIndicator, false)
+            XCTAssertEqual(contentVC1.tableView.bounces, false)
+            exp2.fulfill()
+        }
+        wait(for: [exp2], timeout: 1.0)
+
+        // Reset the content vc
+        let contentVC2 = UITableViewController(nibName: nil, bundle: nil)
+        XCTAssertEqual(contentVC2.tableView.showsVerticalScrollIndicator, true)
+        XCTAssertEqual(contentVC2.tableView.bounces, true)
+        fpc.set(contentViewController: contentVC2)
+        fpc.track(scrollView: contentVC2.tableView)
+        fpc.show(animated: false, completion: nil)
+        XCTAssertEqual(fpc.position, .half)
+        XCTAssertEqual(contentVC2.tableView.showsVerticalScrollIndicator, false)
+        XCTAssertEqual(contentVC2.tableView.bounces, false)
+    }
+
+    func test_getBackdropAlpha_1positions() {
+        class FloatingPanelLayout1Positions: FloatingPanelTestLayout {
+            let initialPosition: FloatingPanelPosition = .full
+            let supportedPositions: Set<FloatingPanelPosition> = [.full]
+        }
+        let delegate = FloatingPanelTestDelegate()
+        delegate.layout = FloatingPanelLayout1Positions()
+
+        let fpc = FloatingPanelController(delegate: delegate)
+        fpc.showForTest()
+
+        let fullPos = fpc.originYOfSurface(for: .full)
+
+        XCTAssertEqual(fpc.floatingPanel.getBackdropAlpha(at: fullPos - 100.0, with: CGPoint(x: 0.0, y: -100.0)), 0.3)
+        XCTAssertEqual(fpc.floatingPanel.getBackdropAlpha(at: fullPos, with: CGPoint(x: 0.0, y: 0.0)), 0.3)
+        XCTAssertEqual(fpc.floatingPanel.getBackdropAlpha(at: fullPos + 100.0, with: CGPoint(x: 0.0, y: 100.0)), 0.3) // ok??
+    }
+
+    func test_getBackdropAlpha_2positions() {
+        class FloatingPanelLayout2Positions: FloatingPanelTestLayout {
+            let initialPosition: FloatingPanelPosition = .half
+            let supportedPositions: Set<FloatingPanelPosition> = [.half, .full]
+        }
+        let delegate = FloatingPanelTestDelegate()
+        delegate.layout = FloatingPanelLayout2Positions()
+
+        let fpc = FloatingPanelController(delegate: delegate)
+        fpc.showForTest()
+
+        let fullPos = fpc.originYOfSurface(for: .full)
+        let halfPos = fpc.originYOfSurface(for: .half)
+        let distance1 = abs(halfPos - fullPos)
+
+        fpc.move(to: .full, animated: false)
+        XCTAssertEqual(fpc.floatingPanel.getBackdropAlpha(at: fullPos, with: CGPoint(x: 0.0, y: 0.0)), 0.3)
+        XCTAssertEqual(fpc.floatingPanel.getBackdropAlpha(at: fullPos + distance1 * 0.5, with: CGPoint(x: 0.0, y: distance1 * 0.5)), 0.3 * 0.5)
+        XCTAssertEqual(fpc.floatingPanel.getBackdropAlpha(at: halfPos, with: CGPoint(x: 0.0, y: distance1)), 0.0)
+
+        fpc.move(to: .half, animated: false)
+        XCTAssertEqual(fpc.floatingPanel.getBackdropAlpha(at: halfPos, with: CGPoint(x: 0.0, y: 0.0)), 0.0)
+        XCTAssertEqual(fpc.floatingPanel.getBackdropAlpha(at: fullPos + distance1 * 0.5, with: CGPoint(x: 0.0, y: -0.5 * distance1)), 0.3 * 0.5)
+        XCTAssertEqual(fpc.floatingPanel.getBackdropAlpha(at: fullPos, with: CGPoint(x: 0.0, y: -1 * distance1)), 0.3)
+    }
+
+    func test_getBackdropAlpha_2positionsWithHidden() {
+        class FloatingPanelLayout2Positions: FloatingPanelTestLayout {
+            let initialPosition: FloatingPanelPosition = .hidden
+            let supportedPositions: Set<FloatingPanelPosition> = [.hidden, .full]
+        }
+        let delegate = FloatingPanelTestDelegate()
+        delegate.layout = FloatingPanelLayout2Positions()
+
+        let fpc = FloatingPanelController(delegate: delegate)
+        fpc.showForTest()
+
+        let fullPos = fpc.originYOfSurface(for: .full)
+        let hiddenPos = fpc.originYOfSurface(for: .hidden)
+
+        XCTAssertEqual(fpc.floatingPanel.getBackdropAlpha(at: fullPos - 100.0, with: CGPoint(x: 0.0, y: -100.0)), 0.3)
+        XCTAssertEqual(fpc.floatingPanel.getBackdropAlpha(at: fullPos, with: CGPoint(x: 0.0, y: 0.0)), 0.3)
+        XCTAssertEqual(fpc.floatingPanel.getBackdropAlpha(at: hiddenPos, with: CGPoint(x: 0.0, y: 100.0)), 0.0)
+    }
+
+    func test_getBackdropAlpha_3positions() {
+        let fpc = FloatingPanelController()
+        fpc.showForTest()
+
+        let fullPos = fpc.originYOfSurface(for: .full)
+        let halfPos = fpc.originYOfSurface(for: .half)
+        let tipPos = fpc.originYOfSurface(for: .tip)
+        let distance1 = abs(halfPos - fullPos)
+        let distance2 = abs(tipPos - halfPos)
+
+        fpc.move(to: .full, animated: false)
+        XCTAssertEqual(fpc.floatingPanel.getBackdropAlpha(at: fullPos, with: CGPoint(x: 0.0, y: 0.0)), 0.3)
+        XCTAssertEqual(fpc.floatingPanel.getBackdropAlpha(at: fullPos + distance1 * 0.5, with: CGPoint(x: 0.0, y: distance1 * 0.5)), 0.3 * 0.5)
+        XCTAssertEqual(fpc.floatingPanel.getBackdropAlpha(at: halfPos, with: CGPoint(x: 0.0, y: distance1)), 0.0)
+
+        fpc.move(to: .half, animated: false)
+        XCTAssertEqual(fpc.floatingPanel.getBackdropAlpha(at: halfPos, with: CGPoint(x: 0.0, y: 0.0)), 0.0)
+        XCTAssertEqual(fpc.floatingPanel.getBackdropAlpha(at: fullPos + distance1 * 0.5, with: CGPoint(x: 0.0, y: -0.5 * distance1)), 0.3 * 0.5)
+        XCTAssertEqual(fpc.floatingPanel.getBackdropAlpha(at: fullPos, with: CGPoint(x: 0.0, y: -1 * distance1)), 0.3)
+
+        fpc.move(to: .tip, animated: false)
+        XCTAssertEqual(fpc.floatingPanel.getBackdropAlpha(at: tipPos, with: CGPoint(x: 0.0, y: 0.0)), 0.0)
+        XCTAssertEqual(fpc.floatingPanel.getBackdropAlpha(at: halfPos + distance2 * 0.5, with: CGPoint(x: 0.0, y: -0.5 * distance2)), 0.0)
+        XCTAssertEqual(fpc.floatingPanel.getBackdropAlpha(at: halfPos, with: CGPoint(x: 0.0, y: -1 * distance2)), 0.0)
+    }
+
+    func test_targetPosition_1positions() {
+        class FloatingPanelLayout1Positions: FloatingPanelTestLayout {
+            let initialPosition: FloatingPanelPosition = .full
+            let supportedPositions: Set<FloatingPanelPosition> = [.full]
+        }
+        let delegate = FloatingPanelTestDelegate()
+        delegate.layout = FloatingPanelLayout1Positions()
+
+        let fpc = FloatingPanelController(delegate: delegate)
+        fpc.showForTest()
+
+        let fullPos = fpc.originYOfSurface(for: .full)
+
+        fpc.move(to: .full, animated: false)
+        assertTargetPosition(fpc.floatingPanel, with: [
+            (#line, fullPos - 10.0, CGPoint(x: 0.0, y: 1000.0), .full), // redirect
+            (#line, fullPos, CGPoint(x: 0.0, y: -1000.0), .full), // redirect
+            (#line, fullPos, CGPoint(x: 0.0, y: -100.0), .full), // redirect
+            (#line, fullPos, CGPoint(x: 0.0, y: 0.0), .full),
+            (#line, fullPos, CGPoint(x: 0.0, y: 100.0), .full), // redirect
+            (#line, fullPos, CGPoint(x: 0.0, y: 1000.0), .full), // redirect
+            (#line, fullPos + 10.0, CGPoint(x: 0.0, y: 100.0), .full), // redirect
+            ])
+    }
+
+    func test_targetPosition_2positions() {
+        class FloatingPanelLayout2Positions: FloatingPanelTestLayout {
+            let initialPosition: FloatingPanelPosition = .half
+            let supportedPositions: Set<FloatingPanelPosition> = [.half, .full]
+        }
+        let delegate = FloatingPanelTestDelegate()
+        delegate.layout = FloatingPanelLayout2Positions()
+
+        let fpc = FloatingPanelController(delegate: delegate)
+        fpc.showForTest()
+
+        let fullPos = fpc.originYOfSurface(for: .full)
+        let halfPos = fpc.originYOfSurface(for: .half)
+
+        fpc.move(to: .full, animated: false)
+        assertTargetPosition(fpc.floatingPanel, with: [
+            (#line, fullPos - 10.0, CGPoint(x: 0.0, y: 1000.0), .half), // project to half
+            (#line, fullPos, CGPoint(x: 0.0, y: -1000.0), .full), // redirect
+            (#line, fullPos, CGPoint(x: 0.0, y: -100.0), .full),
+            (#line, fullPos, CGPoint(x: 0.0, y: 0.0), .full),
+            (#line, fullPos, CGPoint(x: 0.0, y: 100.0), .full),
+            (#line, fullPos, CGPoint(x: 0.0, y: 1000.0), .half), // project to half
+            (#line, fullPos + 10.0, CGPoint(x: 0.0, y: 100.0), .full), // redirect
+            (#line, halfPos - 10.0, CGPoint(x: 0.0, y: -100.0), .half), // redirect
+            (#line, halfPos, CGPoint(x: 0.0, y: -1000.0), .full),  // project to full
+            (#line, halfPos, CGPoint(x: 0.0, y: -100.0), .half),
+            (#line, halfPos, CGPoint(x: 0.0, y: 0.0), .half),
+            (#line, halfPos, CGPoint(x: 0.0, y: 100.0), .half),
+            (#line, halfPos, CGPoint(x: 0.0, y: 1000.0), .half), // redirect
+            (#line, halfPos + 10.0, CGPoint(x: 0.0, y: -1000.0), .full), // project to full
+            ])
+        fpc.move(to: .half, animated: false)
+        assertTargetPosition(fpc.floatingPanel, with: [
+            (#line, fullPos - 10.0, CGPoint(x: 0.0, y: 1000.0), .half), // project to half
+            (#line, fullPos, CGPoint(x: 0.0, y: -1000.0), .full), // redirect
+            (#line, fullPos, CGPoint(x: 0.0, y: -100.0), .full),
+            (#line, fullPos, CGPoint(x: 0.0, y: 0.0), .full),
+            (#line, fullPos, CGPoint(x: 0.0, y: 100.0), .full),
+            (#line, fullPos, CGPoint(x: 0.0, y: 1000.0), .half), // project to half
+            (#line, fullPos + 10.0, CGPoint(x: 0.0, y: 100.0), .full), // redirect
+            (#line, halfPos - 10.0, CGPoint(x: 0.0, y: -100.0), .half), // redirect
+            (#line, halfPos, CGPoint(x: 0.0, y: -1000.0), .full),  // project to full
+            (#line, halfPos, CGPoint(x: 0.0, y: -100.0), .half),
+            (#line, halfPos, CGPoint(x: 0.0, y: 0.0), .half),
+            (#line, halfPos, CGPoint(x: 0.0, y: 100.0), .half),
+            (#line, halfPos, CGPoint(x: 0.0, y: 1000.0), .half), // redirect
+            (#line, halfPos + 10.0, CGPoint(x: 0.0, y: -1000.0), .full), // project to full
+            ])
+    }
+
+    func test_targetPosition_2positionsWithHidden() {
+        class FloatingPanelLayout2Positions: FloatingPanelTestLayout {
+            let initialPosition: FloatingPanelPosition = .hidden
+            let supportedPositions: Set<FloatingPanelPosition> = [.hidden, .full]
+        }
+        let delegate = FloatingPanelTestDelegate()
+        delegate.layout = FloatingPanelLayout2Positions()
+
+        let fpc = FloatingPanelController(delegate: delegate)
+        fpc.showForTest()
+
+        let fullPos = fpc.originYOfSurface(for: .full)
+        let hiddenPos = fpc.originYOfSurface(for: .hidden)
+
+        fpc.move(to: .full, animated: false)
+        assertTargetPosition(fpc.floatingPanel, with: [
+            (#line, fullPos - 10.0, CGPoint(x: 0.0, y: 1000.0), .hidden), // project to hidden
+            (#line, fullPos, CGPoint(x: 0.0, y: -1000.0), .full), // redirect
+            (#line, fullPos, CGPoint(x: 0.0, y: -100.0), .full),
+            (#line, fullPos, CGPoint(x: 0.0, y: 0.0), .full),
+            (#line, fullPos, CGPoint(x: 0.0, y: 100.0), .full),
+            (#line, fullPos, CGPoint(x: 0.0, y: 1000.0), .hidden), // project to hidden
+            (#line, fullPos + 10.0, CGPoint(x: 0.0, y: 100.0), .full), // redirect
+            (#line, hiddenPos - 10.0, CGPoint(x: 0.0, y: -100.0), .hidden), // redirect
+            (#line, hiddenPos, CGPoint(x: 0.0, y: -1000.0), .full),  // project to full
+            (#line, hiddenPos, CGPoint(x: 0.0, y: -100.0), .hidden),
+            (#line, hiddenPos, CGPoint(x: 0.0, y: 0.0), .hidden),
+            (#line, hiddenPos, CGPoint(x: 0.0, y: 100.0), .hidden),
+            (#line, hiddenPos, CGPoint(x: 0.0, y: 1000.0), .hidden), // redirect
+            (#line, hiddenPos + 10.0, CGPoint(x: 0.0, y: -1000.0), .full), // project to full
+            ])
+        fpc.move(to: .hidden, animated: false)
+        assertTargetPosition(fpc.floatingPanel, with: [
+            (#line, fullPos - 10.0, CGPoint(x: 0.0, y: 1000.0), .hidden), // project to hidden
+            (#line, fullPos, CGPoint(x: 0.0, y: -1000.0), .full), // redirect
+            (#line, fullPos, CGPoint(x: 0.0, y: -100.0), .full),
+            (#line, fullPos, CGPoint(x: 0.0, y: 0.0), .full),
+            (#line, fullPos, CGPoint(x: 0.0, y: 100.0), .full),
+            (#line, fullPos, CGPoint(x: 0.0, y: 1000.0), .hidden), // project to hidden
+            (#line, fullPos + 10.0, CGPoint(x: 0.0, y: 100.0), .full), // redirect
+            (#line, hiddenPos - 10.0, CGPoint(x: 0.0, y: -100.0), .hidden), // redirect
+            (#line, hiddenPos, CGPoint(x: 0.0, y: -1000.0), .full),  // project to full
+            (#line, hiddenPos, CGPoint(x: 0.0, y: -100.0), .hidden),
+            (#line, hiddenPos, CGPoint(x: 0.0, y: 0.0), .hidden),
+            (#line, hiddenPos, CGPoint(x: 0.0, y: 100.0), .hidden),
+            (#line, hiddenPos, CGPoint(x: 0.0, y: 1000.0), .hidden), // redirect
+            (#line, hiddenPos + 10.0, CGPoint(x: 0.0, y: -1000.0), .full), // project to full
+            ])
+    }
+
+    func test_targetPosition_2positionsFromFull() {
+        let delegate = FloatingPanelTestDelegate()
+        delegate.layout = FloatingPanelLayout3Positions()
+        let fpc = FloatingPanelController(delegate: delegate)
+        fpc.showForTest()
+
+        let fullPos = fpc.originYOfSurface(for: .full)
+        let halfPos = fpc.originYOfSurface(for: .half)
+        let tipPos = fpc.originYOfSurface(for: .tip)
+        // From .full
+        fpc.move(to: .full, animated: false)
+        assertTargetPosition(fpc.floatingPanel, with: [
+            (#line, fullPos - 500.0, CGPoint(x: 0.0, y: -100.0), .full), // far from topMostState
+            (#line, fullPos - 500.0, CGPoint(x: 0.0, y: 0.0), .full), // far from topMostState
+            (#line, fullPos - 500.0, CGPoint(x: 0.0, y: 100.0), .full), // far from topMostState
+            (#line, fullPos - 10.0, CGPoint(x: 0.0, y: 3000.0), .half), // block projecting to tip at half
+            (#line, fullPos, CGPoint(x: 0.0, y: -100.0), .full),
+            (#line, fullPos, CGPoint(x: 0.0, y: 0.0), .full),
+            (#line, fullPos, CGPoint(x: 0.0, y: 500.0), .half), // project to half
+            (#line, fullPos, CGPoint(x: 0.0, y: 1000.0), .half), // block projecting to tip at half
+            (#line, fullPos, CGPoint(x: 0.0, y: 3000.0), .half), // block projecting to tip at half
+            (#line, fullPos + 10.0, CGPoint(x: 0.0, y: 100.0), .full), // redirect
+            (#line, halfPos - 10.0, CGPoint(x: 0.0, y: -100.0), .half), // redirect
+            (#line, halfPos, CGPoint(x: 0.0, y: -1000.0), .full), //project to full
+            (#line, halfPos, CGPoint(x: 0.0, y: -100.0), .half),
+            (#line, halfPos, CGPoint(x: 0.0, y: 0.0), .half),
+            (#line, halfPos, CGPoint(x: 0.0, y: 100.0), .half),
+            (#line, halfPos, CGPoint(x: 0.0, y: 1000.0), .tip), // project to tip
+            (#line, halfPos + 10.0, CGPoint(x: 0.0, y: 100.0), .half), // redirect
+            (#line, tipPos - 10.0, CGPoint(x: 0.0, y: -100.0), .tip), // redirect
+            (#line, tipPos, CGPoint(x: 0.0, y: -3000.0), .half), // block projecting to full at half
+            (#line, tipPos, CGPoint(x: 0.0, y: -1000.0), .half), // block projecting to full at half
+            (#line, tipPos, CGPoint(x: 0.0, y: -500.0), .half), // project to half
+            (#line, tipPos, CGPoint(x: 0.0, y: -100.0), .tip),
+            (#line, tipPos, CGPoint(x: 0.0, y: 0.0), .tip),
+            (#line, tipPos, CGPoint(x: 0.0, y: 100.0), .tip),
+            (#line, tipPos + 10.0, CGPoint(x: 0.0, y: -3000.0), .half), // block projecting to full at half
+            (#line, tipPos + 500.0, CGPoint(x: 0.0, y: -100.0), .tip), // far from bottomMostState
+            (#line, tipPos + 500.0, CGPoint(x: 0.0, y: 0.0), .tip), // far from bottomMostState
+            (#line, tipPos + 500.0, CGPoint(x: 0.0, y: 100.0), .tip), // far from bottomMostState
+            ])
+    }
+
+    func test_targetPosition_3positionsFromHalf() {
+        let delegate = FloatingPanelTestDelegate()
+        delegate.layout = FloatingPanelLayout3Positions()
+        let fpc = FloatingPanelController(delegate: delegate)
+        fpc.showForTest()
+
+        let fullPos = fpc.originYOfSurface(for: .full)
+        let halfPos = fpc.originYOfSurface(for: .half)
+        let tipPos = fpc.originYOfSurface(for: .tip)
+        // From .half
+        fpc.move(to: .half, animated: false)
+        assertTargetPosition(fpc.floatingPanel, with: [
+            (#line, fullPos - 500.0, CGPoint(x: 0.0, y: -100.0), .full), // far from topMostState
+            (#line, fullPos - 500.0, CGPoint(x: 0.0, y: 0.0), .full), // far from topMostState
+            (#line, fullPos - 500.0, CGPoint(x: 0.0, y: 100.0), .full), // far from topMostState
+            (#line, fullPos, CGPoint(x: 0.0, y: -100.0), .full),
+            (#line, fullPos, CGPoint(x: 0.0, y: 0.0), .full),
+            (#line, fullPos, CGPoint(x: 0.0, y: 500.0), .half), // project to half
+            (#line, fullPos, CGPoint(x: 0.0, y: 1000.0), .half), // block projecting to tip at half
+            (#line, fullPos, CGPoint(x: 0.0, y: 3000.0), .half), // block projecting to tip at half
+            (#line, fullPos + 10.0, CGPoint(x: 0.0, y: 100.0), .full), // redirect
+            (#line, halfPos - 10.0, CGPoint(x: 0.0, y: -100.0), .half), // redirect
+            (#line, halfPos, CGPoint(x: 0.0, y: -1000.0), .full),// project to full
+            (#line, halfPos, CGPoint(x: 0.0, y: -100.0), .half),
+            (#line, halfPos, CGPoint(x: 0.0, y: 0.0), .half),
+            (#line, halfPos, CGPoint(x: 0.0, y: 100.0), .half),
+            (#line, halfPos, CGPoint(x: 0.0, y: 1000.0), .tip), // project to tip
+            (#line, halfPos + 10.0, CGPoint(x: 0.0, y: 100.0), .half), // redirect
+            (#line, tipPos - 10.0, CGPoint(x: 0.0, y: -100.0), .tip), // redirect
+            (#line, tipPos, CGPoint(x: 0.0, y: -3000.0), .half), // block projecting to full at half
+            (#line, tipPos, CGPoint(x: 0.0, y: -1000.0), .half), // block projecting to full at half
+            (#line, tipPos, CGPoint(x: 0.0, y: -500.0), .half), // project to half
+            (#line, tipPos, CGPoint(x: 0.0, y: -100.0), .tip),
+            (#line, tipPos, CGPoint(x: 0.0, y: 0.0), .tip),
+            (#line, tipPos, CGPoint(x: 0.0, y: 100.0), .tip),
+            (#line, tipPos + 500.0, CGPoint(x: 0.0, y: -100.0), .tip), // far from bottomMostState
+            (#line, tipPos + 500.0, CGPoint(x: 0.0, y: 0.0), .tip), // far from bottomMostState
+            (#line, tipPos + 500.0, CGPoint(x: 0.0, y: 100.0), .tip), // far from bottomMostState
+            ])
+    }
+
+    func test_targetPosition_3positionsFromTip() {
+        let delegate = FloatingPanelTestDelegate()
+        delegate.layout = FloatingPanelLayout3Positions()
+        let fpc = FloatingPanelController(delegate: delegate)
+        fpc.showForTest()
+
+        let fullPos = fpc.originYOfSurface(for: .full)
+        let halfPos = fpc.originYOfSurface(for: .half)
+        let tipPos = fpc.originYOfSurface(for: .tip)
+
+        // From .tip
+        fpc.move(to: .tip, animated: false)
+        assertTargetPosition(fpc.floatingPanel, with: [
+            (#line, fullPos - 500.0, CGPoint(x: 0.0, y: -100.0), .full), // far from topMostState
+            (#line, fullPos - 500.0, CGPoint(x: 0.0, y: 0.0), .full), // far from topMostState
+            (#line, fullPos - 500.0, CGPoint(x: 0.0, y: 100.0), .full), // far from topMostState
+            (#line, fullPos, CGPoint(x: 0.0, y: -100.0), .full),
+            (#line, fullPos, CGPoint(x: 0.0, y: 0.0), .full),
+            (#line, fullPos, CGPoint(x: 0.0, y: 500.0), .half), // project to half
+            (#line, fullPos, CGPoint(x: 0.0, y: 1000.0), .half), // block projecting to tip at half
+            (#line, fullPos, CGPoint(x: 0.0, y: 3000.0), .half), // block projecting to tip at half
+            (#line, fullPos + 10.0, CGPoint(x: 0.0, y: 100.0), .full), // redirect
+            (#line, halfPos - 10.0, CGPoint(x: 0.0, y: -100.0), .half), // redirect
+            (#line, halfPos, CGPoint(x: 0.0, y: -3000.0), .full), // project to full
+            (#line, halfPos, CGPoint(x: 0.0, y: -100.0), .half),
+            (#line, halfPos, CGPoint(x: 0.0, y: 0.0), .half),
+            (#line, halfPos, CGPoint(x: 0.0, y: 100.0), .half),
+            (#line, halfPos, CGPoint(x: 0.0, y: 1000.0), .tip), // project to tip
+            (#line, halfPos + 10.0, CGPoint(x: 0.0, y: 100.0), .half), // redirect
+            (#line, tipPos - 10.0, CGPoint(x: 0.0, y: -100.0), .tip), // redirect
+            (#line, tipPos, CGPoint(x: 0.0, y: -3000.0), .half), // block projecting to full at half
+            (#line, tipPos, CGPoint(x: 0.0, y: -1000.0), .half), // block projecting to full at half
+            (#line, tipPos, CGPoint(x: 0.0, y: -500.0), .half), // project to half
+            (#line, tipPos, CGPoint(x: 0.0, y: -100.0), .tip),
+            (#line, tipPos, CGPoint(x: 0.0, y: 0.0), .tip),
+            (#line, tipPos, CGPoint(x: 0.0, y: 100.0), .tip),
+            (#line, tipPos + 500.0, CGPoint(x: 0.0, y: -100.0), .tip), // far from bottomMostState
+            (#line, tipPos + 500.0, CGPoint(x: 0.0, y: 0.0), .tip), // far from bottomMostState
+            (#line, tipPos + 500.0, CGPoint(x: 0.0, y: 100.0), .tip), // far from bottomMostState
+            ])
+    }
+
+    func test_targetPosition_3positionsAllProjection() {
+        let delegate = FloatingPanelTestDelegate()
+        delegate.layout = FloatingPanelLayout3Positions()
+        delegate.behavior = FloatingPanelProjectionalBehavior()
+
+        let fpc = FloatingPanelController(delegate: delegate)
+        fpc.showForTest()
+
+        let fullPos = fpc.originYOfSurface(for: .full)
+        let halfPos = fpc.originYOfSurface(for: .half)
+        let tipPos = fpc.originYOfSurface(for: .tip)
+
+        // From .full
+        fpc.move(to: .full, animated: false)
+        assertTargetPosition(fpc.floatingPanel, with: [
+            (#line, fullPos - 10.0, CGPoint(x: 0.0, y: 3000.0), .tip),
+            (#line, fullPos, CGPoint(x: 0.0, y: 1000.0), .tip),
+            (#line, fullPos, CGPoint(x: 0.0, y: 3000.0), .tip),
+            (#line, halfPos, CGPoint(x: 0.0, y: 1000.0), .tip),
+            (#line, halfPos, CGPoint(x: 0.0, y: -1000.0), .full),
+            (#line, tipPos, CGPoint(x: 0.0, y: -3000.0), .full),
+            (#line, tipPos, CGPoint(x: 0.0, y: -1000.0), .full),
+            (#line, tipPos + 10.0, CGPoint(x: 0.0, y: -3000.0), .full),
+            ])
+
+        // From .half
+        fpc.move(to: .tip, animated: false)
+        assertTargetPosition(fpc.floatingPanel, with: [
+            (#line, fullPos, CGPoint(x: 0.0, y: 1000.0), .tip),
+            (#line, fullPos, CGPoint(x: 0.0, y: 3000.0), .tip),
+            (#line, tipPos, CGPoint(x: 0.0, y: -3000.0), .full),
+            (#line, tipPos, CGPoint(x: 0.0, y: -1000.0), .full),
+            ])
+
+        // From .tip
+        fpc.move(to: .tip, animated: false)
+        assertTargetPosition(fpc.floatingPanel, with: [
+            (#line, fullPos - 10.0, CGPoint(x: 0.0, y: 3000.0), .tip),
+            (#line, fullPos, CGPoint(x: 0.0, y: 1000.0), .tip),
+            (#line, fullPos, CGPoint(x: 0.0, y: 3000.0), .tip),
+            (#line, halfPos, CGPoint(x: 0.0, y: 1000.0), .tip),
+            (#line, halfPos, CGPoint(x: 0.0, y: -1000.0), .full),
+            (#line, tipPos, CGPoint(x: 0.0, y: -3000.0), .full),
+            (#line, tipPos, CGPoint(x: 0.0, y: -1000.0), .full),
+            (#line, tipPos + 10.0, CGPoint(x: 0.0, y: -3000.0), .full),
+            ])
+    }
+
+    func test_targetPosition_3positionsWithHidden() {
+        class FloatingPanelLayout3PositionsWithHidden: FloatingPanelTestLayout {
+            let initialPosition: FloatingPanelPosition = .hidden
+            let supportedPositions: Set<FloatingPanelPosition> = [.hidden, .half, .full]
+        }
+        let delegate = FloatingPanelTestDelegate()
+        delegate.layout = FloatingPanelLayout3PositionsWithHidden()
+
+        let fpc = FloatingPanelController(delegate: delegate)
+        fpc.showForTest()
+        XCTAssertEqual(fpc.position, .hidden)
+
+        fpc.move(to: .full, animated: false)
+        assertTargetPosition(fpc.floatingPanel, with: [
+            (#line, fpc.surfaceView.frame.minY, CGPoint(x: 0.0, y: 1000.0), .half),
+            ])
+        fpc.move(to: .half, animated: false)
+        assertTargetPosition(fpc.floatingPanel, with: [
+            (#line, fpc.surfaceView.frame.minY, CGPoint(x: 0.0, y: -100.0), .half),
+            (#line, fpc.surfaceView.frame.minY, CGPoint(x: 0.0, y: -1000.0), .full),
+            (#line, fpc.surfaceView.frame.minY, CGPoint(x: 0.0, y: 0.0), .half),
+            (#line, fpc.surfaceView.frame.minY, CGPoint(x: 0.0, y: 1000.0), .hidden),
+            ])
+    }
+
+    func test_targetPosition_3positionsWithHiddenWithoutFull() {
+        class FloatingPanelLayout3Positions: FloatingPanelTestLayout {
+            let initialPosition: FloatingPanelPosition = .hidden
+            let supportedPositions: Set<FloatingPanelPosition> = [.hidden, .tip, .half]
+        }
+
+        let delegate = FloatingPanelTestDelegate()
+        delegate.layout = FloatingPanelLayout3Positions()
+        delegate.behavior = FloatingPanelProjectionalBehavior()
+
+        let fpc = FloatingPanelController(delegate: delegate)
+        fpc.showForTest()
+        XCTAssertEqual(fpc.position, .hidden)
+
+        let halfPos = fpc.originYOfSurface(for: .half)
+        let tipPos = fpc.originYOfSurface(for: .tip)
+        //let hiddenPos = fpc.originYOfSurface(for: .hidden)
+
+        fpc.move(to: .half, animated: false)
+        assertTargetPosition(fpc.floatingPanel, with: [
+            (#line, halfPos, CGPoint(x: 0.0, y: -100.0), .half),
+            (#line, halfPos, CGPoint(x: 0.0, y: 0.0), .half),
+            (#line, halfPos, CGPoint(x: 0.0, y: 385.0), .tip), // projection
+            (#line, halfPos, CGPoint(x: 0.0, y: 1000.0), .hidden), // projection
+            (#line, halfPos + 10.0, CGPoint(x: 0.0, y: 100.0), .half), // redirection
+            (#line, tipPos - 10.0, CGPoint(x: 0.0, y: -100.0), .tip), // redirection
+            (#line, tipPos, CGPoint(x: 0.0, y: -3000.0), .half), //projection
+            (#line, tipPos, CGPoint(x: 0.0, y: -10.0), .tip),
+            (#line, tipPos, CGPoint(x: 0.0, y: 0.0), .tip),
+            (#line, tipPos, CGPoint(x: 0.0, y: 10.0), .tip),
+            (#line, tipPos, CGPoint(x: 0.0, y: 1000.0), .hidden), //projection
+            (#line, tipPos + 10.0, CGPoint(x: 0.0, y: 10.0), .tip), // redirection
+            (#line, tipPos - 10.0, CGPoint(x: 0.0, y: 10.0), .tip), // redirection
+            ])
+        fpc.move(to: .tip, animated: false)
+        assertTargetPosition(fpc.floatingPanel, with: [
+            (#line, tipPos, CGPoint(x: 0.0, y: -100.0), .tip),
+            (#line, tipPos, CGPoint(x: 0.0, y: -1000.0), .half),
+            (#line, tipPos, CGPoint(x: 0.0, y: 0.0), .tip),
+            (#line, tipPos, CGPoint(x: 0.0, y: 1000.0), .hidden),
+            ])
+    }
+}
+
+private class FloatingPanelLayout3Positions: FloatingPanelTestLayout {
+    let initialPosition: FloatingPanelPosition = .tip
+    let supportedPositions: Set<FloatingPanelPosition> = [.tip, .half, .full]
+}
+
+private typealias TestParameter = (UInt, CGFloat,CGPoint, FloatingPanelPosition)
+private func assertTargetPosition(_ floatingPanel: FloatingPanel, with params: [TestParameter]) {
+    params.forEach { (line, pos, velocity, result) in
+        floatingPanel.surfaceView.frame.origin.y = pos
+        XCTAssertEqual(floatingPanel.targetPosition(from: pos, with: velocity), result, line: line)
+    }
+}
+
+private class FloatingPanelProjectionalBehavior: FloatingPanelBehavior {
+    func shouldProjectMomentum(_ fpc: FloatingPanelController, for proposedTargetPosition: FloatingPanelPosition) -> Bool {
+        return true
+    }
 }

Framework/Tests/Utils.swift

@@ -0,0 +1,42 @@
+//
+//  Created by Shin Yamamoto on 2019/06/27.
+//  Copyright © 2019 scenee. All rights reserved.
+//
+
+import Foundation
+@testable import FloatingPanel
+
+func waitRunLoop(secs: TimeInterval = 0) {
+    RunLoop.main.run(until: Date(timeIntervalSinceNow: secs))
+}
+
+extension FloatingPanelController {
+    func showForTest() {
+        loadViewIfNeeded()
+        view.frame = CGRect(x: 0, y: 0, width: 375, height: 667)
+        show(animated: false, completion: nil)
+    }
+}
+
+class FloatingPanelTestDelegate: FloatingPanelControllerDelegate {
+    var layout: FloatingPanelLayout?
+    var behavior: FloatingPanelBehavior?
+    func floatingPanel(_ vc: FloatingPanelController, layoutFor newCollection: UITraitCollection) -> FloatingPanelLayout? {
+        return layout
+    }
+    func floatingPanel(_ vc: FloatingPanelController, behaviorFor newCollection: UITraitCollection) -> FloatingPanelBehavior? {
+        return behavior
+    }
+}
+
+protocol FloatingPanelTestLayout: FloatingPanelFullScreenLayout {}
+extension FloatingPanelTestLayout {
+    func insetFor(position: FloatingPanelPosition) -> CGFloat? {
+        switch position {
+        case .full: return 20.0
+        case .half: return 250.0
+        case .tip: return 60.0
+        default: return nil
+        }
+    }
+}

Package.swift

@@ -0,0 +1,27 @@
+// swift-tools-version:5.0
+// The swift-tools-version declares the minimum version of Swift required to build this package.
+
+import PackageDescription
+
+let package = Package(
+    name: "FloatingPanel",
+    platforms: [
+        .iOS(.v10)
+    ],
+    products: [
+        // Products define the executables and libraries produced by a package, and make them visible to other packages.
+        .library(
+            name: "FloatingPanel",
+            targets: ["FloatingPanel"]),
+    ],
+    dependencies: [
+        // Dependencies declare other packages that this package depends on.
+        // .package(url: /* package url */, from: "1.0.0"),
+    ],
+    targets: [
+        // Targets are the basic building blocks of a package. A target can define a module or a test suite.
+        // Targets can depend on other targets in this package, and on products in packages which this package depends on.
+        .target(name: "FloatingPanel", path: "Framework/Sources"),
+    ],
+    swiftLanguageVersions: [.version("5")]
+)

README.md

@@ -93,6 +93,10 @@ For [Carthage](https://github.com/Carthage/Carthage), add the following to your
 github "scenee/FloatingPanel"
 ```
 
+### Swift Package Manager with Xcode 11
+
+Follow [this doc](https://developer.apple.com/documentation/swift_packages/adding_package_dependencies_to_your_app).
+
 ## Getting Started
 
 ### Add a floating panel as a child view controller