progress on new Motion structure

732bcdb5 · Daniel Dahan · 3d9641b4 · 732bcdb5 · 732bcdb5 · 732bcdb5
Commit 732bcdb5 authored Dec 09, 2017 by Daniel Dahan
10 changed files
--- a/Motion.xcodeproj/project.pbxproj
+++ b/Motion.xcodeproj/project.pbxproj
@@ -7,6 +7,9 @@
 	objects = {
 /* Begin PBXBuildFile section */
+		965FE9611FDCC3AF0098BDD0 /* MotionState.swift in Sources */ = {isa = PBXBuildFile; fileRef = 965FE9601FDCC3AF0098BDD0 /* MotionState.swift */; };
+		965FE9631FDCCE030098BDD0 /* Motion+Complete.swift in Sources */ = {isa = PBXBuildFile; fileRef = 965FE9621FDCCE030098BDD0 /* Motion+Complete.swift */; };
+		965FE9651FDCCE910098BDD0 /* MotionProgressRunner.swift in Sources */ = {isa = PBXBuildFile; fileRef = 965FE9641FDCCE910098BDD0 /* MotionProgressRunner.swift */; };
 		96E409651F24F7370015A2B5 /* MotionAnimator.swift in Sources */ = {isa = PBXBuildFile; fileRef = 96E4093D1F24F7370015A2B5 /* MotionAnimator.swift */; };
 		96E409661F24F7370015A2B5 /* MotionAnimatorViewContext.swift in Sources */ = {isa = PBXBuildFile; fileRef = 96E4093E1F24F7370015A2B5 /* MotionAnimatorViewContext.swift */; };
 		96E409671F24F7370015A2B5 /* MotionCoreAnimationViewContext.swift in Sources */ = {isa = PBXBuildFile; fileRef = 96E4093F1F24F7370015A2B5 /* MotionCoreAnimationViewContext.swift */; };
@@ -28,9 +31,7 @@
 		96E409771F24F7370015A2B5 /* MotionAnimationState.swift in Sources */ = {isa = PBXBuildFile; fileRef = 96E409521F24F7370015A2B5 /* MotionAnimationState.swift */; };
 		96E409781F24F7370015A2B5 /* MotionCAAnimation.swift in Sources */ = {isa = PBXBuildFile; fileRef = 96E409531F24F7370015A2B5 /* MotionCAAnimation.swift */; };
 		96E409791F24F7370015A2B5 /* MotionContext.swift in Sources */ = {isa = PBXBuildFile; fileRef = 96E409541F24F7370015A2B5 /* MotionContext.swift */; };
-		96E4097A1F24F7370015A2B5 /* MotionController.swift in Sources */ = {isa = PBXBuildFile; fileRef = 96E409551F24F7370015A2B5 /* MotionController.swift */; };
 		96E4097B1F24F7370015A2B5 /* MotionCoordinateSpace.swift in Sources */ = {isa = PBXBuildFile; fileRef = 96E409561F24F7370015A2B5 /* MotionCoordinateSpace.swift */; };
-		96E4097C1F24F7370015A2B5 /* MotionIndependentController.swift in Sources */ = {isa = PBXBuildFile; fileRef = 96E409571F24F7370015A2B5 /* MotionIndependentController.swift */; };
 		96E4097D1F24F7370015A2B5 /* MotionPlugin.swift in Sources */ = {isa = PBXBuildFile; fileRef = 96E409581F24F7370015A2B5 /* MotionPlugin.swift */; };
 		96E4097E1F24F7370015A2B5 /* MotionSnapshotType.swift in Sources */ = {isa = PBXBuildFile; fileRef = 96E409591F24F7370015A2B5 /* MotionSnapshotType.swift */; };
 		96E4097F1F24F7370015A2B5 /* MotionTransition.swift in Sources */ = {isa = PBXBuildFile; fileRef = 96E4095A1F24F7370015A2B5 /* MotionTransition.swift */; };
@@ -63,9 +64,7 @@
 		96E4099C1F24F7570015A2B5 /* MotionAnimationState.swift in Headers */ = {isa = PBXBuildFile; fileRef = 96E409521F24F7370015A2B5 /* MotionAnimationState.swift */; settings = {ATTRIBUTES = (Public, ); }; };
 		96E4099D1F24F7570015A2B5 /* MotionCAAnimation.swift in Headers */ = {isa = PBXBuildFile; fileRef = 96E409531F24F7370015A2B5 /* MotionCAAnimation.swift */; settings = {ATTRIBUTES = (Public, ); }; };
 		96E4099E1F24F7570015A2B5 /* MotionContext.swift in Headers */ = {isa = PBXBuildFile; fileRef = 96E409541F24F7370015A2B5 /* MotionContext.swift */; settings = {ATTRIBUTES = (Public, ); }; };
-		96E4099F1F24F7570015A2B5 /* MotionController.swift in Headers */ = {isa = PBXBuildFile; fileRef = 96E409551F24F7370015A2B5 /* MotionController.swift */; settings = {ATTRIBUTES = (Public, ); }; };
 		96E409A01F24F7570015A2B5 /* MotionCoordinateSpace.swift in Headers */ = {isa = PBXBuildFile; fileRef = 96E409561F24F7370015A2B5 /* MotionCoordinateSpace.swift */; settings = {ATTRIBUTES = (Public, ); }; };
-		96E409A11F24F7570015A2B5 /* MotionIndependentController.swift in Headers */ = {isa = PBXBuildFile; fileRef = 96E409571F24F7370015A2B5 /* MotionIndependentController.swift */; settings = {ATTRIBUTES = (Public, ); }; };
 		96E409A21F24F7570015A2B5 /* MotionPlugin.swift in Headers */ = {isa = PBXBuildFile; fileRef = 96E409581F24F7370015A2B5 /* MotionPlugin.swift */; settings = {ATTRIBUTES = (Public, ); }; };
 		96E409A31F24F7570015A2B5 /* MotionSnapshotType.swift in Headers */ = {isa = PBXBuildFile; fileRef = 96E409591F24F7370015A2B5 /* MotionSnapshotType.swift */; settings = {ATTRIBUTES = (Public, ); }; };
 		96E409A41F24F7570015A2B5 /* MotionTransition.swift in Headers */ = {isa = PBXBuildFile; fileRef = 96E4095A1F24F7370015A2B5 /* MotionTransition.swift */; settings = {ATTRIBUTES = (Public, ); }; };
@@ -81,6 +80,9 @@
 /* End PBXBuildFile section */
 /* Begin PBXFileReference section */
+		965FE9601FDCC3AF0098BDD0 /* MotionState.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = MotionState.swift; sourceTree = "<group>"; };
+		965FE9621FDCCE030098BDD0 /* Motion+Complete.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = "Motion+Complete.swift"; sourceTree = "<group>"; };
+		965FE9641FDCCE910098BDD0 /* MotionProgressRunner.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = MotionProgressRunner.swift; sourceTree = "<group>"; };
 		96C98DD11E424AB000B22906 /* Motion.framework */ = {isa = PBXFileReference; explicitFileType = wrapper.framework; includeInIndex = 0; path = Motion.framework; sourceTree = BUILT_PRODUCTS_DIR; };
 		96E4093D1F24F7370015A2B5 /* MotionAnimator.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = MotionAnimator.swift; sourceTree = "<group>"; };
 		96E4093E1F24F7370015A2B5 /* MotionAnimatorViewContext.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = MotionAnimatorViewContext.swift; sourceTree = "<group>"; };
@@ -103,9 +105,7 @@
 		96E409521F24F7370015A2B5 /* MotionAnimationState.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = MotionAnimationState.swift; sourceTree = "<group>"; };
 		96E409531F24F7370015A2B5 /* MotionCAAnimation.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = MotionCAAnimation.swift; sourceTree = "<group>"; };
 		96E409541F24F7370015A2B5 /* MotionContext.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = MotionContext.swift; sourceTree = "<group>"; };
-		96E409551F24F7370015A2B5 /* MotionController.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = MotionController.swift; sourceTree = "<group>"; };
 		96E409561F24F7370015A2B5 /* MotionCoordinateSpace.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = MotionCoordinateSpace.swift; sourceTree = "<group>"; };
-		96E409571F24F7370015A2B5 /* MotionIndependentController.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = MotionIndependentController.swift; sourceTree = "<group>"; };
 		96E409581F24F7370015A2B5 /* MotionPlugin.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = MotionPlugin.swift; sourceTree = "<group>"; };
 		96E409591F24F7370015A2B5 /* MotionSnapshotType.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = MotionSnapshotType.swift; sourceTree = "<group>"; };
 		96E4095A1F24F7370015A2B5 /* MotionTransition.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = MotionTransition.swift; sourceTree = "<group>"; };
@@ -146,13 +146,14 @@
 				96E409BC1F24FC300015A2B5 /* LICENSE */,
 				96E4094F1F24F7370015A2B5 /* Motion.h */,
 				96E409501F24F7370015A2B5 /* Motion.swift */,
+				965FE9601FDCC3AF0098BDD0 /* MotionState.swift */,
+				965FE9621FDCCE030098BDD0 /* Motion+Complete.swift */,
+				965FE9641FDCCE910098BDD0 /* MotionProgressRunner.swift */,
 				96E409511F24F7370015A2B5 /* MotionAnimation.swift */,
 				96E409521F24F7370015A2B5 /* MotionAnimationState.swift */,
 				96E409531F24F7370015A2B5 /* MotionCAAnimation.swift */,
 				96E409541F24F7370015A2B5 /* MotionContext.swift */,
-				96E409551F24F7370015A2B5 /* MotionController.swift */,
 				96E409561F24F7370015A2B5 /* MotionCoordinateSpace.swift */,
-				96E409571F24F7370015A2B5 /* MotionIndependentController.swift */,
 				96E409581F24F7370015A2B5 /* MotionPlugin.swift */,
 				96E409591F24F7370015A2B5 /* MotionSnapshotType.swift */,
 				96E4095A1F24F7370015A2B5 /* MotionTransition.swift */,
@@ -235,9 +236,7 @@
 				96E4099C1F24F7570015A2B5 /* MotionAnimationState.swift in Headers */,
 				96E4099D1F24F7570015A2B5 /* MotionCAAnimation.swift in Headers */,
 				96E4099E1F24F7570015A2B5 /* MotionContext.swift in Headers */,
-				96E4099F1F24F7570015A2B5 /* MotionController.swift in Headers */,
 				96E409A01F24F7570015A2B5 /* MotionCoordinateSpace.swift in Headers */,
-				96E409A11F24F7570015A2B5 /* MotionIndependentController.swift in Headers */,
 				96E409A21F24F7570015A2B5 /* MotionPlugin.swift in Headers */,
 				96E409A31F24F7570015A2B5 /* MotionSnapshotType.swift in Headers */,
 				96E409A41F24F7570015A2B5 /* MotionTransition.swift in Headers */,
@@ -314,11 +313,11 @@
 				96E409731F24F7370015A2B5 /* MotionAnimationFillMode.swift in Sources */,
 				96E409791F24F7370015A2B5 /* MotionContext.swift in Sources */,
 				96E409831F24F7370015A2B5 /* DurationPreprocessor.swift in Sources */,
+				965FE9631FDCCE030098BDD0 /* Motion+Complete.swift in Sources */,
 				96E4097D1F24F7370015A2B5 /* MotionPlugin.swift in Sources */,
 				96E409681F24F7370015A2B5 /* MotionHasInsertOrder.swift in Sources */,
 				96E4096E1F24F7370015A2B5 /* Motion+CG.swift in Sources */,
 				96E409851F24F7370015A2B5 /* MatchPreprocessor.swift in Sources */,
-				96E4097C1F24F7370015A2B5 /* MotionIndependentController.swift in Sources */,
 				96E409861F24F7370015A2B5 /* MotionPreprocessor.swift in Sources */,
 				96E409821F24F7370015A2B5 /* CascadePreprocessor.swift in Sources */,
 				96E4096C1F24F7370015A2B5 /* Motion+CALayer.swift in Sources */,
@@ -329,7 +328,6 @@
 				96E409651F24F7370015A2B5 /* MotionAnimator.swift in Sources */,
 				96E409671F24F7370015A2B5 /* MotionCoreAnimationViewContext.swift in Sources */,
 				96E4096D1F24F7370015A2B5 /* Motion+CAMediaTimingFunction.swift in Sources */,
-				96E4097A1F24F7370015A2B5 /* MotionController.swift in Sources */,
 				96E409841F24F7370015A2B5 /* IgnoreSubviewModifiersPreprocessor.swift in Sources */,
 				96E409771F24F7370015A2B5 /* MotionAnimationState.swift in Sources */,
 				96E409761F24F7370015A2B5 /* MotionAnimation.swift in Sources */,
@@ -342,6 +340,8 @@
 				96E409881F24F7370015A2B5 /* TransitionPreprocessor.swift in Sources */,
 				96E4096A1F24F7370015A2B5 /* MotionViewPropertyViewContext.swift in Sources */,
 				96E409661F24F7370015A2B5 /* MotionAnimatorViewContext.swift in Sources */,
+				965FE9651FDCCE910098BDD0 /* MotionProgressRunner.swift in Sources */,
+				965FE9611FDCC3AF0098BDD0 /* MotionState.swift in Sources */,
 				96E4097F1F24F7370015A2B5 /* MotionTransition.swift in Sources */,
 				96E409751F24F7370015A2B5 /* Motion.swift in Sources */,
 				96E4096F1F24F7370015A2B5 /* Motion+Obj-C.swift in Sources */,

--- a/Motion.xcodeproj/xcshareddata/xcschemes/Motion iOS.xcscheme
+++ b/Motion.xcodeproj/xcshareddata/xcschemes/Motion iOS.xcscheme
 <?xml version="1.0" encoding="UTF-8"?>
 <Scheme
-   LastUpgradeVersion = "0900"
+   LastUpgradeVersion = "0920"
   version = "1.3">
   <BuildAction
      parallelizeBuildables = "YES"

--- a/Sources/Extensions/Motion+UIView.swift
+++ b/Sources/Extensions/Motion+UIView.swift
@@ -220,6 +220,7 @@ internal class SnapshotWrapperView: UIView {
    init(contentView: UIView) {
        self.contentView = contentView
        super.init(frame: contentView.frame)
+        contentView.frame = bounds
        addSubview(contentView)
    }
@@ -229,8 +230,7 @@ internal class SnapshotWrapperView: UIView {
    override func layoutSubviews() {
        super.layoutSubviews()
-        contentView.bounds.size = bounds.size
+        contentView.frame = bounds
-        contentView.center = bounds.center
    }
 }
@@ -243,13 +243,17 @@ internal extension UIView {
        if #available(iOS 9.0, *), isHidden && (superview is UICollectionView || superview is UIStackView || self is UITableViewCell) {
            return []
        } else if isHidden && (superview is UICollectionView || self is UITableViewCell) {
            return []
        } else if isMotionEnabledForSubviews {
-            return [self] + subviews.flatMap { $0.flattenedViewHierarchy }
+            return [self] + subviews.flatMap {
-        } else {
+                $0.flattenedViewHierarchy
-            return [self]
+            }
        }
+        return [self]
    }
    /**
@@ -285,7 +289,13 @@ internal extension UIView {
     */
    func slowSnapshotView() -> UIView {
        UIGraphicsBeginImageContextWithOptions(bounds.size, isOpaque, 0)
-        layer.render(in: UIGraphicsGetCurrentContext()!)
+        guard let currentContext = UIGraphicsGetCurrentContext() else {
+            UIGraphicsEndImageContext()
+            return UIView()
+        }
+        layer.render(in: currentContext)
        let image = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext()

--- a/Sources/Motion+Complete.swift
+++ b/Sources/Motion+Complete.swift
+/*
+ * The MIT License (MIT)
+ *
+ * Copyright (C) 2017, Daniel Dahan and CosmicMind, Inc. <http://cosmicmind.com>.
+ * All rights reserved.
+ *
+ * Original Inspiration & Author
+ * Copyright (c) 2016 Luke Zhao <me@lkzhao.com>
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+import UIKit
+extension Motion {
+    /**
+     Complete the transition.
+     - Parameter after: A TimeInterval.
+     - Parameter isFinished: A Boolean indicating if the transition
+     has completed.
+     */
+    func complete(after: TimeInterval, isFinished: Bool) {
+        guard isTransitioning else {
+            return
+        }
+        if after <= 0.001 {
+            complete(isFinished: isFinished)
+            return
+        }
+        let v = (isFinished ? elapsedTime : 1 - elapsedTime) * totalDuration
+        self.isFinished = isFinished
+        currentAnimationDuration = after + v
+        beginTime = CACurrentMediaTime() - v
+    }
+    /**
+     Complete the transition.
+     - Parameter isFinished: A Boolean indicating if the transition
+     has completed.
+     */
+    @objc
+    func complete(isFinished: Bool) {
+        if state == .notified {
+            forceFinishing = isFinished
+        }
+        guard .animating == state || .starting == state else {
+            return
+        }
+        defer {
+            transitionContext = nil
+            fromViewController = nil
+            toViewController = nil
+            isNavigationController = false
+            isTabBarController = false
+            forceNonInteractive = false
+            transitionPairs.removeAll()
+            transitionObservers = nil
+            transitionContainer = nil
+            completionCallback = nil
+            forceFinishing = nil
+            container = nil
+            startingProgress = nil
+            preprocessors.removeAll()
+            animators.removeAll()
+            plugins.removeAll()
+            context = nil
+            elapsedTime = 0
+            totalDuration = 0
+            state = .possible
+        }
+        state = .completing
+        progressRunner.stop()
+        context.clean()
+        if let tv = toView, let fv = fromView {
+            if isFinished && isPresenting && toOverFullScreen {
+                // finished presenting a overFullScreen view controller.
+                context.unhide(rootView: tv)
+                context.removeSnapshots(rootView: tv)
+                context.storeViewAlpha(rootView: fv)
+                fromViewController!.motionStoredSnapshot = container
+                fv.removeFromSuperview()
+                fv.addSubview(container)
+            } else if !isFinished && !isPresenting && fromOverFullScreen {
+                // Cancelled dismissing a overFullScreen view controller.
+                context.unhide(rootView: fv)
+                context.removeSnapshots(rootView: fv)
+                context.storeViewAlpha(rootView: tv)
+                toViewController!.motionStoredSnapshot = container
+                container.superview?.addSubview(tv)
+                tv.addSubview(container)
+            } else {
+                context.unhideAll()
+                context.removeAllSnapshots()
+            }
+            // Move fromView & toView back from our container back to the one supplied by UIKit.
+            if (toOverFullScreen && isFinished) || (fromOverFullScreen && !isFinished) {
+                transitionContainer?.addSubview(isFinished ? fv : tv)
+            }
+            transitionContainer?.addSubview(isFinished ? tv : fv)
+            if isPresenting != isFinished, !isContainerController {
+                // Only happens when present a .overFullScreen view controller.
+                // bug: http://openradar.appspot.com/radar?id=5320103646199808
+                UIApplication.shared.keyWindow?.addSubview(isPresenting ? fv : tv)
+            }
+        }
+        if container.superview == transitionContainer {
+            container.removeFromSuperview()
+        }
+        for a in animators {
+            a.clean()
+        }
+        transitionContainer?.isUserInteractionEnabled = true
+        completionCallback?(isFinished)
+        let tContext = transitionContext
+        let fvc = fromViewController
+        let tvc = toViewController
+        if isFinished {
+            processEndTransitionDelegation(transitionContext: tContext, fromViewController: fvc, toViewController: tvc)
+        } else {
+            processCancelTransitionDelegation(transitionContext: tContext, fromViewController: fvc, toViewController: tvc)
+            tContext?.cancelInteractiveTransition()
+        }
+        tContext?.completeTransition(isFinished)
+    }
+}
--- a/Sources/Motion.swift
+++ b/Sources/Motion.swift
@@ -125,54 +125,176 @@ public protocol MotionViewControllerDelegate {
 func apply(transitions: [MotionTransition], to view: UIView)
 ```
 */
-public class Motion: MotionController {
+import UIKit
+public class Motion: NSObject, MotionProgressRunnerDelegate {
    /// Shared singleton object for controlling the transition
    public static let shared = Motion()
+    /// Plugins that are enabled during the transition.
+    internal static var enabledPlugins = [MotionPlugin.Type]()
+    /// A reference to a fullscreen snapshot.
+    internal var fullScreenSnapshot: UIView!
+    /// A reference to the MotionContext.
+    public internal(set) var context: MotionContext!
+    /// A boolean indicating whether the transition interactive or not.
+    public var isInteractive: Bool {
+        return nil == displayLink
+    }
    /// Source view controller.
    public internal(set) var fromViewController: UIViewController?
    /// Destination view controller.
    public internal(set) var toViewController: UIViewController?
-    /// Whether or not we are presenting the destination view controller.
+    /// A reference to the fromView, fromViewController.view.
-    public internal(set) var isPresenting = true
+    internal var fromView: UIView? {
+        return fromViewController?.view
+    }
+    /// A reference to the toView, toViewController.view.
+    internal var toView: UIView? {
+        return toViewController?.view
+    }
+    /// The color of the transitioning container.
+    internal var containerBackgroundColor: UIColor?
+    /**
+     A UIViewControllerContextTransitioning object provided by UIKit, which
+     might be nil when isTransitioning. This happens when calling motionReplaceViewController
+     */
+    internal weak var transitionContext: UIViewControllerContextTransitioning?
-    /// Progress of the current transition, 0 if a transition is not happening.
+    /// Progress of the current transition. 0 if no transition is happening.
-    public override var elapsedTime: TimeInterval {
+    public internal(set) var elapsedTime: TimeInterval = 0 {
        didSet {
-            guard isTransitioning else {
+            guard .animating == state else {
                return
            }
+            updateTransitionObservers()
+            if isInteractive {
+                updateAnimators()
+            } else {
+                updatePlugins()
+            }
            transitionContext?.updateInteractiveTransition(CGFloat(elapsedTime))
        }
    }
-    /// Indicates whether the transition is animating or not.
+    /// State of the transition.
-    public var isAnimating = false
+    public internal(set) var state = MotionState.possible {
+        didSet {
+            guard .notified != state else {
+                return
+            }
+            guard .starting != state else {
+                return
+            }
+            beginCallback?(.animating == state)
+            beginCallback = nil
+        }
+    }
+    /// A boolean indicating whether a transition is active.
+    public var isTransitioning: Bool {
+        return nil != transitionContainer
+    }
    /**
-     A UIViewControllerContextTransitioning object provided by UIKit, which
+     A view container used to hold all the animating views during a
-     might be nil when isTransitioning. This happens when calling motionReplaceViewController
+     transition.
     */
-    internal weak var transitionContext: UIViewControllerContextTransitioning?
+    public internal(set) var container: UIView!
-    /// A reference to a fullscreen snapshot.
+    /// UIKit's supplied transition container.
-    internal var fullScreenSnapshot: UIView!
+    internal var transitionContainer: UIView?
+    /// An optional begin callbcak.
+    internal var beginCallback: ((Bool) -> Void)?
+    /// An optional completion callback.
+    internal var completionCallback: ((Bool) -> Void)?
+    /// Binds the render cycle to the transition animation.
+    internal var displayLink: CADisplayLink?
+    /// An Array of observers that are updated during a transition.
+    internal var transitionObservers: [MotionTransitionObserver]?
+    /// Max duration used by MotionAnimators and MotionPlugins.
+    public internal(set) var totalDuration: TimeInterval = 0
+    /// The currently running animation duration.
+    internal var currentAnimationDuration: TimeInterval = 0
+    /// A reference to a MotionProgressRunner.
+    lazy var progressRunner: MotionProgressRunner = {
+        let runner = MotionProgressRunner()
+        runner.delegate = self
+        return runner
+    }()
+    /// The start time of the animation.
+    internal var beginTime: TimeInterval? {
+        didSet {
+            guard nil != beginTime else {
+                displayLink?.isPaused = true
+                displayLink?.remove(from: RunLoop.main, forMode: RunLoopMode(rawValue: RunLoopMode.commonModes.rawValue))
+                displayLink = nil
+                return
+            }
+            guard nil == displayLink else {
+                return
+            }
+            displayLink = CADisplayLink(target: self, selector: #selector(handleDisplayLink(_:)))
+            displayLink?.add(to: RunLoop.main, forMode: RunLoopMode(rawValue: RunLoopMode.commonModes.rawValue))
+        }
+    }
+    /// A boolean indicating if the transition has finished.
+    internal var isFinished = true
+    /// An Array of MotionPreprocessors used during a transition.
+    internal lazy var preprocessors = [MotionPreprocessor]()
+    /// An Array of MotionAnimators used during a transition.
+    internal lazy var animators = [MotionAnimator]()
+    /// An Array of MotionPlugins used during a transition.
+    internal lazy var plugins = [MotionPlugin]()
+    /// The matching fromViews to toViews based on the motionIdentifier value.
+    internal lazy var transitionPairs = [(fromViews: [UIView], toViews: [UIView])]()
+    /// Whether or not we are presenting the destination view controller.
+    public var isPresenting = true
+    /// Indicates whether the transition is animating or not.
+    public var isAnimating = false
    /// Default animation type.
    internal var defaultAnimation = MotionTransitionType.auto
-    /// The color of the transitioning container.
-    internal var containerBackgroundColor: UIColor?
    /**
     By default, Motion will always appear to be interactive to UIKit. This forces it to appear non-interactive.
     Used when doing a motionReplaceViewController within a UINavigationController, to fix a bug with
     UINavigationController.setViewControllers not able to handle interactive transitions.
     */
    internal var forceNonInteractive = false
+    internal var forceFinishing: Bool?
+    internal var startingProgress: CGFloat?
    /// Inserts the toViews first.
    internal var insertToViewFirst = false
@@ -206,16 +328,6 @@ public class Motion: MotionController {
        return !isContainerController && (.overFullScreen == v.modalPresentationStyle || .overCurrentContext == v.modalPresentationStyle)
    }
-    /// A reference to the fromView, fromViewController.view.
-    internal var fromView: UIView? {
-        return fromViewController?.view
-    }
-    /// A reference to the toView, toViewController.view.
-    internal var toView: UIView? {
-        return toViewController?.view
-    }
    /// An initializer.
    internal override init() {
        super.init()
@@ -223,169 +335,490 @@ public class Motion: MotionController {
 }
 public extension Motion {
-    /// Turn off built-in animations for the next transition.
-    func disableDefaultAnimationForNextTransition() {
-        defaultAnimation = .none
-    }
    /**
-     Set the default animation for the next transition. This may override the
+     Receive callbacks on each animation frame.
-     root-view's motionTransitions during the transition.
+     Observers will be cleaned when a transition completes.
-     - Parameter animation: A MotionTransitionType.
+     - Parameter observer: A MotionTransitionObserver.
     */
-    func setAnimationForNextTransition(_ animation: MotionTransitionType) {
+    func addTransitionObserver(observer: MotionTransitionObserver) {
-        defaultAnimation = animation
+        if nil == transitionObservers {
+            transitionObservers = []
+        }
+        transitionObservers?.append(observer)
+    }
+}
+private extension Motion {
+    /// Updates the transition observers.
+    func updateTransitionObservers() {
+        guard let observers = transitionObservers else {
+            return
+        }
+        for v in observers {
+            v.motion(transitionObserver: v, didUpdateWith: elapsedTime)
+        }
    }
-    /**
+    /// Updates the animators.
-     Set the container background color for the next transition.
+    func updateAnimators() {
-     - Parameter _ color: An optional UIColor.
+        let t = elapsedTime * totalDuration
-     */
+        for a in animators {
-    func setContainerBackgroundColorForNextTransition(_ color: UIColor?) {
+            a.seek(to: t)
-        containerBackgroundColor = color
+        }
+    }
+    /// Updates the plugins.
+    func updatePlugins() {
+        let t = elapsedTime * totalDuration
+        for p in plugins where p.requirePerFrameCallback {
+            p.seek(to: t)
+        }
    }
 }
-public extension Motion {
+private extension Motion {
    /**
-     A helper transition function.
+     Handler for the DisplayLink updates.
-     - Parameter from: A UIViewController.
+     - Parameter _ link: CADisplayLink.
-     - Parameter to: A UIViewController.
-     - Parameter in view: A UIView.
-     - Parameter completion: An optional completion handler.
     */
-    func transition(from: UIViewController, to: UIViewController, in view: UIView, completion: ((Bool) -> Void)? = nil) {
+    @objc
-        guard !isTransitioning else {
+    func handleDisplayLink(_ link: CADisplayLink) {
+        guard isTransitioning else {
            return
        }
-        isPresenting = true
+        guard 0 < currentAnimationDuration else {
-        transitionContainer = view
+            return
-        fromViewController = from
+        }
-        toViewController = to
-        completionCallback = completion
-        start()
+        guard let t = beginTime else {
+            return
+        }
+        let cTime = CACurrentMediaTime() - t
+        if cTime > currentAnimationDuration {
+            elapsedTime = isFinished ? 1 : 0
+            beginTime = nil
+            complete(isFinished: isFinished)
+        } else {
+            var eTime = cTime / totalDuration
+            if !isFinished {
+                eTime = 1 - eTime
+            }
+            elapsedTime = max(0, min(1, eTime))
+        }
    }
 }
-fileprivate extension Motion {
+public extension Motion {
-    /// Starts the transition animation.
+    /**
-    func start() {
+     Updates the elapsed time for the interactive transition.
+     - Parameter elapsedTime t: the current progress, must be between -1...1.
+     */
+    public func update(elapsedTime: TimeInterval) {
        guard isTransitioning else {
            return
        }
-        prepareViewControllers()
+        beginTime = nil
-        prepareSnapshotView()
+        self.elapsedTime = max(-1, min(1, elapsedTime))
-        prepareTransition()
-        prepareContext()
-        prepareToView()
-        prepareViewHierarchy()
-        processContext()
-        prepareTransitionPairs()
-        processForAnimation()
    }
-}
+    /**
-internal extension Motion {
+     Finish the interactive transition.
-    override func animate() {
+     Will stop the interactive transition and animate from the
-        guard let tv = toView else {
+     current state to the **end** state
+     - Parameter isAnimated: A boolean indicating if the completion is animated.
+     */
+    public func end(isAnimated: Bool = true) {
+        guard isTransitioning else {
            return
        }
-        context.unhide(view: tv)
+        guard isAnimated else {
+            complete(isFinished: true)
+            return
+        }
-        updateContainerBackgroundColor()
+        var t: TimeInterval = 0
-        updateInsertOrder()
-        super.animate()
+        for a in animators {
+            t = max(t, a.resume(at: elapsedTime * totalDuration, isReversed: false))
+        }
-        fullScreenSnapshot?.removeFromSuperview()
+        complete(after: t, isFinished: true)
    }
-    override func complete(isFinished: Bool) {
+    /**
+     Cancel the interactive transition.
+     Will stop the interactive transition and animate from the
+     current state to the **begining** state
+     - Parameter isAnimated: A boolean indicating if the completion is animated.
+     */
+    public func cancel(isAnimated: Bool = true) {
        guard isTransitioning else {
            return
        }
-        guard let c = container else {
+        guard isAnimated else {
+            complete(isFinished: false)
            return
        }
-        guard let tc = transitionContainer else {
+        var d: TimeInterval = 0
+        for a in animators {
+            var t = elapsedTime
+            if t < 0 {
+                t = -t
+            }
+            d = max(d, a.resume(at: t * totalDuration, isReversed: true))
+        }
+        complete(after: d, isFinished: false)
+    }
+    /**
+     Override transition animations during an interactive animation.
+     For example:
+     Motion.shared.apply([.position(x:50, y:50)], to: view)
+     will set the view's position to 50, 50
+     - Parameter transitions: An Array of MotionTransitions.
+     - Parameter to view: A UIView.
+     */
+    public func apply(transitions: [MotionTransition], to view: UIView) {
+        guard isTransitioning else {
            return
        }
-        guard let fv = fromView else {
+        let s = MotionTransitionState(transitions: transitions)
+        let v = context.transitionPairedView(for: view) ?? view
+        for a in animators {
+            a.apply(state: s, to: v)
+        }
+    }
+}
+internal extension Motion {
+    /**
+     Load plugins, processors, animators, container, & context
+     The transitionContainer must already be set.
+     Subclasses should call context.set(fromViews: toViews) after
+     inserting fromViews & toViews into the container
+     */
+    @objc
+    func prepareTransition() {
+        guard isTransitioning else {
+            return
+        }
+        prepareTransitionContainer()
+        prepareContext()
+        preparePreprocessors()
+        prepareAnimators()
+        preparePlugins()
+    }
+    /// Prepares the transition fromView & toView pairs.
+    @objc
+    func prepareTransitionPairs() {
+        guard isTransitioning else {
            return
        }
+        for a in animators {
+            let fv = context.fromViews.filter { (view) -> Bool in
+                return a.canAnimate(view: view, isAppearing: false)
+            }
+            let tv = context.toViews.filter {
+                return a.canAnimate(view: $0, isAppearing: true)
+            }
+            transitionPairs.append((fv, tv))
+        }
        guard let tv = toView else {
            return
        }
-        context.clean()
+        context.hide(view: tv)
+    }
+}
+internal extension Motion {
+    /// Executes the preprocessors' process function.
+    func processContext() {
+        guard isTransitioning else {
+            return
+        }
+        for x in preprocessors {
+            x.process(fromViews: context.fromViews, toViews: context.toViews)
+        }
+    }
+    /**
+     Animates the views. Subclasses should call `prepareTransition` &
+     `prepareTransitionPairs` before calling `animate`.
+     */
+    @objc
+    func animate() {
+        guard .starting == state else {
+            return
+        }
+        state = .animating
+        if let tv = toView {
+            context.unhide(view: tv)
+        }
-        if isFinished && isPresenting && toOverFullScreen {
+        for (fv, tv) in transitionPairs {
-            // finished presenting a overFullScreen view controller.
+            for view in fv {
-            context.unhide(rootView: tv)
+                context.hide(view: view)
-            context.removeSnapshots(rootView: tv)
+            }
-            context.storeViewAlpha(rootView: fv)
-            fromViewController!.motionStoredSnapshot = container
+            for view in tv {
-            fv.removeFromSuperview()
+                context.hide(view: view)
-            fv.addSubview(c)
+            }
-        } else if !isFinished && !isPresenting && fromOverFullScreen {
+        }
-            // Cancelled dismissing a overFullScreen view controller.
-            context.unhide(rootView: fv)
+        var t: TimeInterval = 0
-            context.removeSnapshots(rootView: fv)
+        var b = false
-            context.storeViewAlpha(rootView: tv)
+        for (i, a) in animators.enumerated() {
+            let d = a.animate(fromViews: transitionPairs[i].0, toViews: transitionPairs[i].1)
-            toViewController!.motionStoredSnapshot = container
+            if .infinity == d {
-            tv.removeFromSuperview()
+                b = true
-            tv.addSubview(c)
+            } else {
+                t = max(t, d)
+            }
+        }
+        totalDuration = t
+        if b {
+            update(elapsedTime: 0)
        } else {
-            context.unhideAll()
+            complete(after: t, isFinished: true)
-            context.removeAllSnapshots()
-            c.removeFromSuperview()
        }
-        // Move fromView & toView back from our container back to the one supplied by UIKit.
+        updateContainerBackgroundColor()
-        if (toOverFullScreen && isFinished) || (fromOverFullScreen && !isFinished) {
+        updateInsertOrder()
-            tc.addSubview(isFinished ? fv : tv)
+        fullScreenSnapshot?.removeFromSuperview()
+    }
+}
+private extension Motion {
+    /// Prepares the transition container.
+    func prepareTransitionContainer() {
+        guard let v = transitionContainer else {
+            return
        }
-        tc.addSubview(isFinished ? tv : fv)
+        v.isUserInteractionEnabled = false
+        // a view to hold all the animating views
+        container = UIView(frame: v.bounds)
+        v.addSubview(container!)
+    }
+    /// Prepares the preprocessors.
+    func preparePreprocessors() {
+        for x in [
+            IgnoreSubviewTransitionsPreprocessor(),
+            MatchPreprocessor(),
+            SourcePreprocessor(),
+            CascadePreprocessor(),
+            TransitionPreprocessor(motion: self),
+            DurationPreprocessor()] as [MotionPreprocessor] {
+                preprocessors.append(x)
+        }
-        if isPresenting != isFinished, !isContainerController {
+        for x in preprocessors {
-            // Only happens when present a .overFullScreen view controller.
+            x.context = context
-            // bug: http://openradar.appspot.com/radar?id=5320103646199808
-            UIApplication.shared.keyWindow!.addSubview(isPresenting ? fv : tv)
        }
+    }
+    /// Prepares the animators.
+    func prepareAnimators() {
+        animators.append(MotionTransitionAnimator<MotionCoreAnimationViewContext>())
-        // use temp variables to remember these values
+        if #available(iOS 10, tvOS 10, *) {
-        // because we have to reset everything before calling
+            animators.append(MotionTransitionAnimator<MotionViewPropertyViewContext>())
-        // any delegate or completion block
+        }
-        let tContext = transitionContext
-        let fvc = fromViewController
-        let tvc = toViewController
-        resetTransition()
+        for v in animators {
+            v.context = context
+        }
+    }
+    /// Prepares the plugins.
+    func preparePlugins() {
+        for x in Motion.enabledPlugins.map({
+            return $0.init()
+        }) {
+            plugins.append(x)
+        }
-        super.complete(isFinished: isFinished)
+        for plugin in plugins {
+            preprocessors.append(plugin)
+            animators.append(plugin)
+        }
+    }
+}
+private extension Motion {
+    /// Updates the container background color.
+    func updateContainerBackgroundColor() {
+        if let v = containerBackgroundColor {
+            container?.backgroundColor = v
+        } else if !toOverFullScreen && !fromOverFullScreen {
+            container?.backgroundColor = toView?.backgroundColor
+        }
+    }
+    /// Updates the insertToViewFirst boolean for animators.
+    func updateInsertOrder() {
+        if fromOverFullScreen {
+            insertToViewFirst = true
+        }
-        if isFinished {
+        for v in animators {
-            processEndTransitionDelegation(transitionContext: tContext, fromViewController: fvc, toViewController: tvc)
+            (v as? MotionHasInsertOrder)?.insertToViewFirst = insertToViewFirst
-        } else {
+        }
-            processCancelTransitionDelegation(transitionContext: tContext, fromViewController: fvc, toViewController: tvc)
+    }
+}
+internal extension Motion {
+    /**
+     Checks if a given plugin is enabled.
+     - Parameter plugin: A MotionPlugin.Type.
+     - Returns: A boolean indicating if the plugin is enabled or not.
+     */
+    static func isEnabled(plugin: MotionPlugin.Type) -> Bool {
+        return nil != enabledPlugins.index(where: { return $0 == plugin })
+    }
+    /**
+     Enables a given plugin.
+     - Parameter plugin: A MotionPlugin.Type.
+     */
+    static func enable(plugin: MotionPlugin.Type) {
+        disable(plugin: plugin)
+        enabledPlugins.append(plugin)
+    }
+    /**
+     Disables a given plugin.
+     - Parameter plugin: A MotionPlugin.Type.
+     */
+    static func disable(plugin: MotionPlugin.Type) {
+        guard let index = enabledPlugins.index(where: { return $0 == plugin }) else {
+            return
        }
-        tContext?.completeTransition(isFinished)
+        enabledPlugins.remove(at: index)
    }
 }
-fileprivate extension Motion {
+internal extension Motion {
+    // should call this after `prepareTransitionPairs` & before `processContext`
+    func insert<T>(preprocessor: MotionPreprocessor, before: T.Type) {
+        let i = preprocessors.index { $0 is T } ?? preprocessors.count
+        preprocessor.context = context
+        preprocessors.insert(preprocessor, at: i)
+    }
+}
+public extension Motion {
+    /// Turn off built-in animations for the next transition.
+    func disableDefaultAnimationForNextTransition() {
+        defaultAnimation = .none
+    }
+    /**
+     Set the default animation for the next transition. This may override the
+     root-view's motionTransitions during the transition.
+     - Parameter animation: A MotionTransitionType.
+     */
+    func setAnimationForNextTransition(_ animation: MotionTransitionType) {
+        defaultAnimation = animation
+    }
+    /**
+     Set the container background color for the next transition.
+     - Parameter _ color: An optional UIColor.
+     */
+    func setContainerBackgroundColorForNextTransition(_ color: UIColor?) {
+        containerBackgroundColor = color
+    }
+}
+public extension Motion {
+    /**
+     A helper transition function.
+     - Parameter from: A UIViewController.
+     - Parameter to: A UIViewController.
+     - Parameter in view: A UIView.
+     - Parameter completion: An optional completion handler.
+     */
+    func transition(from: UIViewController, to: UIViewController, in view: UIView, completion: ((Bool) -> Void)? = nil) {
+        guard !isTransitioning else {
+            return
+        }
+        isPresenting = true
+        transitionContainer = view
+        fromViewController = from
+        toViewController = to
+        completionCallback = completion
+        start()
+    }
+}
+private extension Motion {
+    /// Starts the transition animation.
+    func start() {
+        guard .notified == state else {
+            return
+        }
+        state = .starting
+        prepareViewControllers()
+        prepareSnapshotView()
+        prepareTransition()
+        prepareContext()
+        prepareToView()
+        prepareViewHierarchy()
+        processContext()
+        prepareTransitionPairs()
+        processForAnimation()
+    }
+}
+internal extension Motion {
    /// Resets the transition values.
    func resetTransition() {
        transitionContext = nil
@@ -400,7 +833,7 @@ fileprivate extension Motion {
    }
 }
-fileprivate extension Motion {
+internal extension Motion {
    /// Prepares the from and to view controllers.
    func prepareViewControllers() {
        processStartTransitionDelegation(fromViewController: fromViewController, toViewController: toViewController)
@@ -440,6 +873,8 @@ fileprivate extension Motion {
            return
        }
+        context = MotionContext(container: v)
        context.loadViewAlpha(rootView: tv)
        v.addSubview(tv)
@@ -457,8 +892,12 @@ fileprivate extension Motion {
            return
        }
-        tv.frame = fv.frame
+        if let toViewController = toViewController, let transitionContext = transitionContext {
-        tv.updateConstraints()
+            tv.frame = transitionContext.finalFrame(for: toViewController)
+        } else {
+            tv.frame = fv.frame
+        }
        tv.setNeedsLayout()
        tv.layoutIfNeeded()
    }
@@ -478,27 +917,11 @@ fileprivate extension Motion {
 }
 internal extension Motion {
-    override func prepareTransition() {
-        super.prepareTransition()
-        insert(preprocessor: TransitionPreprocessor(motion: self), before: DurationPreprocessor.self)
-    }
-    override func prepareTransitionPairs() {
-        super.prepareTransitionPairs()
-        guard let tv = toView else {
-            return
-        }
-        context.hide(view: tv)
-    }
-}
-fileprivate extension Motion {
    /// Processes the animations.
    func processForAnimation() {
        #if os(tvOS)
            animate()
        #else
            if isNavigationController {
                // When animating within navigationController, we have to dispatch later into the main queue.
@@ -509,6 +932,7 @@ fileprivate extension Motion {
            } else {
                animate()
            }
        #endif
    }
@@ -627,28 +1051,6 @@ fileprivate extension Motion {
    }
 }
-fileprivate extension Motion {
-    /// Updates the container background color.
-    func updateContainerBackgroundColor() {
-        if let v = containerBackgroundColor {
-            container?.backgroundColor = v
-        } else if !toOverFullScreen && !fromOverFullScreen {
-            container?.backgroundColor = toView?.backgroundColor
-        }
-    }
-    /// Updates the insertToViewFirst boolean for animators.
-    func updateInsertOrder() {
-        if fromOverFullScreen {
-            insertToViewFirst = true
-        }
-        for v in animators {
-            (v as? MotionHasInsertOrder)?.insertToViewFirst = insertToViewFirst
-        }
-    }
-}
 internal extension Motion {
    /**
     Helper for processing the MotionViewControllerDelegate.
@@ -696,7 +1098,7 @@ extension Motion: UIViewControllerAnimatedTransitioning {
     - Returns: A TimeInterval that is the total animation time including delays.
     */
    public func transitionDuration(using transitionContext: UIViewControllerContextTransitioning?) -> TimeInterval {
-        return 0 // Will be updated dynamically.
+        return 0 // Time will be updated dynamically.
    }
    public func animationEnded(_ transitionCompleted: Bool) {

--- a/Sources/MotionContext.swift
+++ b/Sources/MotionContext.swift
@@ -77,6 +77,7 @@ internal extension MotionContext {
    func set(fromViews: [UIView], toViews: [UIView]) {
        self.fromViews = fromViews
        self.toViews = toViews
        map(views: fromViews, identifierMap: &motionIdentifierToSourceView)
        map(views: toViews, identifierMap: &motionIdentifierToDestinationView)
    }
@@ -114,8 +115,8 @@ public extension MotionContext {
        get {
            return viewToTargetState[view]
        }
-        set {
+        set(value) {
-            viewToTargetState[view] = newValue
+            viewToTargetState[view] = value
        }
    }
 }
@@ -185,6 +186,7 @@ public extension MotionContext {
            if let visualEffectView = containerView as? UIVisualEffectView {
                containerView = visualEffectView.contentView
            }
        case .global:
            break
        }
@@ -221,8 +223,8 @@ public extension MotionContext {
        case .optimized:
            #if os(tvOS)
                snapshot = view.snapshotView(afterScreenUpdates: true)!
-            #else
+            #else
                if #available(iOS 9.0, *), let stackView = view as? UIStackView {
                    snapshot = stackView.slowSnapshotView()
@@ -246,7 +248,6 @@ public extension MotionContext {
                    // take a snapshot without the background
                    barView.layer.sublayers![0].opacity = 0
                    let realSnapshot = barView.snapshotView(afterScreenUpdates: true)!
                    barView.layer.sublayers![0].opacity = 1
@@ -260,6 +261,7 @@ public extension MotionContext {
                } else {
                    snapshot = view.snapshotView() ?? UIView()
                }
            #endif
        }
@@ -267,6 +269,7 @@ public extension MotionContext {
            if let imageView = view as? UIImageView, imageView.adjustsImageWhenAncestorFocused {
                snapshot.frame = imageView.focusedFrameGuide.layoutFrame
            }
        #endif
        view.layer.cornerRadius = oldCornerRadius
@@ -323,6 +326,7 @@ public extension MotionContext {
            for sibling in nextSiblings {
                insertGlobalViewTree(view: sibling)
            }
        } else {
            containerView.addSubview(snapshot)
        }
@@ -363,7 +367,7 @@ internal extension MotionContext {
     - Parameter view: A UIView.
     */
    func hide(view: UIView) {
-        guard nil == viewToAlphas[view], .noSnapshot != self[view]?.snapshotType else {
+        guard nil == viewToAlphas[view] else {
            return
        }
@@ -372,7 +376,7 @@ internal extension MotionContext {
            viewToAlphas[view] = 1
        } else {
-            viewToAlphas[view] = view.isOpaque ? .infinity : view.alpha
+            viewToAlphas[view] = view.alpha
            view.alpha = 0
        }
    }
@@ -389,10 +393,6 @@ internal extension MotionContext {
        if view is UIVisualEffectView {
            view.isHidden = false
-        } else if oldAlpha == .infinity {
-            view.alpha = 1
-            view.isOpaque = true
        } else {
            view.alpha = oldAlpha
        }

--- a/Sources/MotionController.swift
+++ b/Sources/MotionController.swift
-/*
- * The MIT License (MIT)
- *
- * Copyright (C) 2017, Daniel Dahan and CosmicMind, Inc. <http://cosmicmind.com>.
- * All rights reserved.
- *
- * Original Inspiration & Author
- * Copyright (c) 2016 Luke Zhao <me@lkzhao.com>
- *
- * Permission is hereby granted, free of charge, to any person obtaining a copy
- * of this software and associated documentation files (the "Software"), to deal
- * in the Software without restriction, including without limitation the rights
- * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
- * copies of the Software, and to permit persons to whom the Software is
- * furnished to do so, subject to the following conditions:
- *
- * The above copyright notice and this permission notice shall be included in
- * all copies or substantial portions of the Software.
- *
- * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
- * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
- * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
- * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
- * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
- * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
- * THE SOFTWARE.
- */
-import UIKit
-public class MotionController: NSObject {
-    /// A reference to the MotionContext.
-    public internal(set) var context: MotionContext!
-    /// A boolean indicating whether the transition interactive or not.
-    public var isInteractive: Bool {
-        return nil == displayLink
-    }
-    /// Progress of the current transition. 0 if no transition is happening.
-    public internal(set) var elapsedTime: TimeInterval = 0 {
-        didSet {
-            guard isTransitioning else {
-                return
-            }
-            updateTransitionObservers()
-            guard isInteractive else {
-                updatePlugins()
-                return
-            }
-            updateAnimators()
-        }
-    }
-    /// A boolean indicating whether a transition is active.
-    public var isTransitioning: Bool {
-        return nil != transitionContainer
-    }
-    /**
-     A view container used to hold all the animating views during a 
-     transition.
-     */
-    public internal(set) var container: UIView?
-    /// UIKit's supplied transition container.
-    internal var transitionContainer: UIView?
-    /// An optional completion callback.
-    internal var completionCallback: ((Bool) -> Void)?
-    /// Binds the render cycle to the transition animation.
-    internal var displayLink: CADisplayLink?
-    /// An Array of observers that are updated during a transition.
-    internal var transitionObservers: [MotionTransitionObserver]?
-    /// Max duration used by MotionAnimators and MotionPlugins.
-    public internal(set) var totalDuration: TimeInterval = 0
-    /// The currently running animation duration.
-    internal var currentAnimationDuration: TimeInterval = 0
-    /// The start time of the animation.
-    internal var beginTime: TimeInterval? {
-        didSet {
-            guard nil != beginTime else {
-                displayLink?.isPaused = true
-                displayLink?.remove(from: RunLoop.main, forMode: RunLoopMode(rawValue: RunLoopMode.commonModes.rawValue))
-                displayLink = nil
-                return
-            }
-            guard nil == displayLink else {
-                return
-            }
-            displayLink = CADisplayLink(target: self, selector: #selector(handleDisplayLink(_:)))
-            displayLink?.add(to: RunLoop.main, forMode: RunLoopMode(rawValue: RunLoopMode.commonModes.rawValue))
-        }
-    }
-    /// A boolean indicating if the transition has finished.
-    internal var isFinished = true
-    /// An Array of MotionPreprocessors used during a transition.
-    internal fileprivate(set) lazy var preprocessors = [MotionPreprocessor]()
-    /// An Array of MotionAnimators used during a transition.
-    internal fileprivate(set) lazy var animators = [MotionAnimator]()
-    /// An Array of MotionPlugins used during a transition.
-    internal fileprivate(set) lazy var plugins = [MotionPlugin]()
-    /// The matching fromViews to toViews based on the motionIdentifier value.
-    internal fileprivate(set) lazy var transitionPairs = [(fromViews: [UIView], toViews: [UIView])]()
-    /// Plugins that are enabled during the transition.
-    internal static var enabledPlugins = [MotionPlugin.Type]()
-    /// Initializer.
-    internal override init() {}
-}
-public extension MotionController {
-    /**
-     Receive callbacks on each animation frame.
-     Observers will be cleaned when a transition completes.
-     - Parameter observer: A MotionTransitionObserver.
-     */
-    func addTransitionObserver(observer: MotionTransitionObserver) {
-        if nil == transitionObservers {
-            transitionObservers = []
-        }
-        transitionObservers?.append(observer)
-    }
-}
-fileprivate extension MotionController {
-    /// Updates the transition observers.
-    func updateTransitionObservers() {
-        guard let observers = transitionObservers else {
-            return
-        }
-        for v in observers {
-            v.motion(transitionObserver: v, didUpdateWith: elapsedTime)
-        }
-    }
-    /// Updates the animators.
-    func updateAnimators() {
-        let t = elapsedTime * totalDuration
-        for a in animators {
-            a.seek(to: t)
-        }
-    }
-    /// Updates the plugins.
-    func updatePlugins() {
-        let t = elapsedTime * totalDuration
-        for p in plugins where p.requirePerFrameCallback {
-            p.seek(to: t)
-        }
-    }
-}
-fileprivate extension MotionController {
-    /**
-     Handler for the DisplayLink updates.
-     - Parameter _ link: CADisplayLink.
-     */
-    @objc
-    func handleDisplayLink(_ link: CADisplayLink) {
-        guard isTransitioning else {
-            return
-        }
-        guard 0 < currentAnimationDuration else {
-            return
-        }
-        guard let t = beginTime else {
-            return
-        }
-        let cTime = CACurrentMediaTime() - t
-        if cTime > currentAnimationDuration {
-            elapsedTime = isFinished ? 1 : 0
-            beginTime = nil
-            complete(isFinished: isFinished)
-        } else {
-            var eTime = cTime / totalDuration
-            if !isFinished {
-                eTime = 1 - eTime
-            }
-            elapsedTime = max(0, min(1, eTime))
-        }
-    }
-}
-public extension MotionController {
-    /**
-     Updates the elapsed time for the interactive transition.
-     - Parameter elapsedTime t: the current progress, must be between -1...1.
-     */
-    public func update(elapsedTime t: TimeInterval) {
-        guard isTransitioning else {
-            return
-        }
-        beginTime = nil
-        elapsedTime = max(-1, min(1, t))
-    }
-    /**
-     Finish the interactive transition.
-     Will stop the interactive transition and animate from the
-     current state to the **end** state
-     - Parameter isAnimated: A boolean indicating if the completion is animated.
-     */
-    public func end(isAnimated: Bool = true) {
-        guard isTransitioning else {
-            return
-        }
-        guard isAnimated else {
-            complete(isFinished: true)
-            return
-        }
-        var t: TimeInterval = 0
-        for a in animators {
-            t = max(t, a.resume(at: elapsedTime * totalDuration, isReversed: false))
-        }
-        complete(after: t, isFinished: true)
-    }
-    /**
-     Cancel the interactive transition.
-     Will stop the interactive transition and animate from the
-     current state to the **begining** state
-     - Parameter isAnimated: A boolean indicating if the completion is animated.
-     */
-    public func cancel(isAnimated: Bool = true) {
-        guard isTransitioning else {
-            return
-        }
-        guard isAnimated else {
-            complete(isFinished: false)
-            return
-        }
-        var d: TimeInterval = 0
-        for a in animators {
-            var t = elapsedTime
-            if t < 0 {
-                t = -t
-            }
-            d = max(d, a.resume(at: t * totalDuration, isReversed: true))
-        }
-        complete(after: d, isFinished: false)
-    }
-    /**
-     Override transition animations during an interactive animation.
-     For example:
-     Motion.shared.apply([.position(x:50, y:50)], to: view)
-     will set the view's position to 50, 50
-     - Parameter transitions: An Array of MotionTransitions.
-     - Parameter to view: A UIView.
-     */
-    public func apply(transitions: [MotionTransition], to view: UIView) {
-        guard isTransitioning else {
-            return
-        }
-        let s = MotionTransitionState(transitions: transitions)
-        let v = context.transitionPairedView(for: view) ?? view
-        for a in animators {
-            a.apply(state: s, to: v)
-        }
-    }
-}
-internal extension MotionController {
-    /**
-     Load plugins, processors, animators, container, & context
-     The transitionContainer must already be set.
-     Subclasses should call context.set(fromViews: toViews) after
-     inserting fromViews & toViews into the container
-     */
-    @objc
-    func prepareTransition() {
-        guard isTransitioning else {
-            return
-        }
-        prepareTransitionContainer()
-        prepareContext()
-        preparePreprocessors()
-        prepareAnimators()
-        preparePlugins()
-    }
-    /// Prepares the transition fromView & toView pairs.
-    @objc
-    func prepareTransitionPairs() {
-        guard isTransitioning else {
-            return
-        }
-        for a in animators {
-            let fv = context.fromViews.filter { (view: UIView) -> Bool in
-                return a.canAnimate(view: view, isAppearing: false)
-            }
-            let tv = context.toViews.filter {
-                return a.canAnimate(view: $0, isAppearing: true)
-            }
-            transitionPairs.append((fv, tv))
-        }
-    }
-}
-internal extension MotionController {
-    /// Executes the preprocessors' process function.
-    func processContext() {
-        guard isTransitioning else {
-            return
-        }
-        for x in preprocessors {
-            x.process(fromViews: context.fromViews, toViews: context.toViews)
-        }
-    }
-    /**
-     Animates the views. Subclasses should call `prepareTransition` &
-     `prepareTransitionPairs` before calling `animate`.
-     */
-    @objc
-    func animate() {
-        guard isTransitioning else {
-            return
-        }
-        for (fv, tv) in transitionPairs {
-            for view in fv {
-                context.hide(view: view)
-            }
-            for view in tv {
-                context.hide(view: view)
-            }
-        }
-        var t: TimeInterval = 0
-        var b = false
-        for (i, a) in animators.enumerated() {
-            let d = a.animate(fromViews: transitionPairs[i].0, toViews: transitionPairs[i].1)
-            if .infinity == d {
-                b = true
-            } else {
-                t = max(t, d)
-            }
-        }
-        totalDuration = t
-        if b {
-            update(elapsedTime: 0)
-        } else {
-            complete(after: t, isFinished: true)
-        }
-    }
-    /**
-     Complete the transition.
-     - Parameter after: A TimeInterval.
-     - Parameter isFinished: A Boolean indicating if the transition 
-     has completed.
-     */
-    func complete(after: TimeInterval, isFinished: Bool) {
-        guard isTransitioning else {
-            return
-        }
-        if after <= 0.001 {
-            complete(isFinished: isFinished)
-            return
-        }
-        let v = (isFinished ? elapsedTime : 1 - elapsedTime) * totalDuration
-        self.isFinished = isFinished
-        currentAnimationDuration = after + v
-        beginTime = CACurrentMediaTime() - v
-    }
-    /**
-     Complete the transition.
-     - Parameter isFinished: A Boolean indicating if the transition
-     has completed.
-    */
-    @objc
-    func complete(isFinished: Bool) {
-        guard isTransitioning else {
-            return
-        }
-        for a in animators {
-            a.clean()
-        }
-        transitionContainer?.isUserInteractionEnabled = true
-        let completion = completionCallback
-        transitionObservers = nil
-        transitionContainer = nil
-        completionCallback = nil
-        container = nil
-        context = nil
-        beginTime = nil
-        elapsedTime = 0
-        totalDuration = 0
-        preprocessors.removeAll()
-        animators.removeAll()
-        plugins.removeAll()
-        transitionPairs.removeAll()
-        completion?(isFinished)
-    }
-}
-fileprivate extension MotionController {
-    /// Prepares the transition container.
-    func prepareTransitionContainer() {
-        guard let v = transitionContainer else {
-            return
-        }
-        v.isUserInteractionEnabled = false
-        // a view to hold all the animating views
-        container = UIView(frame: v.bounds)
-        v.addSubview(container!)
-    }
-    /// Prepares the context.
-    func prepareContext() {
-        guard let v = container else {
-            return
-        }
-        context = MotionContext(container: v)
-    }
-    /// Prepares the preprocessors.
-    func preparePreprocessors() {
-        for x in [
-            IgnoreSubviewTransitionsPreprocessor(),
-            MatchPreprocessor(),
-            SourcePreprocessor(),
-            CascadePreprocessor(),
-            DurationPreprocessor()] as [MotionPreprocessor] {
-                preprocessors.append(x)
-        }
-        for x in preprocessors {
-            x.context = context
-        }
-    }
-    /// Prepares the animators.
-    func prepareAnimators() {
-        animators.append(MotionTransitionAnimator<MotionCoreAnimationViewContext>())
-        if #available(iOS 10, tvOS 10, *) {
-            animators.append(MotionTransitionAnimator<MotionViewPropertyViewContext>())
-        }
-        for v in animators {
-            v.context = context
-        }
-    }
-    /// Prepares the plugins.
-    func preparePlugins() {
-        for x in Motion.enabledPlugins.map({
-            return $0.init()
-        }) {
-            plugins.append(x)
-        }
-        for plugin in plugins {
-            preprocessors.append(plugin)
-            animators.append(plugin)
-        }
-    }
-}
-internal extension MotionController {
-    /**
-     Checks if a given plugin is enabled.
-     - Parameter plugin: A MotionPlugin.Type.
-     - Returns: A boolean indicating if the plugin is enabled or not.
-     */
-    static func isEnabled(plugin: MotionPlugin.Type) -> Bool {
-        return nil != enabledPlugins.index(where: { return $0 == plugin })
-    }
-    /**
-     Enables a given plugin.
-     - Parameter plugin: A MotionPlugin.Type.
-     */
-    static func enable(plugin: MotionPlugin.Type) {
-        disable(plugin: plugin)
-        enabledPlugins.append(plugin)
-    }
-    /**
-     Disables a given plugin.
-     - Parameter plugin: A MotionPlugin.Type.
-     */
-    static func disable(plugin: MotionPlugin.Type) {
-        guard let index = enabledPlugins.index(where: { return $0 == plugin }) else {
-            return
-        }
-        enabledPlugins.remove(at: index)
-    }
-}
-internal extension MotionController {
-    // should call this after `prepareTransitionPairs` & before `processContext`
-    func insert<T>(preprocessor: MotionPreprocessor, before: T.Type) {
-        let i = preprocessors.index { $0 is T } ?? preprocessors.count
-        preprocessor.context = context
-        preprocessors.insert(preprocessor, at: i)
-    }
-}
--- a/Sources/MotionProgressRunner.swift
+++ b/Sources/MotionProgressRunner.swift
+/*
+ * The MIT License (MIT)
+ *
+ * Copyright (C) 2017, Daniel Dahan and CosmicMind, Inc. <http://cosmicmind.com>.
+ * All rights reserved.
+ *
+ * Original Inspiration & Author
+ * Copyright (c) 2016 Luke Zhao <me@lkzhao.com>
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+import UIKit
+protocol MotionProgressRunnerDelegate: class {
+    func update(elapsedTime: TimeInterval)
+    func complete(isFinished: Bool)
+}
+class MotionProgressRunner {
+    weak var delegate: MotionProgressRunnerDelegate?
+    var isRunning: Bool {
+        return displayLink != nil
+    }
+    internal var timePassed: TimeInterval = 0
+    internal var duration: TimeInterval = 0
+    internal var displayLink: CADisplayLink?
+    internal var isReversed: Bool = false
+    @objc
+    func displayUpdate(_ link: CADisplayLink) {
+        timePassed += isReversed ? -link.duration : link.duration
+        if isReversed, timePassed <= 1.0 / 120 {
+            delegate?.complete(isFinished: false)
+            stop()
+            return
+        }
+        if !isReversed, timePassed > duration - 1.0 / 120 {
+            delegate?.complete(isFinished: true)
+            stop()
+            return
+        }
+        delegate?.update(elapsedTime: timePassed / duration)
+    }
+    func start(timePassed: TimeInterval, totalTime: TimeInterval, reverse: Bool) {
+        stop()
+        self.timePassed = timePassed
+        self.isReversed = reverse
+        self.duration = totalTime
+        displayLink = CADisplayLink(target: self, selector: #selector(displayUpdate(_:)))
+        displayLink!.add(to: RunLoop.main, forMode: RunLoopMode(rawValue: RunLoopMode.commonModes.rawValue))
+    }
+    func stop() {
+        displayLink?.isPaused = true
+        displayLink?.remove(from: RunLoop.main, forMode: RunLoopMode(rawValue: RunLoopMode.commonModes.rawValue))
+        displayLink = nil
+    }
+}
--- a/Sources/MotionIndependentController.swift
+++ b/Sources/MotionIndependentController.swift
@@ -26,42 +26,23 @@
 * THE SOFTWARE.
 */
-import UIKit
+@objc(MotionState)
+public enum MotionState: Int {
-public class MotionIndependentController: MotionController {
+    /// Motion is able to start a new transition.
-    /// An initializer.
+    case possible
-    public override init() {
-        super.init()
+    /// UIKit has notified Motion about a pending transition.
-    }
+    /// Motion hasn't started preparation.
+    case notified
-    /**
-     Transitions source views to their corresponding destination view
+    /// Motion's `start` method has been called. Preparing the animation.
-     within a given root view.
+    case starting
-     - Parameter rootView: A UIView.
-     - Parameter fromViews: An Array of UIViews.
+    /// Motions's `animate` method has been called. Animation has started.
-     - Parameter toViews: An Array of UIViews.
+    case animating
-     - Parameter completion: An optional callback.
-     */
+    /// Motions's `complete` method has been called. Transition has ended or has
-    public func transition(rootView: UIView, fromViews: [UIView], toViews: [UIView], completion: ((Bool) -> Void)? = nil) {
+    /// been cancelled. Motion is cleaning up.
-        transitionContainer = rootView
+    case completing
-        completionCallback = completion
-        prepareTransition()
-        prepareContext(fromViews: fromViews, toViews: toViews)
-        prepareTransitionPairs()
-        animate()
-    }
 }
-fileprivate extension MotionIndependentController {
-    /** 
-     Prepares the context.
-     - Parameter fromViews: An Array of UIViews.
-     - PArameter toViews: An Array of UIViews.
-     */
-    func prepareContext(fromViews: [UIView], toViews: [UIView]) {
-        context.set(fromViews: fromViews, toViews: toViews)
-        processContext()
-    }
-}
--- a/Sources/Preprocessors/TransitionPreprocessor.swift
+++ b/Sources/Preprocessors/TransitionPreprocessor.swift
@@ -218,7 +218,7 @@ class TransitionPreprocessor: MotionPreprocessor {
        if case .auto = defaultAnimation {
            if isNavigationController, let navAnim = toViewController?.navigationController?.motionNavigationTransitionType {
                defaultAnimation = navAnim
            } else if isTabBarController, let tabAnim = toViewController?.tabBarController?.motionTabBarTransitionType {
                defaultAnimation = tabAnim