Merge pull request #6018 from AvaloniaUI/cancellable-animations-expander-fix

Cancellable animations (for async methods) + Expander fix
# Conflicts:
#	src/Avalonia.Visuals/ApiCompatBaseline.txt

src/Avalonia.Animation/Animation.cs

@@ -3,10 +3,11 @@ using System.Collections.Generic;
 using System.Linq;
 using System.Reactive.Disposables;
 using System.Reactive.Linq;
+using System.Threading;
 using System.Threading.Tasks;
+
 using Avalonia.Animation.Animators;
 using Avalonia.Animation.Easings;
-using Avalonia.Collections;
 using Avalonia.Data;
 using Avalonia.Metadata;
 
@@ -319,7 +320,7 @@ namespace Avalonia.Animation
             return (newAnimatorInstances, subscriptions);
         }
 
-        /// <inheritdocs/>
+        /// <inheritdoc/>
         public IDisposable Apply(Animatable control, IClock clock, IObservable<bool> match, Action onComplete)
         {
             var (animators, subscriptions) = InterpretKeyframes(control);
@@ -344,25 +345,40 @@ namespace Avalonia.Animation
 
                 if (onComplete != null)
                 {
-                    Task.WhenAll(completionTasks).ContinueWith(_ => onComplete());
+                    Task.WhenAll(completionTasks).ContinueWith(
+                        (_, state) => ((Action)state).Invoke(),
+                        onComplete);
                 }
             }
             return new CompositeDisposable(subscriptions);
         }
 
-        /// <inheritdocs/>
-        public Task RunAsync(Animatable control, IClock clock = null)
+        /// <inheritdoc/>
+        public Task RunAsync(Animatable control, IClock clock = null, CancellationToken cancellationToken = default)
         {
+            if (cancellationToken.IsCancellationRequested)
+            {
+                return Task.CompletedTask;
+            }
+
             var run = new TaskCompletionSource<object>();
 
             if (this.IterationCount == IterationCount.Infinite)
                 run.SetException(new InvalidOperationException("Looping animations must not use the Run method."));
 
-            IDisposable subscriptions = null;
+            IDisposable subscriptions = null, cancellation = null;
             subscriptions = this.Apply(control, clock, Observable.Return(true), () =>
             {
-                run.SetResult(null);
+                run.TrySetResult(null);
+                subscriptions?.Dispose();
+                cancellation?.Dispose();
+            });
+
+            cancellation = cancellationToken.Register(() =>
+            {
+                run.TrySetResult(null);
                 subscriptions?.Dispose();
+                cancellation?.Dispose();
             });
 
             return run.Task;

src/Avalonia.Animation/ApiCompatBaseline.txt

@@ -0,0 +1,6 @@
+Compat issues with assembly Avalonia.Animation:
+MembersMustExist : Member 'public System.Threading.Tasks.Task Avalonia.Animation.Animation.RunAsync(Avalonia.Animation.Animatable, Avalonia.Animation.IClock)' does not exist in the implementation but it does exist in the contract.
+InterfacesShouldHaveSameMembers : Interface member 'public System.Threading.Tasks.Task Avalonia.Animation.IAnimation.RunAsync(Avalonia.Animation.Animatable, Avalonia.Animation.IClock)' is present in the contract but not in the implementation.
+MembersMustExist : Member 'public System.Threading.Tasks.Task Avalonia.Animation.IAnimation.RunAsync(Avalonia.Animation.Animatable, Avalonia.Animation.IClock)' does not exist in the implementation but it does exist in the contract.
+InterfacesShouldHaveSameMembers : Interface member 'public System.Threading.Tasks.Task Avalonia.Animation.IAnimation.RunAsync(Avalonia.Animation.Animatable, Avalonia.Animation.IClock, System.Threading.CancellationToken)' is present in the implementation but not in the contract.
+Total Issues: 4

src/Avalonia.Animation/IAnimation.cs

@@ -1,4 +1,5 @@
 using System;
+using System.Threading;
 using System.Threading.Tasks;
 
 namespace Avalonia.Animation
@@ -16,6 +17,6 @@ namespace Avalonia.Animation
         /// <summary>
         /// Run the animation on the specified control.
         /// </summary>
-        Task RunAsync(Animatable control, IClock clock);
+        Task RunAsync(Animatable control, IClock clock, CancellationToken cancellationToken = default);
     }
 }

src/Avalonia.Controls/Expander.cs

@@ -1,7 +1,11 @@
+using System.Threading;
+
 using Avalonia.Animation;
 using Avalonia.Controls.Metadata;
 using Avalonia.Controls.Primitives;
 
+#nullable enable
+
 namespace Avalonia.Controls
 {
     /// <summary>
@@ -36,8 +40,8 @@ namespace Avalonia.Controls
     [PseudoClasses(":expanded", ":up", ":down", ":left", ":right")]
     public class Expander : HeaderedContentControl
     {
-        public static readonly StyledProperty<IPageTransition> ContentTransitionProperty =
-            AvaloniaProperty.Register<Expander, IPageTransition>(nameof(ContentTransition));
+        public static readonly StyledProperty<IPageTransition?> ContentTransitionProperty =
+            AvaloniaProperty.Register<Expander, IPageTransition?>(nameof(ContentTransition));
 
         public static readonly StyledProperty<ExpandDirection> ExpandDirectionProperty =
             AvaloniaProperty.Register<Expander, ExpandDirection>(nameof(ExpandDirection), ExpandDirection.Down);
@@ -50,6 +54,7 @@ namespace Avalonia.Controls
                 defaultBindingMode: Data.BindingMode.TwoWay);
 
         private bool _isExpanded;
+        private CancellationTokenSource? _lastTransitionCts;
 
         static Expander()
         {
@@ -61,7 +66,7 @@ namespace Avalonia.Controls
             UpdatePseudoClasses(ExpandDirection);
         }
 
-        public IPageTransition ContentTransition
+        public IPageTransition? ContentTransition
         {
             get => GetValue(ContentTransitionProperty);
             set => SetValue(ContentTransitionProperty, value);
@@ -83,19 +88,23 @@ namespace Avalonia.Controls
             }
         }
 
-        protected virtual void OnIsExpandedChanged(AvaloniaPropertyChangedEventArgs e)
+        protected virtual async void OnIsExpandedChanged(AvaloniaPropertyChangedEventArgs e)
         {
             if (Content != null && ContentTransition != null && Presenter is Visual visualContent)
             {
                 bool forward = ExpandDirection == ExpandDirection.Left ||
                                 ExpandDirection == ExpandDirection.Up;
+
+                _lastTransitionCts?.Cancel();
+                _lastTransitionCts = new CancellationTokenSource();
+
                 if (IsExpanded)
                 {
-                    ContentTransition.Start(null, visualContent, forward);
+                    await ContentTransition.Start(null, visualContent, forward, _lastTransitionCts.Token);
                 }
                 else
                 {
-                    ContentTransition.Start(visualContent, null, !forward);
+                    await ContentTransition.Start(visualContent, null, forward, _lastTransitionCts.Token);
                 }
             }
         }

src/Avalonia.Controls/Presenters/CarouselPresenter.cs

@@ -186,7 +186,7 @@ namespace Avalonia.Controls.Presenters
 
                 if (PageTransition != null && (from != null || to != null))
                 {
-                    await PageTransition.Start((Visual)from, (Visual)to, fromIndex < toIndex);
+                    await PageTransition.Start((Visual)from, (Visual)to, fromIndex < toIndex, default);
                 }
                 else if (to != null)
                 {

src/Avalonia.ReactiveUI/TransitioningContentControl.cs

@@ -1,4 +1,6 @@
 using System;
+using System.Threading;
+
 using Avalonia.Animation;
 using Avalonia.Controls;
 using Avalonia.Styling;
@@ -22,7 +24,9 @@ namespace Avalonia.ReactiveUI
         /// </summary>
         public static readonly StyledProperty<object?> DefaultContentProperty =
             AvaloniaProperty.Register<TransitioningContentControl, object?>(nameof(DefaultContent));
-        
+
+        private CancellationTokenSource? _lastTransitionCts;
+
         /// <summary>
         /// Gets or sets the animation played when content appears and disappears.
         /// </summary>
@@ -62,11 +66,14 @@ namespace Avalonia.ReactiveUI
         /// <param name="content">New content to set.</param>
         private async void UpdateContentWithTransition(object? content)
         {
+            _lastTransitionCts?.Cancel();
+            _lastTransitionCts = new CancellationTokenSource();
+
             if (PageTransition != null)
-                await PageTransition.Start(this, null, true);
+                await PageTransition.Start(this, null, true, _lastTransitionCts.Token);
             base.Content = content;
             if (PageTransition != null)
-                await PageTransition.Start(null, this, true);
+                await PageTransition.Start(null, this, true, _lastTransitionCts.Token);
         }
     }
 }

src/Avalonia.Visuals/Animation/CompositePageTransition.cs

@@ -1,5 +1,6 @@
 using System.Collections.Generic;
 using System.Linq;
+using System.Threading;
 using System.Threading.Tasks;
 using Avalonia.Metadata;
 
@@ -35,25 +36,11 @@ namespace Avalonia.Animation
         [Content]
         public List<IPageTransition> PageTransitions { get; set; } = new List<IPageTransition>();
 
-        /// <summary>
-        /// Starts the animation.
-        /// </summary>
-        /// <param name="from">
-        /// The control that is being transitioned away from. May be null.
-        /// </param>
-        /// <param name="to">
-        /// The control that is being transitioned to. May be null.
-        /// </param>
-        /// <param name="forward">
-        /// Defines the direction of the transition.
-        /// </param>
-        /// <returns>
-        /// A <see cref="Task"/> that tracks the progress of the animation.
-        /// </returns>
-        public Task Start(Visual from, Visual to, bool forward)
+        /// <inheritdoc />
+        public Task Start(Visual from, Visual to, bool forward, CancellationToken cancellationToken)
         {
             var transitionTasks = PageTransitions
-                .Select(transition => transition.Start(from, to, forward))
+                .Select(transition => transition.Start(from, to, forward, cancellationToken))
                 .ToList();
             return Task.WhenAll(transitionTasks);
         }

src/Avalonia.Visuals/Animation/CrossFade.cs

@@ -1,5 +1,7 @@
 using System;
 using System.Collections.Generic;
+using System.Reactive.Disposables;
+using System.Threading;
 using System.Threading.Tasks;
 using Avalonia.Animation.Easings;
 using Avalonia.Styling;
@@ -97,49 +99,39 @@ namespace Avalonia.Animation
             set => _fadeOutAnimation.Easing = value;
         }
 
-        /// <summary>
-        /// Starts the animation.
-        /// </summary>
-        /// <param name="from">
-        /// The control that is being transitioned away from. May be null.
-        /// </param>
-        /// <param name="to">
-        /// The control that is being transitioned to. May be null.
-        /// </param>
-        /// <returns>
-        /// A <see cref="Task"/> that tracks the progress of the animation.
-        /// </returns>
-        public async Task Start(Visual from, Visual to)
+        /// <inheritdoc cref="Start(Visual, Visual, CancellationToken)" />
+        public async Task Start(Visual from, Visual to, CancellationToken cancellationToken)
         {
-            var tasks = new List<Task>();
-
-            if (to != null)
-            {
-                to.Opacity = 0;
-            }
-
-            if (from != null)
+            if (cancellationToken.IsCancellationRequested)
             {
-                tasks.Add(_fadeOutAnimation.RunAsync(from));
+                return;
             }
 
-            if (to != null)
+            var tasks = new List<Task>();
+            using (var disposables = new CompositeDisposable())
             {
-                to.IsVisible = true;
-                tasks.Add(_fadeInAnimation.RunAsync(to));
+                if (to != null)
+                {
+                    disposables.Add(to.SetValue(Visual.OpacityProperty, 0, Data.BindingPriority.Animation));
+                }
 
-            }
+                if (from != null)
+                {
+                    tasks.Add(_fadeOutAnimation.RunAsync(from, null, cancellationToken));
+                }
 
-            await Task.WhenAll(tasks);
+                if (to != null)
+                {
+                    to.IsVisible = true;
+                    tasks.Add(_fadeInAnimation.RunAsync(to, null, cancellationToken));
+                }
 
-            if (from != null)
-            {
-                from.IsVisible = false;
-            }
+                await Task.WhenAll(tasks);
 
-            if (to != null)
-            {
-                to.Opacity = 1;
+                if (from != null && !cancellationToken.IsCancellationRequested)
+                {
+                    from.IsVisible = false;
+                }
             }
         }
 
@@ -159,9 +151,9 @@ namespace Avalonia.Animation
         /// <returns>
         /// A <see cref="Task"/> that tracks the progress of the animation.
         /// </returns>
-        Task IPageTransition.Start(Visual from, Visual to, bool forward)
+        Task IPageTransition.Start(Visual from, Visual to, bool forward, CancellationToken cancellationToken)
         {
-            return Start(from, to);
+            return Start(from, to, cancellationToken);
         }
     }
 }

src/Avalonia.Visuals/Animation/IPageTransition.cs

@@ -1,3 +1,4 @@
+using System.Threading;
 using System.Threading.Tasks;
 
 namespace Avalonia.Animation
@@ -19,9 +20,12 @@ namespace Avalonia.Animation
         /// <param name="forward">
         /// If the animation is bidirectional, controls the direction of the animation.
         /// </param>
+        /// <param name="cancellationToken">
+        /// Animation cancellation.
+        /// </param>
         /// <returns>
         /// A <see cref="Task"/> that tracks the progress of the animation.
         /// </returns>
-        Task Start(Visual from, Visual to, bool forward);
+        Task Start(Visual from, Visual to, bool forward, CancellationToken cancellationToken);
     }
 }

src/Avalonia.Visuals/Animation/PageSlide.cs

@@ -1,5 +1,6 @@
 using System;
 using System.Collections.Generic;
+using System.Threading;
 using System.Threading.Tasks;
 using Avalonia.Animation.Easings;
 using Avalonia.Media;
@@ -60,23 +61,14 @@ namespace Avalonia.Animation
         /// </summary>
         public Easing SlideOutEasing { get; set; } = new LinearEasing();
 
-        /// <summary>
-        /// Starts the animation.
-        /// </summary>
-        /// <param name="from">
-        /// The control that is being transitioned away from. May be null.
-        /// </param>
-        /// <param name="to">
-        /// The control that is being transitioned to. May be null.
-        /// </param>
-        /// <param name="forward">
-        /// If true, the new page is slid in from the right, or if false from the left.
-        /// </param>
-        /// <returns>
-        /// A <see cref="Task"/> that tracks the progress of the animation.
-        /// </returns>
-        public async Task Start(Visual from, Visual to, bool forward)
+        /// <inheritdoc />
+        public async Task Start(Visual from, Visual to, bool forward, CancellationToken cancellationToken)
         {
+            if (cancellationToken.IsCancellationRequested)
+            {
+                return;
+            }
+
             var tasks = new List<Task>();
             var parent = GetVisualParent(from, to);
             var distance = Orientation == SlideAxis.Horizontal ? parent.Bounds.Width : parent.Bounds.Height;
@@ -109,7 +101,7 @@ namespace Avalonia.Animation
                     },
                     Duration = Duration
                 };
-                tasks.Add(animation.RunAsync(from));
+                tasks.Add(animation.RunAsync(from, null, cancellationToken));
             }
 
             if (to != null)
@@ -140,12 +132,12 @@ namespace Avalonia.Animation
                     },
                     Duration = Duration
                 };
-                tasks.Add(animation.RunAsync(to));
+                tasks.Add(animation.RunAsync(to, null, cancellationToken));
             }
 
             await Task.WhenAll(tasks);
 
-            if (from != null)
+            if (from != null && !cancellationToken.IsCancellationRequested)
             {
                 from.IsVisible = false;
             }

src/Avalonia.Visuals/ApiCompatBaseline.txt

@@ -1,4 +1,10 @@
 Compat issues with assembly Avalonia.Visuals:
+MembersMustExist : Member 'public System.Threading.Tasks.Task Avalonia.Animation.CompositePageTransition.Start(Avalonia.Visual, Avalonia.Visual, System.Boolean)' does not exist in the implementation but it does exist in the contract.
+MembersMustExist : Member 'public System.Threading.Tasks.Task Avalonia.Animation.CrossFade.Start(Avalonia.Visual, Avalonia.Visual)' does not exist in the implementation but it does exist in the contract.
+InterfacesShouldHaveSameMembers : Interface member 'public System.Threading.Tasks.Task Avalonia.Animation.IPageTransition.Start(Avalonia.Visual, Avalonia.Visual, System.Boolean)' is present in the contract but not in the implementation.
+MembersMustExist : Member 'public System.Threading.Tasks.Task Avalonia.Animation.IPageTransition.Start(Avalonia.Visual, Avalonia.Visual, System.Boolean)' does not exist in the implementation but it does exist in the contract.
+InterfacesShouldHaveSameMembers : Interface member 'public System.Threading.Tasks.Task Avalonia.Animation.IPageTransition.Start(Avalonia.Visual, Avalonia.Visual, System.Boolean, System.Threading.CancellationToken)' is present in the implementation but not in the contract.
+MembersMustExist : Member 'public System.Threading.Tasks.Task Avalonia.Animation.PageSlide.Start(Avalonia.Visual, Avalonia.Visual, System.Boolean)' does not exist in the implementation but it does exist in the contract.
 InterfacesShouldHaveSameMembers : Interface member 'public void Avalonia.Platform.IDrawingContextImpl.PopBitmapBlendMode()' is present in the implementation but not in the contract.
 InterfacesShouldHaveSameMembers : Interface member 'public void Avalonia.Platform.IDrawingContextImpl.PushBitmapBlendMode(Avalonia.Visuals.Media.Imaging.BitmapBlendingMode)' is present in the implementation but not in the contract.
 InterfacesShouldHaveSameMembers : Interface member 'public System.Double Avalonia.Platform.IGeometryImpl.ContourLength' is present in the implementation but not in the contract.
@@ -8,11 +14,8 @@ InterfacesShouldHaveSameMembers : Interface member 'public System.Boolean Avalon
 InterfacesShouldHaveSameMembers : Interface member 'public System.Boolean Avalonia.Platform.IGeometryImpl.TryGetSegment(System.Double, System.Double, System.Boolean, Avalonia.Platform.IGeometryImpl)' is present in the implementation but not in the contract.
 InterfacesShouldHaveSameMembers : Interface member 'public Avalonia.Platform.IGeometryImpl Avalonia.Platform.IPlatformRenderInterface.CreateCombinedGeometry(Avalonia.Media.GeometryCombineMode, Avalonia.Media.Geometry, Avalonia.Media.Geometry)' is present in the implementation but not in the contract.
 InterfacesShouldHaveSameMembers : Interface member 'public Avalonia.Platform.IGeometryImpl Avalonia.Platform.IPlatformRenderInterface.CreateGeometryGroup(Avalonia.Media.FillRule, System.Collections.Generic.IReadOnlyList<Avalonia.Media.Geometry>)' is present in the implementation but not in the contract.
-InterfacesShouldHaveSameMembers : Interface member 'public Avalonia.Platform.IGlyphRunImpl Avalonia.Platform.IPlatformRenderInterface.CreateGlyphRun(Avalonia.Media.GlyphRun)' is present in the implementation but not in the contract.
-InterfacesShouldHaveSameMembers : Interface member 'public Avalonia.Platform.IGlyphRunImpl Avalonia.Platform.IPlatformRenderInterface.CreateGlyphRun(Avalonia.Media.GlyphRun, System.Double)' is present in the contract but not in the implementation.
-MembersMustExist : Member 'public Avalonia.Platform.IGlyphRunImpl Avalonia.Platform.IPlatformRenderInterface.CreateGlyphRun(Avalonia.Media.GlyphRun, System.Double)' does not exist in the implementation but it does exist in the contract.
 InterfacesShouldHaveSameMembers : Interface member 'public Avalonia.Platform.IWriteableBitmapImpl Avalonia.Platform.IPlatformRenderInterface.LoadWriteableBitmap(System.IO.Stream)' is present in the implementation but not in the contract.
 InterfacesShouldHaveSameMembers : Interface member 'public Avalonia.Platform.IWriteableBitmapImpl Avalonia.Platform.IPlatformRenderInterface.LoadWriteableBitmap(System.String)' is present in the implementation but not in the contract.
 InterfacesShouldHaveSameMembers : Interface member 'public Avalonia.Platform.IWriteableBitmapImpl Avalonia.Platform.IPlatformRenderInterface.LoadWriteableBitmapToHeight(System.IO.Stream, System.Int32, Avalonia.Visuals.Media.Imaging.BitmapInterpolationMode)' is present in the implementation but not in the contract.
 InterfacesShouldHaveSameMembers : Interface member 'public Avalonia.Platform.IWriteableBitmapImpl Avalonia.Platform.IPlatformRenderInterface.LoadWriteableBitmapToWidth(System.IO.Stream, System.Int32, Avalonia.Visuals.Media.Imaging.BitmapInterpolationMode)' is present in the implementation but not in the contract.
-Total Issues: 17
+Total Issues: 19

tests/Avalonia.Animation.UnitTests/AnimationIterationTests.cs

@@ -9,6 +9,8 @@ using Avalonia.UnitTests;
 using Avalonia.Data;
 using Xunit;
 using Avalonia.Animation.Easings;
+using System.Threading;
+using System.Reactive.Linq;
 
 namespace Avalonia.Animation.UnitTests
 {
@@ -176,5 +178,271 @@ namespace Avalonia.Animation.UnitTests
             clock.Step(TimeSpan.FromSeconds(0.100d));
             Assert.Equal(border.Width, 300d);
         }
+
+        [Fact(Skip = "See #6111")]
+        public void Dispose_Subscription_Should_Stop_Animation()
+        {
+            var keyframe1 = new KeyFrame()
+            {
+                Setters =
+                {
+                    new Setter(Border.WidthProperty, 200d),
+                },
+                Cue = new Cue(1d)
+            };
+
+            var keyframe2 = new KeyFrame()
+            {
+                Setters =
+                {
+                    new Setter(Border.WidthProperty, 100d),
+                },
+                Cue = new Cue(0d)
+            };
+
+            var animation = new Animation()
+            {
+                Duration = TimeSpan.FromSeconds(10),
+                Delay = TimeSpan.FromSeconds(0),
+                DelayBetweenIterations = TimeSpan.FromSeconds(0),
+                IterationCount = new IterationCount(1),
+                Children =
+                {
+                    keyframe2,
+                    keyframe1
+                }
+            };
+
+            var border = new Border()
+            {
+                Height = 100d,
+                Width = 50d
+            };
+            var propertyChangedCount = 0;
+            var animationCompletedCount = 0;
+            border.PropertyChanged += (sender, e) =>
+            {
+                if (e.Property == Control.WidthProperty)
+                {
+                    propertyChangedCount++;
+                }
+            };
+
+            var clock = new TestClock();
+            var disposable = animation.Apply(border, clock, Observable.Return(true), () => animationCompletedCount++);
+
+            Assert.Equal(0, propertyChangedCount);
+
+            clock.Step(TimeSpan.FromSeconds(0));
+            Assert.Equal(0, animationCompletedCount);
+            Assert.Equal(1, propertyChangedCount);
+
+            disposable.Dispose();
+
+            // Clock ticks should be ignored after Dispose
+            clock.Step(TimeSpan.FromSeconds(5));
+            clock.Step(TimeSpan.FromSeconds(6));
+            clock.Step(TimeSpan.FromSeconds(7));
+
+            // On animation disposing (cancellation) on completed is not invoked (is it expected?)
+            Assert.Equal(0, animationCompletedCount);
+            // Initial property changed before cancellation + animation value removal.
+            Assert.Equal(2, propertyChangedCount);
+        }
+
+        [Fact]
+        public void Do_Not_Run_Cancelled_Animation()
+        {
+            var keyframe1 = new KeyFrame()
+            {
+                Setters =
+                {
+                    new Setter(Border.WidthProperty, 200d),
+                },
+                Cue = new Cue(1d)
+            };
+
+            var keyframe2 = new KeyFrame()
+            {
+                Setters =
+                {
+                    new Setter(Border.WidthProperty, 100d),
+                },
+                Cue = new Cue(0d)
+            };
+
+            var animation = new Animation()
+            {
+                Duration = TimeSpan.FromSeconds(10),
+                Delay = TimeSpan.FromSeconds(0),
+                DelayBetweenIterations = TimeSpan.FromSeconds(0),
+                IterationCount = new IterationCount(1),
+                Children =
+                {
+                    keyframe2,
+                    keyframe1
+                }
+            };
+
+            var border = new Border()
+            {
+                Height = 100d,
+                Width = 100d
+            };
+            var propertyChangedCount = 0;
+            border.PropertyChanged += (sender, e) =>
+            {
+                if (e.Property == Control.WidthProperty)
+                {
+                    propertyChangedCount++;
+                }
+            };
+
+            var clock = new TestClock();
+            var cancellationTokenSource = new CancellationTokenSource();
+            cancellationTokenSource.Cancel();
+            var animationRun = animation.RunAsync(border, clock, cancellationTokenSource.Token);
+
+            clock.Step(TimeSpan.FromSeconds(10));
+            Assert.Equal(0, propertyChangedCount);
+            Assert.True(animationRun.IsCompleted);
+        }
+
+        [Fact(Skip = "See #6111")]
+        public void Cancellation_Should_Stop_Animation()
+        {
+            var keyframe1 = new KeyFrame()
+            {
+                Setters =
+                {
+                    new Setter(Border.WidthProperty, 200d),
+                },
+                Cue = new Cue(1d)
+            };
+
+            var keyframe2 = new KeyFrame()
+            {
+                Setters =
+                {
+                    new Setter(Border.WidthProperty, 100d),
+                },
+                Cue = new Cue(0d)
+            };
+
+            var animation = new Animation()
+            {
+                Duration = TimeSpan.FromSeconds(10),
+                Delay = TimeSpan.FromSeconds(0),
+                DelayBetweenIterations = TimeSpan.FromSeconds(0),
+                IterationCount = new IterationCount(1),
+                Children =
+                {
+                    keyframe2,
+                    keyframe1
+                }
+            };
+
+            var border = new Border()
+            {
+                Height = 100d,
+                Width = 50d
+            };
+            var propertyChangedCount = 0;
+            border.PropertyChanged += (sender, e) =>
+            {
+                if (e.Property == Control.WidthProperty)
+                {
+                    propertyChangedCount++;
+                }
+            };
+
+            var clock = new TestClock();
+            var cancellationTokenSource = new CancellationTokenSource();
+            var animationRun = animation.RunAsync(border, clock, cancellationTokenSource.Token);
+
+            Assert.Equal(0, propertyChangedCount);
+
+            clock.Step(TimeSpan.FromSeconds(0));
+            Assert.False(animationRun.IsCompleted);
+            Assert.Equal(1, propertyChangedCount);
+
+            cancellationTokenSource.Cancel();
+            clock.Step(TimeSpan.FromSeconds(1));
+            clock.Step(TimeSpan.FromSeconds(2));
+            clock.Step(TimeSpan.FromSeconds(3));
+            //Assert.Equal(2, propertyChangedCount);
+
+            animationRun.Wait();
+
+            clock.Step(TimeSpan.FromSeconds(6));
+            Assert.True(animationRun.IsCompleted);
+            Assert.Equal(2, propertyChangedCount);
+        }
+
+        [Fact]
+        public void Cancellation_Of_Completed_Animation_Does_Not_Fail()
+        {
+            var keyframe1 = new KeyFrame()
+            {
+                Setters =
+                {
+                    new Setter(Border.WidthProperty, 200d),
+                },
+                Cue = new Cue(1d)
+            };
+
+            var keyframe2 = new KeyFrame()
+            {
+                Setters =
+                {
+                    new Setter(Border.WidthProperty, 100d),
+                },
+                Cue = new Cue(0d)
+            };
+
+            var animation = new Animation()
+            {
+                Duration = TimeSpan.FromSeconds(10),
+                Delay = TimeSpan.FromSeconds(0),
+                DelayBetweenIterations = TimeSpan.FromSeconds(0),
+                IterationCount = new IterationCount(1),
+                Children =
+                {
+                    keyframe2,
+                    keyframe1
+                }
+            };
+
+            var border = new Border()
+            {
+                Height = 100d,
+                Width = 50d
+            };
+            var propertyChangedCount = 0;
+            border.PropertyChanged += (sender, e) =>
+            {
+                if (e.Property == Control.WidthProperty)
+                {
+                    propertyChangedCount++;
+                }
+            };
+
+            var clock = new TestClock();
+            var cancellationTokenSource = new CancellationTokenSource();
+            var animationRun = animation.RunAsync(border, clock, cancellationTokenSource.Token);
+
+            Assert.Equal(0, propertyChangedCount);
+
+            clock.Step(TimeSpan.FromSeconds(0));
+            Assert.False(animationRun.IsCompleted);
+            Assert.Equal(1, propertyChangedCount);
+
+            clock.Step(TimeSpan.FromSeconds(10));
+            Assert.True(animationRun.IsCompleted);
+            Assert.Equal(2, propertyChangedCount);
+
+            cancellationTokenSource.Cancel();
+            animationRun.Wait();
+        }
     }
 }