Re-implement PageSlide.

src/Avalonia.Controls/Expander.cs

@@ -66,9 +66,7 @@ namespace Avalonia.Controls
 
         protected virtual void OnIsExpandedChanged(AvaloniaPropertyChangedEventArgs e)
         {
-            IVisual visualContent = Presenter;
-
-            if (Content != null && ContentTransition != null && visualContent != null)
+            if (Content != null && ContentTransition != null && Presenter is Visual visualContent)
             {
                 bool forward = ExpandDirection == ExpandDirection.Left ||
                                 ExpandDirection == ExpandDirection.Up;
@@ -87,4 +85,4 @@ namespace Avalonia.Controls
         private ExpandDirection _expandDirection;
         private bool _isExpanded;
     }
-}
+}

src/Avalonia.Visuals/Animation/CrossFade.cs

@@ -58,17 +58,6 @@ namespace Avalonia.Animation
                 )
                 {
                     Cue = new Cue(0.0)
-                },
-                new KeyFrame
-                (
-                    new Setter
-                    {
-                        Property = Visual.OpacityProperty,
-                        Value = 1.0
-                    }
-                )
-                {
-                    Cue = new Cue(1.0)
                 }
             };
             _fadeOutAnimation.Duration = _fadeInAnimation.Duration = duration;
@@ -101,7 +90,7 @@ namespace Avalonia.Animation
         /// <returns>
         /// A <see cref="Task"/> that tracks the progress of the animation.
         /// </returns>
-        public async Task Start(IVisual from, IVisual to)
+        public async Task Start(Visual from, Visual to)
         {
             var tasks = new List<Task>();
 
@@ -110,16 +99,15 @@ namespace Avalonia.Animation
                 to.Opacity = 0;
             }
 
-            if (from is Animatable fadeOut)
+            if (from != null)
             {
-                tasks.Add(_fadeOutAnimation.RunAsync(fadeOut));
+                tasks.Add(_fadeOutAnimation.RunAsync(from));
             }
 
-            if (to is Animatable fadeIn)
+            if (to != null)
             {
-                to.Opacity = 0;
                 to.IsVisible = true;
-                tasks.Add(_fadeInAnimation.RunAsync(fadeIn));
+                tasks.Add(_fadeInAnimation.RunAsync(to));
 
             }
 
@@ -128,7 +116,6 @@ namespace Avalonia.Animation
             if (from != null)
             {
                 from.IsVisible = false;
-                from.Opacity = 1;
             }
 
             if (to != null)
@@ -152,7 +139,7 @@ namespace Avalonia.Animation
         /// <returns>
         /// A <see cref="Task"/> that tracks the progress of the animation.
         /// </returns>
-        Task IPageTransition.Start(IVisual from, IVisual to, bool forward)
+        Task IPageTransition.Start(Visual from, Visual to, bool forward)
         {
             return Start(from, to);
         }

src/Avalonia.Visuals/Animation/IPageTransition.cs

@@ -26,6 +26,6 @@ namespace Avalonia.Animation
         /// <returns>
         /// A <see cref="Task"/> that tracks the progress of the animation.
         /// </returns>
-        Task Start(IVisual from, IVisual to, bool forward);
+        Task Start(Visual from, Visual to, bool forward);
     }
 }

src/Avalonia.Visuals/Animation/PageSlide.cs

@@ -6,6 +6,7 @@ using System.Collections.Generic;
 using System.Reactive.Threading.Tasks;
 using System.Threading.Tasks;
 using Avalonia.Media;
+using Avalonia.Styling;
 using Avalonia.VisualTree;
 
 namespace Avalonia.Animation
@@ -67,7 +68,7 @@ namespace Avalonia.Animation
         /// <returns>
         /// A <see cref="Task"/> that tracks the progress of the animation.
         /// </returns>
-        public async Task Start(IVisual from, IVisual to, bool forward)
+        public async Task Start(Visual from, Visual to, bool forward)
         {
             var tasks = new List<Task>();
             var parent = GetVisualParent(from, to);
@@ -79,16 +80,69 @@ namespace Avalonia.Animation
             // in favor of XAML based transition for pages
             if (from != null)
             {
-
+                var animation = new Animation
+                {
+                    new KeyFrame
+                    (
+                        new Setter
+                        {
+                            Property = translateProperty,
+                            Value = 0
+                        }
+                    )
+                    {
+                        Cue = new Cue(0.0)
+                    },
+                    new KeyFrame
+                    (
+                        new Setter
+                        {
+                            Property = translateProperty,
+                            Value = forward ? -distance : distance
+                        }
+                    )
+                    {
+                        Cue = new Cue(1.0)
+                    }
+                };
+                animation.Duration = Duration;
+                tasks.Add(animation.RunAsync(from));
             }
 
             if (to != null)
             {
-
+                to.IsVisible = true;
+                var animation = new Animation
+                {
+
+                    new KeyFrame
+                    (
+                        new Setter
+                        {
+                            Property = translateProperty,
+                            Value = forward ? -distance : distance
+                        }
+                    )
+                    {
+                        Cue = new Cue(0.0)
+                    },
+                    new KeyFrame
+                    (
+                        new Setter
+                        {
+                            Property = translateProperty,
+                            Value = 0
+                        }
+                    )
+                    {
+                        Cue = new Cue(1.0)
+                    },
+                };
+                animation.Duration = Duration;
+                tasks.Add(animation.RunAsync(to));
             }
 
-            // FIXME: This is temporary until animations are fixed.
-            await Task.Delay(1);
+            await Task.WhenAll(tasks);
 
             if (from != null)
             {