Fixed transition backend, transitions are now working.

samples/RenderTest/SideBar.xaml

@@ -32,8 +32,17 @@
     <Setter Property="FontSize" Value="14"/>
     <Setter Property="Margin" Value="0"/>
     <Setter Property="Padding" Value="16"/>
+    <Setter Property="Transitions">
+      <Transitions>
+        <DoubleTransition Property="Opacity" Easing="CircularEaseIn" Duration="0:0:0.5"/>
+      </Transitions>
+    </Setter>
   </Style>
 
+  <Style Selector="TabControl.sidebar TabStripItem:pointerover">
+    <Setter Property="Opacity" Value="0.5"/>
+  </Style>
+  
   <Style Selector="TabControl.sidebar TabStripItem:selected">
     <Setter Property="Background" Value="{DynamicResource ThemeAccentBrush2}"/>
   </Style>

src/Avalonia.Animation/Animatable.cs

@@ -13,35 +13,24 @@ namespace Avalonia.Animation
     /// </summary>
     public class Animatable : AvaloniaObject
     {
-
-        private Transitions _transitions;
+        /// <summary>
+        /// 
+        /// </summary>
+        public static readonly StyledProperty<Transitions> TransitionsProperty =
+                AvaloniaProperty.Register<Animatable, Transitions>(nameof(Transitions));
 
         /// <summary>
         /// Gets or sets the property transitions for the control.
         /// </summary>
         public Transitions Transitions
         {
-            get
-            {
-                return _transitions ?? (_transitions = new Transitions());
-            }
-
-            set
-            {
-                SetAndRaise(TransitionsProperty, ref _transitions, value);
-            }
+            get { return GetValue(TransitionsProperty); }
+            set { SetValue(TransitionsProperty, value); }
         }
 
-        /// <summary>
-        /// Gets or sets the property transitions for the control.
-        /// </summary>
-        public static readonly DirectProperty<Animatable, Transitions> TransitionsProperty =
-                AvaloniaProperty.RegisterDirect<Animatable, Transitions>(nameof(Transitions), o => o.Transitions);
-
         /// <summary>
         /// Reacts to a change in a <see cref="AvaloniaProperty"/> value in 
-        /// order to animate the change if a <see cref="ITransition"/> 
-        /// is set for the property.
+        /// order to animate the change if a <see cref="ITransition"/> is set for the property.
         /// </summary>
         /// <param name="e">The event args.</param>
         protected override void OnPropertyChanged(AvaloniaPropertyChangedEventArgs e)
@@ -50,65 +39,12 @@ namespace Avalonia.Animation
             {
                 var match = Transitions.FirstOrDefault(x => x.Property == e.Property);
 
-
                 if (match != null)
                 {
-                    
-                    //    //BindAnimateProperty(this, e.Property, e.OldValue, e.NewValue, match.Easing, match.Duration);
+                    match.Apply(this, e.OldValue, e.NewValue);
                 }
             }
         }
 
-        ///// <summary>
-        ///// Animates a <see cref="AvaloniaProperty"/>.
-        ///// </summary>
-        ///// <param name="target">The target object.</param>
-        ///// <param name="property">The target property.</param>
-        ///// <param name="start">The value of the property at the start of the animation.</param>
-        ///// <param name="finish">The value of the property at the end of the animation.</param>
-        ///// <param name="easing">The easing function to use.</param>
-        ///// <param name="duration">The duration of the animation.</param>
-        ///// <returns>An <see cref="Animation"/> that can be used to track or stop the animation.</returns>
-        //public static Animation BindAnimateProperty(
-        //    IAvaloniaObject target,
-        //    AvaloniaProperty property,
-        //    object start,
-        //    object finish,
-        //    IEasing easing,
-        //    TimeSpan duration)
-        //{
-        //    var k = start.GetType();
-        //    if (k == typeof(double))
-        //    {
-        //        var o = Timing.GetTimer(duration).Select(progress => easing.Ease(progress, start, finish));
-        //        return new Animation(o, target.Bind(property, o, BindingPriority.Animation));
-        //    }
-        //    else
-        //        return null;
-        //}
-
-        ///// <summary>
-        ///// Animates a <see cref="AvaloniaProperty"/>.
-        ///// </summary>
-        ///// <typeparam name="T">The property type.</typeparam>
-        ///// <param name="target">The target object.</param>
-        ///// <param name="property">The target property.</param>
-        ///// <param name="start">The value of the property at the start of the animation.</param>
-        ///// <param name="finish">The value of the property at the end of the animation.</param>
-        ///// <param name="easing">The easing function to use.</param>
-        ///// <param name="duration">The duration of the animation.</param>
-        ///// <returns>An <see cref="Animation"/> that can be used to track or stop the animation.</returns>
-        //public static Animation<T> Property<T>(
-        //    IAvaloniaObject target,
-        //    AvaloniaProperty<T> property,
-        //    T start,
-        //    T finish,
-        //    IEasing<T> easing,
-        //    TimeSpan duration)
-        //{
-        //    var o = Timing.GetTimer(duration).Select(progress => easing.Ease(progress, start, finish));
-        //    return new Animation<T>(o, target.Bind(property, o, BindingPriority.Animation));
-        //}
-
     }
 }

src/Avalonia.Animation/Transitions/DoubleTransition.cs

@@ -3,6 +3,7 @@
 
 using Avalonia.Metadata;
 using System;
+using System.Reactive.Linq;
 
 namespace Avalonia.Animation
 {
@@ -12,21 +13,14 @@ namespace Avalonia.Animation
     public class DoubleTransition : Transition<double>
     {
         /// <inheritdocs/>
-        public DoubleTransition() : base()
+        public override void DoInterpolation(Animatable control, IObservable<double> progress, double oldValue, double newValue)
         {
-
-        }
-
-        /// <inheritdocs/>
-        public override AvaloniaProperty Property { get; set; }
-
-        /// <inheritdocs/>
-        public override void Apply(Animatable control)
-        {
-            //throw new NotImplementedException();
-
-
-
+            var delta = newValue - oldValue;
+            var transition = progress.Select(p =>
+            {
+                return Easing.Ease(p) * delta + oldValue;
+            });
+            control.Bind(Property, transition.Select(p=>(object)p), Data.BindingPriority.Animation);
         }
     }
 }

src/Avalonia.Animation/Transitions/Transition.cs

@@ -11,13 +11,14 @@ namespace Avalonia.Animation
         /// <summary>
         /// Applies the transition to the specified <see cref="Animatable"/>.
         /// </summary>
-        /// <param name="control"></param>
-        void Apply(Animatable control);
+        void Apply(Animatable control, object oldValue, object newValue);
 
         /// <summary>
         /// Gets the property to be animated.
         /// </summary>
         AvaloniaProperty Property { get; set; }
+
+
     }
 
     /// <summary>
@@ -29,29 +30,41 @@ namespace Avalonia.Animation
         /// Gets the duration of the animation.
         /// </summary> 
         public TimeSpan Duration { get; set; }
-
+ 
         /// <summary>
-        /// Instantiates the base abstract class <see cref="Transition{T}"/>.
+        /// Gets the easing class to be used.
         /// </summary>
-        public Transition()
+        public IEasing Easing { get; set; }
+
+        private AvaloniaProperty _prop;
+
+        /// <inheritdocs/>
+        public AvaloniaProperty Property
         {
-            if(!(typeof(T) == Property.PropertyType))
+            get
             {
-                throw new InvalidCastException
-                    ($"Invalid property type {typeof(T).Name} for this {this.GetType().Name}");
+                return _prop;
+            }
+            set
+            {
+                if (!(typeof(T) == value.PropertyType))                
+                    throw new InvalidCastException
+                        ($"Invalid property type {typeof(T).Name} for this {GetType().Name}");
+
+                _prop = value;
             }
         }
 
         /// <summary>
-        /// Gets the easing class to be used.
+        /// Apply interpolation to the property.
         /// </summary>
-        public IEasing Easing { get; set; }
+        public abstract void DoInterpolation(Animatable control, IObservable<double> progress, T oldValue, T newValue);
 
         /// <inheritdocs/>
-        public abstract AvaloniaProperty Property { get; set; }
-
-        /// <inheritdocs/>
-        public abstract void Apply(Animatable control);
+        public void Apply(Animatable control, object oldValue, object newValue)
+        {
+            DoInterpolation(control, Timing.GetTimer(Duration), (T)oldValue, (T)newValue);
+        }
 
     }
 

src/Avalonia.Visuals/Animation/PageSlide.cs

@@ -76,8 +76,8 @@ namespace Avalonia.Animation
 
             if (from != null)
             {
-                var transform = new TranslateTransform();
-                from.RenderTransform = transform;
+                //var transform = new TranslateTransform();
+                //from.RenderTransform = transform;
                 //tasks.Add(Animate.Property(
                 //    transform,
                 //    translateProperty,
@@ -89,8 +89,8 @@ namespace Avalonia.Animation
 
             if (to != null)
             {
-                var transform = new TranslateTransform();
-                to.RenderTransform = transform;
+                //var transform = new TranslateTransform();
+                //to.RenderTransform = transform;
                 to.IsVisible = true;
                 //tasks.Add(Animate.Property(
                 //    transform,

src/Markup/Avalonia.Markup.Xaml/PortableXaml/AvaloniaDefaultTypeConverters.cs

@@ -49,6 +49,7 @@ namespace Avalonia.Markup.Xaml.PortableXaml
             { typeof(Cursor), typeof(CursorTypeConverter) },
             { typeof(WindowIcon), typeof(IconTypeConverter) },
             { typeof(Easing), typeof(EasingTypeConverter) },
+            { typeof(IEasing), typeof(EasingTypeConverter) },
             //{ typeof(FontWeight), typeof(FontWeightConverter) },
         };