Add RelativePointAnimator

src/Avalonia.Visuals/Animation/Animators/RelativePointAnimator.cs

@@ -0,0 +1,20 @@
+namespace Avalonia.Animation.Animators
+{
+    /// <summary>
+    /// Animator that handles <see cref="RelativePoint"/> properties.
+    /// </summary>
+    public class RelativePointAnimator : Animator<RelativePoint>
+    {
+        private static readonly PointAnimator s_pointAnimator = new PointAnimator();
+
+        public override RelativePoint Interpolate(double progress, RelativePoint oldValue, RelativePoint newValue)
+        {
+            if (oldValue.Unit != newValue.Unit)
+            {
+                return progress >= 1 ? newValue : oldValue;
+            }
+
+            return new RelativePoint(s_pointAnimator.Interpolate(progress, oldValue.Point, newValue.Point), oldValue.Unit);
+        }
+    }
+}

src/Avalonia.Visuals/Animation/Transitions/RelativePointTransition.cs

@@ -0,0 +1,11 @@
+using Avalonia.Animation.Animators;
+
+namespace Avalonia.Animation
+{
+    /// <summary>
+    /// Transition class that handles <see cref="AvaloniaProperty"/> with <see cref="RelativePoint"/> type.
+    /// </summary>  
+    public class RelativePointTransition : AnimatorDrivenTransition<RelativePoint, RelativePointAnimator>
+    {
+    }
+}

src/Avalonia.Visuals/RelativePoint.cs

@@ -1,5 +1,7 @@
 using System;
 using System.Globalization;
+
+using Avalonia.Animation.Animators;
 using Avalonia.Utilities;
 
 namespace Avalonia
@@ -45,6 +47,11 @@ namespace Avalonia
 
         private readonly RelativeUnit _unit;
 
+        static RelativePoint()
+        {
+            Animation.Animation.RegisterAnimator<RelativePointAnimator>(prop => typeof(RelativePoint).IsAssignableFrom(prop.PropertyType));
+        }
+
         /// <summary>
         /// Initializes a new instance of the <see cref="RelativePoint"/> struct.
         /// </summary>