Replace some BindSize calls with RelativeSizeAdjustment

Microsoft.Toolkit.Uwp.UI.Media/Extensions/UIElementExtensions.cs

@@ -2,6 +2,8 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+using System.Numerics;
+using Windows.UI.Composition;
 using Windows.UI.Xaml;
 using Windows.UI.Xaml.Hosting;
 
@@ -48,10 +50,10 @@ namespace Microsoft.Toolkit.Uwp.UI.Media
         /// <param name="e">The <see cref="DependencyPropertyChangedEventArgs"/> instance for the current event.</param>
         private static async void OnVisualFactoryPropertyChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
         {
-            var element = (UIElement)d;
-            var attachedVisual = await ((AttachedVisualFactoryBase)e.NewValue).GetAttachedVisualAsync(element);
+            UIElement element = (UIElement)d;
+            Visual attachedVisual = await ((AttachedVisualFactoryBase)e.NewValue).GetAttachedVisualAsync(element);
 
-            attachedVisual.BindSize(element);
+            attachedVisual.RelativeSizeAdjustment = Vector2.One;
 
             ElementCompositionPreview.SetElementChildVisual(element, attachedVisual);
         }

Microsoft.Toolkit.Uwp.UI.Media/Extensions/Windows.UI.Composition/CompositionObjectExtensions.cs

@@ -18,11 +18,11 @@ namespace Microsoft.Toolkit.Uwp.UI.Media
     internal static class CompositionObjectExtensions
     {
         /// <summary>
-        /// Starts an <see cref="ExpressionAnimation"/> to keep the size of the source <see cref="CompositionObject"/> in sync with the target <see cref="UIElement"/>
+        /// Starts an <see cref="ExpressionAnimation"/> to keep the size of the source <see cref="Visual"/> in sync with the target <see cref="UIElement"/>
         /// </summary>
-        /// <param name="source">The <see cref="CompositionObject"/> to start the animation on</param>
+        /// <param name="source">The <see cref="Visual"/> to start the animation on</param>
         /// <param name="target">The target <see cref="UIElement"/> to read the size updates from</param>
-        public static void BindSize(this CompositionObject source, UIElement target)
+        public static void BindSize(this Visual source, UIElement target)
         {
             var visual = ElementCompositionPreview.GetElementVisual(target);
             var bindSizeAnimation = source.Compositor.CreateExpressionAnimation($"{nameof(visual)}.Size");

Microsoft.Toolkit.Uwp.UI.Media/Pipelines/PipelineBuilder.cs

@@ -5,6 +5,7 @@
 using System;
 using System.Collections.Generic;
 using System.Diagnostics.Contracts;
+using System.Numerics;
 using System.Threading.Tasks;
 using Microsoft.Toolkit.Uwp.UI.Animations;
 using Windows.Graphics.Effects;
@@ -188,7 +189,7 @@ namespace Microsoft.Toolkit.Uwp.UI.Media.Pipelines
         /// <returns>A <see cref="Task{T}"/> that returns the final <see cref="SpriteVisual"/> instance to use</returns>
         public async Task<SpriteVisual> AttachAsync(UIElement target, UIElement reference = null)
         {
-            var visual = Window.Current.Compositor.CreateSpriteVisual();
+            SpriteVisual visual = Window.Current.Compositor.CreateSpriteVisual();
 
             visual.Brush = await BuildAsync();
 
@@ -196,7 +197,14 @@ namespace Microsoft.Toolkit.Uwp.UI.Media.Pipelines
 
             if (reference != null)
             {
-                visual.BindSize(reference);
+                if (reference == target)
+                {
+                    visual.RelativeSizeAdjustment = Vector2.One;
+                }
+                else
+                {
+                    visual.BindSize(reference);
+                }
             }
 
             return visual;