fix(backgroundtransition): animations should ignore background transi…

…tions

src/Uno.UI.Composition/Composition/ColorBrushTransitionState.skia.cs

@@ -1,26 +1,18 @@
 #nullable enable
 
+using System;
 using Windows.UI;
 
 namespace Microsoft.UI.Composition;
 
-internal sealed class ColorBrushTransitionState
+internal readonly record struct ColorBrushTransitionState(
+	BorderVisual Visual,
+	Color FromColor,
+	Color ToColor,
+	long StartTimestamp,
+	long EndTimestamp,
+	bool IsActive)
 {
-	internal ColorBrushTransitionState(BorderVisual visual, Color fromColor, Color toColor, long startTimestamp, long endTimestamp)
-	{
-		Visual = visual;
-		FromColor = fromColor;
-		ToColor = toColor;
-		StartTimestamp = startTimestamp;
-		EndTimestamp = endTimestamp;
-	}
-
-	internal BorderVisual Visual { get; }
-	internal Color FromColor { get; }
-	internal Color ToColor { get; }
-	internal long StartTimestamp { get; }
-	internal long EndTimestamp { get; }
-
 	internal Color CurrentColor
 	{
 		get

src/Uno.UI.Composition/Composition/Compositor.skia.cs

@@ -32,24 +32,42 @@ internal void UnregisterAnimation(CompositionAnimation animation)
 		}
 	}
 
+	internal void DisableBackgroundTransition(BorderVisual visual)
+	{
+		for (int i = 0; i < _backgroundTransitions.Count; i++)
+		{
+			if (_backgroundTransitions[i].Visual == visual)
+			{
+				_backgroundTransitions[i] = _backgroundTransitions[i] with { IsActive = false };
+				break;
+			}
+		}
+	}
+
 	internal void RegisterBackgroundTransition(BorderVisual visual, Color fromColor, Color toColor, TimeSpan duration)
 	{
 		var start = TimestampInTicks;
 		var end = start + duration.Ticks;
 
 		for (int i = 0; i < _backgroundTransitions.Count; i++)
 		{
-			if (_backgroundTransitions[i].Visual == visual)
+			var transition = _backgroundTransitions[i];
+			if (transition.Visual == visual)
 			{
+				if (!transition.IsActive)
+				{
+					_backgroundTransitions[i] = transition with { IsActive = true };
+					return;
+				}
 				// when the background changes when already in a transition, the new transition
 				// picks up from where the preexisting transition stopped.
-				fromColor = _backgroundTransitions[i].CurrentColor;
+				fromColor = transition.CurrentColor;
 				_backgroundTransitions.RemoveAt(i);
 				break;
 			}
 		}
 
-		_backgroundTransitions.Add(new ColorBrushTransitionState(visual, fromColor, toColor, start, end));
+		_backgroundTransitions.Add(new ColorBrushTransitionState(visual, fromColor, toColor, start, end, true));
 	}
 
 	internal bool TryGetEffectiveBackgroundColor(CompositionSpriteShape shape, out Color color)
@@ -58,8 +76,15 @@ internal bool TryGetEffectiveBackgroundColor(CompositionSpriteShape shape, out C
 		{
 			if (transition.Visual.BackgroundShape == shape)
 			{
-				color = transition.CurrentColor;
-				return true;
+				if (transition.IsActive)
+				{
+					color = transition.CurrentColor;
+					return true;
+				}
+				else
+				{
+					break;
+				}
 			}
 		}
 

src/Uno.UI/UI/Xaml/BorderHelper.skia.cs

@@ -47,13 +47,23 @@ public static void UpdateAllBorderProperties(this IBorderInfoProvider @this)
 		@this.UpdateBorderThickness();
 	}
 
-	public static void SetUpBrushTransitionIfAllowed(BorderVisual visual, Brush fromBrush, Brush toBrush, BrushTransition transition)
+	public static void SetUpBrushTransitionIfAllowed(BorderVisual visual, Brush fromBrush, Brush toBrush, BrushTransition transition, bool isAnimation)
 	{
 		if (transition is null)
 		{
 			return;
 		}
 
+		if (isAnimation)
+		{
+			// When an animation sets the background, it skips the transition logic and is applied immediately.
+			// However, it "deactivates" the currently active transition if one exists. Once the animation is done,
+			// the deactivated transition is reactivated and continues as if it was running (i.e. it's not paused,
+			// but takes into account the duration during which it was deactivated).
+			visual.Compositor.DeactivateBackgroundTransition(visual);
+			return;
+		}
+
 		var oldBrush = fromBrush as SolidColorBrush;
 		var newBrush = toBrush as SolidColorBrush;
 
@@ -69,7 +79,7 @@ newBrush is not null
 			// SolidColorBrush animations work only on static brushes. Neither brush can be animating.
 			//&& oldBrushIsNullOrStatic
 			//&& !newBrush->IsEffectiveValueInSparseStorage(KnownPropertyIndex::SolidColorBrush_ColorAnimation)
-			)
+		   )
 		{
 			visual.Compositor.RegisterBackgroundTransition(visual, oldBrush?.Color ?? Colors.Transparent, newBrush.Color, transition.Duration);
 		}

src/Uno.UI/UI/Xaml/Controls/Border/Border.cs

@@ -311,7 +311,12 @@ protected override void OnBackgroundChanged(DependencyPropertyChangedEventArgs e
 	{
 #if UNO_HAS_BORDER_VISUAL
 		this.UpdateBackground();
-		BorderHelper.SetUpBrushTransitionIfAllowed((BorderVisual)this.Visual, e.OldValue as Brush, e.NewValue as Brush, this.BackgroundTransition);
+		BorderHelper.SetUpBrushTransitionIfAllowed(
+			(BorderVisual)this.Visual,
+			e.OldValue as Brush,
+			e.NewValue as Brush,
+			this.BackgroundTransition,
+			(this as IDependencyObjectStoreProvider).Store.GetPropertyDetails(BackgroundProperty).CurrentHighestValuePrecedence == DependencyPropertyValuePrecedences.Animations);
 #else
 		UpdateBorder();
 #endif

src/Uno.UI/UI/Xaml/Controls/ContentPresenter/ContentPresenter.cs

@@ -1219,7 +1219,12 @@ protected override void OnBackgroundChanged(DependencyPropertyChangedEventArgs e
 	{
 #if UNO_HAS_BORDER_VISUAL
 		this.UpdateBackground();
-		BorderHelper.SetUpBrushTransitionIfAllowed((BorderVisual)this.Visual, e.OldValue as Brush, e.NewValue as Brush, this.BackgroundTransition);
+		BorderHelper.SetUpBrushTransitionIfAllowed(
+			(BorderVisual)this.Visual,
+			e.OldValue as Brush,
+			e.NewValue as Brush,
+			this.BackgroundTransition,
+			(this as IDependencyObjectStoreProvider).Store.GetPropertyDetails(BackgroundProperty).CurrentHighestValuePrecedence == DependencyPropertyValuePrecedences.Animations);
 #else
 		UpdateBorder();
 #endif

src/Uno.UI/UI/Xaml/Controls/Panel/Panel.cs

@@ -239,7 +239,12 @@ protected override void OnBackgroundChanged(DependencyPropertyChangedEventArgs e
 	{
 #if UNO_HAS_BORDER_VISUAL
 		this.UpdateBackground();
-		BorderHelper.SetUpBrushTransitionIfAllowed((BorderVisual)this.Visual, e.OldValue as Brush, e.NewValue as Brush, this.BackgroundTransition);
+		BorderHelper.SetUpBrushTransitionIfAllowed(
+			(BorderVisual)this.Visual,
+			e.OldValue as Brush,
+			e.NewValue as Brush,
+			this.BackgroundTransition,
+			(this as IDependencyObjectStoreProvider).Store.GetPropertyDetails(BackgroundProperty).CurrentHighestValuePrecedence == DependencyPropertyValuePrecedences.Animations);
 #else
 		UpdateBorder();
 #endif