fix: Storyboard Completed event not firing for dependent animations without EnableDependentAnimation

src/Uno.UI.RuntimeTests/Tests/Windows_UI_Xaml_Media_Animation/Given_Storyboard.cs

@@ -50,4 +50,71 @@ public async Task When_Empty_Storyboard_Paused()
 		Assert.AreEqual(ClockState.Active, storyboard.GetCurrentState());
 		await TestServices.WindowHelper.WaitFor(() => completed);
 	}
+
+	[TestMethod]
+	public async Task When_DependentAnimation_Without_EnableDependentAnimation_Completes()
+	{
+		var border = new Microsoft.UI.Xaml.Controls.Border
+		{
+			Width = 100,
+			Height = 100
+		};
+
+		var animation = new DoubleAnimation
+		{
+			From = 100,
+			To = 200,
+			Duration = new Duration(System.TimeSpan.FromMilliseconds(100)),
+			EnableDependentAnimation = false // Explicitly set to false
+		};
+
+		Storyboard.SetTarget(animation, border);
+		Storyboard.SetTargetProperty(animation, "Height");
+
+		var storyboard = new Storyboard();
+		storyboard.Children.Add(animation);
+
+		bool completed = false;
+		storyboard.Completed += (s, e) => completed = true;
+
+		storyboard.Begin();
+
+		// The Completed event should fire even though the animation doesn't actually run
+		await TestServices.WindowHelper.WaitFor(() => completed, timeoutMS: 2000);
+		Assert.IsTrue(completed, "Storyboard.Completed should fire even for dependent animations without EnableDependentAnimation");
+	}
+
+	[TestMethod]
+	public async Task When_DependentAnimation_Stopped_Before_Completion()
+	{
+		var border = new Microsoft.UI.Xaml.Controls.Border
+		{
+			Width = 100,
+			Height = 100
+		};
+
+		var animation = new DoubleAnimation
+		{
+			From = 100,
+			To = 200,
+			Duration = new Duration(System.TimeSpan.FromMilliseconds(100)),
+			EnableDependentAnimation = false
+		};
+
+		Storyboard.SetTarget(animation, border);
+		Storyboard.SetTargetProperty(animation, "Height");
+
+		var storyboard = new Storyboard();
+		storyboard.Children.Add(animation);
+
+		bool completed = false;
+		storyboard.Completed += (s, e) => completed = true;
+
+		storyboard.Begin();
+		storyboard.Stop(); // Stop immediately
+
+		// Completed should not fire when stopped before completion
+		await TestServices.WindowHelper.WaitForIdle();
+		Assert.IsFalse(completed, "Storyboard.Completed should not fire when stopped before completion");
+	}
 }

src/Uno.UI/UI/Xaml/Media/Animation/ColorAnimationUsingKeyFrames.cs

@@ -244,6 +244,17 @@
 
 			if (!EnableDependentAnimation && this.GetIsDependantAnimation())
 			{ // Don't start the animator its a dependent animation
+				// However, we still need to complete the animation to maintain consistency with WinUI
+				State = TimelineState.Active;
+				_ = Dispatcher.RunAsync(CoreDispatcherPriority.Normal, () =>
+				{
+					if (State == TimelineState.Stopped)
+					{
+						// If the animation was force-stopped, don't trigger completion
+						return;
+					}
+					OnEnd();
+				});
 				return;
 			}
 

src/Uno.UI/UI/Xaml/Media/Animation/DoubleAnimationUsingKeyFrames.cs

@@ -214,6 +214,17 @@
 
 			if (!EnableDependentAnimation && this.GetIsDependantAnimation())
 			{ // Don't start the animator its a dependent animation
+				// However, we still need to complete the animation to maintain consistency with WinUI
+				State = TimelineState.Active;
+				_ = Dispatcher.RunAsync(CoreDispatcherPriority.Normal, () =>
+				{
+					if (State == TimelineState.Stopped)
+					{
+						// If the animation was force-stopped, don't trigger completion
+						return;
+					}
+					OnEnd();
+				});
 				return;
 			}
 

src/Uno.UI/UI/Xaml/Media/Animation/Timeline.animation.cs

@@ -284,6 +284,17 @@
 
 				if (!EnableDependentAnimation && _owner.GetIsDependantAnimation())
 				{ // Don't start the animator its a dependent animation
+					// However, we still need to complete the animation to maintain consistency with WinUI
+					State = TimelineState.Active;
+					_ = _owner.Dispatcher.RunAsync(CoreDispatcherPriority.Normal, () =>
+					{
+						if (State == TimelineState.Stopped)
+						{
+							// If the animation was force-stopped, don't trigger completion
+							return;
+						}
+						OnEnd();
+					});
 					return;
 				}