SetImplicitShowAnimation not working in ItemsControl with ItemsStackPanel

[Arlodotexe]

Describe the bug

When an ImplicitShowAnimation is set on an element that's hosted inside of an ItemsControl that uses <ItemsStackPanel> as the ItemsPanelTemplate, the animation appear to not run.

Steps to reproduce the bug

Download and run the complete sample from CompositionAnimationsItemsControl.zip

To summarize:

1. Set up the ItemsControl

   <ItemsControl>
   <ItemsControl.Items>
       <Rectangle x:Name="Rect" Height="200" Width="200" Fill="Red" Visibility="Collapsed" Opacity="0" />
   </ItemsControl.Items>
   
   <ItemsControl.ItemsPanel>
       <ItemsPanelTemplate>
           <!--  Orientation does not matter  -->
           <ItemsStackPanel Orientation="Horizontal" />
       </ItemsPanelTemplate>
   </ItemsControl.ItemsPanel>
   </ItemsControl>

2. Set up the ImplicitShowAnimation

Compositor compositor = ElementCompositionPreview.GetElementVisual(Rect).Compositor; var animation = compositor.CreateScalarKeyFrameAnimation(); animation.Duration = System.TimeSpan.FromSeconds(1); animation.InsertKeyFrame(0, 0); animation.InsertKeyFrame(1, 1); animation.Target = "Opacity";

ElementCompositionPreview.SetImplicitShowAnimation(Rect, animation);

3. Trigger the animation
```csharp
Rect.Visibility = Windows.UI.Xaml.Visibility.Visible;

Expected behavior

The rectangle should fade in.

Screenshots

No response

NuGet package version

Microsoft.UI.Xaml 2.7.0

Windows app type

• [x] UWP
• [ ] Win32

Device form factor

Desktop

Windows version

No response

Additional context

Tested on Windows 11 22000.348

[StephenLPeters]

@gegao18 or @stmoy is this an understood issue? I don't see anything obviously wrong.

[dpaulino]

I've been hitting this bug with my app. Any updates here?

[michael-hawker]

Bumping, based on https://github.com/microsoft/microsoft-ui-xaml/discussions/8638