WinUI 3 ScrollViewer does not bubble PointerCaptureLost event when ancestor calls CapturePointer in PointerPressed

[rozele]

Describe the bug

In UWP, if you have something like:

var stackPanel = new StackPanel();
var scrollViewer = new ScrollViewer();
stackPanel.Children.Add(scrollViewer);
stackPanel.PointerPressed += (sender, args) => {
  stackPanel.CapturePointer(args.Pointer);
}
stackPanel.PointerCaptureLost += (sender, args) => {
  Debug.WriteLine("PointerCaptureLost");
}

when you start a direct manipulation on the ScrollViewer with a touch gesture, the PointerCaptureLost event bubbles to the StackPanel. In WinUI 3, this does not occur.

This manifests in a limitation for React Native Windows, which uses pointer routed events at the top-level WinUI component to proxy events to JavaScript, and relies on ScrollViewer bubbling the PointerCaptureLost event to know when to cancel a gesture sequence emitted to JavaScript.

Steps to reproduce the bug

1. Set up code like the above, where a ScrollViewer is nested in a WinUI component ancestor that calls CapturePointer in it's PointerPressed callback.
2. Subscribe the PointerCaptureLost event on the ancestor that captures the pointer.
3. Use a pan gesture to scroll the ScrollViewer
4. Observe that the PointerCaptureLost event does not bubble to the ancestor, nor does PointerReleased (expected) or PointerCanceled, so we have no terminal event to establish that a touch gesture has been interrupted / canceled.

Expected behavior

WinUI 3 ScrollViewer should bubble a PointerCaptureLost event like it does in UWP when a touch gesture results in direct manipulation in a ScrollViewer.

Screenshots

No response

NuGet package version

WinUI 3 - Windows App SDK 1.5.5: 1.5.240627000

Windows version

Windows 11 (22H2): Build 22621

Additional context

No response

[github-actions]

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• ScrollViewer children are silently losing pointer events after PointerExited with pen & touch (#9290), similarity score: 0.82

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[rozele]

What makes this an even bigger problem is that WinUI 3 also does not appear to bubble the PointerReleased event to the ancestor unless we call CapturePointer on it, for either mouse or touch (rendering our root-level pointer dispatch approach pointless).

[codendone]

This was resolved as duplicate of an internal bug. Changing this to fixed. It looks like the fix is in 1.6-experimental2 and 1.6-preview1.