EffectiveViewportChangedEventArgs of EffectiveViewportChanged event differ in XAML Islands vs UWP

[lyahdav]

Describe the bug

In XAML Islands when using the FrameworkElement.EffectiveViewportChanged Event, the EffectiveViewportChangedEventArgs return different results than in a UWP app.

Steps to reproduce the bug

1. Run this solution setting the XamlIslandsApp project as Startup Project and then UwpXamlApp project: https://github.com/lyahdav/XamlPlayground/tree/scroll-viewer-visibility
2. Scroll the ScrollViewer
3. Look at Output pane in Visual Studio and compare results

Expected behavior

EffectiveViewportChangedEventArgs should match between XAML Islands and UWP apps.

Some differences:

• EffectiveViewport Width/Height is always 1 in XAML Islands
• MaxViewport Width/Height is always 1 in XAML Islands
• When an element is fully visible or below the bottom of ScrollViewer, BringIntoViewDistanceY is incorrect in XAML Islands

Screenshots

Here's a table of the differences:

Here's a video comparison of one scenario that differs. UWP:

uwp.mov

XAML Islands:

islands.mov

NuGet package version

No response

Windows app type

• UWP
• Win32

Device form factor

Desktop

Windows version

May 2021 Update (19043)

Additional context

Possibly related issue: #3001

[StephenLPeters]

@marb2000 @bpulliam and @RBrid FYI

[github-actions]

This issue is stale because it has been open 180 days with no activity. Remove stale label or comment or this will be closed in 5 days.

[lyahdav]

This issue is stale because it has been open 180 days with no activity. Remove stale label or comment or this will be closed in 5 days.

This should still be relevant.

[ranjeshj]

@lyahdav does this still repro with WinUI3 version 1.4 or 1.5 experimental ? There have been fixes in this area. The related issue you mentioned has also been fixed. Could you please verify and reopen if this still repros? Thanks!

[lyahdav]

@ranjeshj I just confirmed with WinAppSDK 1.4.3 it seems these issues are resolved.