[Windows] Fix for issues caused by setting Shell.FlyoutWidth on WinUI when binding context values are changed

[Tamilarasan-Paranthaman]

Root Cause of the issue

• The base.ArrangeOverride was not being called, which caused layout inconsistencies, such as disappearing text during runtime updates or pressing the Alt key. This occurred because the internal arrangement logic provided by the base implementation was skipped, leading to incomplete layout updates.

Description of Change

• Added a call to base.ArrangeOverride(finalSize) to ensure that the internal layout logic provided by the base class is executed before applying custom arrangement logic. Updated the ArrangeOverride implementation to handle both the base arrangement and the custom layout logic for the _content element effectively. Ensured that the method consistently returns finalSize to confirm that the allocated size has been fully used, maintaining alignment with the layout system.

Issues Fixed

Fixes #19496
Fixes #23214

Tested the behaviour in the following platforms

• Windows
• Android
• iOS
• Mac

Screenshot

Before Issue Fix	After Issue Fix
Before-Fix-FL-Width.mp4	After-Fix-FL-Width.mp4

[jsuarezruiz]

/azp run

[azure-pipelines]

Azure Pipelines successfully started running 3 pipeline(s).

[jsuarezruiz]

Could include an UITest and use get the Label counter value to validate it with an Assert?

[Tamilarasan-Paranthaman]

@jsuarezruiz, ensuring this through an assert was not functioning properly in this scenario, possibly because the text only disappeared from the view. As a result, the test passed without this fix. I have added a UI test with VerifyScreenshot to address the issue. Could you please review it and share your feedback?

[jsuarezruiz]

/azp run

[azure-pipelines]

Azure Pipelines successfully started running 3 pipeline(s).