WinUI 3 resize rendering bug

[Iemand005]

Describe the bug

When resizing any WinUI 3 app, the right and bottom side of the window flicker and jump between the previous and next frame.

Why is this important?

The windows should resize fluently like UWP apps do, instead every WinUI 3 app feels jittery and laggy when resizing because Mica becomes visible behind elements and a black bar flickers into view. It's especially bothersome when resizing from the left or top side.

Steps to reproduce the bug

1. Open any WinUI 3 app
2. Resize it

Actual behavior

The window resizes and jitters.

Expected behavior

The window resizes and is stable, like UWP apps (example: Microsoft Store).

Screenshots

20251006-2228-17.4894755.mp4

20251006-2236-59.1449266.mp4

20251006-2237-56.2910551.mp4

20251006-2238-30.6096507.mp4

NuGet package version

None

Windows version

Windows 11 (24H2): Build 26100

Additional context

No response

[castorix]

Similar to this old thread : #5148

[Iemand005]

So this has been a known issue for 4 years and people complained and nothing is done about it?? This ruins the user experience of Windows completely. Does nobody get bothered by how horribly ugly it is to look at? Everywhere you look on Windows you see this.

Sorry but window resizing is one of the most absolute basic things an OS and UI library should handle properly. This is absolutely unbelievable and it's really not how you make developers happy. This should've been moved very high up the priority list years ago.

This has a huge impact on the entire OS and makes it feel like outdated clunky garbage.

I'm done with WinUI.