XAML content hosted by DesktopWindowXamlSource has a diagonal white line when resizing it

[Pinguin2001]

Describe the bug

While resizing XAML content hosted by DesktopWindowXamlSource a white diagonal line is displayed

Steps to reproduce the bug

1. Resize a XAML windows
2. Observe a white line

Expected behavior

No white line appears

Screenshots

https://github.com/user-attachments/assets/63c91e3d-bc0f-4693-9bf8-97d3552b3d98
https://github.com/user-attachments/assets/7b51087c-2005-4c92-985e-2b08194f86c7

NuGet package version

WinUI 3 - Windows App SDK 1.7.3: 1.7.250606001

Windows version

Windows Insider Build (xxxxx), Windows 11 (24H2): Build 26100

Additional context

Note: It does not display on CoreWindow

[castorix]

I cannot reproduce this bug, but with a different configuration : Windows 10 22H2, Windows App SDK 1.7.250401001
(I tested with the sample in VB.NET (VB_WinUI3_DesktopWindowXamlSource), also by commenting OnResize and adding in Form1_Load

Dim sb = m_dwxs.SiteBridge
sb.ResizePolicy = Content.ContentSizePolicy.ResizeContentToParentWindow

[DarranRowe]

Are your video drivers up to date?

Under the surface, Xaml uses composition to draw. Composition uses Direct3D to draw to the composition surface. What you are seeing there could be the triangles making up the 2D texture not quite fitting together properly, and so it is rendering a line along the seam.

[Pinguin2001]

Yes they are, I have observed this for at least two years on various devices running various builds.

[DarranRowe]

Have you had the opportunity to verify what happens with a different manufacturer's graphics adapter?

I personally see no issue on a Radeon RX 7800XT, and a Qualcomm Adreno X1-85. At the moment, I don't have the ability to test on a GeForce GPU or an Intel GPU. But this is still possible that it is a GPU driver issue.

One thing that could be useful to try out if you can, see if you can replicate this using Windows.UI.Composition and Direct2D. I have an idea of one thing I can try personally, see if using WARP will change anything.

[Pinguin2001]

I have tested it on a system with an Intel Iris Xe on 27913 and it does not appear to be the case on there. It is a very odd issue, that seems to be occuring in specific conditions.