Apps with a custom background flash a white background for a couple frames on some devices

• .NET Core Version: (e.g. 3.0 Preview1, or daily build number, use dotnet --info) 6.0.100
• Windows version: (winver) Windows 11 10.0.22000
• Does the bug reproduce also in WPF for .NET Framework 4.8?:
• Is this bug related specifically to tooling in Visual Studio (e.g. XAML Designer, Code editing, etc…)? If yes, please file the issue via the instructions here.
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Problem description: Apps with a custom background flash a white background for a couple frames on some devices (previously asked Stack overflow to no avail, pointed to likely a software issue) Actual behavior: Window flashes white before fully loading. Expected behavior: Window opens with the correct background color instantly Minimal repro:

dotnet new wpf

edit MainWindow.xaml to have a background attribute

dotnet build

and run the app.

[batzen]

This also started to happen on my machine like a week ago. It’s does not seem to be isolated to WPF as it also happens with Edge. See (increased gif frame delay to 250 ms to make it really visible):

[batzen]

@torum As i already wrote above, this is not a pure WPF issue. The underlying problem is caused by Windows itself. ControlzEx has code to mitigate the white flash and the resize flickering.