WinUI 3 app started via debugger will always have unicolor (black) title bar

[whiskhub]

Describe the bug

WinUI 3 apps started via the Visual Studio debugger will always show a unicolor (black/white) title bar based on the Windows color theme. No Mica effect will be shown.

Setting DWMWA_USE_IMMERSIVE_DARK_MODE via DwmSetWindowAttribute has no influence here.

Starting the app via start menu etc. will instead always show a light Mica title bar, which is the default and expected Win32 behavior.

Steps to reproduce the bug

1. Create blank WinUI 3 app
2. Start the app via Visual Studio debugger
3. You will see an unicolor black/white title bar

Expected behavior

Same behavior for the title bar color if starting the app via Visual Studio debugger, or in other ways like start menu. Currently expected behavior would be a light Mica title bar.

Screenshots

Title bar when started via Visual Strudio:

Title bar when started via start menu:

NuGet package version

WinUI 3 - Windows App SDK 1.6.0: 1.6.240829007

Windows version

Windows 11 (22H2): Build 22621

Additional context

No response

[codendone]

Actually, this is caused by #9988. Turning off the "Enable in-app toolbar" option in the Debugging->XAML Hot Reload settings in Visual Studio makes this go away. The in-app toolbar needs to know if ExtendsContentIntoTitleBar is set, which is how #9988 is triggered. We'll track with that issue.