[Bug]: SystemTrayIcon does not sync with mainwindow theme even I tracked mainwindow already in app.xaml.cs

[hoshiizumiya]

Describe the bug

https://github.com/ghost1372/DevWinUI/blob/main/dev/DevWinUI/Common/TrayIcon/SystemTrayIcon.cs

Steps to reproduce the bug

If the main window theme(Dark/Light) is not the same as system. The Systemtrayicon is always follow with the system settings. There is the picture like:

As shown in the screenshots, the MenuFlyoutSubItem does not appear when using a Flyout instead of a MenuFlyout in the XAML file. Additionally, I don't understand why the theme for the three buttons in the top-right corner is incorrect. I used DevWinUI for all related situation. These screenshots may help identify the issue (I've bound the SystemTrayIcon to the MainWindow).

Expected behavior

No response

Screenshots

No response

NuGet package version

None

IDE

Visual Studio 2026

Additional context

No response

[ghost1372]

@hoshiizumiya I added a SetTheme method so the trayicon theme can be updated whenever the app theme changes.
This is a WinUI bug where changing the app theme only updates the window content theme instead of the entire application theme, so the trayicon cannot follow the theme change.

Anyway, make sure to call SetTheme when you change your app theme so the tray icon matches the app’s theme.

[hoshiizumiya]

@ghost1372 Thank you very much! And what about the second question: As shown in the screenshots, the MenuFlyoutSubItem does not appear when using a Flyout instead of a MenuFlyout in the XAML file.

[ghost1372]

@ghost1372 Thank you very much! And what about the second question: As shown in the screenshots, the MenuFlyoutSubItem does not appear when using a Flyout instead of a MenuFlyout in the XAML file.

Dont use Flyout.
Stick with MenuFlyout

[hoshiizumiya]

@ghost1372 It's too sad. The MenuFlyout control has more features than MenuFlyoutSubItem. I'm not sure what caused this problem. 😢 The flyout itself works (Curiously the pop-up animation is inconsistent with its background), but the MenuFlyoutSubItem in the flyout doesn't display properly, which is as if there's no window to host the XAML content.

[ghost1372]

Sorry about that. I'll take a look at it whenever I get a chance. But it seems like the problem is with WinUI itself.