Steps to reproduce

1. Open app on iPadOS 18. Ensure iOS Settings > Display & Brightness is set to Light appearance.
2. Open app Settings > Reading preferences > change to "Light".
3. Background app, go to iOS Settings, go to Display & Brightness and choose Dark appearance
4. Go back to Wikipedia app.

Expected results

Floating tab bar should be frozen on light mode

Actual results

Floating tab bar switches to dark mode, but the rest of the app remains on light mode.

Screenshots

Environments observed

App version: 7.7.1 (4944) but not a new issue
OS versions: 18.3
Device model: iPad mini
Device language: EN

Engineering Notes

We run this code to override the root navigation controllers' user interface style when the user changes their theme, as well as when the app launches. I think we need try running similar logic at the same moment on WMFAppViewController itself (which is a UITabBarController subclass).

NSString *themeName = [NSUserDefaults.standardUserDefaults themeName];
if ([WMFTheme isDefaultThemeName:themeName]) {
    self.overrideUserInterfaceStyle = UIUserInterfaceStyleUnspecified;
} else if ([WMFTheme isDarkThemeName:themeName]) {
    self.overrideUserInterfaceStyle = UIUserInterfaceStyleDark;
} else {
    self.overrideUserInterfaceStyle = UIUserInterfaceStyleLight;
}