System Brightness does not work in FluentApp on Windows

[RemcoSchrijver]

The defined system brightness does not function when on used on Windows in combination with a FluentApp.

The following line does not work:

fluent_ui/lib/src/app.dart

Line 390 in 3975a77

final platformBrightness = MediaQuery.platformBrightnessOf(context);

Workaround right now is:
FluentApp( theme: ThemeData( brightness: MediaQueryData.fromWindow(WidgetsBinding.instance!.window).platformBrightness, ) )

Not entirely sure if there is a better way to do this?

[WinXaito]

The following line does not work:

In fact, yes that's work. That's only doesn't work on root context. Do this for confirm that:

builder: (context, _) {
    print(MediaQuery.platformBrightnessOf(context));
    return Text('text')
},

flutter: Brightness.dark

---

Your theme is not correct, because you need to create a themeData for dark and light theme.

Add this for resolve your problem:

return FluentApp(
  themeMode: ThemeMode.system,
  theme: ThemeData(
    brightness: Brightness.light,
  ),
  darkTheme: ThemeData(
    brightness: Brightness.dark,
  ),
  ...
);

---

Please reopen this issue if that doesn't solve your problem.