Windows bug: Update the window theme without taking into account the preferred theme.

[axoroll7]

Issue

If the preferred system theme is lightMode, it is impossible to switch to darkMode, on Windows.

await windowManager.setBrightness(Brightness.light);
await windowManager.setBrightness(Brightness.dark);

Solution

The preferred theme should not be taken into account, like the MacOS implementation.
In the swift file for MacOS, the theme is simply updated by passing an argument :

public func setBrightness(_ args: [String: Any]) {
    let brightness: String = args["brightness"] as! String
    if (brightness == "dark") {
        mainWindow.appearance = NSAppearance(named: NSAppearance.Name.vibrantDark)
    } else {
        mainWindow.appearance = NSAppearance(named: NSAppearance.Name.vibrantLight)
    }
    mainWindow.invalidateShadow()
}

But in the file for Windows, the system preferred theme is retrieved, and utilized incorrectly. Instead of doing:

BOOL enable_dark_mode = light_mode == 0 && brightness == "dark";

It should be:

BOOL enable_dark_mode = brightness == "dark";

(Apologies, English isn't my first language.)

[axoroll7]

My apologies, after some tests I concluded the initial method is also valid. It didn't work at first in my tests because I didn't take into account that flutter changes automatically the title bar when the MaterialApp theme changes. That's another issue. Thank you

[axoroll7]

If anyone is wondering how I managed to work around my problem, I put a debouncing in my stream listener to let the flutter engine do its change before mine. My stream is activated on themeMode changes, or platformBrightness if themeMode is ThemeMode.system.