• This PR adds a method to set the root window background color at runtime.
• The second commit uses this method to make the Android editor’s root window color match the editor background color.

What I mean by "root window" here?

The root window is the one on which the Godot app is rendered. It’s only visible in areas where Godot doesn’t render, the status bar, navigation bar, and display cutouts.

#108557 added an export option to set this background color at export time. However, there are valid reasons to want to change it at runtime. For example, I want to change it dynamically based on the app’s theme color.

Currently, it’s already possible to change this color at runtime using JavaClassWrapper and AndroidRuntime. Since I was already adding a method to change it for the Editor, I figured it made sense to expose it as well. That’s the only reason.

func set_system_bar_color(color: Color, override_appearance := false) -> void:
	if not android_runtime:
		return
	
	var activity = android_runtime.getActivity()
	var callable = func ():
		var window = activity.getWindow()
		var decorView = window.getDecorView()
		decorView.setBackgroundColor(color.to_argb32())
		
		if (is_light_system_bars != (color.get_luminance() > 0.45)) or override_appearance:
			is_light_system_bars = color.get_luminance() > 0.45
			var WindowInsetsControllerCompat = JavaClassWrapper.wrap("androidx.core.view.WindowInsetsControllerCompat")
			var controller = WindowInsetsControllerCompat.call("<init>", window, window.getDecorView())
			controller.setAppearanceLightNavigationBars(is_light_system_bars)
			controller.setAppearanceLightStatusBars(is_light_system_bars)
	
	activity.runOnUiThread(android_runtime.createRunnableFromGodotCallable(callable))

Update: It's not trivial to do this via JavaClassWrapper. See #109667