Unintuitive ability to change WindowDescriptor

[SUPERCILEX]

Bevy version

0.6

What you did

fn full_screen_toggle(mut window: ResMut<WindowDescriptor>, keyboard_input: Res<Input<KeyCode>>) {
    if keyboard_input.just_released(KeyCode::F) {
        window.mode = if window.mode == WindowMode::Windowed {
            WindowMode::BorderlessFullscreen
        } else {
            WindowMode::Windowed
        };
    }
}

What you expected to happen

I thought the window mode would change.

What actually happened

Nothing. I would have expected this to fail to compile or panic so I'd know that's not the API to use.

Additional information

This is the right way to do it:

fn full_screen_toggle(mut windows: ResMut<Windows>, keyboard_input: Res<Input<KeyCode>>) {
    if keyboard_input.just_released(KeyCode::F) {
        let window = windows.get_primary_mut().unwrap();
        window.set_mode(if window.mode() == WindowMode::Windowed {
            WindowMode::BorderlessFullscreen
        } else {
            WindowMode::Windowed
        });
    }
}

[DJMcNab]

Duplicate of #2879