on macOS, toggling fullscreen via the titlebar is not reflected in the settings

[kuroneko]

You can use the fullscreen/maximize button on the app titlebar to fullscreen the window, however this is done without the game's awareness that it has happened, leaving the item in the settings menu out of step with what's actually happening.

[kuroneko]

There doesn't appear to be a nice way to do this at all right now. SDL2 doesn't emit an event when fullscreen space state is toggled on macos, and polling would require pulling the window object from the SysWM interface and having to deal with ObjC API calls from C++.