Fullscreen is scaled when triggered by Alt-Enter, does not when triggered from the code

[SynedraAcus]

When entering fullscreen mode via pressing Alt-Enter, the application is scaled to fill the screen. When, on the other hand, window.fullscreen is set to true from within the application, it just blacks out the surroundings of the window, while the app stays the same size in pixels (window.resiseable is disabled in my game, so TK_RESIZED is not emitted).

I have observed this behaviour when running a Python game on Linux Mint 19 x64, but redditor /u/cornlord has reproduced it with this C code on Void Linux.

[SynedraAcus]

Some potentially relevant discussion is available in this Reddit thread.