On programs that run in "fullscreen" mode, when I change the "fullscreen" resolution to something that is lower than what my desktop resolution is, I can scroll past the edges of the program by moving my mouse to the edge of the screen and see my desktop. This is really buggy and actually crashed my system, on top of being incredibly annoying.
How do you disable this? I don't even know what it is called, and I can't find ANYTHING except for this, really, unanswered question from 2003: https://www.linuxquestions.org/questions/linux-software-2/disabling-virtual-screen-mouse-scrolling-in-x-111237/
If anybody wants to see an example, then you can probably do it yourself by installing SuperTux 2, changing the fullscreen resolution to something like 640x480, then checking the fullscreen box, and moving your mouse to the edge of the screen.