When you exit fullscreen the window can no longer be resized. It is stuck at either the default size or the size passed in with the command line parameters.
The way to fix this is to make the Display resizable after you set fullscreen.
Display.setFullscreen(fullscreen);
Display.setResizable(false);
Display.setResizable(true);
It needs to be set to false first because the implementation caches the last value and will not update the Window if it is already resizable in the cached state.
Related issues
Comments


@SunCat I did not find that when I searched, sorry about that.

Thank you for your report anyway, you are probably the first who found the reason, thank you very much!

I also made a quick mod and put it on Curse. "Fullscreen Fix"
Duplicate of MC-68754
Please search before creating a new issue!