Using SDL_GetWindowBordersSize() messes up everything.

SDL_GetWindowBordersSize() being used at main.c:12 in this repo: https://github.com/cptclvtch/HFSTS/commit/d6d761365e33d660085f52e4c745a6a545a9ef07 messes up the GUI.

Even if all other window handling is commented out in that section, the simple use of that get function messes up all of Nuklear.

Start with main.c:12 in the repository and the referenced commit, then reproduce the GUI failure with SDL_GetWindowBordersSize() enabled and disabled. Compare the window-handling path with Nuklear's rendering behavior; done means identifying the cause and confirming that the GUI remains functional without unrelated window handling regressions.

Written by the indexing model from the issue text.