Create a 2D window and then manually focus a different window on your desktop, call SDL_PumpEvents() so the X11 driver sets its this->hidden->switch_waiting, then set a fullscreen OpenGL window (which makes the X11 driver tear down and create a new window instead of just resizing the existing one), poll for events, and the newly-created window will think it needs to pop back to a window. Fixed by resetting switch_waiting to zero if X11_CreateWindow() had to tear down a previous window.

Makefile.in
configure
aclocal.m4
config.log
config.cache
autom4te*
depcomp
libtool
config.status
Makefile
sdl-config
SDL.spec
SDL.qpg
.DS_Store