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.

.TH "SDL_UnlockAudio" "3" "Tue 11 Sep 2001, 22:58" "SDL" "SDL API Reference" 
.SH "NAME"
SDL_UnlockAudio\- Unlock the callback function
.SH "SYNOPSIS"
.PP
\fB#include "SDL\&.h"
.sp
\fBvoid \fBSDL_UnlockAudio\fP\fR(\fBvoid\fR)
.SH "DESCRIPTION"
.PP
Unlocks a previous \fI\fBSDL_LockAudio\fP\fR call\&.
.SH "SEE ALSO"
.PP
\fI\fBSDL_OpenAudio\fP\fR
...\" created by instant / docbook-to-man, Tue 11 Sep 2001, 22:58