NAME
	  glXSwapBuffers - exchange front and back buffers


     C SPECIFICATION
	  void glXSwapBuffers( Display *dpy,
			       GLXDrawable drawable )


     PARAMETERS
	  dpy	    Specifies the connection to	the X server.

	  drawable  Specifies the drawable whose buffers are to	be
		    swapped.

     DESCRIPTION
	  glXSwapBuffers promotes the contents of the back buffer of
	  drawable to become the contents of the front buffer of
	  drawable.  The contents of the back buffer then become
	  undefined.  The update typically takes place during the
	  vertical retrace of the monitor, rather than immediately
	  after	glXSwapBuffers is called.

	  glXSwapBuffers performs an implicit glFlush before it
	  returns.  Subsequent OpenGL commands may be issued
	  immediately after calling glXSwapBuffers, but	are not
	  executed until the buffer exchange is	completed.

	  If drawable was not created with respect to a	double-
	  buffered visual, glXSwapBuffers has no effect, and no	error
	  is generated.

     NOTES
	  The contents of the back buffer become undefined after a
	  swap.	Note that this applies to pbuffers as well as windows.

	  All GLX rendering contexts share the same notion of which
	  are front buffers and	which are back buffers.	 One
	  consequence is that when multiple clients are	rendering to
	  the same double-buffered window, all of them should finish
	  rendering before one of them issues the command to swap
	  buffers.  The	clients	are responsible	for implementing this
	  synchronization.  Typically this is accomplished by
	  executing glFinish and then using a semaphore	in shared
	  memory to rendezvous before swapping.

     ERRORS
	  GLXBadDrawable is generated if drawable is not a valid GLX
	  drawable.

	  GLXBadCurrentWindow is generated if dpy and drawable are
	  respectively the display and drawable	associated with	the
	  current context of the calling thread, and drawable
	  identifies a window that is no longer	valid.

     SEE ALSO
	  glFlush, glXBindSwapBarrierSGIX, glXJoinSwapGroupSGIX,
	  glXSwapIntervalSGI