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glutOverlayDisplayFunc(3GLUT)	     GLUT	 glutOverlayDisplayFunc(3GLUT)

       glutOverlayDisplayFunc -	sets the overlay display callback for the cur-
       rent window.

       void glutOverlayDisplayFunc(void	(*func)(void));

       func	 The new overlay display callback function.

       glutDisplayFunc sets the	overlay	display	callback for the current  win-
       dow.  The overlay display callback is functionally the same as the win-
       dow's display callback except that the overlay display callback is used
       to redisplay the	window's overlay.

       When  GLUT determines that the overlay plane for	the window needs to be
       redisplayed, the	overlay	display	callback for  the  window  is  called.
       Before the callback, the	current	window is set to the window needing to
       be redisplayed and the layer in use is set to the overlay. The  overlay
       display	callback  is called with no parameters.	The entire overlay re-
       gion should be redisplayed in response to the callback  (this  includes
       ancillary buffers if your program depends on their state).

       GLUT  determines	 when the overlay display callback should be triggered
       based on	the window's overlay redisplay state.  The  overlay  redisplay
       state  for  a  window  can be either set	explicitly by calling glutPos-
       tOverlayRedisplay or implicitly as the result of	window damage reported
       by  the	window system. Multiple	posted overlay redisplays for a	window
       are coalesced by	GLUT to	minimize the number of overlay	display	 call-
       backs called.

       Upon  return  from  the	overlay	 display callback, the overlay damaged
       state of	the window (returned by	calling	glutLayerGet(GLUT_OVERLAY_DAM-
       AGED) is	cleared.

       The  overlay  display  callback	can be deregistered by passing NULL to
       glutOverlayDisplayFunc. The overlay display callback is initially  NULL
       when  an	 overlay is established. See glutDisplayFunc to	understand how
       the display callback alone is used if an	overlay	 display  callback  is
       not registered.

       glutDisplayFunc,	glutPostOverlayRedisplay

       Mark J. Kilgard (

GLUT				      3.7	 glutOverlayDisplayFunc(3GLUT)


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