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glutOverlayDisplayFunc(3GLUT)	     GLUT	 glutOverlayDisplayFunc(3GLUT)

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

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

ARGUMENTS
       func	 The new overlay display callback function.

DESCRIPTION
       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.

SEE ALSO
       glutDisplayFunc,	glutPostOverlayRedisplay

AUTHOR
       Mark J. Kilgard (mjk@nvidia.com)

GLUT				      3.7	 glutOverlayDisplayFunc(3GLUT)

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