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
       region 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(GLUTOVERLAYDAM-
       AGED) is cleared.

       The  overlay  display  callback  can be deregistered by passing NUL to
       glutOverlayDisplayFunc. The overlay display callback is initially  NUL
       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)