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glutDisplayFunc(3GLUT)                              GLUT                              glutDisplayFunc(3GLUT)



NAME
       glutDisplayFunc - sets the display callback for the current window.

SYNTAX
       #include <GLUT/glut.h>

       void glutDisplayFunc(void (*func)(void));

ARGUMENTS
       func      The new display callback function.

DESCRIPTION
       glutDisplayFunc sets the display callback for the current window.  When GLUT determines that the nor-mal normal
       mal plane for the window needs to be redisplayed, the display callback  for  the  window  is  called.
       Before  the  callback,  the  current window is set to the window needing to be redisplayed and (if no
       overlay display callback is registered) the layer in use is set to  the  normal  plane.  The  display
       callback  is  called  with  no  parameters.  The  entire normal plane region should be redisplayed in
       response to the callback (this includes ancillary buffers if your program depends on their state).

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

       When an overlay is established for a window, but there is no overlay display callback registered, the
       display callback is used for redisplaying both the overlay and normal plane  (that  is,  it  will  be
       called  if  either the redisplay state or overlay redisplay state is set). In this case, the layer in
       use is not implicitly changed on entry to the display callback.

       See glutOverlayDisplayFunc to understand how distinct callbacks for the overlay and normal plane of a
       window may be established.

       When  a window is created, no display callback exists for the window. It is the responsibility of the
       programmer to install a display callback for the window before the window is shown. A  display  call-back callback
       back must be registered for any window that is shown. If a window becomes displayed without a display
       callback being registered, a fatal error occurs. Passing NULL to glutDisplayFunc  is  illegal  as  of
       GLUT  3.0;  there is no way to ``deregister'' a display callback (though another callback routine can
       always be registered).

       Upon return from the display callback, the normal damaged state of the window  (returned  by  calling
       glutLayerGet(GLUT_NORMAL_DAMAGED)  is cleared. If there is no overlay display callback registered the
       overlay damaged state of the window (returned by calling glutLayerGet(GLUT_OVERLAY_DAMAGED)  is  also
       cleared.

SEE ALSO
       glutCreateMenu(3G), glutPostRedisplay(3G), glutOverlayDisplayFunc(3G)


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



GLUT                                                 3.7                              glutDisplayFunc(3GLUT)