glutOverlayDisplayFunc(3GLUT) GLUT glutOverlayDisplayFunc(3GLUT)NAMEglutOverlayDisplayFunc - sets the overlay display callback
for the current 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 window. The overlay display callback is function
ally the same as the window's display callback except that
the overlay display callback is used to redisplay the win
dow'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 dis
play 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 glutPostOverlayRedisplay
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 callbacks called.
Upon return from the overlay display callback, the overlay
damaged state of the window (returned by calling glutLay
erGet(GLUT_OVERLAY_DAMAGED) is cleared.
The overlay display callback can be deregistered by pass
ing 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 regis
tered.
SEE ALSO
glutDisplayFunc, glutPostOverlayRedisplay
AUTHOR
Mark J. Kilgard (mjk@nvidia.com)
GLUT 3.7 1
