glutVisibilityFunc  - sets the visibility callback for the
       current window.

SYNTAX

       void glutVisibilityFunc(void (*func)(int state));

ARGUMENTS

       func      The new visibility callback function.

DESCRIPTION

       glutVisibilityFunc sets the visibility  callback  for  the
       current  window.  The  visibility callback for a window is
       called when the visibility of a window changes. The  state
       callback parameter is either GLUT_NOT_VISIBLE or GLUT_VIS-
       IBLE depending on the current visibility  of  the  window.
       GLUT_VISIBLE  does  not distinguish a window being totally
       versus partially visible. GLUT_NOT_VISIBLE means  no  part
       of  the  window is visible, i.e., until the window's visi-
       bility changes, all further rendering  to  the  window  is
       discarded.

       GLUT considers a window visible if any pixel of the window
       is visible or any pixel of any descendant window is  visi-
       ble on the screen.

       Passing NULL to glutVisibilityFunc disables the generation
       of the visibility callback.

       If the visibility callback for a window  is  disabled  and
       later  re-enabled,  the visibility status of the window is
       undefined;  any  change  in  window  visibility  will   be
       reported, that is if you disable a visibility callback and
       re-enable the callback, you are guaranteed the next  visi-
       bility change will be reported.

SEE ALSO

       glutCreateWindow, glutPopWindow

AUTHOR

       Mark J. Kilgard (mjk@nvidia.com)