glutVisibilityFunc  - sets the visibility callback for the
current window.

glutVisibilityFunc
	glutVisibilityFunc(func) -> None

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

func      The new visibility callback function.

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.

Setting  the visibility callback for a window disables the
window status  callback  set  for  the  window  (and  vice
versa).   The  window status callback is set with glutWin-
dowStatusFunc.  glutVisibilityFunc is deprecated in  favor
of the more informative glutWindowStatusFunc.

glutCreateWindow, glutPopWindow, glutWindowStatusFunc

Mark J. Kilgard (mjk@nvidia.com)