Next: 7.8 glutEntryFunc Up: 7 Callback Registration Previous: 7.6 glutMotionFuncglutPassiveMotionFunc

## 7.7 glutVisibilityFunc

`glutVisibilityFunc` sets the visibility callback for the current window.

Usage

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

`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_VISIBLE` 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 visibility 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 visible 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 visibility change will be reported.

Next: 7.8 glutEntryFunc Up: 7 Callback Registration Previous: 7.6 glutMotionFuncglutPassiveMotionFunc