glutEntryFunc sets the mouse enter/leave callback for the current window.
Usage
void glutEntryFunc(void (*func)(int state));
Description
glutEntryFunc sets the mouse enter/leave callback for the current window. The state callback parameter is either GLUT_LEFT or GLUT_ENTERED depending on if the mouse pointer has last left or entered the window.
Passing NULL to glutEntryFunc disables the generation of the mouse enter/leave callback.
Some window systems may not generate accurate enter/leave callbacks.
X Implementation Notes
An X implementation of GLUT should generate accurate enter/leave callbacks.