glutRemoveOverlay -- removes the overlay (if one exists) from the current window.
void glutRemoveOverlay (void);
glutRemoveOverlay removes the overlay (if one exists). It is safe to call glutRemoveOverlay even if no overlay is currently established--it does nothing in this case. Implicitly, the window's layer in use changes to the normal plane immediately once the overlay is removed.
If the program intends to re-establish the overlay later, it is typically faster and less resource intensive to use glutHideOverlay and glutShowOverlay to simply change the display status of the overlay.