As practice I have always been putting a "glutPostRedisplay();" at the end of the mouse callback routine specified by "glutMouseFunc(mouseCallBack);".

However, now I notice (for at least one program) that the "glutPostRedisplay()" calls seems not required to instigate a redraw. The glutMouseFunc() spec says nothing about an automatic redraw after the callback routine is invoked. Is there an automatic redraw always? Thanks.