glutMainLoop man page
glutMainLoop — The standard GLUT event loop entry point.
OpenGLUT - mainloop
This is the main driving force for an event-driven OpenGLUT program. It alternates between calling glutMainLoopEvent() to process pending events and then either sleeping or calling your idle function (see glutIdleFunc()).
return, but GLUT's version of this function never returned. And you must do special things to OpenGLUT to cause OpenGLUT's version to return.
The cross-reference section for this function's documentation should ideally contain every callback, but the list would be tediously long and prone to omissions.
For OpenGLUT developers' internal documentation: Runs until the
Talking to other message systems (e.g., network layers) can be a bit bothersome under the GLUT event model.
glutMainLoopEvent(3) glutLeaveMainLoop(3) glutIdleFunc(3)
glutIdleFunc(3), glutInit(3), glutLeaveMainLoop(3), glutMainLoopEvent(3), glutSetOption(3), glutTimerFunc(3).