GLUT Program Structure

The typical structure of the main() function of a GLUT program is: 

glutInit(&argc, argv);
glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE | GLUT_DEPTH);
glutInitWindowSize(512,512);
Set initial window options 
glutCreateWindow(argv[0]);
Open window 
glutDisplayFunc(drawEverything);
glutKeyboardFunc(key);
glutSpecialFunc(specialkey);
glutIdleFunc(idle);
Define callback functions 
myGLinit();
Do some OpenGL stuff 
glutMainLoop();
Run GLUT's event loop

The GLUT main loop detects and responds to events. "Events" include such things as keys being pressed, the mouse moving, or the window being resized. glutPostRedisplay() generates a special event indicating that the drawing function should be called again.
The main loop has the following rough structure:

There are generally two approaches to how a program redraws:

Which approach is used defines where glutPostRedisplay() is called - in the event-handling functions, or in the idle function.

Programs that animate their scenes in real-time, not just in immediate response to user inputs, will want to redraw continually, and so call glutPostRedisplay() in their idle function.


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