Callbacks

After calling glutMainLoop, control only returns to your program only if some event occurs. The following routines specify the events that you wish to listen for, and which procedure of yours to call for each.

Warning: Unlike all OpenGL functions, in which (x,y) coordinates are made relative to an idealized window, the (x,y) mouse coordinates are given in viewport coordinates (i.e., pixels). Furthermore, the origin is in the upper left corner, so y values increase as you go down the window.

glutDisplayFunc(void (*)(void)):

Call the given function to redisplay everything (required).

glutReshapeFunc(void (*)(int width, int height)):

Call the given function when window is resized (and originally created). See the function glViewport(), which typically should be called after each resizing.

glutIdleFunc(void (*)(void)):

Call the given function with each refresh cycle of the display.

glutMouseFunc(void (*)(int button, int state, int x, int y)):

Call the given function when a mouse button is clicked. The button argument is any of GLUT_LEFT_BUTTON, GLUT_MIDDLE_BUTTON, GLUT_RIGHT_BUTTON, and the state is either GLUT_DOWN or GLUT_UP. The (x,y) coordinates give the current mouse position, relative to the upper left corner.

glutMotionFunc(void (*)(int x, int y)):

Call the given function when the mouse is dragged (with button held down). The arguments (x,y) give the mouse coordinates relative to the upper left corner.

glutPassiveMotionFunc(void (*)(int x, int y)):

Call the given function when the mouse is moved.

glutKeyboardFunc(void (*)(unsigned char key, int x, int y)):

Call the given function when a keyboard key is hit. (This only handles ASCII characters. There is a different callback for function and arrow keys.)

Please report any errors or send comments to Dave Mount

Last updated: Sat, Feb 8, 2003.