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glutIdleFunc(3GLUT)                  GLUT                  glutIdleFunc(3GLUT)

NAME
       glutIdleFunc - sets the global idle callback.

SYNTAX

       void glutIdleFunc(void (*func)(void));

ARGUMENTS
       func      The new idle callback function.

DESCRIPTION
       glutIdleFunc sets the global idle callback to be func so a GLUT program
       can perform background processing tasks or continuous animation when
       window system events are not being received. If enabled, the idle
       callback is continuously called when events are not being received. The
       callback routine has no parameters. The current window and current menu
       will not be changed before the idle callback.  Programs with multiple
       windows and/or menus should explicitly set the current window and/or
       current menu and not rely on its current setting.

       The amount of computation and rendering done in an idle callback should
       be minimized to avoid affecting the program's interactive response. In
       general, not more than a single frame of rendering should be done in an
       idle callback.

       Passing NULL to glutIdleFunc disables the generation of the idle
       callback.

EXAMPLE
       A typical idle callback to animate a window might look like:

         void
         idle(void)
         {
           time += 0.05;
           glutSetWindow(window);
           glutPostRedisplay();
         }

       Notice how the idle callback does not do any actual drawing; it only
       advances the time scene state global variable.  That is left to the
       window's display callback which will be triggered by the call to
       glutPostRedisplay.

       If you use the idle callback for animation, you should be sure to stop
       rendering when the window is not visible.  This is easy to set up with
       a visibility callback.  For example:

         void
         visible(int vis)
         {
           if (vis == GLUT_VISIBLE)
             glutIdleFunc(idle);
           else
             glutIdleFunc(NULL);
         }

       If you do use the idle callback for animation, one thing you should not
       do is setup the idle callback before calling glutMainLoop.  It is much
       better to use the visibility callback to install idle callback when the
       window first becomes visible on the screen.

SEE ALSO
       glutTimerFunc, glutVisibilityFunc

AUTHOR
       Mark J. Kilgard (mjk@nvidia.com)

GLUT                                  3.7                  glutIdleFunc(3GLUT)