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  continu-
       ously called when events are not being received. The call-
       back 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 explic-
       itly  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 pro-
       gram's interactive response. In general, not more  than  a
       single  frame of rendering should be done in an idle call-
       back.

       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  draw-
       ing;  it  only  advances the time scene state global vari-
       able.  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
           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 call-
       ing 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)