glutIdleFunc(3GLUT) GLUT glutIdleFunc(3GLUT)NAMEglutIdleFunc - sets the global idle callback.
SYNTAX
void glutIdleFunc(void (*func)(void));
ARGUMENTS
func The new idle callback function.
DESCRIPTIONglutIdleFunc 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
visible(int vis)
GLUT 3.7 1
glutIdleFunc(3GLUT) GLUT glutIdleFunc(3GLUT)
{
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)
GLUT 3.7 2
