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><head><title>glutIdleFunc</title><link rel="stylesheet" href="style.css" type="text/css"/><meta name="generator" content="DocBook XSL Stylesheets V1.59.1"/><link rel="home" href="index.xml" title="PyOpenGL 2.0.1.07 Man Pages"/><link rel="up" href="reference-GLUT.xml" title="GLUT"/><link rel="previous" href="glutGetModifiers.3GLUT.xml" title="glutGetModifiers"/><link rel="next" href="glutIgnoreKeyRepeat.3GLUT.xml" title="glutIgnoreKeyRepeat"/></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">glutIdleFunc</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="glutGetModifiers.3GLUT.xml">Prev</a></td><th width="60%" align="center">GLUT</th><td width="20%" align="right"><a accesskey="n" href="glutIgnoreKeyRepeat.3GLUT.xml">Next</a></td></tr></table><hr/></div><div class="refentry" lang="en"><a name="glutIdleFunc.3GLUT"/><div class="titlepage"/><div class="refnamediv"><a name="glutIdleFunc.3GLUT-name"/><h2>Name</h2><p>glutIdleFunc — sets the global idle callback.</p></div><div class="refsynopsisdiv"><a name="glutIdleFunc.3GLUT-c_spec"/><h2>C Specification</h2><table class="funcprototype" border="0" cellpadding="0" cellspacing="0"><tr><td valign="top"><code>void<tt>glutIdleFunc</tt></code></td><td valign="top"><code>(</code></td><td valign="top"><code>void(*<i><tt>func</tt></i>)());</code></td></tr></table></div><div class="refsynopsisdiv"><a name="glutIdleFunc.3GLUT-python_spec"/><h2>Python Specification</h2><table class="funcprototype" border="0" cellpadding="0" cellspacing="0"><tr><td valign="top"><code><tt>glutIdleFunc</tt></code></td><td valign="top"><code>(</code></td><td valign="top"><code><i><tt>func</tt></i>) →<tt>None</tt></code></td></tr></table></div><div class="refsect1" lang="en"><a name="glutIdleFunc.3GLUT-parameters"/><h2>Parameters</h2><div class="variablelist"><dl><dt><span class="term"><i><tt>func</tt></i></span></dt><dd>
The new idle callback function.
</dd></dl></div></div><div class="refsect1" lang="en"><a name="glutIdleFunc.3GLUT-description"/><h2>Description</h2><p>
<tt>glutIdleFunc</tt> 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.
</p><p>
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.
</p><p>
Passing <tt>NULL</tt> to <tt>glutIdleFunc</tt> disables the generation of the idle callback.
</p></div><div class="refsect1" lang="en"><a name="glutIdleFunc.3GLUT-example"/><h2>Example</h2><p>
A typical idle callback to animate a window might look like:
</p><pre class="programlisting">void idle(void)
{
time += 0.05;
glutSetWindow(window);
glutPostRedisplay();
}</pre><p>
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.
</p><p>
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:
</p><pre class="programlisting">void visible(int vis)
{
if (vis == GLUT_VISIBLE)
glutIdleFunc(idle);
else
glutIdleFunc(NULL);
}</pre><p>
If you do use the idle callback for animation, one thing you should <span class="emphasis"><em>not</em></span> do is setup the idle
callback before calling <a href="glutMainLoop.3GLUT.xml"><tt>glutMainLoop</tt></a>. It is much better to use the visibility
callback to install idle callback when the window first becomes visible on the screen.
</p></div><div class="refsect1" lang="en"><a name="glutIdleFunc.3GLUT-see_also"/><h2>See Also</h2><p>
<span class="simplelist"><a href="glutTimerFunc.3GLUT.xml">glutTimerFunc</a>, <a href="glutVisibilityFunc.3GLUT.xml">glutVisibilityFunc</a></span>
</p></div></div><div class="navfooter"><hr/><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="glutGetModifiers.3GLUT.xml">Prev</a></td><td width="20%" align="center"><a accesskey="u" href="reference-GLUT.xml">Up</a></td><td width="40%" align="right"><a accesskey="n" href="glutIgnoreKeyRepeat.3GLUT.xml">Next</a></td></tr><tr><td width="40%" align="left" valign="top">glutGetModifiers</td><td width="20%" align="center"><a accesskey="h" href="index.xml">Home</a></td><td width="40%" align="right" valign="top">glutIgnoreKeyRepeat</td></tr></table></div></body></html>
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