title: How to change the monitor brightness by X11 RandR extension library?
body: <p>I can simply change my monitor brightness via</p>
  
  <pre><code>xrandr --output VGA1 --brightness 0.25
  </code></pre>
  
  <p>Though it is software-only modification, it does the trick anyway. According to the man page, <code>xrandr</code> is the primitive command line interface to RandR extension, so it is quiet possible to change my monitor brightness programmatically. However, I didn't find any related API in its header file <a href="http://www.x.org/archive/current/doc/man/man3/Xrandr.3.xhtml" rel="nofollow"><code>&lt;X11/extensions/Xrandr.h&gt;</code></a>.</p>
  
  <p>How to change the monitor brightness by X11 RandR extension library in C?</p>