/tags/power/Recent content in Power on LifeHugoen-usWed, 07 Sep 2011 23:23:00 +0530/post/2011/2011-09-07-changing-brightness-from-gnome-shell/Wed, 07 Sep 2011 23:23:00 +0530/post/2011/2011-09-07-changing-brightness-from-gnome-shell/<p><code>gnome-power-manager</code> was rewritten for GNOME 3.2 and merged directly into <code>gnome-settings-daemon</code> (g-s-d) as a plugin responsible for system power policy. Most power management is handled by UPower, with backlight brightness being a key exception. Backlight is managed at the session level by <code>gnome-settings-daemon</code> via its power plugin using XRandR or standard <code>sysfs</code>, depending on hardware and driver support.</p> <p>To read screen brightness over D-Bus:</p> <div class="highlight"><pre tabindex="0" style="color:#f8f8f2;background-color:#272822;-moz-tab-size:4;-o-tab-size:4;tab-size:4;-webkit-text-size-adjust:none;"><code class="language-bash" data-lang="bash"><span style="display:flex;"><span>gdbus call --session <span style="color:#ae81ff">\ </span></span></span><span style="display:flex;"><span> --dest org.gnome.SettingsDaemon <span style="color:#ae81ff">\ </span></span></span><span style="display:flex;"><span> --object-path /org/gnome/SettingsDaemon/Power <span style="color:#ae81ff">\ </span></span></span><span style="display:flex;"><span> --method org.gnome.SettingsDaemon.Power.Screen.GetPercentage </span></span></code></pre></div><p>Why bother with this? On a tablet device (such as the WeTab), brightness settings were buried deep in system menus and cumbersome to reach. With the custom GNOME Shell brightness extension (<a href="http://people.redhat.com/rkhadgar/personal/gnome3-tablet/brightness.tar.xz">download archive</a>), you can adjust screen brightness directly from the top bar. This requires patching <code>gnome-settings-daemon</code> to emit the <code>Changed</code> signal (<a href="https://bugzilla.gnome.org/show_bug.cgi?id=658493">GNOME Bug 658493</a>).</p>