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<div class="section" id="dbus-support">
<span id="ref-dbus"></span><h1>DBus Support<a class="headerlink" href="#dbus-support" title="Permalink to this headline">¶</a></h1>
<p>PyQt4 provides two different modules that implement support for DBus. The
<tt class="xref py py-mod docutils literal"><span class="pre">QtDBus</span></tt> module provides wrappers for the standard Qt DBus classes.
The <tt class="xref py py-mod docutils literal"><span class="pre">dbus.mainloop.qt</span></tt> module add support for the Qt event loop to the
standard <tt class="docutils literal"><span class="pre">dbus-python</span></tt> Python module.</p>
<div class="section" id="qtdbus">
<h2><tt class="xref py py-mod docutils literal"><span class="pre">QtDBus</span></tt><a class="headerlink" href="#qtdbus" title="Permalink to this headline">¶</a></h2>
<p>The <tt class="xref py py-mod docutils literal"><span class="pre">QtDBus</span></tt> module is used in a similar way to the C++ library it
wraps. The main difference is in the way it supports the demarshalling of
DBus structures. C++ relies on the template-based registration of types using
<tt class="docutils literal"><span class="pre">qDBusRegisterMetaType()</span></tt> which isn’t possible from Python. Instead a slot
that accepts a DBus structure in an argument should specify a slot with a
single <tt class="xref py py-class docutils literal"><span class="pre">QDBusMessage</span></tt> argument. The implementation of the
slot should then extract the arguments from the message using its
<tt class="xref py py-meth docutils literal"><span class="pre">arguments()</span></tt> method.</p>
<p>For example, say we have a DBus method called <tt class="docutils literal"><span class="pre">setColors()</span></tt> that has a single
argument that is an array of structures of three integers (red, green and
blue). The DBus signature of the argument would then be <tt class="docutils literal"><span class="pre">a(iii)</span></tt>. In C++
you would typically define a class to hold the red, green and blue values and
so your code would include the following (incomplete) fragments:</p>
<div class="highlight-python"><pre>struct Color
{
int red;
int green;
int blue;
};
Q_DECLARE_METATYPE(Color)
qDBusRegisterMetaType<Color>();
class ServerAdaptor : public QDBusAbstractAdaptor
{
Q_OBJECT
public slots:
void setColors(QList<const Color &> colors);
};</pre>
</div>
<p>The Python version is, of course, much simpler:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="k">class</span> <span class="nc">ServerAdaptor</span><span class="p">(</span><span class="n">QDBusAbstractAdaptor</span><span class="p">):</span>
<span class="nd">@pyqtSlot</span><span class="p">(</span><span class="n">QDBusMessage</span><span class="p">)</span>
<span class="k">def</span> <span class="nf">setColors</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">message</span><span class="p">):</span>
<span class="c"># Get the single argument.</span>
<span class="n">colors</span> <span class="o">=</span> <span class="n">message</span><span class="o">.</span><span class="n">arguments</span><span class="p">()[</span><span class="mi">0</span><span class="p">]</span>
<span class="c"># The argument will be a list of 3-tuples of ints.</span>
<span class="k">for</span> <span class="n">red</span><span class="p">,</span> <span class="n">green</span><span class="p">,</span> <span class="n">blue</span> <span class="ow">in</span> <span class="n">colors</span><span class="p">:</span>
<span class="k">print</span><span class="p">(</span><span class="s">"RGB:"</span><span class="p">,</span> <span class="n">red</span><span class="p">,</span> <span class="n">green</span><span class="p">,</span> <span class="n">blue</span><span class="p">)</span>
</pre></div>
</div>
<p>Note that this technique can be used for arguments of any type, it is only
require if DBus structures are involved.</p>
</div>
<div class="section" id="dbus-mainloop-qt">
<h2><tt class="xref py py-mod docutils literal"><span class="pre">dbus.mainloop.qt</span></tt><a class="headerlink" href="#dbus-mainloop-qt" title="Permalink to this headline">¶</a></h2>
<p>The <tt class="xref py py-mod docutils literal"><span class="pre">dbus.mainloop.qt</span></tt> module provides support for the Qt event loop to
<tt class="docutils literal"><span class="pre">dbus-python</span></tt>. The module’s API is almost identical to that of the
<tt class="xref py py-mod docutils literal"><span class="pre">dbus.mainloop.glib</span></tt> modules that provides support for the GLib event
loop.</p>
<p>The <tt class="xref py py-mod docutils literal"><span class="pre">dbus.mainloop.qt</span></tt> module contains the following function.</p>
<dl class="function">
<dt id="DBusQtMainLoop">
<tt class="descname">DBusQtMainLoop</tt><big>(</big><em>set_as_default=False</em><big>)</big><a class="headerlink" href="#DBusQtMainLoop" title="Permalink to this definition">¶</a></dt>
<dd><p>Create a <tt class="docutils literal"><span class="pre">dbus.mainloop.NativeMainLoop</span></tt> object that uses the the Qt event
loop.</p>
<table class="docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field-odd field"><th class="field-name">Parameters:</th><td class="field-body"><strong>set_as_default</strong> – is optionally set to make the main loop instance the default for all
new Connection and Bus instances. It may only be specified as a
keyword argument, and not as a positional argument.</td>
</tr>
</tbody>
</table>
</dd></dl>
<p>The following code fragment is all that is normally needed to set up the
standard <tt class="docutils literal"><span class="pre">dbus-python</span></tt> language bindings package to be used with PyQt4:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="kn">from</span> <span class="nn">dbus.mainloop.qt</span> <span class="kn">import</span> <span class="n">DBusQtMainLoop</span>
<span class="n">DBusQtMainLoop</span><span class="p">(</span><span class="n">set_as_default</span><span class="o">=</span><span class="bp">True</span><span class="p">)</span>
</pre></div>
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<h3><a href="index.html">Table Of Contents</a></h3>
<ul>
<li><a class="reference internal" href="#">DBus Support</a><ul>
<li><a class="reference internal" href="#qtdbus"><tt class="docutils literal"><span class="pre">QtDBus</span></tt></a></li>
<li><a class="reference internal" href="#dbus-mainloop-qt"><tt class="docutils literal"><span class="pre">dbus.mainloop.qt</span></tt></a></li>
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