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<div class="chapter" title="Chapter 20. Plugs and Sockets">
<div class="titlepage"><div><div><h2 class="title">
<a name="chapter-plugs-sockets"></a>Chapter 20. Plugs and Sockets</h2></div></div></div>
<div class="toc">
<p><b>Table of Contents</b></p>
<ul>
<li><span class="sect1"><a href="chapter-plugs-sockets.html#sec-plugs-sockets-overview">Overview</a></span></li>
<li><span class="sect1"><a href="sec-plugs-sockets-example.html">Plugs and Sockets Example</a></span></li>
</ul>
</div>
<div class="sect1" title="Overview">
<div class="titlepage"><div><div><h2 class="title" style="clear: both">
<a name="sec-plugs-sockets-overview"></a>Overview</h2></div></div></div>
<p>
From time to time, it may be useful to be able to embed a widget from
another application within your application. <span class="application">gtkmm</span> allows you to do
this with the <code class="classname">Gtk::Socket</code> and
<code class="classname">Gtk::Plug</code> classes. It is not anticipated that very
many applications will need this functionality, but in the rare case that
you need to display a widget that is running in a completely different
process, these classes can be very helpful.
</p>
<p>
The communication between a <code class="classname">Socket</code> and a
<code class="classname">Plug</code> follows the XEmbed protocol. This protocol has
also been implemented in other toolkits (e.g. Qt), which allows the same
level of integration when embedding a Qt widget in GTK+ or vice versa.
</p>
<p>
The way that <code class="classname">Sockets</code> and
<code class="classname">Plugs</code> work together is through their window ids.
Both a <code class="classname">Socket</code> and a <code class="classname">Plug</code>
have IDs that can be retrieved with their <code class="methodname">get_id()</code>
member functions. The use of these IDs will be explained below in <a class="xref" href="chapter-plugs-sockets.html#sec-connecting-plugs-sockets" title="Connecting Plugs and Sockets">the section called “Connecting Plugs and Sockets”</a>.
</p>
<div class="sect2" title="Sockets">
<div class="titlepage"><div><div><h3 class="title">
<a name="sec-sockets"></a>Sockets</h3></div></div></div>
<p>
A <code class="classname">Socket</code> is a special kind of container widget that
provides the ability to embed widgets from one process into another
process in a way that is transparent to the user.
</p>
</div>
<div class="sect2" title="Plugs">
<div class="titlepage"><div><div><h3 class="title">
<a name="sec-plugs"></a>Plugs</h3></div></div></div>
<p>
A <code class="classname">Plug</code> is a special kind of Window that can be
plugged into a <code class="classname">Socket</code>. Besides the normal
properties and methods of <code class="classname">Gtk::Window</code>, a
<code class="classname">Plug</code> provides a constructor that takes the ID of
a <code class="classname">Socket</code>, which will automatically embed the
<code class="classname">Plug</code> into the <code class="classname">Socket</code> that
matches that ID.
</p>
<p>
Since a <code class="classname">Plug</code> is just a special type of
<code class="classname">Gtk::Window</code> class, you can add containers or
widgets to it like you would to any other window.
</p>
</div>
<div class="sect2" title="Connecting Plugs and Sockets">
<div class="titlepage"><div><div><h3 class="title">
<a name="sec-connecting-plugs-sockets"></a>Connecting Plugs and Sockets</h3></div></div></div>
<p>
After a <code class="classname">Socket</code> or <code class="classname">Plug</code>
object is realized, you can obtain its ID with its
<code class="methodname">get_id()</code> function. This ID can then be shared with
other processes so that other processes know how to connect to
eachother.
</p>
<p>
There are two basic strategies that can be used:
</p>
<div class="itemizedlist"><ul class="itemizedlist" type="disc">
<li class="listitem"><p>
Create a <code class="classname">Socket</code> object in one process and
pass the ID of that <code class="classname">Socket</code> to another
process so that it can create a <code class="classname">Plug</code> object
by specifying the given <code class="classname">Socket</code> ID in its
constructor. There is no way to assign a
<code class="classname">Plug</code> to a particular
<code class="classname">Socket</code> after creation, so you must pass the
<code class="classname">Socket</code> ID to the
<code class="classname">Plug</code>'s constructor.
</p></li>
<li class="listitem"><p>
Create a <code class="classname">Plug</code> independantly from any
particular <code class="classname">Socket</code> and pass the ID of the
<code class="classname">Plug</code> to other processes that need to use
it. The ID of the <code class="classname">Plug</code> can be associated
with a particular <code class="classname">Socket</code> object using the
<code class="methodname">Socket::add_id()</code> function. This is the
approach used in the example below.
</p></li>
</ul></div>
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