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<div class="appendix" title="Appendix C. Creating your own signals">
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<a name="chapter-custom-signals"></a>Appendix C. Creating your own signals</h2></div></div></div>
<p>
Now that you've seen signals and signal handlers in <span class="application">gtkmm</span>, you
might like to use the same technique to allow interaction between your
own classes. That's actually very simple by using the
<span class="application">libsigc++</span> library directly.
</p>
<p>
This isn't purely a <span class="application">gtkmm</span> or GUI issue. <span class="application">gtkmm</span> uses
<span class="application">libsigc++</span> to implement its proxy wrappers for the
<span class="application">GTK+</span> signal system, but for new,
non-GTK+ signals, you can create pure C++ signals, using the
<code class="classname">sigc::signal<></code> template.
</p>
<p>
For instance, to create a signal that sends 2 parameters, a <span class="type">bool</span>
and an <span class="type">int</span>, just declare a <code class="classname">sigc::signal</code>,
like so:
</p>
<pre class="programlisting">
sigc::signal<void, bool int> signal_something;
</pre>
<p>
</p>
<p>
You could just declare that signal as a public member variable, but
some people find that distasteful and prefer to make it available via
an accessor method, like so:
</p>
<pre class="programlisting">
class Server
{
//signal accessor:
typedef sigc::signal<void, bool, int> type_signal_something;
type_signal_something signal_something();
protected:
type_signal_something m_signal_something;
};
Server::type_signal_something Server::signal_something()
{
return m_signal_something;
}
</pre>
<p>
</p>
<p>
You can then connect to the signal using the same syntax used when
connecting to <span class="application">gtkmm</span> signals. For instance,
</p>
<pre class="programlisting">
server.signal_something().connect(
sigc::mem_fun(client, &Client::on_server_something) );
</pre>
<p>
</p>
<p>
See <code class="filename">examples/book/signals/custom/</code> for a full
working example.
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