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<div class="appendix" title="Appendix C. Creating your own signals">
<div class="titlepage"><div><div><h2 class="title">
<a name="chapter-custom-signals"></a>Appendix C. Creating your own signals</h2></div></div></div>
<div class="toc">
<p><b>Table of Contents</b></p>
<ul><li><span class="sect1"><a href="chapter-custom-signals.html#chapter-custom-signals-example">Example</a></span></li></ul>
</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&lt;&gt;</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&lt;void, bool, int&gt; 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
{
public:
  //signal accessor:
  typedef sigc::signal&lt;void, bool, int&gt; 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, &amp;Client::on_server_something) );
</pre>
<p>
</p>
<div class="sect1" title="Example">
<div class="titlepage"><div><div><h2 class="title" style="clear: both">
<a name="chapter-custom-signals-example"></a>Example</h2></div></div></div>
<p>
This is a full working example that defines and uses custom signal.
</p>
<p><a class="ulink" href="http://git.gnome.org/browse/gtkmm-documentation/tree/examples/book/signals/custom/?h=master" target="_top">Source Code</a></p>
<p>File: <code class="filename">client.h</code> (For use with gtkmm 3, not gtkmm 2)
</p>
<pre class="programlisting">
#ifndef GTKMM_EXAMPLE_CLIENT_H
#define GTKMM_EXAMPLE_CLIENT_H

#include &lt;sigc++/sigc++.h&gt;

//Client must inherit from sigc::trackable.
//because libsigc++ needs to keep track of the lifetime of signal handlers.
class Client : public sigc::trackable
{
public:
  Client();
  virtual ~Client();

  //Signal handler:
  void on_server_something(bool a, int b);
};

#endif //GTKMM_EXAMPLE_CLIENT_H
</pre>
<p>File: <code class="filename">server.h</code> (For use with gtkmm 3, not gtkmm 2)
</p>
<pre class="programlisting">
#ifndef GTKMM_EXAMPLE_SERVER_H
#define GTKMM_EXAMPLE_SERVER_H

#include &lt;sigc++/sigc++.h&gt;

class Server
{
public:
  Server();
  virtual ~Server();

  void do_something();

  //signal accessor:
  typedef sigc::signal&lt;void, bool, int&gt; type_signal_something;
  type_signal_something signal_something();

protected:
  type_signal_something m_signal_something;
};

#endif //GTKMM_EXAMPLE_SERVER_H
</pre>
<p>File: <code class="filename">server.cc</code> (For use with gtkmm 3, not gtkmm 2)
</p>
<pre class="programlisting">
#include "server.h"
#include &lt;iostream&gt;

Server::Server()
{
}

Server::~Server()
{
}

Server::type_signal_something Server::signal_something()
{
  return m_signal_something;
}

void Server::do_something()
{
  m_signal_something.emit(false, 5);
}

</pre>
<p>File: <code class="filename">main.cc</code> (For use with gtkmm 3, not gtkmm 2)
</p>
<pre class="programlisting">
#include "server.h"
#include "client.h"
#include &lt;iostream&gt;

int main(int, char**)
{
  Server server;
  Client client;

  //Connect a Server signal to the signal handler in Client.
  server.signal_something().connect(sigc::mem_fun(client,
              &amp;Client::on_server_something) );

  std::cout &lt;&lt; "Before Server::do_something()" &lt;&lt; std::endl;

  //Tell the server to do something that will eventually cause it to emit the
  //"something" signal.
  server.do_something();    // Client::on_server_something() will run before
                            // Server::do_something() has completed.

  std::cout &lt;&lt; "After Server::do_something()" &lt;&lt; std::endl;

  return 0;
}
</pre>
<p>File: <code class="filename">client.cc</code> (For use with gtkmm 3, not gtkmm 2)
</p>
<pre class="programlisting">
#include "client.h"
#include &lt;iostream&gt;

Client::Client()
{
}

Client::~Client()
{
}

void Client::on_server_something(bool a, int b)
{
  std::cout &lt;&lt; "Client::on_server_something() called with these parameters: "
      &lt;&lt; a &lt;&lt; ", " &lt;&lt; b &lt;&lt; std::endl;
}
</pre>
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gtkmm-documentation 3.2.1-1 / usr / share / doc / gtkmm-documentation / tutorial / html / chapter-custom-signals.html
