src/parsec/disk-image/parsec/parsec-benchmark/pkgs/libs/glib/src/docs/reference/gobject/html/howto-signals.html - public/gem5-resources - Git at Google

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 <div class="chapter" title="How to create and use signals">
 <div class="titlepage"><div><div><h2 class="title">
 <a name="howto-signals"></a>How to create and use signals</h2></div></div></div>
 <div class="toc"><dl><dt><span class="sect1"><a href="howto-signals.html#howto-simple-signals">Simple use of signals</a></span></dt></dl></div>
 <p>
     The signal system which was built in GType is pretty complex and
     flexible: it is possible for its users to connect at runtime any
     number of callbacks (implemented in any language for which a binding
     exists)
     <sup>[<a name="id644978" href="#ftn.id644978" class="footnote">14</a>]</sup>
     to any signal and to stop the emission of any signal at any
     state of the signal emission process. This flexibility makes it
     possible to use GSignal for much more than just emit signals which
     can be received by numerous clients.
   </p>
 <div class="sect1" title="Simple use of signals">
 <div class="titlepage"><div><div><h2 class="title" style="clear: both">
 <a name="howto-simple-signals"></a>Simple use of signals</h2></div></div></div>
 <p>
       The most basic use of signals is to implement simple event
       notification: for example, if we have a MamanFile object, and
       if this object has a write method, we might wish to be notified
       whenever someone has changed something via our MamanFile instance.
       The code below shows how the user can connect a callback to the
       "changed" signal.
 </p>
 <pre class="programlisting">
 file = g_object_new (MAMAN_FILE_TYPE, NULL);

 g_signal_connect (file, "changed", G_CALLBACK (changed_event), NULL);

 maman_file_write (file, buffer, strlen (buffer));
 </pre>
 <p>
     </p>
 <p>
       The <span class="type">MamanFile</span> signal is registered in the class_init
       function:
 </p>
 <pre class="programlisting">
 file_signals[CHANGED] =
   g_signal_newv ("changed",
                  G_TYPE_FROM_CLASS (gobject_class),
                  G_SIGNAL_RUN_LAST | G_SIGNAL_NO_RECURSE | G_SIGNAL_NO_HOOKS,
                  NULL /* closure */,
                  NULL /* accumulator */,
                  NULL /* accumulator data */,
                  g_cclosure_marshal_VOID__VOID,
                  G_TYPE_NONE /* return_type */,
                  0     /* n_params */,
                  NULL  /* param_types */);
 </pre>
 <p>
       and the signal is emitted in <code class="function">maman_file_write</code>:
 </p>
 <pre class="programlisting">
 void
 maman_file_write (MamanFile    *self,
                   const guchar *buffer,
                   gssize        size)
 {
   /* First write data. */

   /* Then, notify user of data written. */
   g_signal_emit (self, file_signals[CHANGED], 0 /* details */);
 }
 </pre>
 <p>
       As shown above, you can safely set the details parameter to zero if
       you do not know what it can be used for. For a discussion of what you
       could used it for, see <a class="xref" href="signal.html#signal-detail" title="The detail argument">the section called “The <span class="emphasis"><em>detail</em></span> argument”</a>
     </p>
 <p>
       The signature of the signal handler in the above example is defined as
       <code class="function">g_cclosure_marshal_VOID__VOID</code>. Its name follows
       a simple convention which encodes the function parameter and return value
       types in the function name. Specifically, the value in front of the
       double underscore is the type of the return value, while the value(s)
       after the double underscore denote the parameter types.
     </p>
 <p>
       The header <code class="filename">gobject/gmarshal.h</code> defines a set of
       commonly needed closures that one can use. If you want to have complex
       marshallers for your signals you should probably use glib-genmarshal
       to autogenerate them from a file containing their return and
       parameter types.
     </p>
 </div>
 <div class="footnotes">
 <br><hr width="100" align="left">
 <div class="footnote"><p><sup>[<a name="ftn.id644978" href="#id644978" class="para">14</a>] </sup>A Python callback can be connected to any signal on any
       C-based GObject.
       </p></div>
 </div>
 </div>
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	<div class="chapter" title="How to create and use signals">
	<div class="titlepage"><div><div><h2 class="title">
	<a name="howto-signals"></a>How to create and use signals</h2></div></div></div>
	<div class="toc"><dl><dt><span class="sect1"><a href="howto-signals.html#howto-simple-signals">Simple use of signals</a></span></dt></dl></div>
	<p>
	The signal system which was built in GType is pretty complex and
	flexible: it is possible for its users to connect at runtime any
	number of callbacks (implemented in any language for which a binding
	exists)
	<sup>[<a name="id644978" href="#ftn.id644978" class="footnote">14</a>]</sup>
	to any signal and to stop the emission of any signal at any
	state of the signal emission process. This flexibility makes it
	possible to use GSignal for much more than just emit signals which
	can be received by numerous clients.
	</p>
	<div class="sect1" title="Simple use of signals">
	<div class="titlepage"><div><div><h2 class="title" style="clear: both">
	<a name="howto-simple-signals"></a>Simple use of signals</h2></div></div></div>
	<p>
	The most basic use of signals is to implement simple event
	notification: for example, if we have a MamanFile object, and
	if this object has a write method, we might wish to be notified
	whenever someone has changed something via our MamanFile instance.
	The code below shows how the user can connect a callback to the
	"changed" signal.
	</p>
	<pre class="programlisting">
	file = g_object_new (MAMAN_FILE_TYPE, NULL);

	g_signal_connect (file, "changed", G_CALLBACK (changed_event), NULL);

	maman_file_write (file, buffer, strlen (buffer));
	</pre>
	<p>
	</p>
	<p>
	The <span class="type">MamanFile</span> signal is registered in the class_init
	function:
	</p>
	<pre class="programlisting">
	file_signals[CHANGED] =
	g_signal_newv ("changed",
	G_TYPE_FROM_CLASS (gobject_class),
	G_SIGNAL_RUN_LAST \| G_SIGNAL_NO_RECURSE \| G_SIGNAL_NO_HOOKS,
	NULL /* closure */,
	NULL /* accumulator */,
	NULL /* accumulator data */,
	g_cclosure_marshal_VOID__VOID,
	G_TYPE_NONE /* return_type */,
	0 /* n_params */,
	NULL /* param_types */);
	</pre>
	<p>
	and the signal is emitted in <code class="function">maman_file_write</code>:
	</p>
	<pre class="programlisting">
	void
	maman_file_write (MamanFile *self,
	const guchar *buffer,
	gssize size)
	{
	/* First write data. */

	/* Then, notify user of data written. */
	g_signal_emit (self, file_signals[CHANGED], 0 /* details */);
	}
	</pre>
	<p>
	As shown above, you can safely set the details parameter to zero if
	you do not know what it can be used for. For a discussion of what you
	could used it for, see <a class="xref" href="signal.html#signal-detail" title="The detail argument">the section called “The <span class="emphasis"><em>detail</em></span> argument”</a>
	</p>
	<p>
	The signature of the signal handler in the above example is defined as
	<code class="function">g_cclosure_marshal_VOID__VOID</code>. Its name follows
	a simple convention which encodes the function parameter and return value
	types in the function name. Specifically, the value in front of the
	double underscore is the type of the return value, while the value(s)
	after the double underscore denote the parameter types.
	</p>
	<p>
	The header <code class="filename">gobject/gmarshal.h</code> defines a set of
	commonly needed closures that one can use. If you want to have complex
	marshallers for your signals you should probably use glib-genmarshal
	to autogenerate them from a file containing their return and
	parameter types.
	</p>
	</div>
	<div class="footnotes">
	<br><hr width="100" align="left">
	<div class="footnote"><p><sup>[<a name="ftn.id644978" href="#id644978" class="para">14</a>] </sup>A Python callback can be connected to any signal on any
	C-based GObject.
	</p></div>
	</div>
	</div>
	<div class="footer">
	<hr>
	Generated by GTK-Doc V1.14</div>
	</body>
	</html>