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<h2><span class="refentrytitle"><a name="GstBus.top_of_page"></a>GstBus</span></h2>
<p>GstBus — Asynchronous message bus subsystem</p>
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<div class="refsynopsisdiv">
<a name="GstBus.synopsis"></a><h2>Synopsis</h2>
<pre class="synopsis">
#include <gst/gst.h>
struct <a class="link" href="GstBus.html#GstBus-struct" title="struct GstBus">GstBus</a>;
enum <a class="link" href="GstBus.html#GstBusFlags" title="enum GstBusFlags">GstBusFlags</a>;
enum <a class="link" href="GstBus.html#GstBusSyncReply" title="enum GstBusSyncReply">GstBusSyncReply</a>;
<a href="http://library.gnome.org/devel/glib/unstable/glib-Basic-Types.html#gboolean"><span class="returnvalue">gboolean</span></a> (<a class="link" href="GstBus.html#GstBusFunc" title="GstBusFunc ()">*GstBusFunc</a>) (<em class="parameter"><code><a class="link" href="GstBus.html" title="GstBus"><span class="type">GstBus</span></a> *bus</code></em>,
<em class="parameter"><code><a class="link" href="gstreamer-GstMessage.html#GstMessage" title="struct GstMessage"><span class="type">GstMessage</span></a> *message</code></em>,
<em class="parameter"><code><a href="http://library.gnome.org/devel/glib/unstable/glib-Basic-Types.html#gpointer"><span class="type">gpointer</span></a> user_data</code></em>);
<a class="link" href="GstBus.html#GstBusSyncReply" title="enum GstBusSyncReply"><span class="returnvalue">GstBusSyncReply</span></a> (<a class="link" href="GstBus.html#GstBusSyncHandler" title="GstBusSyncHandler ()">*GstBusSyncHandler</a>) (<em class="parameter"><code><a class="link" href="GstBus.html" title="GstBus"><span class="type">GstBus</span></a> *bus</code></em>,
<em class="parameter"><code><a class="link" href="gstreamer-GstMessage.html#GstMessage" title="struct GstMessage"><span class="type">GstMessage</span></a> *message</code></em>,
<em class="parameter"><code><a href="http://library.gnome.org/devel/glib/unstable/glib-Basic-Types.html#gpointer"><span class="type">gpointer</span></a> user_data</code></em>);
<a class="link" href="GstBus.html" title="GstBus"><span class="returnvalue">GstBus</span></a> * <a class="link" href="GstBus.html#gst-bus-new" title="gst_bus_new ()">gst_bus_new</a> (<em class="parameter"><code><span class="type">void</span></code></em>);
<a href="http://library.gnome.org/devel/glib/unstable/glib-Basic-Types.html#gboolean"><span class="returnvalue">gboolean</span></a> <a class="link" href="GstBus.html#gst-bus-post" title="gst_bus_post ()">gst_bus_post</a> (<em class="parameter"><code><a class="link" href="GstBus.html" title="GstBus"><span class="type">GstBus</span></a> *bus</code></em>,
<em class="parameter"><code><a class="link" href="gstreamer-GstMessage.html#GstMessage" title="struct GstMessage"><span class="type">GstMessage</span></a> *message</code></em>);
<a href="http://library.gnome.org/devel/glib/unstable/glib-Basic-Types.html#gboolean"><span class="returnvalue">gboolean</span></a> <a class="link" href="GstBus.html#gst-bus-have-pending" title="gst_bus_have_pending ()">gst_bus_have_pending</a> (<em class="parameter"><code><a class="link" href="GstBus.html" title="GstBus"><span class="type">GstBus</span></a> *bus</code></em>);
<a class="link" href="gstreamer-GstMessage.html#GstMessage" title="struct GstMessage"><span class="returnvalue">GstMessage</span></a> * <a class="link" href="GstBus.html#gst-bus-peek" title="gst_bus_peek ()">gst_bus_peek</a> (<em class="parameter"><code><a class="link" href="GstBus.html" title="GstBus"><span class="type">GstBus</span></a> *bus</code></em>);
<a class="link" href="gstreamer-GstMessage.html#GstMessage" title="struct GstMessage"><span class="returnvalue">GstMessage</span></a> * <a class="link" href="GstBus.html#gst-bus-pop" title="gst_bus_pop ()">gst_bus_pop</a> (<em class="parameter"><code><a class="link" href="GstBus.html" title="GstBus"><span class="type">GstBus</span></a> *bus</code></em>);
<a class="link" href="gstreamer-GstMessage.html#GstMessage" title="struct GstMessage"><span class="returnvalue">GstMessage</span></a> * <a class="link" href="GstBus.html#gst-bus-pop-filtered" title="gst_bus_pop_filtered ()">gst_bus_pop_filtered</a> (<em class="parameter"><code><a class="link" href="GstBus.html" title="GstBus"><span class="type">GstBus</span></a> *bus</code></em>,
<em class="parameter"><code><a class="link" href="gstreamer-GstMessage.html#GstMessageType" title="enum GstMessageType"><span class="type">GstMessageType</span></a> types</code></em>);
<a class="link" href="gstreamer-GstMessage.html#GstMessage" title="struct GstMessage"><span class="returnvalue">GstMessage</span></a> * <a class="link" href="GstBus.html#gst-bus-timed-pop" title="gst_bus_timed_pop ()">gst_bus_timed_pop</a> (<em class="parameter"><code><a class="link" href="GstBus.html" title="GstBus"><span class="type">GstBus</span></a> *bus</code></em>,
<em class="parameter"><code><a class="link" href="GstClock.html#GstClockTime" title="GstClockTime"><span class="type">GstClockTime</span></a> timeout</code></em>);
<a class="link" href="gstreamer-GstMessage.html#GstMessage" title="struct GstMessage"><span class="returnvalue">GstMessage</span></a> * <a class="link" href="GstBus.html#gst-bus-timed-pop-filtered" title="gst_bus_timed_pop_filtered ()">gst_bus_timed_pop_filtered</a> (<em class="parameter"><code><a class="link" href="GstBus.html" title="GstBus"><span class="type">GstBus</span></a> *bus</code></em>,
<em class="parameter"><code><a class="link" href="GstClock.html#GstClockTime" title="GstClockTime"><span class="type">GstClockTime</span></a> timeout</code></em>,
<em class="parameter"><code><a class="link" href="gstreamer-GstMessage.html#GstMessageType" title="enum GstMessageType"><span class="type">GstMessageType</span></a> types</code></em>);
<span class="returnvalue">void</span> <a class="link" href="GstBus.html#gst-bus-set-flushing" title="gst_bus_set_flushing ()">gst_bus_set_flushing</a> (<em class="parameter"><code><a class="link" href="GstBus.html" title="GstBus"><span class="type">GstBus</span></a> *bus</code></em>,
<em class="parameter"><code><a href="http://library.gnome.org/devel/glib/unstable/glib-Basic-Types.html#gboolean"><span class="type">gboolean</span></a> flushing</code></em>);
<span class="returnvalue">void</span> <a class="link" href="GstBus.html#gst-bus-set-sync-handler" title="gst_bus_set_sync_handler ()">gst_bus_set_sync_handler</a> (<em class="parameter"><code><a class="link" href="GstBus.html" title="GstBus"><span class="type">GstBus</span></a> *bus</code></em>,
<em class="parameter"><code><a class="link" href="GstBus.html#GstBusSyncHandler" title="GstBusSyncHandler ()"><span class="type">GstBusSyncHandler</span></a> func</code></em>,
<em class="parameter"><code><a href="http://library.gnome.org/devel/glib/unstable/glib-Basic-Types.html#gpointer"><span class="type">gpointer</span></a> user_data</code></em>,
<em class="parameter"><code><a href="http://library.gnome.org/devel/glib/unstable/glib-Datasets.html#GDestroyNotify"><span class="type">GDestroyNotify</span></a> notify</code></em>);
<a class="link" href="GstBus.html#GstBusSyncReply" title="enum GstBusSyncReply"><span class="returnvalue">GstBusSyncReply</span></a> <a class="link" href="GstBus.html#gst-bus-sync-signal-handler" title="gst_bus_sync_signal_handler ()">gst_bus_sync_signal_handler</a> (<em class="parameter"><code><a class="link" href="GstBus.html" title="GstBus"><span class="type">GstBus</span></a> *bus</code></em>,
<em class="parameter"><code><a class="link" href="gstreamer-GstMessage.html#GstMessage" title="struct GstMessage"><span class="type">GstMessage</span></a> *message</code></em>,
<em class="parameter"><code><a href="http://library.gnome.org/devel/glib/unstable/glib-Basic-Types.html#gpointer"><span class="type">gpointer</span></a> data</code></em>);
<a href="http://library.gnome.org/devel/glib/unstable/glib-The-Main-Event-Loop.html#GSource"><span class="returnvalue">GSource</span></a> * <a class="link" href="GstBus.html#gst-bus-create-watch" title="gst_bus_create_watch ()">gst_bus_create_watch</a> (<em class="parameter"><code><a class="link" href="GstBus.html" title="GstBus"><span class="type">GstBus</span></a> *bus</code></em>);
<a href="http://library.gnome.org/devel/glib/unstable/glib-Basic-Types.html#guint"><span class="returnvalue">guint</span></a> <a class="link" href="GstBus.html#gst-bus-add-watch-full" title="gst_bus_add_watch_full ()">gst_bus_add_watch_full</a> (<em class="parameter"><code><a class="link" href="GstBus.html" title="GstBus"><span class="type">GstBus</span></a> *bus</code></em>,
<em class="parameter"><code><a href="http://library.gnome.org/devel/glib/unstable/glib-Basic-Types.html#gint"><span class="type">gint</span></a> priority</code></em>,
<em class="parameter"><code><a class="link" href="GstBus.html#GstBusFunc" title="GstBusFunc ()"><span class="type">GstBusFunc</span></a> func</code></em>,
<em class="parameter"><code><a href="http://library.gnome.org/devel/glib/unstable/glib-Basic-Types.html#gpointer"><span class="type">gpointer</span></a> user_data</code></em>,
<em class="parameter"><code><a href="http://library.gnome.org/devel/glib/unstable/glib-Datasets.html#GDestroyNotify"><span class="type">GDestroyNotify</span></a> notify</code></em>);
<a href="http://library.gnome.org/devel/glib/unstable/glib-Basic-Types.html#guint"><span class="returnvalue">guint</span></a> <a class="link" href="GstBus.html#gst-bus-add-watch" title="gst_bus_add_watch ()">gst_bus_add_watch</a> (<em class="parameter"><code><a class="link" href="GstBus.html" title="GstBus"><span class="type">GstBus</span></a> *bus</code></em>,
<em class="parameter"><code><a class="link" href="GstBus.html#GstBusFunc" title="GstBusFunc ()"><span class="type">GstBusFunc</span></a> func</code></em>,
<em class="parameter"><code><a href="http://library.gnome.org/devel/glib/unstable/glib-Basic-Types.html#gpointer"><span class="type">gpointer</span></a> user_data</code></em>);
<span class="returnvalue">void</span> <a class="link" href="GstBus.html#gst-bus-disable-sync-message-emission" title="gst_bus_disable_sync_message_emission ()">gst_bus_disable_sync_message_emission</a>
(<em class="parameter"><code><a class="link" href="GstBus.html" title="GstBus"><span class="type">GstBus</span></a> *bus</code></em>);
<span class="returnvalue">void</span> <a class="link" href="GstBus.html#gst-bus-enable-sync-message-emission" title="gst_bus_enable_sync_message_emission ()">gst_bus_enable_sync_message_emission</a>
(<em class="parameter"><code><a class="link" href="GstBus.html" title="GstBus"><span class="type">GstBus</span></a> *bus</code></em>);
<a href="http://library.gnome.org/devel/glib/unstable/glib-Basic-Types.html#gboolean"><span class="returnvalue">gboolean</span></a> <a class="link" href="GstBus.html#gst-bus-async-signal-func" title="gst_bus_async_signal_func ()">gst_bus_async_signal_func</a> (<em class="parameter"><code><a class="link" href="GstBus.html" title="GstBus"><span class="type">GstBus</span></a> *bus</code></em>,
<em class="parameter"><code><a class="link" href="gstreamer-GstMessage.html#GstMessage" title="struct GstMessage"><span class="type">GstMessage</span></a> *message</code></em>,
<em class="parameter"><code><a href="http://library.gnome.org/devel/glib/unstable/glib-Basic-Types.html#gpointer"><span class="type">gpointer</span></a> data</code></em>);
<span class="returnvalue">void</span> <a class="link" href="GstBus.html#gst-bus-add-signal-watch" title="gst_bus_add_signal_watch ()">gst_bus_add_signal_watch</a> (<em class="parameter"><code><a class="link" href="GstBus.html" title="GstBus"><span class="type">GstBus</span></a> *bus</code></em>);
<span class="returnvalue">void</span> <a class="link" href="GstBus.html#gst-bus-add-signal-watch-full" title="gst_bus_add_signal_watch_full ()">gst_bus_add_signal_watch_full</a> (<em class="parameter"><code><a class="link" href="GstBus.html" title="GstBus"><span class="type">GstBus</span></a> *bus</code></em>,
<em class="parameter"><code><a href="http://library.gnome.org/devel/glib/unstable/glib-Basic-Types.html#gint"><span class="type">gint</span></a> priority</code></em>);
<span class="returnvalue">void</span> <a class="link" href="GstBus.html#gst-bus-remove-signal-watch" title="gst_bus_remove_signal_watch ()">gst_bus_remove_signal_watch</a> (<em class="parameter"><code><a class="link" href="GstBus.html" title="GstBus"><span class="type">GstBus</span></a> *bus</code></em>);
<a class="link" href="gstreamer-GstMessage.html#GstMessage" title="struct GstMessage"><span class="returnvalue">GstMessage</span></a> * <a class="link" href="GstBus.html#gst-bus-poll" title="gst_bus_poll ()">gst_bus_poll</a> (<em class="parameter"><code><a class="link" href="GstBus.html" title="GstBus"><span class="type">GstBus</span></a> *bus</code></em>,
<em class="parameter"><code><a class="link" href="gstreamer-GstMessage.html#GstMessageType" title="enum GstMessageType"><span class="type">GstMessageType</span></a> events</code></em>,
<em class="parameter"><code><a class="link" href="GstClock.html#GstClockTime" title="GstClockTime"><span class="type">GstClockTime</span></a> timeout</code></em>);
</pre>
</div>
<div class="refsect1">
<a name="GstBus.object-hierarchy"></a><h2>Object Hierarchy</h2>
<pre class="synopsis">
<a href="http://library.gnome.org/devel/gobject/unstable/gobject-The-Base-Object-Type.html#GObject">GObject</a>
+----<a href="http://library.gnome.org/devel/gobject/unstable/gobject-The-Base-Object-Type.html#GInitiallyUnowned">GInitiallyUnowned</a>
+----<a class="link" href="GstObject.html" title="GstObject">GstObject</a>
+----GstBus
</pre>
</div>
<div class="refsect1">
<a name="GstBus.properties"></a><h2>Properties</h2>
<pre class="synopsis">
"<a class="link" href="GstBus.html#GstBus--enable-async" title='The "enable-async" property'>enable-async</a>" <a href="http://library.gnome.org/devel/glib/unstable/glib-Basic-Types.html#gboolean"><span class="type">gboolean</span></a> : Write / Construct Only
</pre>
</div>
<div class="refsect1">
<a name="GstBus.signals"></a><h2>Signals</h2>
<pre class="synopsis">
"<a class="link" href="GstBus.html#GstBus-message" title='The "message" signal'>message</a>" : <a href="http://library.gnome.org/devel/gobject/unstable/gobject-Signals.html#G-SIGNAL-DETAILED:CAPS"><code class="literal">Has Details</code></a>
"<a class="link" href="GstBus.html#GstBus-sync-message" title='The "sync-message" signal'>sync-message</a>" : <a href="http://library.gnome.org/devel/gobject/unstable/gobject-Signals.html#G-SIGNAL-DETAILED:CAPS"><code class="literal">Has Details</code></a>
</pre>
</div>
<div class="refsect1">
<a name="GstBus.description"></a><h2>Description</h2>
<p>
The <a class="link" href="GstBus.html" title="GstBus"><span class="type">GstBus</span></a> is an object responsible for delivering <a class="link" href="gstreamer-GstMessage.html#GstMessage" title="struct GstMessage"><span class="type">GstMessage</span></a> packets in
a first-in first-out way from the streaming threads (see <a class="link" href="GstTask.html" title="GstTask"><span class="type">GstTask</span></a>) to the
application.
</p>
<p>
Since the application typically only wants to deal with delivery of these
messages from one thread, the GstBus will marshall the messages between
different threads. This is important since the actual streaming of media
is done in another thread than the application.
</p>
<p>
The GstBus provides support for <a href="http://library.gnome.org/devel/glib/unstable/glib-The-Main-Event-Loop.html#GSource"><span class="type">GSource</span></a> based notifications. This makes it
possible to handle the delivery in the glib mainloop.
</p>
<p>
The <a href="http://library.gnome.org/devel/glib/unstable/glib-The-Main-Event-Loop.html#GSource"><span class="type">GSource</span></a> callback function <a class="link" href="GstBus.html#gst-bus-async-signal-func" title="gst_bus_async_signal_func ()"><code class="function">gst_bus_async_signal_func()</code></a> can be used to
convert all bus messages into signal emissions.
</p>
<p>
A message is posted on the bus with the <a class="link" href="GstBus.html#gst-bus-post" title="gst_bus_post ()"><code class="function">gst_bus_post()</code></a> method. With the
<a class="link" href="GstBus.html#gst-bus-peek" title="gst_bus_peek ()"><code class="function">gst_bus_peek()</code></a> and <a class="link" href="GstBus.html#gst-bus-pop" title="gst_bus_pop ()"><code class="function">gst_bus_pop()</code></a> methods one can look at or retrieve a
previously posted message.
</p>
<p>
The bus can be polled with the <a class="link" href="GstBus.html#gst-bus-poll" title="gst_bus_poll ()"><code class="function">gst_bus_poll()</code></a> method. This methods blocks
up to the specified timeout value until one of the specified messages types
is posted on the bus. The application can then <a class="link" href="GstBus.html#gst-bus-pop" title="gst_bus_pop ()"><code class="function">gst_bus_pop()</code></a> the messages
from the bus to handle them.
Alternatively the application can register an asynchronous bus function
using <a class="link" href="GstBus.html#gst-bus-add-watch-full" title="gst_bus_add_watch_full ()"><code class="function">gst_bus_add_watch_full()</code></a> or <a class="link" href="GstBus.html#gst-bus-add-watch" title="gst_bus_add_watch ()"><code class="function">gst_bus_add_watch()</code></a>. This function will
install a <a href="http://library.gnome.org/devel/glib/unstable/glib-The-Main-Event-Loop.html#GSource"><span class="type">GSource</span></a> in the default glib main loop and will deliver messages
a short while after they have been posted. Note that the main loop should
be running for the asynchronous callbacks.
</p>
<p>
It is also possible to get messages from the bus without any thread
marshalling with the <a class="link" href="GstBus.html#gst-bus-set-sync-handler" title="gst_bus_set_sync_handler ()"><code class="function">gst_bus_set_sync_handler()</code></a> method. This makes it
possible to react to a message in the same thread that posted the
message on the bus. This should only be used if the application is able
to deal with messages from different threads.
</p>
<p>
Every <a class="link" href="GstPipeline.html" title="GstPipeline"><span class="type">GstPipeline</span></a> has one bus.
</p>
<p>
Note that a <a class="link" href="GstPipeline.html" title="GstPipeline"><span class="type">GstPipeline</span></a> will set its bus into flushing state when changing
from READY to NULL state.
</p>
<p>
Last reviewed on 2012-03-28 (0.11.3)
</p>
</div>
<div class="refsect1">
<a name="GstBus.details"></a><h2>Details</h2>
<div class="refsect2">
<a name="GstBus-struct"></a><h3>struct GstBus</h3>
<pre class="programlisting">struct GstBus;</pre>
<p>
The opaque <a class="link" href="GstBus.html" title="GstBus"><span class="type">GstBus</span></a> data structure.
</p>
</div>
<hr>
<div class="refsect2">
<a name="GstBusFlags"></a><h3>enum GstBusFlags</h3>
<pre class="programlisting">typedef enum {
GST_BUS_FLUSHING = (GST_OBJECT_FLAG_LAST << 0),
/* padding */
GST_BUS_FLAG_LAST = (GST_OBJECT_FLAG_LAST << 1)
} GstBusFlags;
</pre>
<p>
The standard flags that a bus may have.
</p>
<div class="variablelist"><table border="0" class="variablelist">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody>
<tr>
<td><p><a name="GST-BUS-FLUSHING:CAPS"></a><span class="term"><code class="literal">GST_BUS_FLUSHING</code></span></p></td>
<td>The bus is currently dropping all messages
</td>
</tr>
<tr>
<td><p><a name="GST-BUS-FLAG-LAST:CAPS"></a><span class="term"><code class="literal">GST_BUS_FLAG_LAST</code></span></p></td>
<td>offset to define more flags
</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2">
<a name="GstBusSyncReply"></a><h3>enum GstBusSyncReply</h3>
<pre class="programlisting">typedef enum {
GST_BUS_DROP = 0,
GST_BUS_PASS = 1,
GST_BUS_ASYNC = 2
} GstBusSyncReply;
</pre>
<p>
The result values for a GstBusSyncHandler.
</p>
<div class="variablelist"><table border="0" class="variablelist">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody>
<tr>
<td><p><a name="GST-BUS-DROP:CAPS"></a><span class="term"><code class="literal">GST_BUS_DROP</code></span></p></td>
<td>drop the message
</td>
</tr>
<tr>
<td><p><a name="GST-BUS-PASS:CAPS"></a><span class="term"><code class="literal">GST_BUS_PASS</code></span></p></td>
<td>pass the message to the async queue
</td>
</tr>
<tr>
<td><p><a name="GST-BUS-ASYNC:CAPS"></a><span class="term"><code class="literal">GST_BUS_ASYNC</code></span></p></td>
<td>pass message to async queue, continue if message is handled
</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2">
<a name="GstBusFunc"></a><h3>GstBusFunc ()</h3>
<pre class="programlisting"><a href="http://library.gnome.org/devel/glib/unstable/glib-Basic-Types.html#gboolean"><span class="returnvalue">gboolean</span></a> (*GstBusFunc) (<em class="parameter"><code><a class="link" href="GstBus.html" title="GstBus"><span class="type">GstBus</span></a> *bus</code></em>,
<em class="parameter"><code><a class="link" href="gstreamer-GstMessage.html#GstMessage" title="struct GstMessage"><span class="type">GstMessage</span></a> *message</code></em>,
<em class="parameter"><code><a href="http://library.gnome.org/devel/glib/unstable/glib-Basic-Types.html#gpointer"><span class="type">gpointer</span></a> user_data</code></em>);</pre>
<p>
Specifies the type of function passed to <a class="link" href="GstBus.html#gst-bus-add-watch" title="gst_bus_add_watch ()"><code class="function">gst_bus_add_watch()</code></a> or
<a class="link" href="GstBus.html#gst-bus-add-watch-full" title="gst_bus_add_watch_full ()"><code class="function">gst_bus_add_watch_full()</code></a>, which is called from the mainloop when a message
is available on the bus.
</p>
<p>
The message passed to the function will be unreffed after execution of this
function so it should not be freed in the function.
</p>
<p>
Note that this function is used as a GSourceFunc which means that returning
FALSE will remove the GSource from the mainloop.
</p>
<div class="variablelist"><table border="0" class="variablelist">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody>
<tr>
<td><p><span class="term"><em class="parameter"><code>bus</code></em> :</span></p></td>
<td>the <a class="link" href="GstBus.html" title="GstBus"><span class="type">GstBus</span></a> that sent the message</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>message</code></em> :</span></p></td>
<td>the <a class="link" href="gstreamer-GstMessage.html#GstMessage" title="struct GstMessage"><span class="type">GstMessage</span></a>
</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>user_data</code></em> :</span></p></td>
<td>user data that has been given, when registering the handler</td>
</tr>
<tr>
<td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td>
<td>
<a href="http://library.gnome.org/devel/glib/unstable/glib-Standard-Macros.html#FALSE:CAPS"><code class="literal">FALSE</code></a> if the event source should be removed.</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2">
<a name="GstBusSyncHandler"></a><h3>GstBusSyncHandler ()</h3>
<pre class="programlisting"><a class="link" href="GstBus.html#GstBusSyncReply" title="enum GstBusSyncReply"><span class="returnvalue">GstBusSyncReply</span></a> (*GstBusSyncHandler) (<em class="parameter"><code><a class="link" href="GstBus.html" title="GstBus"><span class="type">GstBus</span></a> *bus</code></em>,
<em class="parameter"><code><a class="link" href="gstreamer-GstMessage.html#GstMessage" title="struct GstMessage"><span class="type">GstMessage</span></a> *message</code></em>,
<em class="parameter"><code><a href="http://library.gnome.org/devel/glib/unstable/glib-Basic-Types.html#gpointer"><span class="type">gpointer</span></a> user_data</code></em>);</pre>
<p>
Handler will be invoked synchronously, when a new message has been injected
into the bus. This function is mostly used internally. Only one sync handler
can be attached to a given bus.
</p>
<p>
If the handler returns GST_BUS_DROP, it should unref the message, else the
message should not be unreffed by the sync handler.
</p>
<div class="variablelist"><table border="0" class="variablelist">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody>
<tr>
<td><p><span class="term"><em class="parameter"><code>bus</code></em> :</span></p></td>
<td>the <a class="link" href="GstBus.html" title="GstBus"><span class="type">GstBus</span></a> that sent the message</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>message</code></em> :</span></p></td>
<td>the <a class="link" href="gstreamer-GstMessage.html#GstMessage" title="struct GstMessage"><span class="type">GstMessage</span></a>
</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>user_data</code></em> :</span></p></td>
<td>user data that has been given, when registering the handler</td>
</tr>
<tr>
<td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td>
<td>
<a class="link" href="GstBus.html#GstBusSyncReply" title="enum GstBusSyncReply"><span class="type">GstBusSyncReply</span></a> stating what to do with the message</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2">
<a name="gst-bus-new"></a><h3>gst_bus_new ()</h3>
<pre class="programlisting"><a class="link" href="GstBus.html" title="GstBus"><span class="returnvalue">GstBus</span></a> * gst_bus_new (<em class="parameter"><code><span class="type">void</span></code></em>);</pre>
<p>
Creates a new <a class="link" href="GstBus.html" title="GstBus"><span class="type">GstBus</span></a> instance.
</p>
<div class="variablelist"><table border="0" class="variablelist">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody><tr>
<td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td>
<td>a new <a class="link" href="GstBus.html" title="GstBus"><span class="type">GstBus</span></a> instance. <span class="annotation">[<acronym title="Free data after the code is done."><span class="acronym">transfer full</span></acronym>]</span>
</td>
</tr></tbody>
</table></div>
</div>
<hr>
<div class="refsect2">
<a name="gst-bus-post"></a><h3>gst_bus_post ()</h3>
<pre class="programlisting"><a href="http://library.gnome.org/devel/glib/unstable/glib-Basic-Types.html#gboolean"><span class="returnvalue">gboolean</span></a> gst_bus_post (<em class="parameter"><code><a class="link" href="GstBus.html" title="GstBus"><span class="type">GstBus</span></a> *bus</code></em>,
<em class="parameter"><code><a class="link" href="gstreamer-GstMessage.html#GstMessage" title="struct GstMessage"><span class="type">GstMessage</span></a> *message</code></em>);</pre>
<p>
Post a message on the given bus. Ownership of the message
is taken by the bus.
</p>
<div class="variablelist"><table border="0" class="variablelist">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody>
<tr>
<td><p><span class="term"><em class="parameter"><code>bus</code></em> :</span></p></td>
<td>a <a class="link" href="GstBus.html" title="GstBus"><span class="type">GstBus</span></a> to post on</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>message</code></em> :</span></p></td>
<td>the <a class="link" href="gstreamer-GstMessage.html#GstMessage" title="struct GstMessage"><span class="type">GstMessage</span></a> to post. <span class="annotation">[<acronym title="Free data after the code is done."><span class="acronym">transfer full</span></acronym>]</span>
</td>
</tr>
<tr>
<td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td>
<td>TRUE if the message could be posted, FALSE if the bus is flushing.
MT safe.</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2">
<a name="gst-bus-have-pending"></a><h3>gst_bus_have_pending ()</h3>
<pre class="programlisting"><a href="http://library.gnome.org/devel/glib/unstable/glib-Basic-Types.html#gboolean"><span class="returnvalue">gboolean</span></a> gst_bus_have_pending (<em class="parameter"><code><a class="link" href="GstBus.html" title="GstBus"><span class="type">GstBus</span></a> *bus</code></em>);</pre>
<p>
Check if there are pending messages on the bus that
should be handled.
</p>
<div class="variablelist"><table border="0" class="variablelist">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody>
<tr>
<td><p><span class="term"><em class="parameter"><code>bus</code></em> :</span></p></td>
<td>a <a class="link" href="GstBus.html" title="GstBus"><span class="type">GstBus</span></a> to check</td>
</tr>
<tr>
<td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td>
<td>TRUE if there are messages on the bus to be handled, FALSE
otherwise.
MT safe.</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2">
<a name="gst-bus-peek"></a><h3>gst_bus_peek ()</h3>
<pre class="programlisting"><a class="link" href="gstreamer-GstMessage.html#GstMessage" title="struct GstMessage"><span class="returnvalue">GstMessage</span></a> * gst_bus_peek (<em class="parameter"><code><a class="link" href="GstBus.html" title="GstBus"><span class="type">GstBus</span></a> *bus</code></em>);</pre>
<p>
Peek the message on the top of the bus' queue. The message will remain
on the bus' message queue. A reference is returned, and needs to be unreffed
by the caller.
</p>
<div class="variablelist"><table border="0" class="variablelist">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody>
<tr>
<td><p><span class="term"><em class="parameter"><code>bus</code></em> :</span></p></td>
<td>a <a class="link" href="GstBus.html" title="GstBus"><span class="type">GstBus</span></a>
</td>
</tr>
<tr>
<td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td>
<td>the <a class="link" href="gstreamer-GstMessage.html#GstMessage" title="struct GstMessage"><span class="type">GstMessage</span></a> that is on the bus, or NULL if the
bus is empty.
MT safe. <span class="annotation">[<acronym title="Free data after the code is done."><span class="acronym">transfer full</span></acronym>]</span>
</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2">
<a name="gst-bus-pop"></a><h3>gst_bus_pop ()</h3>
<pre class="programlisting"><a class="link" href="gstreamer-GstMessage.html#GstMessage" title="struct GstMessage"><span class="returnvalue">GstMessage</span></a> * gst_bus_pop (<em class="parameter"><code><a class="link" href="GstBus.html" title="GstBus"><span class="type">GstBus</span></a> *bus</code></em>);</pre>
<p>
Get a message from the bus.
</p>
<div class="variablelist"><table border="0" class="variablelist">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody>
<tr>
<td><p><span class="term"><em class="parameter"><code>bus</code></em> :</span></p></td>
<td>a <a class="link" href="GstBus.html" title="GstBus"><span class="type">GstBus</span></a> to pop</td>
</tr>
<tr>
<td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td>
<td>the <a class="link" href="gstreamer-GstMessage.html#GstMessage" title="struct GstMessage"><span class="type">GstMessage</span></a> that is on the bus, or NULL if the
bus is empty. The message is taken from the bus and needs to be unreffed
with <a class="link" href="gstreamer-GstMessage.html#gst-message-unref" title="gst_message_unref ()"><code class="function">gst_message_unref()</code></a> after usage.
MT safe. <span class="annotation">[<acronym title="Free data after the code is done."><span class="acronym">transfer full</span></acronym>]</span>
</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2">
<a name="gst-bus-pop-filtered"></a><h3>gst_bus_pop_filtered ()</h3>
<pre class="programlisting"><a class="link" href="gstreamer-GstMessage.html#GstMessage" title="struct GstMessage"><span class="returnvalue">GstMessage</span></a> * gst_bus_pop_filtered (<em class="parameter"><code><a class="link" href="GstBus.html" title="GstBus"><span class="type">GstBus</span></a> *bus</code></em>,
<em class="parameter"><code><a class="link" href="gstreamer-GstMessage.html#GstMessageType" title="enum GstMessageType"><span class="type">GstMessageType</span></a> types</code></em>);</pre>
<p>
Get a message matching <em class="parameter"><code>type</code></em> from the bus. Will discard all messages on
the bus that do not match <em class="parameter"><code>type</code></em> and that have been posted before the first
message that does match <em class="parameter"><code>type</code></em>. If there is no message matching <em class="parameter"><code>type</code></em> on
the bus, all messages will be discarded.
</p>
<div class="variablelist"><table border="0" class="variablelist">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody>
<tr>
<td><p><span class="term"><em class="parameter"><code>bus</code></em> :</span></p></td>
<td>a <a class="link" href="GstBus.html" title="GstBus"><span class="type">GstBus</span></a> to pop</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>types</code></em> :</span></p></td>
<td>message types to take into account</td>
</tr>
<tr>
<td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td>
<td>the next <a class="link" href="gstreamer-GstMessage.html#GstMessage" title="struct GstMessage"><span class="type">GstMessage</span></a> matching <em class="parameter"><code>type</code></em> that is on
the bus, or NULL if the bus is empty or there is no message matching
<em class="parameter"><code>type</code></em>. The message is taken from the bus and needs to be unreffed with
<a class="link" href="gstreamer-GstMessage.html#gst-message-unref" title="gst_message_unref ()"><code class="function">gst_message_unref()</code></a> after usage.
MT safe. <span class="annotation">[<acronym title="Free data after the code is done."><span class="acronym">transfer full</span></acronym>]</span>
</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2">
<a name="gst-bus-timed-pop"></a><h3>gst_bus_timed_pop ()</h3>
<pre class="programlisting"><a class="link" href="gstreamer-GstMessage.html#GstMessage" title="struct GstMessage"><span class="returnvalue">GstMessage</span></a> * gst_bus_timed_pop (<em class="parameter"><code><a class="link" href="GstBus.html" title="GstBus"><span class="type">GstBus</span></a> *bus</code></em>,
<em class="parameter"><code><a class="link" href="GstClock.html#GstClockTime" title="GstClockTime"><span class="type">GstClockTime</span></a> timeout</code></em>);</pre>
<p>
Get a message from the bus, waiting up to the specified timeout.
</p>
<p>
If <em class="parameter"><code>timeout</code></em> is 0, this function behaves like <a class="link" href="GstBus.html#gst-bus-pop" title="gst_bus_pop ()"><code class="function">gst_bus_pop()</code></a>. If <em class="parameter"><code>timeout</code></em> is
<a class="link" href="GstClock.html#GST-CLOCK-TIME-NONE:CAPS" title="GST_CLOCK_TIME_NONE"><span class="type">GST_CLOCK_TIME_NONE</span></a>, this function will block forever until a message was
posted on the bus.
</p>
<div class="variablelist"><table border="0" class="variablelist">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody>
<tr>
<td><p><span class="term"><em class="parameter"><code>bus</code></em> :</span></p></td>
<td>a <a class="link" href="GstBus.html" title="GstBus"><span class="type">GstBus</span></a> to pop</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>timeout</code></em> :</span></p></td>
<td>a timeout</td>
</tr>
<tr>
<td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td>
<td>the <a class="link" href="gstreamer-GstMessage.html#GstMessage" title="struct GstMessage"><span class="type">GstMessage</span></a> that is on the bus after the
specified timeout or NULL if the bus is empty after the timeout expired.
The message is taken from the bus and needs to be unreffed with
<a class="link" href="gstreamer-GstMessage.html#gst-message-unref" title="gst_message_unref ()"><code class="function">gst_message_unref()</code></a> after usage.
MT safe. <span class="annotation">[<acronym title="Free data after the code is done."><span class="acronym">transfer full</span></acronym>]</span>
</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2">
<a name="gst-bus-timed-pop-filtered"></a><h3>gst_bus_timed_pop_filtered ()</h3>
<pre class="programlisting"><a class="link" href="gstreamer-GstMessage.html#GstMessage" title="struct GstMessage"><span class="returnvalue">GstMessage</span></a> * gst_bus_timed_pop_filtered (<em class="parameter"><code><a class="link" href="GstBus.html" title="GstBus"><span class="type">GstBus</span></a> *bus</code></em>,
<em class="parameter"><code><a class="link" href="GstClock.html#GstClockTime" title="GstClockTime"><span class="type">GstClockTime</span></a> timeout</code></em>,
<em class="parameter"><code><a class="link" href="gstreamer-GstMessage.html#GstMessageType" title="enum GstMessageType"><span class="type">GstMessageType</span></a> types</code></em>);</pre>
<p>
Get a message from the bus whose type matches the message type mask <em class="parameter"><code>types</code></em>,
waiting up to the specified timeout (and discarding any messages that do not
match the mask provided).
</p>
<p>
If <em class="parameter"><code>timeout</code></em> is 0, this function behaves like <a class="link" href="GstBus.html#gst-bus-pop-filtered" title="gst_bus_pop_filtered ()"><code class="function">gst_bus_pop_filtered()</code></a>. If
<em class="parameter"><code>timeout</code></em> is <a class="link" href="GstClock.html#GST-CLOCK-TIME-NONE:CAPS" title="GST_CLOCK_TIME_NONE"><span class="type">GST_CLOCK_TIME_NONE</span></a>, this function will block forever until a
matching message was posted on the bus.
</p>
<div class="variablelist"><table border="0" class="variablelist">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody>
<tr>
<td><p><span class="term"><em class="parameter"><code>bus</code></em> :</span></p></td>
<td>a <a class="link" href="GstBus.html" title="GstBus"><span class="type">GstBus</span></a> to pop from</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>timeout</code></em> :</span></p></td>
<td>a timeout in nanoseconds, or GST_CLOCK_TIME_NONE to wait forever</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>types</code></em> :</span></p></td>
<td>message types to take into account, GST_MESSAGE_ANY for any type</td>
</tr>
<tr>
<td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td>
<td>a <a class="link" href="gstreamer-GstMessage.html#GstMessage" title="struct GstMessage"><span class="type">GstMessage</span></a> matching the filter in <em class="parameter"><code>types</code></em>,
or NULL if no matching message was found on the bus until the timeout
expired. The message is taken from the bus and needs to be unreffed
with <a class="link" href="gstreamer-GstMessage.html#gst-message-unref" title="gst_message_unref ()"><code class="function">gst_message_unref()</code></a> after usage.
MT safe. <span class="annotation">[<acronym title="Free data after the code is done."><span class="acronym">transfer full</span></acronym>]</span>
</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2">
<a name="gst-bus-set-flushing"></a><h3>gst_bus_set_flushing ()</h3>
<pre class="programlisting"><span class="returnvalue">void</span> gst_bus_set_flushing (<em class="parameter"><code><a class="link" href="GstBus.html" title="GstBus"><span class="type">GstBus</span></a> *bus</code></em>,
<em class="parameter"><code><a href="http://library.gnome.org/devel/glib/unstable/glib-Basic-Types.html#gboolean"><span class="type">gboolean</span></a> flushing</code></em>);</pre>
<p>
If <em class="parameter"><code>flushing</code></em>, flush out and unref any messages queued in the bus. Releases
references to the message origin objects. Will flush future messages until
<a class="link" href="GstBus.html#gst-bus-set-flushing" title="gst_bus_set_flushing ()"><code class="function">gst_bus_set_flushing()</code></a> sets <em class="parameter"><code>flushing</code></em> to <a href="http://library.gnome.org/devel/glib/unstable/glib-Standard-Macros.html#FALSE:CAPS"><span class="type">FALSE</span></a>.
</p>
<p>
MT safe.
</p>
<div class="variablelist"><table border="0" class="variablelist">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody>
<tr>
<td><p><span class="term"><em class="parameter"><code>bus</code></em> :</span></p></td>
<td>a <a class="link" href="GstBus.html" title="GstBus"><span class="type">GstBus</span></a>
</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>flushing</code></em> :</span></p></td>
<td>whether or not to flush the bus</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2">
<a name="gst-bus-set-sync-handler"></a><h3>gst_bus_set_sync_handler ()</h3>
<pre class="programlisting"><span class="returnvalue">void</span> gst_bus_set_sync_handler (<em class="parameter"><code><a class="link" href="GstBus.html" title="GstBus"><span class="type">GstBus</span></a> *bus</code></em>,
<em class="parameter"><code><a class="link" href="GstBus.html#GstBusSyncHandler" title="GstBusSyncHandler ()"><span class="type">GstBusSyncHandler</span></a> func</code></em>,
<em class="parameter"><code><a href="http://library.gnome.org/devel/glib/unstable/glib-Basic-Types.html#gpointer"><span class="type">gpointer</span></a> user_data</code></em>,
<em class="parameter"><code><a href="http://library.gnome.org/devel/glib/unstable/glib-Datasets.html#GDestroyNotify"><span class="type">GDestroyNotify</span></a> notify</code></em>);</pre>
<p>
Sets the synchronous handler on the bus. The function will be called
every time a new message is posted on the bus. Note that the function
will be called in the same thread context as the posting object. This
function is usually only called by the creator of the bus. Applications
should handle messages asynchronously using the gst_bus watch and poll
functions.
</p>
<p>
You cannot replace an existing sync_handler. You can pass NULL to this
function, which will clear the existing handler.
</p>
<div class="variablelist"><table border="0" class="variablelist">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody>
<tr>
<td><p><span class="term"><em class="parameter"><code>bus</code></em> :</span></p></td>
<td>a <a class="link" href="GstBus.html" title="GstBus"><span class="type">GstBus</span></a> to install the handler on</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>func</code></em> :</span></p></td>
<td>The handler function to install. <span class="annotation">[<acronym title="NULL is ok, both for passing and for returning."><span class="acronym">allow-none</span></acronym>]</span>
</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>user_data</code></em> :</span></p></td>
<td>User data that will be sent to the handler function.</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>notify</code></em> :</span></p></td>
<td>called when <em class="parameter"><code>user_data</code></em> becomes unused</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2">
<a name="gst-bus-sync-signal-handler"></a><h3>gst_bus_sync_signal_handler ()</h3>
<pre class="programlisting"><a class="link" href="GstBus.html#GstBusSyncReply" title="enum GstBusSyncReply"><span class="returnvalue">GstBusSyncReply</span></a> gst_bus_sync_signal_handler (<em class="parameter"><code><a class="link" href="GstBus.html" title="GstBus"><span class="type">GstBus</span></a> *bus</code></em>,
<em class="parameter"><code><a class="link" href="gstreamer-GstMessage.html#GstMessage" title="struct GstMessage"><span class="type">GstMessage</span></a> *message</code></em>,
<em class="parameter"><code><a href="http://library.gnome.org/devel/glib/unstable/glib-Basic-Types.html#gpointer"><span class="type">gpointer</span></a> data</code></em>);</pre>
<p>
A helper GstBusSyncHandler that can be used to convert all synchronous
messages into signals.
</p>
<div class="variablelist"><table border="0" class="variablelist">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody>
<tr>
<td><p><span class="term"><em class="parameter"><code>bus</code></em> :</span></p></td>
<td>a <a class="link" href="GstBus.html" title="GstBus"><span class="type">GstBus</span></a>
</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>message</code></em> :</span></p></td>
<td>the <a class="link" href="gstreamer-GstMessage.html#GstMessage" title="struct GstMessage"><span class="type">GstMessage</span></a> received</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>data</code></em> :</span></p></td>
<td>user data</td>
</tr>
<tr>
<td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td>
<td>GST_BUS_PASS</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2">
<a name="gst-bus-create-watch"></a><h3>gst_bus_create_watch ()</h3>
<pre class="programlisting"><a href="http://library.gnome.org/devel/glib/unstable/glib-The-Main-Event-Loop.html#GSource"><span class="returnvalue">GSource</span></a> * gst_bus_create_watch (<em class="parameter"><code><a class="link" href="GstBus.html" title="GstBus"><span class="type">GstBus</span></a> *bus</code></em>);</pre>
<p>
Create watch for this bus. The GSource will be dispatched whenever
a message is on the bus. After the GSource is dispatched, the
message is popped off the bus and unreffed.
</p>
<div class="variablelist"><table border="0" class="variablelist">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody>
<tr>
<td><p><span class="term"><em class="parameter"><code>bus</code></em> :</span></p></td>
<td>a <a class="link" href="GstBus.html" title="GstBus"><span class="type">GstBus</span></a> to create the watch for</td>
</tr>
<tr>
<td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td>
<td>a <a href="http://library.gnome.org/devel/glib/unstable/glib-The-Main-Event-Loop.html#GSource"><span class="type">GSource</span></a> that can be added to a mainloop. <span class="annotation">[<acronym title="Free data after the code is done."><span class="acronym">transfer full</span></acronym>]</span>
</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2">
<a name="gst-bus-add-watch-full"></a><h3>gst_bus_add_watch_full ()</h3>
<pre class="programlisting"><a href="http://library.gnome.org/devel/glib/unstable/glib-Basic-Types.html#guint"><span class="returnvalue">guint</span></a> gst_bus_add_watch_full (<em class="parameter"><code><a class="link" href="GstBus.html" title="GstBus"><span class="type">GstBus</span></a> *bus</code></em>,
<em class="parameter"><code><a href="http://library.gnome.org/devel/glib/unstable/glib-Basic-Types.html#gint"><span class="type">gint</span></a> priority</code></em>,
<em class="parameter"><code><a class="link" href="GstBus.html#GstBusFunc" title="GstBusFunc ()"><span class="type">GstBusFunc</span></a> func</code></em>,
<em class="parameter"><code><a href="http://library.gnome.org/devel/glib/unstable/glib-Basic-Types.html#gpointer"><span class="type">gpointer</span></a> user_data</code></em>,
<em class="parameter"><code><a href="http://library.gnome.org/devel/glib/unstable/glib-Datasets.html#GDestroyNotify"><span class="type">GDestroyNotify</span></a> notify</code></em>);</pre>
<p>
Adds a bus watch to the default main context with the given <em class="parameter"><code>priority</code></em> (e.g.
<a href="http://library.gnome.org/devel/glib/unstable/glib-The-Main-Event-Loop.html#G-PRIORITY-DEFAULT:CAPS"><code class="literal">G_PRIORITY_DEFAULT</code></a>). It is also possible to use a non-default main
context set up using <a href="http://library.gnome.org/devel/glib/unstable/glib-The-Main-Event-Loop.html#g-main-context-push-thread-default"><code class="function">g_main_context_push_thread_default()</code></a> (before
one had to create a bus watch source and attach it to the desired main
context 'manually').
</p>
<p>
This function is used to receive asynchronous messages in the main loop.
There can only be a single bus watch per bus, you must remove it before you
can set a new one.
</p>
<p>
When <em class="parameter"><code>func</code></em> is called, the message belongs to the caller; if you want to
keep a copy of it, call <a class="link" href="gstreamer-GstMessage.html#gst-message-ref" title="gst_message_ref ()"><code class="function">gst_message_ref()</code></a> before leaving <em class="parameter"><code>func</code></em>.
</p>
<p>
The watch can be removed using <a href="http://library.gnome.org/devel/glib/unstable/glib-The-Main-Event-Loop.html#g-source-remove"><code class="function">g_source_remove()</code></a> or by returning FALSE
from <em class="parameter"><code>func</code></em>.
</p>
<p>
MT safe.
</p>
<div class="variablelist"><table border="0" class="variablelist">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody>
<tr>
<td><p><span class="term"><em class="parameter"><code>bus</code></em> :</span></p></td>
<td>a <a class="link" href="GstBus.html" title="GstBus"><span class="type">GstBus</span></a> to create the watch for.</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>priority</code></em> :</span></p></td>
<td>The priority of the watch.</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>func</code></em> :</span></p></td>
<td>A function to call when a message is received.</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>user_data</code></em> :</span></p></td>
<td>user data passed to <em class="parameter"><code>func</code></em>.</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>notify</code></em> :</span></p></td>
<td>the function to call when the source is removed.</td>
</tr>
<tr>
<td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td>
<td>The event source id.
Rename to: gst_bus_add_watch</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2">
<a name="gst-bus-add-watch"></a><h3>gst_bus_add_watch ()</h3>
<pre class="programlisting"><a href="http://library.gnome.org/devel/glib/unstable/glib-Basic-Types.html#guint"><span class="returnvalue">guint</span></a> gst_bus_add_watch (<em class="parameter"><code><a class="link" href="GstBus.html" title="GstBus"><span class="type">GstBus</span></a> *bus</code></em>,
<em class="parameter"><code><a class="link" href="GstBus.html#GstBusFunc" title="GstBusFunc ()"><span class="type">GstBusFunc</span></a> func</code></em>,
<em class="parameter"><code><a href="http://library.gnome.org/devel/glib/unstable/glib-Basic-Types.html#gpointer"><span class="type">gpointer</span></a> user_data</code></em>);</pre>
<p>
Adds a bus watch to the default main context with the default priority
(<a href="http://library.gnome.org/devel/glib/unstable/glib-The-Main-Event-Loop.html#G-PRIORITY-DEFAULT:CAPS"><code class="literal">G_PRIORITY_DEFAULT</code></a>). It is also possible to use a non-default main
context set up using <a href="http://library.gnome.org/devel/glib/unstable/glib-The-Main-Event-Loop.html#g-main-context-push-thread-default"><code class="function">g_main_context_push_thread_default()</code></a> (before
one had to create a bus watch source and attach it to the desired main
context 'manually').
</p>
<p>
This function is used to receive asynchronous messages in the main loop.
There can only be a single bus watch per bus, you must remove it before you
can set a new one.
</p>
<p>
The watch can be removed using <a href="http://library.gnome.org/devel/glib/unstable/glib-The-Main-Event-Loop.html#g-source-remove"><code class="function">g_source_remove()</code></a> or by returning FALSE
from <em class="parameter"><code>func</code></em>.
</p>
<div class="variablelist"><table border="0" class="variablelist">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody>
<tr>
<td><p><span class="term"><em class="parameter"><code>bus</code></em> :</span></p></td>
<td>a <a class="link" href="GstBus.html" title="GstBus"><span class="type">GstBus</span></a> to create the watch for</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>func</code></em> :</span></p></td>
<td>A function to call when a message is received.</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>user_data</code></em> :</span></p></td>
<td>user data passed to <em class="parameter"><code>func</code></em>.</td>
</tr>
<tr>
<td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td>
<td>The event source id.
MT safe.</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2">
<a name="gst-bus-disable-sync-message-emission"></a><h3>gst_bus_disable_sync_message_emission ()</h3>
<pre class="programlisting"><span class="returnvalue">void</span> gst_bus_disable_sync_message_emission
(<em class="parameter"><code><a class="link" href="GstBus.html" title="GstBus"><span class="type">GstBus</span></a> *bus</code></em>);</pre>
<p>
Instructs GStreamer to stop emitting the "sync-message" signal for this bus.
See <a class="link" href="GstBus.html#gst-bus-enable-sync-message-emission" title="gst_bus_enable_sync_message_emission ()"><code class="function">gst_bus_enable_sync_message_emission()</code></a> for more information.
</p>
<p>
In the event that multiple pieces of code have called
<a class="link" href="GstBus.html#gst-bus-enable-sync-message-emission" title="gst_bus_enable_sync_message_emission ()"><code class="function">gst_bus_enable_sync_message_emission()</code></a>, the sync-message emissions will only
be stopped after all calls to <a class="link" href="GstBus.html#gst-bus-enable-sync-message-emission" title="gst_bus_enable_sync_message_emission ()"><code class="function">gst_bus_enable_sync_message_emission()</code></a> were
"cancelled" by calling this function. In this way the semantics are exactly
the same as <a class="link" href="GstObject.html#gst-object-ref" title="gst_object_ref ()"><code class="function">gst_object_ref()</code></a> that which calls enable should also call
disable.
</p>
<p>
MT safe.
</p>
<div class="variablelist"><table border="0" class="variablelist">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody><tr>
<td><p><span class="term"><em class="parameter"><code>bus</code></em> :</span></p></td>
<td>a <a class="link" href="GstBus.html" title="GstBus"><span class="type">GstBus</span></a> on which you previously called
<a class="link" href="GstBus.html#gst-bus-enable-sync-message-emission" title="gst_bus_enable_sync_message_emission ()"><code class="function">gst_bus_enable_sync_message_emission()</code></a>
</td>
</tr></tbody>
</table></div>
</div>
<hr>
<div class="refsect2">
<a name="gst-bus-enable-sync-message-emission"></a><h3>gst_bus_enable_sync_message_emission ()</h3>
<pre class="programlisting"><span class="returnvalue">void</span> gst_bus_enable_sync_message_emission
(<em class="parameter"><code><a class="link" href="GstBus.html" title="GstBus"><span class="type">GstBus</span></a> *bus</code></em>);</pre>
<p>
Instructs GStreamer to emit the "sync-message" signal after running the bus's
sync handler. This function is here so that code can ensure that they can
synchronously receive messages without having to affect what the bin's sync
handler is.
</p>
<p>
This function may be called multiple times. To clean up, the caller is
responsible for calling <a class="link" href="GstBus.html#gst-bus-disable-sync-message-emission" title="gst_bus_disable_sync_message_emission ()"><code class="function">gst_bus_disable_sync_message_emission()</code></a> as many times
as this function is called.
</p>
<p>
While this function looks similar to <a class="link" href="GstBus.html#gst-bus-add-signal-watch" title="gst_bus_add_signal_watch ()"><code class="function">gst_bus_add_signal_watch()</code></a>, it is not
exactly the same -- this function enables <span class="emphasis"><em>synchronous</em></span> emission of
signals when messages arrive; <a class="link" href="GstBus.html#gst-bus-add-signal-watch" title="gst_bus_add_signal_watch ()"><code class="function">gst_bus_add_signal_watch()</code></a> adds an idle callback
to pop messages off the bus <span class="emphasis"><em>asynchronously</em></span>. The sync-message signal
comes from the thread of whatever object posted the message; the "message"
signal is marshalled to the main thread via the main loop.
</p>
<p>
MT safe.
</p>
<div class="variablelist"><table border="0" class="variablelist">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody><tr>
<td><p><span class="term"><em class="parameter"><code>bus</code></em> :</span></p></td>
<td>a <a class="link" href="GstBus.html" title="GstBus"><span class="type">GstBus</span></a> on which you want to receive the "sync-message" signal</td>
</tr></tbody>
</table></div>
</div>
<hr>
<div class="refsect2">
<a name="gst-bus-async-signal-func"></a><h3>gst_bus_async_signal_func ()</h3>
<pre class="programlisting"><a href="http://library.gnome.org/devel/glib/unstable/glib-Basic-Types.html#gboolean"><span class="returnvalue">gboolean</span></a> gst_bus_async_signal_func (<em class="parameter"><code><a class="link" href="GstBus.html" title="GstBus"><span class="type">GstBus</span></a> *bus</code></em>,
<em class="parameter"><code><a class="link" href="gstreamer-GstMessage.html#GstMessage" title="struct GstMessage"><span class="type">GstMessage</span></a> *message</code></em>,
<em class="parameter"><code><a href="http://library.gnome.org/devel/glib/unstable/glib-Basic-Types.html#gpointer"><span class="type">gpointer</span></a> data</code></em>);</pre>
<p>
A helper <a class="link" href="GstBus.html#GstBusFunc" title="GstBusFunc ()"><span class="type">GstBusFunc</span></a> that can be used to convert all asynchronous messages
into signals.
</p>
<div class="variablelist"><table border="0" class="variablelist">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody>
<tr>
<td><p><span class="term"><em class="parameter"><code>bus</code></em> :</span></p></td>
<td>a <a class="link" href="GstBus.html" title="GstBus"><span class="type">GstBus</span></a>
</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>message</code></em> :</span></p></td>
<td>the <a class="link" href="gstreamer-GstMessage.html#GstMessage" title="struct GstMessage"><span class="type">GstMessage</span></a> received</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>data</code></em> :</span></p></td>
<td>user data</td>
</tr>
<tr>
<td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td>
<td>TRUE</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2">
<a name="gst-bus-add-signal-watch"></a><h3>gst_bus_add_signal_watch ()</h3>
<pre class="programlisting"><span class="returnvalue">void</span> gst_bus_add_signal_watch (<em class="parameter"><code><a class="link" href="GstBus.html" title="GstBus"><span class="type">GstBus</span></a> *bus</code></em>);</pre>
<p>
Adds a bus signal watch to the default main context with the default priority
(<a href="http://library.gnome.org/devel/glib/unstable/glib-The-Main-Event-Loop.html#G-PRIORITY-DEFAULT:CAPS"><code class="literal">G_PRIORITY_DEFAULT</code></a>). It is also possible to use a non-default
main context set up using <a href="http://library.gnome.org/devel/glib/unstable/glib-The-Main-Event-Loop.html#g-main-context-push-thread-default"><code class="function">g_main_context_push_thread_default()</code></a> (before
one had to create a bus watch source and attach it to the desired main
context 'manually').
</p>
<p>
After calling this statement, the bus will emit the "message" signal for each
message posted on the bus.
</p>
<p>
This function may be called multiple times. To clean up, the caller is
responsible for calling <a class="link" href="GstBus.html#gst-bus-remove-signal-watch" title="gst_bus_remove_signal_watch ()"><code class="function">gst_bus_remove_signal_watch()</code></a> as many times as this
function is called.
</p>
<p>
MT safe.
</p>
<div class="variablelist"><table border="0" class="variablelist">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody><tr>
<td><p><span class="term"><em class="parameter"><code>bus</code></em> :</span></p></td>
<td>a <a class="link" href="GstBus.html" title="GstBus"><span class="type">GstBus</span></a> on which you want to receive the "message" signal</td>
</tr></tbody>
</table></div>
</div>
<hr>
<div class="refsect2">
<a name="gst-bus-add-signal-watch-full"></a><h3>gst_bus_add_signal_watch_full ()</h3>
<pre class="programlisting"><span class="returnvalue">void</span> gst_bus_add_signal_watch_full (<em class="parameter"><code><a class="link" href="GstBus.html" title="GstBus"><span class="type">GstBus</span></a> *bus</code></em>,
<em class="parameter"><code><a href="http://library.gnome.org/devel/glib/unstable/glib-Basic-Types.html#gint"><span class="type">gint</span></a> priority</code></em>);</pre>
<p>
Adds a bus signal watch to the default main context with the given <em class="parameter"><code>priority</code></em>
(e.g. <a href="http://library.gnome.org/devel/glib/unstable/glib-The-Main-Event-Loop.html#G-PRIORITY-DEFAULT:CAPS"><code class="literal">G_PRIORITY_DEFAULT</code></a>). It is also possible to use a non-default main
context set up using <a href="http://library.gnome.org/devel/glib/unstable/glib-The-Main-Event-Loop.html#g-main-context-push-thread-default"><code class="function">g_main_context_push_thread_default()</code></a>
(before one had to create a bus watch source and attach it to the desired
main context 'manually').
</p>
<p>
After calling this statement, the bus will emit the "message" signal for each
message posted on the bus when the main loop is running.
</p>
<p>
This function may be called multiple times. To clean up, the caller is
responsible for calling <a class="link" href="GstBus.html#gst-bus-remove-signal-watch" title="gst_bus_remove_signal_watch ()"><code class="function">gst_bus_remove_signal_watch()</code></a> as many times as this
function is called.
</p>
<p>
There can only be a single bus watch per bus, you must remove any signal
watch before you can set another type of watch.
</p>
<p>
MT safe.
</p>
<div class="variablelist"><table border="0" class="variablelist">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody>
<tr>
<td><p><span class="term"><em class="parameter"><code>bus</code></em> :</span></p></td>
<td>a <a class="link" href="GstBus.html" title="GstBus"><span class="type">GstBus</span></a> on which you want to receive the "message" signal</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>priority</code></em> :</span></p></td>
<td>The priority of the watch.</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2">
<a name="gst-bus-remove-signal-watch"></a><h3>gst_bus_remove_signal_watch ()</h3>
<pre class="programlisting"><span class="returnvalue">void</span> gst_bus_remove_signal_watch (<em class="parameter"><code><a class="link" href="GstBus.html" title="GstBus"><span class="type">GstBus</span></a> *bus</code></em>);</pre>
<p>
Removes a signal watch previously added with <a class="link" href="GstBus.html#gst-bus-add-signal-watch" title="gst_bus_add_signal_watch ()"><code class="function">gst_bus_add_signal_watch()</code></a>.
</p>
<p>
MT safe.
</p>
<div class="variablelist"><table border="0" class="variablelist">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody><tr>
<td><p><span class="term"><em class="parameter"><code>bus</code></em> :</span></p></td>
<td>a <a class="link" href="GstBus.html" title="GstBus"><span class="type">GstBus</span></a> you previously added a signal watch to</td>
</tr></tbody>
</table></div>
</div>
<hr>
<div class="refsect2">
<a name="gst-bus-poll"></a><h3>gst_bus_poll ()</h3>
<pre class="programlisting"><a class="link" href="gstreamer-GstMessage.html#GstMessage" title="struct GstMessage"><span class="returnvalue">GstMessage</span></a> * gst_bus_poll (<em class="parameter"><code><a class="link" href="GstBus.html" title="GstBus"><span class="type">GstBus</span></a> *bus</code></em>,
<em class="parameter"><code><a class="link" href="gstreamer-GstMessage.html#GstMessageType" title="enum GstMessageType"><span class="type">GstMessageType</span></a> events</code></em>,
<em class="parameter"><code><a class="link" href="GstClock.html#GstClockTime" title="GstClockTime"><span class="type">GstClockTime</span></a> timeout</code></em>);</pre>
<p>
Poll the bus for messages. Will block while waiting for messages to come.
You can specify a maximum time to poll with the <em class="parameter"><code>timeout</code></em> parameter. If
<em class="parameter"><code>timeout</code></em> is negative, this function will block indefinitely.
</p>
<p>
All messages not in <em class="parameter"><code>events</code></em> will be popped off the bus and will be ignored.
</p>
<p>
Because poll is implemented using the "message" signal enabled by
<a class="link" href="GstBus.html#gst-bus-add-signal-watch" title="gst_bus_add_signal_watch ()"><code class="function">gst_bus_add_signal_watch()</code></a>, calling <a class="link" href="GstBus.html#gst-bus-poll" title="gst_bus_poll ()"><code class="function">gst_bus_poll()</code></a> will cause the "message"
signal to be emitted for every message that poll sees. Thus a "message"
signal handler will see the same messages that this function sees -- neither
will steal messages from the other.
</p>
<p>
This function will run a main loop from the default main context when
polling.
</p>
<p>
You should never use this function, since it is pure evil. This is
especially true for GUI applications based on Gtk+ or Qt, but also for any
other non-trivial application that uses the GLib main loop. As this function
runs a GLib main loop, any callback attached to the default GLib main
context may be invoked. This could be timeouts, GUI events, I/O events etc.;
even if <a class="link" href="GstBus.html#gst-bus-poll" title="gst_bus_poll ()"><code class="function">gst_bus_poll()</code></a> is called with a 0 timeout. Any of these callbacks
may do things you do not expect, e.g. destroy the main application window or
some other resource; change other application state; display a dialog and
run another main loop until the user clicks it away. In short, using this
function may add a lot of complexity to your code through unexpected
re-entrancy and unexpected changes to your application's state.
</p>
<p>
For 0 timeouts use <a class="link" href="GstBus.html#gst-bus-pop-filtered" title="gst_bus_pop_filtered ()"><code class="function">gst_bus_pop_filtered()</code></a> instead of this function; for
other short timeouts use <a class="link" href="GstBus.html#gst-bus-timed-pop-filtered" title="gst_bus_timed_pop_filtered ()"><code class="function">gst_bus_timed_pop_filtered()</code></a>; everything else is
better handled by setting up an asynchronous bus watch and doing things
from there.
</p>
<div class="variablelist"><table border="0" class="variablelist">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody>
<tr>
<td><p><span class="term"><em class="parameter"><code>bus</code></em> :</span></p></td>
<td>a <a class="link" href="GstBus.html" title="GstBus"><span class="type">GstBus</span></a>
</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>events</code></em> :</span></p></td>
<td>a mask of <a class="link" href="gstreamer-GstMessage.html#GstMessageType" title="enum GstMessageType"><span class="type">GstMessageType</span></a>, representing the set of message types to
poll for.</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>timeout</code></em> :</span></p></td>
<td>the poll timeout, as a <a class="link" href="GstClock.html#GstClockTime" title="GstClockTime"><span class="type">GstClockTime</span></a>, or <a class="link" href="GstClock.html#GST-CLOCK-TIME-NONE:CAPS" title="GST_CLOCK_TIME_NONE"><span class="type">GST_CLOCK_TIME_NONE</span></a> to poll
indefinitely.</td>
</tr>
<tr>
<td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td>
<td>the message that was received, or NULL if the
poll timed out. The message is taken from the bus and needs to be
unreffed with <a class="link" href="gstreamer-GstMessage.html#gst-message-unref" title="gst_message_unref ()"><code class="function">gst_message_unref()</code></a> after usage. <span class="annotation">[<acronym title="Free data after the code is done."><span class="acronym">transfer full</span></acronym>]</span>
</td>
</tr>
</tbody>
</table></div>
</div>
</div>
<div class="refsect1">
<a name="GstBus.property-details"></a><h2>Property Details</h2>
<div class="refsect2">
<a name="GstBus--enable-async"></a><h3>The <code class="literal">"enable-async"</code> property</h3>
<pre class="programlisting"> "enable-async" <a href="http://library.gnome.org/devel/glib/unstable/glib-Basic-Types.html#gboolean"><span class="type">gboolean</span></a> : Write / Construct Only</pre>
<p>Enable async message delivery for bus watches and gst_bus_pop().</p>
<p>Default value: TRUE</p>
</div>
</div>
<div class="refsect1">
<a name="GstBus.signal-details"></a><h2>Signal Details</h2>
<div class="refsect2">
<a name="GstBus-message"></a><h3>The <code class="literal">"message"</code> signal</h3>
<pre class="programlisting"><span class="returnvalue">void</span> user_function (<a class="link" href="GstBus.html" title="GstBus"><span class="type">GstBus</span></a> *bus,
<a class="link" href="gstreamer-GstMessage.html#GstMessage" title="struct GstMessage"><span class="type">GstMessage</span></a> *message,
<a href="http://library.gnome.org/devel/glib/unstable/glib-Basic-Types.html#gpointer"><span class="type">gpointer</span></a> user_data) : <a href="http://library.gnome.org/devel/gobject/unstable/gobject-Signals.html#G-SIGNAL-DETAILED:CAPS"><code class="literal">Has Details</code></a></pre>
<p>
A message has been posted on the bus. This signal is emitted from a
GSource added to the mainloop. this signal will only be emitted when
there is a mainloop running.
</p>
<div class="variablelist"><table border="0" class="variablelist">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody>
<tr>
<td><p><span class="term"><em class="parameter"><code>bus</code></em> :</span></p></td>
<td>the object which received the signal</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>message</code></em> :</span></p></td>
<td>the message that has been posted asynchronously</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>user_data</code></em> :</span></p></td>
<td>user data set when the signal handler was connected.</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2">
<a name="GstBus-sync-message"></a><h3>The <code class="literal">"sync-message"</code> signal</h3>
<pre class="programlisting"><span class="returnvalue">void</span> user_function (<a class="link" href="GstBus.html" title="GstBus"><span class="type">GstBus</span></a> *bus,
<a class="link" href="gstreamer-GstMessage.html#GstMessage" title="struct GstMessage"><span class="type">GstMessage</span></a> *message,
<a href="http://library.gnome.org/devel/glib/unstable/glib-Basic-Types.html#gpointer"><span class="type">gpointer</span></a> user_data) : <a href="http://library.gnome.org/devel/gobject/unstable/gobject-Signals.html#G-SIGNAL-DETAILED:CAPS"><code class="literal">Has Details</code></a></pre>
<p>
A message has been posted on the bus. This signal is emitted from the
thread that posted the message so one has to be careful with locking.
</p>
<p>
This signal will not be emitted by default, you have to call
<a class="link" href="GstBus.html#gst-bus-enable-sync-message-emission" title="gst_bus_enable_sync_message_emission ()"><code class="function">gst_bus_enable_sync_message_emission()</code></a> before.
</p>
<div class="variablelist"><table border="0" class="variablelist">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody>
<tr>
<td><p><span class="term"><em class="parameter"><code>bus</code></em> :</span></p></td>
<td>the object which received the signal</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>message</code></em> :</span></p></td>
<td>the message that has been posted synchronously</td>
</tr>
<tr>
<td><p><span class="term"><em class="parameter"><code>user_data</code></em> :</span></p></td>
<td>user data set when the signal handler was connected.</td>
</tr>
</tbody>
</table></div>
</div>
</div>
<div class="refsect1">
<a name="GstBus.see-also"></a><h2>See Also</h2>
<a class="link" href="gstreamer-GstMessage.html#GstMessage" title="struct GstMessage"><span class="type">GstMessage</span></a>, <a class="link" href="GstElement.html" title="GstElement"><span class="type">GstElement</span></a>
</div>
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