2 * Copyright (C) 2004 Wim Taymans <wim@fluendo.com>
4 * gstbus.c: GstBus subsystem
6 * This library is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU Library General Public
8 * License as published by the Free Software Foundation; either
9 * version 2 of the License, or (at your option) any later version.
11 * This library is distributed in the hope that it will be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14 * Library General Public License for more details.
16 * You should have received a copy of the GNU Library General Public
17 * License along with this library; if not, write to the
18 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
19 * Boston, MA 02111-1307, USA.
24 * @short_description: Asynchronous message bus subsystem
25 * @see_also: #GstMessage, #GstElement
27 * The #GstBus is an object responsible for delivering #GstMessage packets in
28 * a first-in first-out way from the streaming threads (see #GstTask) to the
31 * Since the application typically only wants to deal with delivery of these
32 * messages from one thread, the GstBus will marshall the messages between
33 * different threads. This is important since the actual streaming of media
34 * is done in another thread than the application.
36 * The GstBus provides support for #GSource based notifications. This makes it
37 * possible to handle the delivery in the glib mainloop.
39 * The #GSource callback function gst_bus_async_signal_func() can be used to
40 * convert all bus messages into signal emissions.
42 * A message is posted on the bus with the gst_bus_post() method. With the
43 * gst_bus_peek() and gst_bus_pop() methods one can look at or retrieve a
44 * previously posted message.
46 * The bus can be polled with the gst_bus_poll() method. This methods blocks
47 * up to the specified timeout value until one of the specified messages types
48 * is posted on the bus. The application can then gst_bus_pop() the messages
49 * from the bus to handle them.
50 * Alternatively the application can register an asynchronous bus function
51 * using gst_bus_add_watch_full() or gst_bus_add_watch(). This function will
52 * install a #GSource in the default glib main loop and will deliver messages
53 * a short while after they have been posted. Note that the main loop should
54 * be running for the asynchronous callbacks.
56 * It is also possible to get messages from the bus without any thread
57 * marshalling with the gst_bus_set_sync_handler() method. This makes it
58 * possible to react to a message in the same thread that posted the
59 * message on the bus. This should only be used if the application is able
60 * to deal with messages from different threads.
62 * Every #GstPipeline has one bus.
64 * Note that a #GstPipeline will set its bus into flushing state when changing
65 * from READY to NULL state.
67 * Last reviewed on 2006-03-12 (0.10.5)
70 #include "gst_private.h"
75 #include <sys/types.h>
81 #define GST_CAT_DEFAULT GST_CAT_BUS
91 static void gst_bus_dispose (GObject * object);
93 static void gst_bus_set_main_context (GstBus * bus, GMainContext * ctx);
95 static GstObjectClass *parent_class = NULL;
96 static guint gst_bus_signals[LAST_SIGNAL] = { 0 };
100 guint num_sync_message_emitters;
103 GMainContext *main_context;
106 G_DEFINE_TYPE (GstBus, gst_bus, GST_TYPE_OBJECT);
108 /* fixme: do something about this */
110 marshal_VOID__MINIOBJECT (GClosure * closure, GValue * return_value,
111 guint n_param_values, const GValue * param_values, gpointer invocation_hint,
112 gpointer marshal_data)
114 typedef void (*marshalfunc_VOID__MINIOBJECT) (gpointer obj, gpointer arg1,
116 register marshalfunc_VOID__MINIOBJECT callback;
117 register GCClosure *cc = (GCClosure *) closure;
118 register gpointer data1, data2;
120 g_return_if_fail (n_param_values == 2);
122 if (G_CCLOSURE_SWAP_DATA (closure)) {
123 data1 = closure->data;
124 data2 = g_value_peek_pointer (param_values + 0);
126 data1 = g_value_peek_pointer (param_values + 0);
127 data2 = closure->data;
130 (marshalfunc_VOID__MINIOBJECT) (marshal_data ? marshal_data :
133 callback (data1, gst_value_get_mini_object (param_values + 1), data2);
137 gst_bus_class_init (GstBusClass * klass)
139 GObjectClass *gobject_class = (GObjectClass *) klass;
141 parent_class = g_type_class_peek_parent (klass);
143 gobject_class->dispose = gst_bus_dispose;
146 * GstBus::sync-message:
147 * @bus: the object which received the signal
148 * @message: the message that has been posted synchronously
150 * A message has been posted on the bus. This signal is emitted from the
151 * thread that posted the message so one has to be careful with locking.
153 * This signal will not be emitted by default, you have to set up
154 * gst_bus_sync_signal_handler() as a sync handler if you want this
155 * signal to be emitted when a message is posted on the bus, like this:
157 * gst_bus_set_sync_handler (bus, gst_bus_sync_signal_handler, yourdata);
160 gst_bus_signals[SYNC_MESSAGE] =
161 g_signal_new ("sync-message", G_TYPE_FROM_CLASS (klass),
162 G_SIGNAL_RUN_LAST | G_SIGNAL_DETAILED,
163 G_STRUCT_OFFSET (GstBusClass, sync_message), NULL, NULL,
164 marshal_VOID__MINIOBJECT, G_TYPE_NONE, 1, GST_TYPE_MESSAGE);
168 * @bus: the object which received the signal
169 * @message: the message that has been posted asynchronously
171 * A message has been posted on the bus. This signal is emitted from a
172 * GSource added to the mainloop. this signal will only be emitted when
173 * there is a mainloop running.
175 gst_bus_signals[ASYNC_MESSAGE] =
176 g_signal_new ("message", G_TYPE_FROM_CLASS (klass),
177 G_SIGNAL_RUN_LAST | G_SIGNAL_DETAILED,
178 G_STRUCT_OFFSET (GstBusClass, message), NULL, NULL,
179 marshal_VOID__MINIOBJECT, G_TYPE_NONE, 1, GST_TYPE_MESSAGE);
181 g_type_class_add_private (klass, sizeof (GstBusPrivate));
185 gst_bus_init (GstBus * bus)
187 bus->queue = g_queue_new ();
188 bus->queue_lock = g_mutex_new ();
190 bus->priv = G_TYPE_INSTANCE_GET_PRIVATE (bus, GST_TYPE_BUS, GstBusPrivate);
191 bus->priv->queue_cond = g_cond_new ();
193 GST_DEBUG_OBJECT (bus, "created");
197 gst_bus_dispose (GObject * object)
199 GstBus *bus = GST_BUS (object);
204 g_mutex_lock (bus->queue_lock);
206 message = g_queue_pop_head (bus->queue);
208 gst_message_unref (message);
209 } while (message != NULL);
210 g_queue_free (bus->queue);
212 g_mutex_unlock (bus->queue_lock);
213 g_mutex_free (bus->queue_lock);
214 bus->queue_lock = NULL;
215 g_cond_free (bus->priv->queue_cond);
216 bus->priv->queue_cond = NULL;
219 if (bus->priv->main_context) {
220 g_main_context_unref (bus->priv->main_context);
221 bus->priv->main_context = NULL;
224 G_OBJECT_CLASS (parent_class)->dispose (object);
228 gst_bus_wakeup_main_context (GstBus * bus)
232 GST_OBJECT_LOCK (bus);
233 if ((ctx = bus->priv->main_context))
234 g_main_context_ref (ctx);
235 GST_OBJECT_UNLOCK (bus);
237 g_main_context_wakeup (ctx);
240 g_main_context_unref (ctx);
244 gst_bus_set_main_context (GstBus * bus, GMainContext * ctx)
246 GST_OBJECT_LOCK (bus);
248 if (bus->priv->main_context != NULL) {
249 g_main_context_unref (bus->priv->main_context);
250 bus->priv->main_context = NULL;
254 bus->priv->main_context = g_main_context_ref (ctx);
257 GST_DEBUG_OBJECT (bus, "setting main context to %p, GLib default context: %p",
258 ctx, g_main_context_default ());
260 GST_OBJECT_UNLOCK (bus);
266 * Creates a new #GstBus instance.
268 * Returns: (transfer full): a new #GstBus instance
275 result = g_object_newv (gst_bus_get_type (), 0, NULL);
276 GST_DEBUG_OBJECT (result, "created new bus");
283 * @bus: a #GstBus to post on
284 * @message: (transfer full): the #GstMessage to post
286 * Post a message on the given bus. Ownership of the message
287 * is taken by the bus.
289 * Returns: TRUE if the message could be posted, FALSE if the bus is flushing.
294 gst_bus_post (GstBus * bus, GstMessage * message)
296 GstBusSyncReply reply = GST_BUS_PASS;
297 GstBusSyncHandler handler;
298 gboolean emit_sync_message;
299 gpointer handler_data;
301 g_return_val_if_fail (GST_IS_BUS (bus), FALSE);
302 g_return_val_if_fail (GST_IS_MESSAGE (message), FALSE);
304 GST_DEBUG_OBJECT (bus, "[msg %p] posting on bus, type %s, %" GST_PTR_FORMAT
305 " from source %" GST_PTR_FORMAT,
306 message, GST_MESSAGE_TYPE_NAME (message), message->structure,
309 GST_OBJECT_LOCK (bus);
310 /* check if the bus is flushing */
311 if (GST_OBJECT_FLAG_IS_SET (bus, GST_BUS_FLUSHING))
314 handler = bus->sync_handler;
315 handler_data = bus->sync_handler_data;
316 emit_sync_message = bus->priv->num_sync_message_emitters > 0;
317 GST_OBJECT_UNLOCK (bus);
319 /* first call the sync handler if it is installed */
321 reply = handler (bus, message, handler_data);
323 /* emit sync-message if requested to do so via
324 gst_bus_enable_sync_message_emission. terrible but effective */
325 if (emit_sync_message && reply != GST_BUS_DROP
326 && handler != gst_bus_sync_signal_handler)
327 gst_bus_sync_signal_handler (bus, message, NULL);
329 /* now see what we should do with the message */
332 /* drop the message */
333 GST_DEBUG_OBJECT (bus, "[msg %p] dropped", message);
336 /* pass the message to the async queue, refcount passed in the queue */
337 GST_DEBUG_OBJECT (bus, "[msg %p] pushing on async queue", message);
338 g_mutex_lock (bus->queue_lock);
339 g_queue_push_tail (bus->queue, message);
340 g_cond_broadcast (bus->priv->queue_cond);
341 g_mutex_unlock (bus->queue_lock);
342 GST_DEBUG_OBJECT (bus, "[msg %p] pushed on async queue", message);
344 gst_bus_wakeup_main_context (bus);
349 /* async delivery, we need a mutex and a cond to block
351 GMutex *lock = g_mutex_new ();
352 GCond *cond = g_cond_new ();
354 GST_MESSAGE_COND (message) = cond;
355 GST_MESSAGE_GET_LOCK (message) = lock;
357 GST_DEBUG_OBJECT (bus, "[msg %p] waiting for async delivery", message);
359 /* now we lock the message mutex, send the message to the async
360 * queue. When the message is handled by the app and destroyed,
361 * the cond will be signalled and we can continue */
363 g_mutex_lock (bus->queue_lock);
364 g_queue_push_tail (bus->queue, message);
365 g_cond_broadcast (bus->priv->queue_cond);
366 g_mutex_unlock (bus->queue_lock);
368 gst_bus_wakeup_main_context (bus);
370 /* now block till the message is freed */
371 g_cond_wait (cond, lock);
372 g_mutex_unlock (lock);
374 GST_DEBUG_OBJECT (bus, "[msg %p] delivered asynchronously", message);
381 g_warning ("invalid return from bus sync handler");
389 GST_DEBUG_OBJECT (bus, "bus is flushing");
390 gst_message_unref (message);
391 GST_OBJECT_UNLOCK (bus);
398 * gst_bus_have_pending:
399 * @bus: a #GstBus to check
401 * Check if there are pending messages on the bus that
404 * Returns: TRUE if there are messages on the bus to be handled, FALSE
410 gst_bus_have_pending (GstBus * bus)
414 g_return_val_if_fail (GST_IS_BUS (bus), FALSE);
416 g_mutex_lock (bus->queue_lock);
417 /* see if there is a message on the bus */
418 result = !g_queue_is_empty (bus->queue);
419 g_mutex_unlock (bus->queue_lock);
425 * gst_bus_set_flushing:
427 * @flushing: whether or not to flush the bus
429 * If @flushing, flush out and unref any messages queued in the bus. Releases
430 * references to the message origin objects. Will flush future messages until
431 * gst_bus_set_flushing() sets @flushing to #FALSE.
436 gst_bus_set_flushing (GstBus * bus, gboolean flushing)
440 GST_OBJECT_LOCK (bus);
443 GST_OBJECT_FLAG_SET (bus, GST_BUS_FLUSHING);
445 GST_DEBUG_OBJECT (bus, "set bus flushing");
447 while ((message = gst_bus_pop (bus)))
448 gst_message_unref (message);
450 GST_DEBUG_OBJECT (bus, "unset bus flushing");
451 GST_OBJECT_FLAG_UNSET (bus, GST_BUS_FLUSHING);
454 GST_OBJECT_UNLOCK (bus);
458 * gst_bus_timed_pop_filtered:
459 * @bus: a #GstBus to pop from
460 * @timeout: a timeout in nanoseconds, or GST_CLOCK_TIME_NONE to wait forever
461 * @types: message types to take into account, GST_MESSAGE_ANY for any type
463 * Get a message from the bus whose type matches the message type mask @types,
464 * waiting up to the specified timeout (and discarding any messages that do not
465 * match the mask provided).
467 * If @timeout is 0, this function behaves like gst_bus_pop_filtered(). If
468 * @timeout is #GST_CLOCK_TIME_NONE, this function will block forever until a
469 * matching message was posted on the bus.
471 * Returns: (transfer full): a #GstMessage matching the filter in @types,
472 * or NULL if no matching message was found on the bus until the timeout
473 * expired. The message is taken from the bus and needs to be unreffed
474 * with gst_message_unref() after usage.
481 gst_bus_timed_pop_filtered (GstBus * bus, GstClockTime timeout,
482 GstMessageType types)
485 GTimeVal *timeval, abstimeout;
486 gboolean first_round = TRUE;
488 g_return_val_if_fail (GST_IS_BUS (bus), NULL);
489 g_return_val_if_fail (types != 0, NULL);
491 g_mutex_lock (bus->queue_lock);
494 GST_LOG_OBJECT (bus, "have %d messages", g_queue_get_length (bus->queue));
496 while ((message = g_queue_pop_head (bus->queue))) {
497 GST_DEBUG_OBJECT (bus, "got message %p, %s from %s, type mask is %u",
498 message, GST_MESSAGE_TYPE_NAME (message),
499 GST_OBJECT_NAME (GST_MESSAGE_SRC (message)), (guint) types);
500 if ((GST_MESSAGE_TYPE (message) & types) != 0) {
501 /* exit the loop, we have a message */
504 GST_DEBUG_OBJECT (bus, "discarding message, does not match mask");
505 gst_message_unref (message);
510 /* no need to wait, exit loop */
514 if (timeout == GST_CLOCK_TIME_NONE) {
517 } else if (first_round) {
518 glong add = timeout / 1000;
521 /* no need to wait */
524 /* make timeout absolute */
525 g_get_current_time (&abstimeout);
526 g_time_val_add (&abstimeout, add);
527 timeval = &abstimeout;
529 GST_DEBUG_OBJECT (bus, "blocking for message, timeout %ld", add);
531 /* calculated the absolute end time already, no need to do it again */
532 GST_DEBUG_OBJECT (bus, "blocking for message, again");
533 timeval = &abstimeout; /* fool compiler */
535 if (!g_cond_timed_wait (bus->priv->queue_cond, bus->queue_lock, timeval)) {
536 GST_INFO_OBJECT (bus, "timed out, breaking loop");
539 GST_INFO_OBJECT (bus, "we got woken up, recheck for message");
545 g_mutex_unlock (bus->queue_lock);
553 * @bus: a #GstBus to pop
554 * @timeout: a timeout
556 * Get a message from the bus, waiting up to the specified timeout.
558 * If @timeout is 0, this function behaves like gst_bus_pop(). If @timeout is
559 * #GST_CLOCK_TIME_NONE, this function will block forever until a message was
562 * Returns: (transfer full): the #GstMessage that is on the bus after the
563 * specified timeout or NULL if the bus is empty after the timeout expired.
564 * The message is taken from the bus and needs to be unreffed with
565 * gst_message_unref() after usage.
572 gst_bus_timed_pop (GstBus * bus, GstClockTime timeout)
574 g_return_val_if_fail (GST_IS_BUS (bus), NULL);
576 return gst_bus_timed_pop_filtered (bus, timeout, GST_MESSAGE_ANY);
580 * gst_bus_pop_filtered:
581 * @bus: a #GstBus to pop
582 * @types: message types to take into account
584 * Get a message matching @type from the bus. Will discard all messages on
585 * the bus that do not match @type and that have been posted before the first
586 * message that does match @type. If there is no message matching @type on
587 * the bus, all messages will be discarded.
589 * Returns: (transfer full): the next #GstMessage matching @type that is on
590 * the bus, or NULL if the bus is empty or there is no message matching
591 * @type. The message is taken from the bus and needs to be unreffed with
592 * gst_message_unref() after usage.
599 gst_bus_pop_filtered (GstBus * bus, GstMessageType types)
601 g_return_val_if_fail (GST_IS_BUS (bus), NULL);
602 g_return_val_if_fail (types != 0, NULL);
604 return gst_bus_timed_pop_filtered (bus, 0, types);
609 * @bus: a #GstBus to pop
611 * Get a message from the bus.
613 * Returns: (transfer full): the #GstMessage that is on the bus, or NULL if the
614 * bus is empty. The message is taken from the bus and needs to be unreffed
615 * with gst_message_unref() after usage.
620 gst_bus_pop (GstBus * bus)
622 g_return_val_if_fail (GST_IS_BUS (bus), NULL);
624 return gst_bus_timed_pop_filtered (bus, 0, GST_MESSAGE_ANY);
631 * Peek the message on the top of the bus' queue. The message will remain
632 * on the bus' message queue. A reference is returned, and needs to be unreffed
635 * Returns: (transfer full): the #GstMessage that is on the bus, or NULL if the
641 gst_bus_peek (GstBus * bus)
645 g_return_val_if_fail (GST_IS_BUS (bus), NULL);
647 g_mutex_lock (bus->queue_lock);
648 message = g_queue_peek_head (bus->queue);
650 gst_message_ref (message);
651 g_mutex_unlock (bus->queue_lock);
653 GST_DEBUG_OBJECT (bus, "peek on bus, got message %p", message);
659 * gst_bus_set_sync_handler:
660 * @bus: a #GstBus to install the handler on
661 * @func: The handler function to install
662 * @data: User data that will be sent to the handler function.
664 * Sets the synchronous handler on the bus. The function will be called
665 * every time a new message is posted on the bus. Note that the function
666 * will be called in the same thread context as the posting object. This
667 * function is usually only called by the creator of the bus. Applications
668 * should handle messages asynchronously using the gst_bus watch and poll
671 * You cannot replace an existing sync_handler. You can pass NULL to this
672 * function, which will clear the existing handler.
675 gst_bus_set_sync_handler (GstBus * bus, GstBusSyncHandler func, gpointer data)
677 g_return_if_fail (GST_IS_BUS (bus));
679 GST_OBJECT_LOCK (bus);
681 /* Assert if the user attempts to replace an existing sync_handler,
682 * other than to clear it */
683 if (func != NULL && bus->sync_handler != NULL)
686 bus->sync_handler = func;
687 bus->sync_handler_data = data;
688 GST_OBJECT_UNLOCK (bus);
694 GST_OBJECT_UNLOCK (bus);
695 g_warning ("cannot replace existing sync handler");
700 /* GSource for the bus
710 gst_bus_source_prepare (GSource * source, gint * timeout)
712 GstBusSource *bsrc = (GstBusSource *) source;
714 /* we do this here now that we know that we're attached to a main context
715 * (we don't support detaching a source from a main context and then
716 * re-attaching it to a different main context) */
717 if (G_UNLIKELY (!bsrc->inited)) {
718 gst_bus_set_main_context (bsrc->bus, g_source_get_context (source));
723 return gst_bus_have_pending (bsrc->bus);
727 gst_bus_source_check (GSource * source)
729 GstBusSource *bsrc = (GstBusSource *) source;
731 return gst_bus_have_pending (bsrc->bus);
735 gst_bus_source_dispatch (GSource * source, GSourceFunc callback,
738 GstBusFunc handler = (GstBusFunc) callback;
739 GstBusSource *bsource = (GstBusSource *) source;
744 g_return_val_if_fail (bsource != NULL, FALSE);
748 g_return_val_if_fail (GST_IS_BUS (bus), FALSE);
750 message = gst_bus_pop (bus);
752 /* The message queue might be empty if some other thread or callback set
753 * the bus to flushing between check/prepare and dispatch */
754 if (G_UNLIKELY (message == NULL))
760 GST_DEBUG_OBJECT (bus, "source %p calling dispatch with %" GST_PTR_FORMAT,
763 keep = handler (bus, message, user_data);
764 gst_message_unref (message);
766 GST_DEBUG_OBJECT (bus, "source %p handler returns %d", source, keep);
772 g_warning ("GstBus watch dispatched without callback\n"
773 "You must call g_source_set_callback().");
774 gst_message_unref (message);
780 gst_bus_source_finalize (GSource * source)
782 GstBusSource *bsource = (GstBusSource *) source;
787 GST_DEBUG_OBJECT (bus, "finalize source %p", source);
789 GST_OBJECT_LOCK (bus);
790 if (bus->priv->watch_id == source)
791 bus->priv->watch_id = NULL;
792 GST_OBJECT_UNLOCK (bus);
794 gst_bus_set_main_context (bsource->bus, NULL);
795 gst_object_unref (bsource->bus);
799 static GSourceFuncs gst_bus_source_funcs = {
800 gst_bus_source_prepare,
801 gst_bus_source_check,
802 gst_bus_source_dispatch,
803 gst_bus_source_finalize
807 * gst_bus_create_watch:
808 * @bus: a #GstBus to create the watch for
810 * Create watch for this bus. The GSource will be dispatched whenever
811 * a message is on the bus. After the GSource is dispatched, the
812 * message is popped off the bus and unreffed.
814 * Returns: (transfer full): a #GSource that can be added to a mainloop.
817 gst_bus_create_watch (GstBus * bus)
819 GstBusSource *source;
821 g_return_val_if_fail (GST_IS_BUS (bus), NULL);
823 source = (GstBusSource *) g_source_new (&gst_bus_source_funcs,
824 sizeof (GstBusSource));
826 #if GLIB_CHECK_VERSION(2,26,0)
827 g_source_set_name ((GSource *) source, "GStreamer message bus watch");
830 source->bus = gst_object_ref (bus);
831 source->inited = FALSE;
833 return (GSource *) source;
836 /* must be called with the bus OBJECT LOCK */
838 gst_bus_add_watch_full_unlocked (GstBus * bus, gint priority,
839 GstBusFunc func, gpointer user_data, GDestroyNotify notify)
845 if (bus->priv->watch_id) {
846 GST_ERROR_OBJECT (bus,
847 "Tried to add new watch while one was already there");
851 source = gst_bus_create_watch (bus);
853 if (priority != G_PRIORITY_DEFAULT)
854 g_source_set_priority (source, priority);
856 g_source_set_callback (source, (GSourceFunc) func, user_data, notify);
858 ctx = g_main_context_get_thread_default ();
859 id = g_source_attach (source, ctx);
860 g_source_unref (source);
863 bus->priv->watch_id = source;
866 GST_DEBUG_OBJECT (bus, "New source %p with id %u", source, id);
871 * gst_bus_add_watch_full:
872 * @bus: a #GstBus to create the watch for.
873 * @priority: The priority of the watch.
874 * @func: A function to call when a message is received.
875 * @user_data: user data passed to @func.
876 * @notify: the function to call when the source is removed.
878 * Adds a bus watch to the default main context with the given @priority (e.g.
879 * %G_PRIORITY_DEFAULT). Since 0.10.33 it is also possible to use a non-default
880 * main context set up using g_main_context_push_thread_default() (before
881 * one had to create a bus watch source and attach it to the desired main
882 * context 'manually').
884 * This function is used to receive asynchronous messages in the main loop.
885 * There can only be a single bus watch per bus, you must remove it before you
888 * When @func is called, the message belongs to the caller; if you want to
889 * keep a copy of it, call gst_message_ref() before leaving @func.
891 * The watch can be removed using g_source_remove() or by returning FALSE
894 * Returns: The event source id.
899 gst_bus_add_watch_full (GstBus * bus, gint priority,
900 GstBusFunc func, gpointer user_data, GDestroyNotify notify)
904 g_return_val_if_fail (GST_IS_BUS (bus), 0);
906 GST_OBJECT_LOCK (bus);
907 id = gst_bus_add_watch_full_unlocked (bus, priority, func, user_data, notify);
908 GST_OBJECT_UNLOCK (bus);
915 * @bus: a #GstBus to create the watch for
916 * @func: A function to call when a message is received.
917 * @user_data: user data passed to @func.
919 * Adds a bus watch to the default main context with the default priority
920 * (%G_PRIORITY_DEFAULT). Since 0.10.33 it is also possible to use a non-default
921 * main context set up using g_main_context_push_thread_default() (before
922 * one had to create a bus watch source and attach it to the desired main
923 * context 'manually').
925 * This function is used to receive asynchronous messages in the main loop.
926 * There can only be a single bus watch per bus, you must remove it before you
929 * The watch can be removed using g_source_remove() or by returning FALSE
932 * Returns: The event source id.
937 gst_bus_add_watch (GstBus * bus, GstBusFunc func, gpointer user_data)
939 return gst_bus_add_watch_full (bus, G_PRIORITY_DEFAULT, func,
947 gboolean source_running;
948 GstMessageType events;
953 poll_func (GstBus * bus, GstMessage * message, GstBusPollData * poll_data)
957 if (!g_main_loop_is_running (poll_data->loop)) {
958 GST_DEBUG ("mainloop %p not running", poll_data->loop);
962 type = GST_MESSAGE_TYPE (message);
964 if (type & poll_data->events) {
965 g_assert (poll_data->message == NULL);
966 /* keep ref to message */
967 poll_data->message = gst_message_ref (message);
968 GST_DEBUG ("mainloop %p quit", poll_data->loop);
969 g_main_loop_quit (poll_data->loop);
971 GST_DEBUG ("type %08x does not match %08x", type, poll_data->events);
976 poll_timeout (GstBusPollData * poll_data)
978 GST_DEBUG ("mainloop %p quit", poll_data->loop);
979 g_main_loop_quit (poll_data->loop);
981 /* we don't remove the GSource as this would free our poll_data,
982 * which we still need */
987 poll_destroy (GstBusPollData * poll_data, gpointer unused)
989 poll_data->source_running = FALSE;
990 if (!poll_data->timeout_id) {
991 g_main_loop_unref (poll_data->loop);
992 g_slice_free (GstBusPollData, poll_data);
997 poll_destroy_timeout (GstBusPollData * poll_data)
999 poll_data->timeout_id = 0;
1000 if (!poll_data->source_running) {
1001 g_main_loop_unref (poll_data->loop);
1002 g_slice_free (GstBusPollData, poll_data);
1009 * @events: a mask of #GstMessageType, representing the set of message types to
1011 * @timeout: the poll timeout, as a #GstClockTimeDiff, or -1 to poll
1014 * Poll the bus for messages. Will block while waiting for messages to come.
1015 * You can specify a maximum time to poll with the @timeout parameter. If
1016 * @timeout is negative, this function will block indefinitely.
1018 * All messages not in @events will be popped off the bus and will be ignored.
1020 * Because poll is implemented using the "message" signal enabled by
1021 * gst_bus_add_signal_watch(), calling gst_bus_poll() will cause the "message"
1022 * signal to be emitted for every message that poll sees. Thus a "message"
1023 * signal handler will see the same messages that this function sees -- neither
1024 * will steal messages from the other.
1026 * This function will run a main loop from the default main context when
1029 * You should never use this function, since it is pure evil. This is
1030 * especially true for GUI applications based on Gtk+ or Qt, but also for any
1031 * other non-trivial application that uses the GLib main loop. As this function
1032 * runs a GLib main loop, any callback attached to the default GLib main
1033 * context may be invoked. This could be timeouts, GUI events, I/O events etc.;
1034 * even if gst_bus_poll() is called with a 0 timeout. Any of these callbacks
1035 * may do things you do not expect, e.g. destroy the main application window or
1036 * some other resource; change other application state; display a dialog and
1037 * run another main loop until the user clicks it away. In short, using this
1038 * function may add a lot of complexity to your code through unexpected
1039 * re-entrancy and unexpected changes to your application's state.
1041 * For 0 timeouts use gst_bus_pop_filtered() instead of this function; for
1042 * other short timeouts use gst_bus_timed_pop_filtered(); everything else is
1043 * better handled by setting up an asynchronous bus watch and doing things
1046 * Returns: (transfer full): the message that was received, or NULL if the
1047 * poll timed out. The message is taken from the bus and needs to be
1048 * unreffed with gst_message_unref() after usage.
1051 gst_bus_poll (GstBus * bus, GstMessageType events, GstClockTimeDiff timeout)
1053 GstBusPollData *poll_data;
1057 poll_data = g_slice_new (GstBusPollData);
1058 poll_data->source_running = TRUE;
1059 poll_data->loop = g_main_loop_new (NULL, FALSE);
1060 poll_data->events = events;
1061 poll_data->message = NULL;
1064 poll_data->timeout_id = g_timeout_add_full (G_PRIORITY_DEFAULT_IDLE,
1065 timeout / GST_MSECOND, (GSourceFunc) poll_timeout, poll_data,
1066 (GDestroyNotify) poll_destroy_timeout);
1068 poll_data->timeout_id = 0;
1070 id = g_signal_connect_data (bus, "message", G_CALLBACK (poll_func), poll_data,
1071 (GClosureNotify) poll_destroy, 0);
1073 /* these can be nested, so it's ok */
1074 gst_bus_add_signal_watch (bus);
1076 GST_DEBUG ("running mainloop %p", poll_data->loop);
1077 g_main_loop_run (poll_data->loop);
1078 GST_DEBUG ("mainloop stopped %p", poll_data->loop);
1080 gst_bus_remove_signal_watch (bus);
1083 ret = poll_data->message;
1085 if (poll_data->timeout_id)
1086 g_source_remove (poll_data->timeout_id);
1088 /* poll_data will be freed now */
1089 g_signal_handler_disconnect (bus, id);
1091 GST_DEBUG_OBJECT (bus, "finished poll with message %p", ret);
1097 * gst_bus_async_signal_func:
1099 * @message: the #GstMessage received
1102 * A helper #GstBusFunc that can be used to convert all asynchronous messages
1108 gst_bus_async_signal_func (GstBus * bus, GstMessage * message, gpointer data)
1112 g_return_val_if_fail (GST_IS_BUS (bus), TRUE);
1113 g_return_val_if_fail (message != NULL, TRUE);
1115 detail = gst_message_type_to_quark (GST_MESSAGE_TYPE (message));
1117 g_signal_emit (bus, gst_bus_signals[ASYNC_MESSAGE], detail, message);
1119 /* we never remove this source based on signal emission return values */
1124 * gst_bus_sync_signal_handler:
1126 * @message: the #GstMessage received
1129 * A helper GstBusSyncHandler that can be used to convert all synchronous
1130 * messages into signals.
1132 * Returns: GST_BUS_PASS
1135 gst_bus_sync_signal_handler (GstBus * bus, GstMessage * message, gpointer data)
1139 g_return_val_if_fail (GST_IS_BUS (bus), GST_BUS_DROP);
1140 g_return_val_if_fail (message != NULL, GST_BUS_DROP);
1142 detail = gst_message_type_to_quark (GST_MESSAGE_TYPE (message));
1144 g_signal_emit (bus, gst_bus_signals[SYNC_MESSAGE], detail, message);
1146 return GST_BUS_PASS;
1150 * gst_bus_enable_sync_message_emission:
1151 * @bus: a #GstBus on which you want to receive the "sync-message" signal
1153 * Instructs GStreamer to emit the "sync-message" signal after running the bus's
1154 * sync handler. This function is here so that code can ensure that they can
1155 * synchronously receive messages without having to affect what the bin's sync
1158 * This function may be called multiple times. To clean up, the caller is
1159 * responsible for calling gst_bus_disable_sync_message_emission() as many times
1160 * as this function is called.
1162 * While this function looks similar to gst_bus_add_signal_watch(), it is not
1163 * exactly the same -- this function enables <emphasis>synchronous</emphasis> emission of
1164 * signals when messages arrive; gst_bus_add_signal_watch() adds an idle callback
1165 * to pop messages off the bus <emphasis>asynchronously</emphasis>. The sync-message signal
1166 * comes from the thread of whatever object posted the message; the "message"
1167 * signal is marshalled to the main thread via the main loop.
1172 gst_bus_enable_sync_message_emission (GstBus * bus)
1174 g_return_if_fail (GST_IS_BUS (bus));
1176 GST_OBJECT_LOCK (bus);
1177 bus->priv->num_sync_message_emitters++;
1178 GST_OBJECT_UNLOCK (bus);
1182 * gst_bus_disable_sync_message_emission:
1183 * @bus: a #GstBus on which you previously called
1184 * gst_bus_enable_sync_message_emission()
1186 * Instructs GStreamer to stop emitting the "sync-message" signal for this bus.
1187 * See gst_bus_enable_sync_message_emission() for more information.
1189 * In the event that multiple pieces of code have called
1190 * gst_bus_enable_sync_message_emission(), the sync-message emissions will only
1191 * be stopped after all calls to gst_bus_enable_sync_message_emission() were
1192 * "cancelled" by calling this function. In this way the semantics are exactly
1193 * the same as gst_object_ref() that which calls enable should also call
1199 gst_bus_disable_sync_message_emission (GstBus * bus)
1201 g_return_if_fail (GST_IS_BUS (bus));
1202 g_return_if_fail (bus->num_signal_watchers == 0);
1204 GST_OBJECT_LOCK (bus);
1205 bus->priv->num_sync_message_emitters--;
1206 GST_OBJECT_UNLOCK (bus);
1210 * gst_bus_add_signal_watch_full:
1211 * @bus: a #GstBus on which you want to receive the "message" signal
1212 * @priority: The priority of the watch.
1214 * Adds a bus signal watch to the default main context with the given @priority
1215 * (e.g. %G_PRIORITY_DEFAULT). Since 0.10.33 it is also possible to use a
1216 * non-default main context set up using g_main_context_push_thread_default()
1217 * (before one had to create a bus watch source and attach it to the desired
1218 * main context 'manually').
1220 * After calling this statement, the bus will emit the "message" signal for each
1221 * message posted on the bus when the main loop is running.
1223 * This function may be called multiple times. To clean up, the caller is
1224 * responsible for calling gst_bus_remove_signal_watch() as many times as this
1225 * function is called.
1227 * There can only be a single bus watch per bus, you must remove any signal
1228 * watch before you can set another type of watch.
1233 gst_bus_add_signal_watch_full (GstBus * bus, gint priority)
1235 g_return_if_fail (GST_IS_BUS (bus));
1237 /* I know the callees don't take this lock, so go ahead and abuse it */
1238 GST_OBJECT_LOCK (bus);
1240 if (bus->num_signal_watchers > 0)
1243 /* this should not fail because the counter above takes care of it */
1244 g_assert (bus->signal_watch_id == 0);
1246 bus->signal_watch_id =
1247 gst_bus_add_watch_full_unlocked (bus, priority, gst_bus_async_signal_func,
1250 if (G_UNLIKELY (bus->signal_watch_id == 0))
1255 bus->num_signal_watchers++;
1257 GST_OBJECT_UNLOCK (bus);
1263 g_critical ("Could not add signal watch to bus %s", GST_OBJECT_NAME (bus));
1264 GST_OBJECT_UNLOCK (bus);
1270 * gst_bus_add_signal_watch:
1271 * @bus: a #GstBus on which you want to receive the "message" signal
1273 * Adds a bus signal watch to the default main context with the default priority
1274 * (%G_PRIORITY_DEFAULT). Since 0.10.33 it is also possible to use a non-default
1275 * main context set up using g_main_context_push_thread_default() (before
1276 * one had to create a bus watch source and attach it to the desired main
1277 * context 'manually').
1279 * After calling this statement, the bus will emit the "message" signal for each
1280 * message posted on the bus.
1282 * This function may be called multiple times. To clean up, the caller is
1283 * responsible for calling gst_bus_remove_signal_watch() as many times as this
1284 * function is called.
1289 gst_bus_add_signal_watch (GstBus * bus)
1291 gst_bus_add_signal_watch_full (bus, G_PRIORITY_DEFAULT);
1295 * gst_bus_remove_signal_watch:
1296 * @bus: a #GstBus you previously added a signal watch to
1298 * Removes a signal watch previously added with gst_bus_add_signal_watch().
1303 gst_bus_remove_signal_watch (GstBus * bus)
1307 g_return_if_fail (GST_IS_BUS (bus));
1309 /* I know the callees don't take this lock, so go ahead and abuse it */
1310 GST_OBJECT_LOCK (bus);
1312 if (bus->num_signal_watchers == 0)
1315 bus->num_signal_watchers--;
1317 if (bus->num_signal_watchers > 0)
1320 id = bus->signal_watch_id;
1321 bus->signal_watch_id = 0;
1323 GST_DEBUG_OBJECT (bus, "removing signal watch %u", id);
1326 GST_OBJECT_UNLOCK (bus);
1329 g_source_remove (id);
1336 g_critical ("Bus %s has no signal watches attached", GST_OBJECT_NAME (bus));
1337 GST_OBJECT_UNLOCK (bus);