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., 51 Franklin St, Fifth Floor,
19 * Boston, MA 02110-1301, 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.
68 #include "gst_private.h"
73 #include <sys/types.h>
75 #include "gstatomicqueue.h"
80 #include "glib-compat-private.h"
82 #define GST_CAT_DEFAULT GST_CAT_BUS
92 #define DEFAULT_ENABLE_ASYNC (TRUE)
100 static void gst_bus_dispose (GObject * object);
101 static void gst_bus_finalize (GObject * object);
103 static guint gst_bus_signals[LAST_SIGNAL] = { 0 };
105 struct _GstBusPrivate
107 GstAtomicQueue *queue;
110 GstBusSyncHandler sync_handler;
111 gpointer sync_handler_data;
112 GDestroyNotify sync_handler_notify;
114 guint num_signal_watchers;
116 guint num_sync_message_emitters;
117 GSource *signal_watch;
119 gboolean enable_async;
124 #define gst_bus_parent_class parent_class
125 G_DEFINE_TYPE (GstBus, gst_bus, GST_TYPE_OBJECT);
128 gst_bus_set_property (GObject * object,
129 guint prop_id, const GValue * value, GParamSpec * pspec)
131 GstBus *bus = GST_BUS_CAST (object);
134 case PROP_ENABLE_ASYNC:
135 bus->priv->enable_async = g_value_get_boolean (value);
138 G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
144 gst_bus_constructed (GObject * object)
146 GstBus *bus = GST_BUS_CAST (object);
148 if (bus->priv->enable_async) {
149 bus->priv->poll = gst_poll_new_timer ();
150 gst_poll_get_read_gpollfd (bus->priv->poll, &bus->priv->pollfd);
155 gst_bus_class_init (GstBusClass * klass)
157 GObjectClass *gobject_class = (GObjectClass *) klass;
159 gobject_class->dispose = gst_bus_dispose;
160 gobject_class->finalize = gst_bus_finalize;
161 gobject_class->set_property = gst_bus_set_property;
162 gobject_class->constructed = gst_bus_constructed;
165 * GstBus::enable-async:
167 * Enable async message delivery support for bus watches,
168 * gst_bus_pop() and similar API. Without this only the
169 * synchronous message handlers are called.
171 * This property is used to create the child element buses
174 g_object_class_install_property (gobject_class, PROP_ENABLE_ASYNC,
175 g_param_spec_boolean ("enable-async", "Enable Async",
176 "Enable async message delivery for bus watches and gst_bus_pop()",
177 DEFAULT_ENABLE_ASYNC,
178 G_PARAM_CONSTRUCT_ONLY | G_PARAM_WRITABLE | G_PARAM_STATIC_STRINGS));
181 * GstBus::sync-message:
182 * @bus: the object which received the signal
183 * @message: the message that has been posted synchronously
185 * A message has been posted on the bus. This signal is emitted from the
186 * thread that posted the message so one has to be careful with locking.
188 * This signal will not be emitted by default, you have to call
189 * gst_bus_enable_sync_message_emission() before.
191 gst_bus_signals[SYNC_MESSAGE] =
192 g_signal_new ("sync-message", G_TYPE_FROM_CLASS (klass),
193 G_SIGNAL_RUN_LAST | G_SIGNAL_DETAILED,
194 G_STRUCT_OFFSET (GstBusClass, sync_message), NULL, NULL,
195 g_cclosure_marshal_generic, G_TYPE_NONE, 1, GST_TYPE_MESSAGE);
199 * @bus: the object which received the signal
200 * @message: the message that has been posted asynchronously
202 * A message has been posted on the bus. This signal is emitted from a
203 * GSource added to the mainloop. this signal will only be emitted when
204 * there is a mainloop running.
206 gst_bus_signals[ASYNC_MESSAGE] =
207 g_signal_new ("message", G_TYPE_FROM_CLASS (klass),
208 G_SIGNAL_RUN_LAST | G_SIGNAL_DETAILED,
209 G_STRUCT_OFFSET (GstBusClass, message), NULL, NULL,
210 g_cclosure_marshal_generic, G_TYPE_NONE, 1, GST_TYPE_MESSAGE);
212 g_type_class_add_private (klass, sizeof (GstBusPrivate));
216 gst_bus_init (GstBus * bus)
218 bus->priv = G_TYPE_INSTANCE_GET_PRIVATE (bus, GST_TYPE_BUS, GstBusPrivate);
219 bus->priv->enable_async = DEFAULT_ENABLE_ASYNC;
220 g_mutex_init (&bus->priv->queue_lock);
221 bus->priv->queue = gst_atomic_queue_new (32);
223 /* clear floating flag */
224 gst_object_ref_sink (bus);
226 GST_DEBUG_OBJECT (bus, "created");
230 gst_bus_dispose (GObject * object)
232 GstBus *bus = GST_BUS (object);
234 if (bus->priv->queue) {
237 g_mutex_lock (&bus->priv->queue_lock);
239 message = gst_atomic_queue_pop (bus->priv->queue);
241 gst_message_unref (message);
242 } while (message != NULL);
243 gst_atomic_queue_unref (bus->priv->queue);
244 bus->priv->queue = NULL;
245 g_mutex_unlock (&bus->priv->queue_lock);
246 g_mutex_clear (&bus->priv->queue_lock);
249 gst_poll_free (bus->priv->poll);
250 bus->priv->poll = NULL;
253 G_OBJECT_CLASS (parent_class)->dispose (object);
257 gst_bus_finalize (GObject * object)
259 GstBus *bus = GST_BUS (object);
261 if (bus->priv->sync_handler_notify)
262 bus->priv->sync_handler_notify (bus->priv->sync_handler_data);
264 G_OBJECT_CLASS (parent_class)->finalize (object);
270 * Creates a new #GstBus instance.
272 * Returns: (transfer full): a new #GstBus instance
279 result = g_object_newv (gst_bus_get_type (), 0, NULL);
280 GST_DEBUG_OBJECT (result, "created new bus");
287 * @bus: a #GstBus to post on
288 * @message: (transfer full): the #GstMessage to post
290 * Post a message on the given bus. Ownership of the message
291 * is taken by the bus.
293 * Returns: %TRUE if the message could be posted, %FALSE if the bus is flushing.
298 gst_bus_post (GstBus * bus, GstMessage * message)
300 GstBusSyncReply reply = GST_BUS_PASS;
301 GstBusSyncHandler handler;
302 gboolean emit_sync_message;
303 gpointer handler_data;
305 g_return_val_if_fail (GST_IS_BUS (bus), FALSE);
306 g_return_val_if_fail (GST_IS_MESSAGE (message), FALSE);
308 GST_DEBUG_OBJECT (bus, "[msg %p] posting on bus %" GST_PTR_FORMAT, message,
311 GST_OBJECT_LOCK (bus);
312 /* check if the bus is flushing */
313 if (GST_OBJECT_FLAG_IS_SET (bus, GST_BUS_FLUSHING))
316 handler = bus->priv->sync_handler;
317 handler_data = bus->priv->sync_handler_data;
318 emit_sync_message = bus->priv->num_sync_message_emitters > 0;
319 GST_OBJECT_UNLOCK (bus);
321 /* first call the sync handler if it is installed */
323 reply = handler (bus, message, handler_data);
325 /* emit sync-message if requested to do so via
326 gst_bus_enable_sync_message_emission. terrible but effective */
327 if (emit_sync_message && reply != GST_BUS_DROP
328 && handler != gst_bus_sync_signal_handler)
329 gst_bus_sync_signal_handler (bus, message, NULL);
331 /* If this is a bus without async message delivery
332 * always drop the message */
333 if (!bus->priv->poll)
334 reply = GST_BUS_DROP;
336 /* now see what we should do with the message */
339 /* drop the message */
340 GST_DEBUG_OBJECT (bus, "[msg %p] dropped", message);
343 /* pass the message to the async queue, refcount passed in the queue */
344 GST_DEBUG_OBJECT (bus, "[msg %p] pushing on async queue", message);
345 gst_atomic_queue_push (bus->priv->queue, message);
346 gst_poll_write_control (bus->priv->poll);
347 GST_DEBUG_OBJECT (bus, "[msg %p] pushed on async queue", message);
352 /* async delivery, we need a mutex and a cond to block
354 GCond *cond = GST_MESSAGE_GET_COND (message);
355 GMutex *lock = GST_MESSAGE_GET_LOCK (message);
360 GST_DEBUG_OBJECT (bus, "[msg %p] waiting for async delivery", message);
362 /* now we lock the message mutex, send the message to the async
363 * queue. When the message is handled by the app and destroyed,
364 * the cond will be signalled and we can continue */
367 gst_atomic_queue_push (bus->priv->queue, message);
368 gst_poll_write_control (bus->priv->poll);
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);
376 g_mutex_clear (lock);
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 /* see if there is a message on the bus */
417 result = gst_atomic_queue_length (bus->priv->queue) != 0;
423 * gst_bus_set_flushing:
425 * @flushing: whether or not to flush the bus
427 * If @flushing, flush out and unref any messages queued in the bus. Releases
428 * references to the message origin objects. Will flush future messages until
429 * gst_bus_set_flushing() sets @flushing to %FALSE.
434 gst_bus_set_flushing (GstBus * bus, gboolean flushing)
438 GST_OBJECT_LOCK (bus);
441 GST_OBJECT_FLAG_SET (bus, GST_BUS_FLUSHING);
443 GST_DEBUG_OBJECT (bus, "set bus flushing");
445 while ((message = gst_bus_pop (bus)))
446 gst_message_unref (message);
448 GST_DEBUG_OBJECT (bus, "unset bus flushing");
449 GST_OBJECT_FLAG_UNSET (bus, GST_BUS_FLUSHING);
452 GST_OBJECT_UNLOCK (bus);
456 * gst_bus_timed_pop_filtered:
457 * @bus: a #GstBus to pop from
458 * @timeout: a timeout in nanoseconds, or GST_CLOCK_TIME_NONE to wait forever
459 * @types: message types to take into account, GST_MESSAGE_ANY for any type
461 * Get a message from the bus whose type matches the message type mask @types,
462 * waiting up to the specified timeout (and discarding any messages that do not
463 * match the mask provided).
465 * If @timeout is 0, this function behaves like gst_bus_pop_filtered(). If
466 * @timeout is #GST_CLOCK_TIME_NONE, this function will block forever until a
467 * matching message was posted on the bus.
469 * Returns: (transfer full) (nullable): a #GstMessage matching the
470 * filter in @types, or %NULL if no matching message was found on
471 * the bus until the timeout expired. The message is taken from
472 * the bus and needs to be unreffed with gst_message_unref() after
478 gst_bus_timed_pop_filtered (GstBus * bus, GstClockTime timeout,
479 GstMessageType types)
483 gboolean first_round = TRUE;
484 GstClockTime elapsed = 0;
486 g_return_val_if_fail (GST_IS_BUS (bus), NULL);
487 g_return_val_if_fail (types != 0, NULL);
488 g_return_val_if_fail (timeout == 0 || bus->priv->poll != NULL, NULL);
490 g_mutex_lock (&bus->priv->queue_lock);
495 GST_LOG_OBJECT (bus, "have %d messages",
496 gst_atomic_queue_length (bus->priv->queue));
498 while ((message = gst_atomic_queue_pop (bus->priv->queue))) {
500 gst_poll_read_control (bus->priv->poll);
502 GST_DEBUG_OBJECT (bus, "got message %p, %s from %s, type mask is %u",
503 message, GST_MESSAGE_TYPE_NAME (message),
504 GST_MESSAGE_SRC_NAME (message), (guint) types);
505 if ((GST_MESSAGE_TYPE (message) & types) != 0) {
506 /* Extra check to ensure extended types don't get matched unless
508 if ((GST_MESSAGE_TYPE_IS_EXTENDED (message) == FALSE)
509 || (types & GST_MESSAGE_EXTENDED)) {
510 /* exit the loop, we have a message */
515 GST_DEBUG_OBJECT (bus, "discarding message, does not match mask");
516 gst_message_unref (message);
520 /* no need to wait, exit loop */
524 else if (timeout != GST_CLOCK_TIME_NONE) {
526 g_get_current_time (&then);
529 g_get_current_time (&now);
531 elapsed = GST_TIMEVAL_TO_TIME (now) - GST_TIMEVAL_TO_TIME (then);
533 if (elapsed > timeout)
538 /* only here in timeout case */
539 g_assert (bus->priv->poll);
540 g_mutex_unlock (&bus->priv->queue_lock);
541 ret = gst_poll_wait (bus->priv->poll, timeout - elapsed);
542 g_mutex_lock (&bus->priv->queue_lock);
545 GST_INFO_OBJECT (bus, "timed out, breaking loop");
548 GST_INFO_OBJECT (bus, "we got woken up, recheck for message");
554 g_mutex_unlock (&bus->priv->queue_lock);
562 * @bus: a #GstBus to pop
563 * @timeout: a timeout
565 * Get a message from the bus, waiting up to the specified timeout.
567 * If @timeout is 0, this function behaves like gst_bus_pop(). If @timeout is
568 * #GST_CLOCK_TIME_NONE, this function will block forever until a message was
571 * Returns: (transfer full) (nullable): the #GstMessage that is on the
572 * bus after the specified timeout or %NULL if the bus is empty
573 * after the timeout expired. The message is taken from the bus
574 * and needs to be unreffed with gst_message_unref() after usage.
579 gst_bus_timed_pop (GstBus * bus, GstClockTime timeout)
581 g_return_val_if_fail (GST_IS_BUS (bus), NULL);
583 return gst_bus_timed_pop_filtered (bus, timeout, GST_MESSAGE_ANY);
587 * gst_bus_pop_filtered:
588 * @bus: a #GstBus to pop
589 * @types: message types to take into account
591 * Get a message matching @type from the bus. Will discard all messages on
592 * the bus that do not match @type and that have been posted before the first
593 * message that does match @type. If there is no message matching @type on
594 * the bus, all messages will be discarded. It is not possible to use message
595 * enums beyond #GST_MESSAGE_EXTENDED in the @events mask.
597 * Returns: (transfer full) (nullable): the next #GstMessage matching
598 * @type that is on the bus, or %NULL if the bus is empty or there
599 * is no message matching @type. The message is taken from the bus
600 * and needs to be unreffed with gst_message_unref() after usage.
605 gst_bus_pop_filtered (GstBus * bus, GstMessageType types)
607 g_return_val_if_fail (GST_IS_BUS (bus), NULL);
608 g_return_val_if_fail (types != 0, NULL);
610 return gst_bus_timed_pop_filtered (bus, 0, types);
615 * @bus: a #GstBus to pop
617 * Get a message from the bus.
619 * Returns: (transfer full) (nullable): the #GstMessage that is on the
620 * bus, or %NULL if the bus is empty. The message is taken from
621 * the bus and needs to be unreffed with gst_message_unref() after
627 gst_bus_pop (GstBus * bus)
629 g_return_val_if_fail (GST_IS_BUS (bus), NULL);
631 return gst_bus_timed_pop_filtered (bus, 0, GST_MESSAGE_ANY);
638 * Peek the message on the top of the bus' queue. The message will remain
639 * on the bus' message queue. A reference is returned, and needs to be unreffed
642 * Returns: (transfer full) (nullable): the #GstMessage that is on the
643 * bus, or %NULL if the bus is empty.
648 gst_bus_peek (GstBus * bus)
652 g_return_val_if_fail (GST_IS_BUS (bus), NULL);
654 g_mutex_lock (&bus->priv->queue_lock);
655 message = gst_atomic_queue_peek (bus->priv->queue);
657 gst_message_ref (message);
658 g_mutex_unlock (&bus->priv->queue_lock);
660 GST_DEBUG_OBJECT (bus, "peek on bus, got message %p", message);
666 * gst_bus_set_sync_handler:
667 * @bus: a #GstBus to install the handler on
668 * @func: (allow-none): The handler function to install
669 * @user_data: User data that will be sent to the handler function.
670 * @notify: called when @user_data becomes unused
672 * Sets the synchronous handler on the bus. The function will be called
673 * every time a new message is posted on the bus. Note that the function
674 * will be called in the same thread context as the posting object. This
675 * function is usually only called by the creator of the bus. Applications
676 * should handle messages asynchronously using the gst_bus watch and poll
679 * You cannot replace an existing sync_handler. You can pass %NULL to this
680 * function, which will clear the existing handler.
683 gst_bus_set_sync_handler (GstBus * bus, GstBusSyncHandler func,
684 gpointer user_data, GDestroyNotify notify)
686 GDestroyNotify old_notify;
688 g_return_if_fail (GST_IS_BUS (bus));
690 GST_OBJECT_LOCK (bus);
691 /* Assert if the user attempts to replace an existing sync_handler,
692 * other than to clear it */
693 if (func != NULL && bus->priv->sync_handler != NULL)
696 if ((old_notify = bus->priv->sync_handler_notify)) {
697 gpointer old_data = bus->priv->sync_handler_data;
699 bus->priv->sync_handler_data = NULL;
700 bus->priv->sync_handler_notify = NULL;
701 GST_OBJECT_UNLOCK (bus);
703 old_notify (old_data);
705 GST_OBJECT_LOCK (bus);
707 bus->priv->sync_handler = func;
708 bus->priv->sync_handler_data = user_data;
709 bus->priv->sync_handler_notify = notify;
710 GST_OBJECT_UNLOCK (bus);
716 GST_OBJECT_UNLOCK (bus);
717 g_warning ("cannot replace existing sync handler");
722 /* GSource for the bus
731 gst_bus_source_prepare (GSource * source, gint * timeout)
738 gst_bus_source_check (GSource * source)
740 GstBusSource *bsrc = (GstBusSource *) source;
742 return bsrc->bus->priv->pollfd.revents & (G_IO_IN | G_IO_HUP | G_IO_ERR);
746 gst_bus_source_dispatch (GSource * source, GSourceFunc callback,
749 GstBusFunc handler = (GstBusFunc) callback;
750 GstBusSource *bsource = (GstBusSource *) source;
755 g_return_val_if_fail (bsource != NULL, FALSE);
759 g_return_val_if_fail (GST_IS_BUS (bus), FALSE);
761 message = gst_bus_pop (bus);
763 /* The message queue might be empty if some other thread or callback set
764 * the bus to flushing between check/prepare and dispatch */
765 if (G_UNLIKELY (message == NULL))
771 GST_DEBUG_OBJECT (bus, "source %p calling dispatch with %" GST_PTR_FORMAT,
774 keep = handler (bus, message, user_data);
775 gst_message_unref (message);
777 GST_DEBUG_OBJECT (bus, "source %p handler returns %d", source, keep);
783 g_warning ("GstBus watch dispatched without callback\n"
784 "You must call g_source_set_callback().");
785 gst_message_unref (message);
791 gst_bus_source_finalize (GSource * source)
793 GstBusSource *bsource = (GstBusSource *) source;
798 GST_DEBUG_OBJECT (bus, "finalize source %p", source);
800 GST_OBJECT_LOCK (bus);
801 if (bus->priv->signal_watch == source)
802 bus->priv->signal_watch = NULL;
803 GST_OBJECT_UNLOCK (bus);
805 gst_object_unref (bsource->bus);
809 static GSourceFuncs gst_bus_source_funcs = {
810 gst_bus_source_prepare,
811 gst_bus_source_check,
812 gst_bus_source_dispatch,
813 gst_bus_source_finalize
817 * gst_bus_create_watch:
818 * @bus: a #GstBus to create the watch for
820 * Create watch for this bus. The GSource will be dispatched whenever
821 * a message is on the bus. After the GSource is dispatched, the
822 * message is popped off the bus and unreffed.
824 * Returns: (transfer full): a #GSource that can be added to a mainloop.
827 gst_bus_create_watch (GstBus * bus)
829 GstBusSource *source;
831 g_return_val_if_fail (GST_IS_BUS (bus), NULL);
832 g_return_val_if_fail (bus->priv->poll != NULL, NULL);
834 source = (GstBusSource *) g_source_new (&gst_bus_source_funcs,
835 sizeof (GstBusSource));
837 g_source_set_name ((GSource *) source, "GStreamer message bus watch");
839 source->bus = gst_object_ref (bus);
840 g_source_add_poll ((GSource *) source, &bus->priv->pollfd);
842 return (GSource *) source;
845 /* must be called with the bus OBJECT LOCK */
847 gst_bus_add_watch_full_unlocked (GstBus * bus, gint priority,
848 GstBusFunc func, gpointer user_data, GDestroyNotify notify)
854 if (bus->priv->signal_watch) {
855 GST_ERROR_OBJECT (bus,
856 "Tried to add new watch while one was already there");
860 source = gst_bus_create_watch (bus);
862 if (priority != G_PRIORITY_DEFAULT)
863 g_source_set_priority (source, priority);
865 g_source_set_callback (source, (GSourceFunc) func, user_data, notify);
867 ctx = g_main_context_get_thread_default ();
868 id = g_source_attach (source, ctx);
869 g_source_unref (source);
872 bus->priv->signal_watch = source;
875 GST_DEBUG_OBJECT (bus, "New source %p with id %u", source, id);
880 * gst_bus_add_watch_full:
881 * @bus: a #GstBus to create the watch for.
882 * @priority: The priority of the watch.
883 * @func: A function to call when a message is received.
884 * @user_data: user data passed to @func.
885 * @notify: the function to call when the source is removed.
887 * Adds a bus watch to the default main context with the given @priority (e.g.
888 * %G_PRIORITY_DEFAULT). It is also possible to use a non-default main
889 * context set up using g_main_context_push_thread_default() (before
890 * one had to create a bus watch source and attach it to the desired main
891 * context 'manually').
893 * This function is used to receive asynchronous messages in the main loop.
894 * There can only be a single bus watch per bus, you must remove it before you
897 * When @func is called, the message belongs to the caller; if you want to
898 * keep a copy of it, call gst_message_ref() before leaving @func.
900 * The watch can be removed using g_source_remove() or by returning %FALSE
905 * Returns: The event source id or 0 if @bus already got an event source.
906 * Rename to: gst_bus_add_watch
909 gst_bus_add_watch_full (GstBus * bus, gint priority,
910 GstBusFunc func, gpointer user_data, GDestroyNotify notify)
914 g_return_val_if_fail (GST_IS_BUS (bus), 0);
916 GST_OBJECT_LOCK (bus);
917 id = gst_bus_add_watch_full_unlocked (bus, priority, func, user_data, notify);
918 GST_OBJECT_UNLOCK (bus);
924 * gst_bus_add_watch: (skip)
925 * @bus: a #GstBus to create the watch for
926 * @func: A function to call when a message is received.
927 * @user_data: user data passed to @func.
929 * Adds a bus watch to the default main context with the default priority
930 * (%G_PRIORITY_DEFAULT). It is also possible to use a non-default main
931 * context set up using g_main_context_push_thread_default() (before
932 * one had to create a bus watch source and attach it to the desired main
933 * context 'manually').
935 * This function is used to receive asynchronous messages in the main loop.
936 * There can only be a single bus watch per bus, you must remove it before you
939 * The watch can be removed using g_source_remove() or by returning %FALSE
942 * Returns: The event source id or 0 if @bus already got an event source.
947 gst_bus_add_watch (GstBus * bus, GstBusFunc func, gpointer user_data)
949 return gst_bus_add_watch_full (bus, G_PRIORITY_DEFAULT, func,
957 gboolean source_running;
958 GstMessageType events;
963 poll_func (GstBus * bus, GstMessage * message, GstBusPollData * poll_data)
967 if (!g_main_loop_is_running (poll_data->loop)) {
968 GST_DEBUG ("mainloop %p not running", poll_data->loop);
972 type = GST_MESSAGE_TYPE (message);
974 if (type & poll_data->events) {
975 g_assert (poll_data->message == NULL);
976 /* keep ref to message */
977 poll_data->message = gst_message_ref (message);
978 GST_DEBUG ("mainloop %p quit", poll_data->loop);
979 g_main_loop_quit (poll_data->loop);
981 GST_DEBUG ("type %08x does not match %08x", type, poll_data->events);
986 poll_timeout (GstBusPollData * poll_data)
988 GST_DEBUG ("mainloop %p quit", poll_data->loop);
989 g_main_loop_quit (poll_data->loop);
991 /* we don't remove the GSource as this would free our poll_data,
992 * which we still need */
997 poll_destroy (GstBusPollData * poll_data, gpointer unused)
999 poll_data->source_running = FALSE;
1000 if (!poll_data->timeout_id) {
1001 g_main_loop_unref (poll_data->loop);
1002 g_slice_free (GstBusPollData, poll_data);
1007 poll_destroy_timeout (GstBusPollData * poll_data)
1009 poll_data->timeout_id = 0;
1010 if (!poll_data->source_running) {
1011 g_main_loop_unref (poll_data->loop);
1012 g_slice_free (GstBusPollData, poll_data);
1019 * @events: a mask of #GstMessageType, representing the set of message types to
1020 * poll for (note special handling of extended message types below)
1021 * @timeout: the poll timeout, as a #GstClockTime, or #GST_CLOCK_TIME_NONE to poll
1024 * Poll the bus for messages. Will block while waiting for messages to come.
1025 * You can specify a maximum time to poll with the @timeout parameter. If
1026 * @timeout is negative, this function will block indefinitely.
1028 * All messages not in @events will be popped off the bus and will be ignored.
1029 * It is not possible to use message enums beyond #GST_MESSAGE_EXTENDED in the
1032 * Because poll is implemented using the "message" signal enabled by
1033 * gst_bus_add_signal_watch(), calling gst_bus_poll() will cause the "message"
1034 * signal to be emitted for every message that poll sees. Thus a "message"
1035 * signal handler will see the same messages that this function sees -- neither
1036 * will steal messages from the other.
1038 * This function will run a main loop from the default main context when
1041 * You should never use this function, since it is pure evil. This is
1042 * especially true for GUI applications based on Gtk+ or Qt, but also for any
1043 * other non-trivial application that uses the GLib main loop. As this function
1044 * runs a GLib main loop, any callback attached to the default GLib main
1045 * context may be invoked. This could be timeouts, GUI events, I/O events etc.;
1046 * even if gst_bus_poll() is called with a 0 timeout. Any of these callbacks
1047 * may do things you do not expect, e.g. destroy the main application window or
1048 * some other resource; change other application state; display a dialog and
1049 * run another main loop until the user clicks it away. In short, using this
1050 * function may add a lot of complexity to your code through unexpected
1051 * re-entrancy and unexpected changes to your application's state.
1053 * For 0 timeouts use gst_bus_pop_filtered() instead of this function; for
1054 * other short timeouts use gst_bus_timed_pop_filtered(); everything else is
1055 * better handled by setting up an asynchronous bus watch and doing things
1058 * Returns: (transfer full) (nullable): the message that was received,
1059 * or %NULL if the poll timed out. The message is taken from the
1060 * bus and needs to be unreffed with gst_message_unref() after
1064 gst_bus_poll (GstBus * bus, GstMessageType events, GstClockTime timeout)
1066 GstBusPollData *poll_data;
1070 poll_data = g_slice_new (GstBusPollData);
1071 poll_data->source_running = TRUE;
1072 poll_data->loop = g_main_loop_new (NULL, FALSE);
1073 poll_data->events = events;
1074 poll_data->message = NULL;
1076 if (timeout != GST_CLOCK_TIME_NONE)
1077 poll_data->timeout_id = g_timeout_add_full (G_PRIORITY_DEFAULT_IDLE,
1078 timeout / GST_MSECOND, (GSourceFunc) poll_timeout, poll_data,
1079 (GDestroyNotify) poll_destroy_timeout);
1081 poll_data->timeout_id = 0;
1083 id = g_signal_connect_data (bus, "message", G_CALLBACK (poll_func), poll_data,
1084 (GClosureNotify) poll_destroy, 0);
1086 /* these can be nested, so it's ok */
1087 gst_bus_add_signal_watch (bus);
1089 GST_DEBUG ("running mainloop %p", poll_data->loop);
1090 g_main_loop_run (poll_data->loop);
1091 GST_DEBUG ("mainloop stopped %p", poll_data->loop);
1093 gst_bus_remove_signal_watch (bus);
1096 ret = poll_data->message;
1098 if (poll_data->timeout_id)
1099 g_source_remove (poll_data->timeout_id);
1101 /* poll_data will be freed now */
1102 g_signal_handler_disconnect (bus, id);
1104 GST_DEBUG_OBJECT (bus, "finished poll with message %p", ret);
1110 * gst_bus_async_signal_func:
1112 * @message: the #GstMessage received
1115 * A helper #GstBusFunc that can be used to convert all asynchronous messages
1121 gst_bus_async_signal_func (GstBus * bus, GstMessage * message, gpointer data)
1125 g_return_val_if_fail (GST_IS_BUS (bus), TRUE);
1126 g_return_val_if_fail (message != NULL, TRUE);
1128 detail = gst_message_type_to_quark (GST_MESSAGE_TYPE (message));
1130 g_signal_emit (bus, gst_bus_signals[ASYNC_MESSAGE], detail, message);
1132 /* we never remove this source based on signal emission return values */
1137 * gst_bus_sync_signal_handler:
1139 * @message: the #GstMessage received
1142 * A helper GstBusSyncHandler that can be used to convert all synchronous
1143 * messages into signals.
1145 * Returns: GST_BUS_PASS
1148 gst_bus_sync_signal_handler (GstBus * bus, GstMessage * message, gpointer data)
1152 g_return_val_if_fail (GST_IS_BUS (bus), GST_BUS_DROP);
1153 g_return_val_if_fail (message != NULL, GST_BUS_DROP);
1155 detail = gst_message_type_to_quark (GST_MESSAGE_TYPE (message));
1157 g_signal_emit (bus, gst_bus_signals[SYNC_MESSAGE], detail, message);
1159 return GST_BUS_PASS;
1163 * gst_bus_enable_sync_message_emission:
1164 * @bus: a #GstBus on which you want to receive the "sync-message" signal
1166 * Instructs GStreamer to emit the "sync-message" signal after running the bus's
1167 * sync handler. This function is here so that code can ensure that they can
1168 * synchronously receive messages without having to affect what the bin's sync
1171 * This function may be called multiple times. To clean up, the caller is
1172 * responsible for calling gst_bus_disable_sync_message_emission() as many times
1173 * as this function is called.
1175 * While this function looks similar to gst_bus_add_signal_watch(), it is not
1176 * exactly the same -- this function enables <emphasis>synchronous</emphasis> emission of
1177 * signals when messages arrive; gst_bus_add_signal_watch() adds an idle callback
1178 * to pop messages off the bus <emphasis>asynchronously</emphasis>. The sync-message signal
1179 * comes from the thread of whatever object posted the message; the "message"
1180 * signal is marshalled to the main thread via the main loop.
1185 gst_bus_enable_sync_message_emission (GstBus * bus)
1187 g_return_if_fail (GST_IS_BUS (bus));
1189 GST_OBJECT_LOCK (bus);
1190 bus->priv->num_sync_message_emitters++;
1191 GST_OBJECT_UNLOCK (bus);
1195 * gst_bus_disable_sync_message_emission:
1196 * @bus: a #GstBus on which you previously called
1197 * gst_bus_enable_sync_message_emission()
1199 * Instructs GStreamer to stop emitting the "sync-message" signal for this bus.
1200 * See gst_bus_enable_sync_message_emission() for more information.
1202 * In the event that multiple pieces of code have called
1203 * gst_bus_enable_sync_message_emission(), the sync-message emissions will only
1204 * be stopped after all calls to gst_bus_enable_sync_message_emission() were
1205 * "cancelled" by calling this function. In this way the semantics are exactly
1206 * the same as gst_object_ref() that which calls enable should also call
1212 gst_bus_disable_sync_message_emission (GstBus * bus)
1214 g_return_if_fail (GST_IS_BUS (bus));
1215 g_return_if_fail (bus->priv->num_sync_message_emitters > 0);
1217 GST_OBJECT_LOCK (bus);
1218 bus->priv->num_sync_message_emitters--;
1219 GST_OBJECT_UNLOCK (bus);
1223 * gst_bus_add_signal_watch_full:
1224 * @bus: a #GstBus on which you want to receive the "message" signal
1225 * @priority: The priority of the watch.
1227 * Adds a bus signal watch to the default main context with the given @priority
1228 * (e.g. %G_PRIORITY_DEFAULT). It is also possible to use a non-default main
1229 * context set up using g_main_context_push_thread_default()
1230 * (before one had to create a bus watch source and attach it to the desired
1231 * main context 'manually').
1233 * After calling this statement, the bus will emit the "message" signal for each
1234 * message posted on the bus when the main loop is running.
1236 * This function may be called multiple times. To clean up, the caller is
1237 * responsible for calling gst_bus_remove_signal_watch() as many times as this
1238 * function is called.
1240 * There can only be a single bus watch per bus, you must remove any signal
1241 * watch before you can set another type of watch.
1246 gst_bus_add_signal_watch_full (GstBus * bus, gint priority)
1248 g_return_if_fail (GST_IS_BUS (bus));
1250 /* I know the callees don't take this lock, so go ahead and abuse it */
1251 GST_OBJECT_LOCK (bus);
1253 if (bus->priv->num_signal_watchers > 0)
1256 /* this should not fail because the counter above takes care of it */
1257 g_assert (!bus->priv->signal_watch);
1259 gst_bus_add_watch_full_unlocked (bus, priority, gst_bus_async_signal_func,
1262 if (G_UNLIKELY (!bus->priv->signal_watch))
1267 bus->priv->num_signal_watchers++;
1269 GST_OBJECT_UNLOCK (bus);
1275 g_critical ("Could not add signal watch to bus %s", GST_OBJECT_NAME (bus));
1276 GST_OBJECT_UNLOCK (bus);
1282 * gst_bus_add_signal_watch:
1283 * @bus: a #GstBus on which you want to receive the "message" signal
1285 * Adds a bus signal watch to the default main context with the default priority
1286 * (%G_PRIORITY_DEFAULT). It is also possible to use a non-default
1287 * main context set up using g_main_context_push_thread_default() (before
1288 * one had to create a bus watch source and attach it to the desired main
1289 * context 'manually').
1291 * After calling this statement, the bus will emit the "message" signal for each
1292 * message posted on the bus.
1294 * This function may be called multiple times. To clean up, the caller is
1295 * responsible for calling gst_bus_remove_signal_watch() as many times as this
1296 * function is called.
1301 gst_bus_add_signal_watch (GstBus * bus)
1303 gst_bus_add_signal_watch_full (bus, G_PRIORITY_DEFAULT);
1307 * gst_bus_remove_signal_watch:
1308 * @bus: a #GstBus you previously added a signal watch to
1310 * Removes a signal watch previously added with gst_bus_add_signal_watch().
1315 gst_bus_remove_signal_watch (GstBus * bus)
1317 GSource *source = NULL;
1319 g_return_if_fail (GST_IS_BUS (bus));
1321 /* I know the callees don't take this lock, so go ahead and abuse it */
1322 GST_OBJECT_LOCK (bus);
1324 if (bus->priv->num_signal_watchers == 0)
1327 bus->priv->num_signal_watchers--;
1329 if (bus->priv->num_signal_watchers > 0)
1332 GST_DEBUG_OBJECT (bus, "removing signal watch %u",
1333 g_source_get_id (bus->priv->signal_watch));
1335 source = bus->priv->signal_watch;
1338 GST_OBJECT_UNLOCK (bus);
1341 g_source_destroy (source);
1348 g_critical ("Bus %s has no signal watches attached", GST_OBJECT_NAME (bus));
1349 GST_OBJECT_UNLOCK (bus);