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>
77 #include "gstatomicqueue.h"
82 #include "glib-compat-private.h"
84 #define GST_CAT_DEFAULT GST_CAT_BUS
94 #define DEFAULT_ENABLE_ASYNC (TRUE)
102 static void gst_bus_dispose (GObject * object);
104 static guint gst_bus_signals[LAST_SIGNAL] = { 0 };
106 struct _GstBusPrivate
108 GstAtomicQueue *queue;
111 GstBusSyncHandler sync_handler;
112 gpointer sync_handler_data;
114 guint signal_watch_id;
115 guint num_signal_watchers;
117 guint num_sync_message_emitters;
120 gboolean enable_async;
125 #define gst_bus_parent_class parent_class
126 G_DEFINE_TYPE (GstBus, gst_bus, GST_TYPE_OBJECT);
129 gst_bus_set_property (GObject * object,
130 guint prop_id, const GValue * value, GParamSpec * pspec)
132 GstBus *bus = GST_BUS_CAST (object);
135 case PROP_ENABLE_ASYNC:
136 bus->priv->enable_async = g_value_get_boolean (value);
139 G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
145 gst_bus_constructed (GObject * object)
147 GstBus *bus = GST_BUS_CAST (object);
149 if (bus->priv->enable_async) {
150 bus->priv->poll = gst_poll_new_timer ();
151 gst_poll_get_read_gpollfd (bus->priv->poll, &bus->priv->pollfd);
156 gst_bus_class_init (GstBusClass * klass)
158 GObjectClass *gobject_class = (GObjectClass *) klass;
160 gobject_class->dispose = gst_bus_dispose;
161 gobject_class->set_property = gst_bus_set_property;
162 gobject_class->constructed = gst_bus_constructed;
164 /* GstBus:enable-async:
166 * Enable async message delivery support for bus watches,
167 * gst_bus_pop() and similar API. Without this only the
168 * synchronous message handlers are called.
170 * This property is used to create the child element buses
175 g_object_class_install_property (gobject_class, PROP_ENABLE_ASYNC,
176 g_param_spec_boolean ("enable-async", "Enable Async",
177 "Enable async message delivery for bus watches and gst_bus_pop()",
178 DEFAULT_ENABLE_ASYNC,
179 G_PARAM_CONSTRUCT_ONLY | G_PARAM_WRITABLE | G_PARAM_STATIC_STRINGS));
182 * GstBus::sync-message:
183 * @bus: the object which received the signal
184 * @message: the message that has been posted synchronously
186 * A message has been posted on the bus. This signal is emitted from the
187 * thread that posted the message so one has to be careful with locking.
189 * This signal will not be emitted by default, you have to set up
190 * gst_bus_sync_signal_handler() as a sync handler if you want this
191 * signal to be emitted when a message is posted on the bus, like this:
193 * gst_bus_set_sync_handler (bus, gst_bus_sync_signal_handler, yourdata);
196 gst_bus_signals[SYNC_MESSAGE] =
197 g_signal_new ("sync-message", G_TYPE_FROM_CLASS (klass),
198 G_SIGNAL_RUN_LAST | G_SIGNAL_DETAILED,
199 G_STRUCT_OFFSET (GstBusClass, sync_message), NULL, NULL,
200 g_cclosure_marshal_generic, G_TYPE_NONE, 1, GST_TYPE_MESSAGE);
204 * @bus: the object which received the signal
205 * @message: the message that has been posted asynchronously
207 * A message has been posted on the bus. This signal is emitted from a
208 * GSource added to the mainloop. this signal will only be emitted when
209 * there is a mainloop running.
211 gst_bus_signals[ASYNC_MESSAGE] =
212 g_signal_new ("message", G_TYPE_FROM_CLASS (klass),
213 G_SIGNAL_RUN_LAST | G_SIGNAL_DETAILED,
214 G_STRUCT_OFFSET (GstBusClass, message), NULL, NULL,
215 g_cclosure_marshal_generic, G_TYPE_NONE, 1, GST_TYPE_MESSAGE);
217 g_type_class_add_private (klass, sizeof (GstBusPrivate));
221 gst_bus_init (GstBus * bus)
223 bus->priv = G_TYPE_INSTANCE_GET_PRIVATE (bus, GST_TYPE_BUS, GstBusPrivate);
224 bus->priv->enable_async = DEFAULT_ENABLE_ASYNC;
225 g_mutex_init (&bus->priv->queue_lock);
226 bus->priv->queue = gst_atomic_queue_new (32);
228 GST_DEBUG_OBJECT (bus, "created");
232 gst_bus_dispose (GObject * object)
234 GstBus *bus = GST_BUS (object);
236 if (bus->priv->queue) {
239 g_mutex_lock (&bus->priv->queue_lock);
241 message = gst_atomic_queue_pop (bus->priv->queue);
243 gst_message_unref (message);
244 } while (message != NULL);
245 gst_atomic_queue_unref (bus->priv->queue);
246 bus->priv->queue = NULL;
247 g_mutex_unlock (&bus->priv->queue_lock);
248 g_mutex_clear (&bus->priv->queue_lock);
251 gst_poll_free (bus->priv->poll);
252 bus->priv->poll = NULL;
255 G_OBJECT_CLASS (parent_class)->dispose (object);
261 * Creates a new #GstBus instance.
263 * Returns: (transfer full): a new #GstBus instance
270 result = g_object_newv (gst_bus_get_type (), 0, NULL);
271 GST_DEBUG_OBJECT (result, "created new bus");
278 * @bus: a #GstBus to post on
279 * @message: (transfer full): the #GstMessage to post
281 * Post a message on the given bus. Ownership of the message
282 * is taken by the bus.
284 * Returns: TRUE if the message could be posted, FALSE if the bus is flushing.
289 gst_bus_post (GstBus * bus, GstMessage * message)
291 GstBusSyncReply reply = GST_BUS_PASS;
292 GstBusSyncHandler handler;
293 gboolean emit_sync_message;
294 gpointer handler_data;
296 g_return_val_if_fail (GST_IS_BUS (bus), FALSE);
297 g_return_val_if_fail (GST_IS_MESSAGE (message), FALSE);
299 GST_DEBUG_OBJECT (bus, "[msg %p] posting on bus %" GST_PTR_FORMAT, message,
302 GST_OBJECT_LOCK (bus);
303 /* check if the bus is flushing */
304 if (GST_OBJECT_FLAG_IS_SET (bus, GST_BUS_FLUSHING))
307 handler = bus->priv->sync_handler;
308 handler_data = bus->priv->sync_handler_data;
309 emit_sync_message = bus->priv->num_sync_message_emitters > 0;
310 GST_OBJECT_UNLOCK (bus);
312 /* first call the sync handler if it is installed */
314 reply = handler (bus, message, handler_data);
316 /* emit sync-message if requested to do so via
317 gst_bus_enable_sync_message_emission. terrible but effective */
318 if (emit_sync_message && reply != GST_BUS_DROP
319 && handler != gst_bus_sync_signal_handler)
320 gst_bus_sync_signal_handler (bus, message, NULL);
322 /* If this is a bus without async message delivery
323 * always drop the message */
324 if (!bus->priv->poll)
325 reply = GST_BUS_DROP;
327 /* now see what we should do with the message */
330 /* drop the message */
331 GST_DEBUG_OBJECT (bus, "[msg %p] dropped", message);
334 /* pass the message to the async queue, refcount passed in the queue */
335 GST_DEBUG_OBJECT (bus, "[msg %p] pushing on async queue", message);
336 gst_atomic_queue_push (bus->priv->queue, message);
337 gst_poll_write_control (bus->priv->poll);
338 GST_DEBUG_OBJECT (bus, "[msg %p] pushed on async queue", message);
343 /* async delivery, we need a mutex and a cond to block
345 GCond *cond = GST_MESSAGE_GET_COND (message);
346 GMutex *lock = GST_MESSAGE_GET_LOCK (message);
351 GST_DEBUG_OBJECT (bus, "[msg %p] waiting for async delivery", message);
353 /* now we lock the message mutex, send the message to the async
354 * queue. When the message is handled by the app and destroyed,
355 * the cond will be signalled and we can continue */
358 gst_atomic_queue_push (bus->priv->queue, message);
359 gst_poll_write_control (bus->priv->poll);
361 /* now block till the message is freed */
362 g_cond_wait (cond, lock);
363 g_mutex_unlock (lock);
365 GST_DEBUG_OBJECT (bus, "[msg %p] delivered asynchronously", message);
367 g_mutex_clear (lock);
372 g_warning ("invalid return from bus sync handler");
380 GST_DEBUG_OBJECT (bus, "bus is flushing");
381 gst_message_unref (message);
382 GST_OBJECT_UNLOCK (bus);
389 * gst_bus_have_pending:
390 * @bus: a #GstBus to check
392 * Check if there are pending messages on the bus that
395 * Returns: TRUE if there are messages on the bus to be handled, FALSE
401 gst_bus_have_pending (GstBus * bus)
405 g_return_val_if_fail (GST_IS_BUS (bus), FALSE);
407 /* see if there is a message on the bus */
408 result = gst_atomic_queue_length (bus->priv->queue) != 0;
414 * gst_bus_set_flushing:
416 * @flushing: whether or not to flush the bus
418 * If @flushing, flush out and unref any messages queued in the bus. Releases
419 * references to the message origin objects. Will flush future messages until
420 * gst_bus_set_flushing() sets @flushing to #FALSE.
425 gst_bus_set_flushing (GstBus * bus, gboolean flushing)
429 GST_OBJECT_LOCK (bus);
432 GST_OBJECT_FLAG_SET (bus, GST_BUS_FLUSHING);
434 GST_DEBUG_OBJECT (bus, "set bus flushing");
436 while ((message = gst_bus_pop (bus)))
437 gst_message_unref (message);
439 GST_DEBUG_OBJECT (bus, "unset bus flushing");
440 GST_OBJECT_FLAG_UNSET (bus, GST_BUS_FLUSHING);
443 GST_OBJECT_UNLOCK (bus);
447 * gst_bus_timed_pop_filtered:
448 * @bus: a #GstBus to pop from
449 * @timeout: a timeout in nanoseconds, or GST_CLOCK_TIME_NONE to wait forever
450 * @types: message types to take into account, GST_MESSAGE_ANY for any type
452 * Get a message from the bus whose type matches the message type mask @types,
453 * waiting up to the specified timeout (and discarding any messages that do not
454 * match the mask provided).
456 * If @timeout is 0, this function behaves like gst_bus_pop_filtered(). If
457 * @timeout is #GST_CLOCK_TIME_NONE, this function will block forever until a
458 * matching message was posted on the bus.
460 * Returns: (transfer full): a #GstMessage matching the filter in @types,
461 * or NULL if no matching message was found on the bus until the timeout
462 * expired. The message is taken from the bus and needs to be unreffed
463 * with gst_message_unref() after usage.
470 gst_bus_timed_pop_filtered (GstBus * bus, GstClockTime timeout,
471 GstMessageType types)
475 gboolean first_round = TRUE;
476 GstClockTime elapsed = 0;
478 g_return_val_if_fail (GST_IS_BUS (bus), NULL);
479 g_return_val_if_fail (types != 0, NULL);
480 g_return_val_if_fail (timeout == 0 || bus->priv->poll != NULL, NULL);
482 g_mutex_lock (&bus->priv->queue_lock);
487 GST_LOG_OBJECT (bus, "have %d messages",
488 gst_atomic_queue_length (bus->priv->queue));
490 while ((message = gst_atomic_queue_pop (bus->priv->queue))) {
492 gst_poll_read_control (bus->priv->poll);
494 GST_DEBUG_OBJECT (bus, "got message %p, %s from %s, type mask is %u",
495 message, GST_MESSAGE_TYPE_NAME (message),
496 GST_MESSAGE_SRC_NAME (message), (guint) types);
497 if ((GST_MESSAGE_TYPE (message) & types) != 0) {
498 /* exit the loop, we have a message */
501 GST_DEBUG_OBJECT (bus, "discarding message, does not match mask");
502 gst_message_unref (message);
507 /* no need to wait, exit loop */
511 else if (timeout != GST_CLOCK_TIME_NONE) {
513 g_get_current_time (&then);
516 g_get_current_time (&now);
518 elapsed = GST_TIMEVAL_TO_TIME (now) - GST_TIMEVAL_TO_TIME (then);
520 if (elapsed > timeout)
525 /* only here in timeout case */
526 g_assert (bus->priv->poll);
527 g_mutex_unlock (&bus->priv->queue_lock);
528 ret = gst_poll_wait (bus->priv->poll, timeout - elapsed);
529 g_mutex_lock (&bus->priv->queue_lock);
532 GST_INFO_OBJECT (bus, "timed out, breaking loop");
535 GST_INFO_OBJECT (bus, "we got woken up, recheck for message");
541 g_mutex_unlock (&bus->priv->queue_lock);
549 * @bus: a #GstBus to pop
550 * @timeout: a timeout
552 * Get a message from the bus, waiting up to the specified timeout.
554 * If @timeout is 0, this function behaves like gst_bus_pop(). If @timeout is
555 * #GST_CLOCK_TIME_NONE, this function will block forever until a message was
558 * Returns: (transfer full): the #GstMessage that is on the bus after the
559 * specified timeout or NULL if the bus is empty after the timeout expired.
560 * The message is taken from the bus and needs to be unreffed with
561 * gst_message_unref() after usage.
568 gst_bus_timed_pop (GstBus * bus, GstClockTime timeout)
570 g_return_val_if_fail (GST_IS_BUS (bus), NULL);
572 return gst_bus_timed_pop_filtered (bus, timeout, GST_MESSAGE_ANY);
576 * gst_bus_pop_filtered:
577 * @bus: a #GstBus to pop
578 * @types: message types to take into account
580 * Get a message matching @type from the bus. Will discard all messages on
581 * the bus that do not match @type and that have been posted before the first
582 * message that does match @type. If there is no message matching @type on
583 * the bus, all messages will be discarded.
585 * Returns: (transfer full): the next #GstMessage matching @type that is on
586 * the bus, or NULL if the bus is empty or there is no message matching
587 * @type. The message is taken from the bus and needs to be unreffed with
588 * gst_message_unref() after usage.
595 gst_bus_pop_filtered (GstBus * bus, GstMessageType types)
597 g_return_val_if_fail (GST_IS_BUS (bus), NULL);
598 g_return_val_if_fail (types != 0, NULL);
600 return gst_bus_timed_pop_filtered (bus, 0, types);
605 * @bus: a #GstBus to pop
607 * Get a message from the bus.
609 * Returns: (transfer full): the #GstMessage that is on the bus, or NULL if the
610 * bus is empty. The message is taken from the bus and needs to be unreffed
611 * with gst_message_unref() after usage.
616 gst_bus_pop (GstBus * bus)
618 g_return_val_if_fail (GST_IS_BUS (bus), NULL);
620 return gst_bus_timed_pop_filtered (bus, 0, GST_MESSAGE_ANY);
627 * Peek the message on the top of the bus' queue. The message will remain
628 * on the bus' message queue. A reference is returned, and needs to be unreffed
631 * Returns: (transfer full): the #GstMessage that is on the bus, or NULL if the
637 gst_bus_peek (GstBus * bus)
641 g_return_val_if_fail (GST_IS_BUS (bus), NULL);
643 g_mutex_lock (&bus->priv->queue_lock);
644 message = gst_atomic_queue_peek (bus->priv->queue);
646 gst_message_ref (message);
647 g_mutex_unlock (&bus->priv->queue_lock);
649 GST_DEBUG_OBJECT (bus, "peek on bus, got message %p", message);
655 * gst_bus_set_sync_handler:
656 * @bus: a #GstBus to install the handler on
657 * @func: The handler function to install
658 * @data: User data that will be sent to the handler function.
660 * Sets the synchronous handler on the bus. The function will be called
661 * every time a new message is posted on the bus. Note that the function
662 * will be called in the same thread context as the posting object. This
663 * function is usually only called by the creator of the bus. Applications
664 * should handle messages asynchronously using the gst_bus watch and poll
667 * You cannot replace an existing sync_handler. You can pass NULL to this
668 * function, which will clear the existing handler.
671 gst_bus_set_sync_handler (GstBus * bus, GstBusSyncHandler func, gpointer data)
673 g_return_if_fail (GST_IS_BUS (bus));
675 GST_OBJECT_LOCK (bus);
677 /* Assert if the user attempts to replace an existing sync_handler,
678 * other than to clear it */
679 if (func != NULL && bus->priv->sync_handler != NULL)
682 bus->priv->sync_handler = func;
683 bus->priv->sync_handler_data = data;
684 GST_OBJECT_UNLOCK (bus);
690 GST_OBJECT_UNLOCK (bus);
691 g_warning ("cannot replace existing sync handler");
696 /* GSource for the bus
705 gst_bus_source_prepare (GSource * source, gint * timeout)
712 gst_bus_source_check (GSource * source)
714 GstBusSource *bsrc = (GstBusSource *) source;
716 return bsrc->bus->priv->pollfd.revents & (G_IO_IN | G_IO_HUP | G_IO_ERR);
720 gst_bus_source_dispatch (GSource * source, GSourceFunc callback,
723 GstBusFunc handler = (GstBusFunc) callback;
724 GstBusSource *bsource = (GstBusSource *) source;
729 g_return_val_if_fail (bsource != NULL, FALSE);
733 g_return_val_if_fail (GST_IS_BUS (bus), FALSE);
735 message = gst_bus_pop (bus);
737 /* The message queue might be empty if some other thread or callback set
738 * the bus to flushing between check/prepare and dispatch */
739 if (G_UNLIKELY (message == NULL))
745 GST_DEBUG_OBJECT (bus, "source %p calling dispatch with %" GST_PTR_FORMAT,
748 keep = handler (bus, message, user_data);
749 gst_message_unref (message);
751 GST_DEBUG_OBJECT (bus, "source %p handler returns %d", source, keep);
757 g_warning ("GstBus watch dispatched without callback\n"
758 "You must call g_source_set_callback().");
759 gst_message_unref (message);
765 gst_bus_source_finalize (GSource * source)
767 GstBusSource *bsource = (GstBusSource *) source;
772 GST_DEBUG_OBJECT (bus, "finalize source %p", source);
774 GST_OBJECT_LOCK (bus);
775 if (bus->priv->watch_id == source)
776 bus->priv->watch_id = NULL;
777 GST_OBJECT_UNLOCK (bus);
779 gst_object_unref (bsource->bus);
783 static GSourceFuncs gst_bus_source_funcs = {
784 gst_bus_source_prepare,
785 gst_bus_source_check,
786 gst_bus_source_dispatch,
787 gst_bus_source_finalize
791 * gst_bus_create_watch:
792 * @bus: a #GstBus to create the watch for
794 * Create watch for this bus. The GSource will be dispatched whenever
795 * a message is on the bus. After the GSource is dispatched, the
796 * message is popped off the bus and unreffed.
798 * Returns: (transfer full): a #GSource that can be added to a mainloop.
801 gst_bus_create_watch (GstBus * bus)
803 GstBusSource *source;
805 g_return_val_if_fail (GST_IS_BUS (bus), NULL);
806 g_return_val_if_fail (bus->priv->poll != NULL, NULL);
808 source = (GstBusSource *) g_source_new (&gst_bus_source_funcs,
809 sizeof (GstBusSource));
811 g_source_set_name ((GSource *) source, "GStreamer message bus watch");
813 source->bus = gst_object_ref (bus);
814 g_source_add_poll ((GSource *) source, &bus->priv->pollfd);
816 return (GSource *) source;
819 /* must be called with the bus OBJECT LOCK */
821 gst_bus_add_watch_full_unlocked (GstBus * bus, gint priority,
822 GstBusFunc func, gpointer user_data, GDestroyNotify notify)
828 if (bus->priv->watch_id) {
829 GST_ERROR_OBJECT (bus,
830 "Tried to add new watch while one was already there");
834 source = gst_bus_create_watch (bus);
836 if (priority != G_PRIORITY_DEFAULT)
837 g_source_set_priority (source, priority);
839 g_source_set_callback (source, (GSourceFunc) func, user_data, notify);
841 ctx = g_main_context_get_thread_default ();
842 id = g_source_attach (source, ctx);
843 g_source_unref (source);
846 bus->priv->watch_id = source;
849 GST_DEBUG_OBJECT (bus, "New source %p with id %u", source, id);
854 * gst_bus_add_watch_full:
855 * @bus: a #GstBus to create the watch for.
856 * @priority: The priority of the watch.
857 * @func: A function to call when a message is received.
858 * @user_data: user data passed to @func.
859 * @notify: the function to call when the source is removed.
861 * Adds a bus watch to the default main context with the given @priority (e.g.
862 * %G_PRIORITY_DEFAULT). Since 0.10.33 it is also possible to use a non-default
863 * main context set up using g_main_context_push_thread_default() (before
864 * one had to create a bus watch source and attach it to the desired main
865 * context 'manually').
867 * This function is used to receive asynchronous messages in the main loop.
868 * There can only be a single bus watch per bus, you must remove it before you
871 * When @func is called, the message belongs to the caller; if you want to
872 * keep a copy of it, call gst_message_ref() before leaving @func.
874 * The watch can be removed using g_source_remove() or by returning FALSE
877 * Returns: The event source id.
878 * Rename to: gst_bus_add_watch
882 gst_bus_add_watch_full (GstBus * bus, gint priority,
883 GstBusFunc func, gpointer user_data, GDestroyNotify notify)
887 g_return_val_if_fail (GST_IS_BUS (bus), 0);
889 GST_OBJECT_LOCK (bus);
890 id = gst_bus_add_watch_full_unlocked (bus, priority, func, user_data, notify);
891 GST_OBJECT_UNLOCK (bus);
897 * gst_bus_add_watch: (skip)
898 * @bus: a #GstBus to create the watch for
899 * @func: A function to call when a message is received.
900 * @user_data: user data passed to @func.
902 * Adds a bus watch to the default main context with the default priority
903 * (%G_PRIORITY_DEFAULT). Since 0.10.33 it is also possible to use a non-default
904 * main context set up using g_main_context_push_thread_default() (before
905 * one had to create a bus watch source and attach it to the desired main
906 * context 'manually').
908 * This function is used to receive asynchronous messages in the main loop.
909 * There can only be a single bus watch per bus, you must remove it before you
912 * The watch can be removed using g_source_remove() or by returning FALSE
915 * Returns: The event source id.
920 gst_bus_add_watch (GstBus * bus, GstBusFunc func, gpointer user_data)
922 return gst_bus_add_watch_full (bus, G_PRIORITY_DEFAULT, func,
930 gboolean source_running;
931 GstMessageType events;
936 poll_func (GstBus * bus, GstMessage * message, GstBusPollData * poll_data)
940 if (!g_main_loop_is_running (poll_data->loop)) {
941 GST_DEBUG ("mainloop %p not running", poll_data->loop);
945 type = GST_MESSAGE_TYPE (message);
947 if (type & poll_data->events) {
948 g_assert (poll_data->message == NULL);
949 /* keep ref to message */
950 poll_data->message = gst_message_ref (message);
951 GST_DEBUG ("mainloop %p quit", poll_data->loop);
952 g_main_loop_quit (poll_data->loop);
954 GST_DEBUG ("type %08x does not match %08x", type, poll_data->events);
959 poll_timeout (GstBusPollData * poll_data)
961 GST_DEBUG ("mainloop %p quit", poll_data->loop);
962 g_main_loop_quit (poll_data->loop);
964 /* we don't remove the GSource as this would free our poll_data,
965 * which we still need */
970 poll_destroy (GstBusPollData * poll_data, gpointer unused)
972 poll_data->source_running = FALSE;
973 if (!poll_data->timeout_id) {
974 g_main_loop_unref (poll_data->loop);
975 g_slice_free (GstBusPollData, poll_data);
980 poll_destroy_timeout (GstBusPollData * poll_data)
982 poll_data->timeout_id = 0;
983 if (!poll_data->source_running) {
984 g_main_loop_unref (poll_data->loop);
985 g_slice_free (GstBusPollData, poll_data);
992 * @events: a mask of #GstMessageType, representing the set of message types to
994 * @timeout: the poll timeout, as a #GstClockTimeDiff, or -1 to poll
997 * Poll the bus for messages. Will block while waiting for messages to come.
998 * You can specify a maximum time to poll with the @timeout parameter. If
999 * @timeout is negative, this function will block indefinitely.
1001 * All messages not in @events will be popped off the bus and will be ignored.
1003 * Because poll is implemented using the "message" signal enabled by
1004 * gst_bus_add_signal_watch(), calling gst_bus_poll() will cause the "message"
1005 * signal to be emitted for every message that poll sees. Thus a "message"
1006 * signal handler will see the same messages that this function sees -- neither
1007 * will steal messages from the other.
1009 * This function will run a main loop from the default main context when
1012 * You should never use this function, since it is pure evil. This is
1013 * especially true for GUI applications based on Gtk+ or Qt, but also for any
1014 * other non-trivial application that uses the GLib main loop. As this function
1015 * runs a GLib main loop, any callback attached to the default GLib main
1016 * context may be invoked. This could be timeouts, GUI events, I/O events etc.;
1017 * even if gst_bus_poll() is called with a 0 timeout. Any of these callbacks
1018 * may do things you do not expect, e.g. destroy the main application window or
1019 * some other resource; change other application state; display a dialog and
1020 * run another main loop until the user clicks it away. In short, using this
1021 * function may add a lot of complexity to your code through unexpected
1022 * re-entrancy and unexpected changes to your application's state.
1024 * For 0 timeouts use gst_bus_pop_filtered() instead of this function; for
1025 * other short timeouts use gst_bus_timed_pop_filtered(); everything else is
1026 * better handled by setting up an asynchronous bus watch and doing things
1029 * Returns: (transfer full): the message that was received, or NULL if the
1030 * poll timed out. The message is taken from the bus and needs to be
1031 * unreffed with gst_message_unref() after usage.
1034 gst_bus_poll (GstBus * bus, GstMessageType events, GstClockTimeDiff timeout)
1036 GstBusPollData *poll_data;
1040 poll_data = g_slice_new (GstBusPollData);
1041 poll_data->source_running = TRUE;
1042 poll_data->loop = g_main_loop_new (NULL, FALSE);
1043 poll_data->events = events;
1044 poll_data->message = NULL;
1047 poll_data->timeout_id = g_timeout_add_full (G_PRIORITY_DEFAULT_IDLE,
1048 timeout / GST_MSECOND, (GSourceFunc) poll_timeout, poll_data,
1049 (GDestroyNotify) poll_destroy_timeout);
1051 poll_data->timeout_id = 0;
1053 id = g_signal_connect_data (bus, "message", G_CALLBACK (poll_func), poll_data,
1054 (GClosureNotify) poll_destroy, 0);
1056 /* these can be nested, so it's ok */
1057 gst_bus_add_signal_watch (bus);
1059 GST_DEBUG ("running mainloop %p", poll_data->loop);
1060 g_main_loop_run (poll_data->loop);
1061 GST_DEBUG ("mainloop stopped %p", poll_data->loop);
1063 gst_bus_remove_signal_watch (bus);
1066 ret = poll_data->message;
1068 if (poll_data->timeout_id)
1069 g_source_remove (poll_data->timeout_id);
1071 /* poll_data will be freed now */
1072 g_signal_handler_disconnect (bus, id);
1074 GST_DEBUG_OBJECT (bus, "finished poll with message %p", ret);
1080 * gst_bus_async_signal_func:
1082 * @message: the #GstMessage received
1085 * A helper #GstBusFunc that can be used to convert all asynchronous messages
1091 gst_bus_async_signal_func (GstBus * bus, GstMessage * message, gpointer data)
1095 g_return_val_if_fail (GST_IS_BUS (bus), TRUE);
1096 g_return_val_if_fail (message != NULL, TRUE);
1098 detail = gst_message_type_to_quark (GST_MESSAGE_TYPE (message));
1100 g_signal_emit (bus, gst_bus_signals[ASYNC_MESSAGE], detail, message);
1102 /* we never remove this source based on signal emission return values */
1107 * gst_bus_sync_signal_handler:
1109 * @message: the #GstMessage received
1112 * A helper GstBusSyncHandler that can be used to convert all synchronous
1113 * messages into signals.
1115 * Returns: GST_BUS_PASS
1118 gst_bus_sync_signal_handler (GstBus * bus, GstMessage * message, gpointer data)
1122 g_return_val_if_fail (GST_IS_BUS (bus), GST_BUS_DROP);
1123 g_return_val_if_fail (message != NULL, GST_BUS_DROP);
1125 detail = gst_message_type_to_quark (GST_MESSAGE_TYPE (message));
1127 g_signal_emit (bus, gst_bus_signals[SYNC_MESSAGE], detail, message);
1129 return GST_BUS_PASS;
1133 * gst_bus_enable_sync_message_emission:
1134 * @bus: a #GstBus on which you want to receive the "sync-message" signal
1136 * Instructs GStreamer to emit the "sync-message" signal after running the bus's
1137 * sync handler. This function is here so that code can ensure that they can
1138 * synchronously receive messages without having to affect what the bin's sync
1141 * This function may be called multiple times. To clean up, the caller is
1142 * responsible for calling gst_bus_disable_sync_message_emission() as many times
1143 * as this function is called.
1145 * While this function looks similar to gst_bus_add_signal_watch(), it is not
1146 * exactly the same -- this function enables <emphasis>synchronous</emphasis> emission of
1147 * signals when messages arrive; gst_bus_add_signal_watch() adds an idle callback
1148 * to pop messages off the bus <emphasis>asynchronously</emphasis>. The sync-message signal
1149 * comes from the thread of whatever object posted the message; the "message"
1150 * signal is marshalled to the main thread via the main loop.
1155 gst_bus_enable_sync_message_emission (GstBus * bus)
1157 g_return_if_fail (GST_IS_BUS (bus));
1159 GST_OBJECT_LOCK (bus);
1160 bus->priv->num_sync_message_emitters++;
1161 GST_OBJECT_UNLOCK (bus);
1165 * gst_bus_disable_sync_message_emission:
1166 * @bus: a #GstBus on which you previously called
1167 * gst_bus_enable_sync_message_emission()
1169 * Instructs GStreamer to stop emitting the "sync-message" signal for this bus.
1170 * See gst_bus_enable_sync_message_emission() for more information.
1172 * In the event that multiple pieces of code have called
1173 * gst_bus_enable_sync_message_emission(), the sync-message emissions will only
1174 * be stopped after all calls to gst_bus_enable_sync_message_emission() were
1175 * "cancelled" by calling this function. In this way the semantics are exactly
1176 * the same as gst_object_ref() that which calls enable should also call
1182 gst_bus_disable_sync_message_emission (GstBus * bus)
1184 g_return_if_fail (GST_IS_BUS (bus));
1185 g_return_if_fail (bus->priv->num_signal_watchers == 0);
1187 GST_OBJECT_LOCK (bus);
1188 bus->priv->num_sync_message_emitters--;
1189 GST_OBJECT_UNLOCK (bus);
1193 * gst_bus_add_signal_watch_full:
1194 * @bus: a #GstBus on which you want to receive the "message" signal
1195 * @priority: The priority of the watch.
1197 * Adds a bus signal watch to the default main context with the given @priority
1198 * (e.g. %G_PRIORITY_DEFAULT). Since 0.10.33 it is also possible to use a
1199 * non-default main context set up using g_main_context_push_thread_default()
1200 * (before one had to create a bus watch source and attach it to the desired
1201 * main context 'manually').
1203 * After calling this statement, the bus will emit the "message" signal for each
1204 * message posted on the bus when the main loop is running.
1206 * This function may be called multiple times. To clean up, the caller is
1207 * responsible for calling gst_bus_remove_signal_watch() as many times as this
1208 * function is called.
1210 * There can only be a single bus watch per bus, you must remove any signal
1211 * watch before you can set another type of watch.
1216 gst_bus_add_signal_watch_full (GstBus * bus, gint priority)
1218 g_return_if_fail (GST_IS_BUS (bus));
1220 /* I know the callees don't take this lock, so go ahead and abuse it */
1221 GST_OBJECT_LOCK (bus);
1223 if (bus->priv->num_signal_watchers > 0)
1226 /* this should not fail because the counter above takes care of it */
1227 g_assert (bus->priv->signal_watch_id == 0);
1229 bus->priv->signal_watch_id =
1230 gst_bus_add_watch_full_unlocked (bus, priority, gst_bus_async_signal_func,
1233 if (G_UNLIKELY (bus->priv->signal_watch_id == 0))
1238 bus->priv->num_signal_watchers++;
1240 GST_OBJECT_UNLOCK (bus);
1246 g_critical ("Could not add signal watch to bus %s", GST_OBJECT_NAME (bus));
1247 GST_OBJECT_UNLOCK (bus);
1253 * gst_bus_add_signal_watch:
1254 * @bus: a #GstBus on which you want to receive the "message" signal
1256 * Adds a bus signal watch to the default main context with the default priority
1257 * (%G_PRIORITY_DEFAULT). Since 0.10.33 it is also possible to use a non-default
1258 * main context set up using g_main_context_push_thread_default() (before
1259 * one had to create a bus watch source and attach it to the desired main
1260 * context 'manually').
1262 * After calling this statement, the bus will emit the "message" signal for each
1263 * message posted on the bus.
1265 * This function may be called multiple times. To clean up, the caller is
1266 * responsible for calling gst_bus_remove_signal_watch() as many times as this
1267 * function is called.
1272 gst_bus_add_signal_watch (GstBus * bus)
1274 gst_bus_add_signal_watch_full (bus, G_PRIORITY_DEFAULT);
1278 * gst_bus_remove_signal_watch:
1279 * @bus: a #GstBus you previously added a signal watch to
1281 * Removes a signal watch previously added with gst_bus_add_signal_watch().
1286 gst_bus_remove_signal_watch (GstBus * bus)
1290 g_return_if_fail (GST_IS_BUS (bus));
1292 /* I know the callees don't take this lock, so go ahead and abuse it */
1293 GST_OBJECT_LOCK (bus);
1295 if (bus->priv->num_signal_watchers == 0)
1298 bus->priv->num_signal_watchers--;
1300 if (bus->priv->num_signal_watchers > 0)
1303 id = bus->priv->signal_watch_id;
1304 bus->priv->signal_watch_id = 0;
1306 GST_DEBUG_OBJECT (bus, "removing signal watch %u", id);
1309 GST_OBJECT_UNLOCK (bus);
1312 g_source_remove (id);
1319 g_critical ("Bus %s has no signal watches attached", GST_OBJECT_NAME (bus));
1320 GST_OBJECT_UNLOCK (bus);