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.
67 * Last reviewed on 2012-03-28 (0.11.3)
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);
103 static void gst_bus_finalize (GObject * object);
105 static guint gst_bus_signals[LAST_SIGNAL] = { 0 };
107 struct _GstBusPrivate
109 GstAtomicQueue *queue;
112 GstBusSyncHandler sync_handler;
113 gpointer sync_handler_data;
114 GDestroyNotify sync_handler_notify;
116 guint signal_watch_id;
117 guint num_signal_watchers;
119 guint num_sync_message_emitters;
122 gboolean enable_async;
127 #define gst_bus_parent_class parent_class
128 G_DEFINE_TYPE (GstBus, gst_bus, GST_TYPE_OBJECT);
131 gst_bus_set_property (GObject * object,
132 guint prop_id, const GValue * value, GParamSpec * pspec)
134 GstBus *bus = GST_BUS_CAST (object);
137 case PROP_ENABLE_ASYNC:
138 bus->priv->enable_async = g_value_get_boolean (value);
141 G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
147 gst_bus_constructed (GObject * object)
149 GstBus *bus = GST_BUS_CAST (object);
151 if (bus->priv->enable_async) {
152 bus->priv->poll = gst_poll_new_timer ();
153 gst_poll_get_read_gpollfd (bus->priv->poll, &bus->priv->pollfd);
158 gst_bus_class_init (GstBusClass * klass)
160 GObjectClass *gobject_class = (GObjectClass *) klass;
162 gobject_class->dispose = gst_bus_dispose;
163 gobject_class->finalize = gst_bus_finalize;
164 gobject_class->set_property = gst_bus_set_property;
165 gobject_class->constructed = gst_bus_constructed;
168 * GstBus::enable-async:
170 * Enable async message delivery support for bus watches,
171 * gst_bus_pop() and similar API. Without this only the
172 * synchronous message handlers are called.
174 * This property is used to create the child element buses
177 g_object_class_install_property (gobject_class, PROP_ENABLE_ASYNC,
178 g_param_spec_boolean ("enable-async", "Enable Async",
179 "Enable async message delivery for bus watches and gst_bus_pop()",
180 DEFAULT_ENABLE_ASYNC,
181 G_PARAM_CONSTRUCT_ONLY | G_PARAM_WRITABLE | G_PARAM_STATIC_STRINGS));
184 * GstBus::sync-message:
185 * @bus: the object which received the signal
186 * @message: the message that has been posted synchronously
188 * A message has been posted on the bus. This signal is emitted from the
189 * thread that posted the message so one has to be careful with locking.
191 * This signal will not be emitted by default, you have to call
192 * gst_bus_enable_sync_message_emission() before.
194 gst_bus_signals[SYNC_MESSAGE] =
195 g_signal_new ("sync-message", G_TYPE_FROM_CLASS (klass),
196 G_SIGNAL_RUN_LAST | G_SIGNAL_DETAILED,
197 G_STRUCT_OFFSET (GstBusClass, sync_message), NULL, NULL,
198 g_cclosure_marshal_generic, G_TYPE_NONE, 1, GST_TYPE_MESSAGE);
202 * @bus: the object which received the signal
203 * @message: the message that has been posted asynchronously
205 * A message has been posted on the bus. This signal is emitted from a
206 * GSource added to the mainloop. this signal will only be emitted when
207 * there is a mainloop running.
209 gst_bus_signals[ASYNC_MESSAGE] =
210 g_signal_new ("message", G_TYPE_FROM_CLASS (klass),
211 G_SIGNAL_RUN_LAST | G_SIGNAL_DETAILED,
212 G_STRUCT_OFFSET (GstBusClass, message), NULL, NULL,
213 g_cclosure_marshal_generic, G_TYPE_NONE, 1, GST_TYPE_MESSAGE);
215 g_type_class_add_private (klass, sizeof (GstBusPrivate));
219 gst_bus_init (GstBus * bus)
221 bus->priv = G_TYPE_INSTANCE_GET_PRIVATE (bus, GST_TYPE_BUS, GstBusPrivate);
222 bus->priv->enable_async = DEFAULT_ENABLE_ASYNC;
223 g_mutex_init (&bus->priv->queue_lock);
224 bus->priv->queue = gst_atomic_queue_new (32);
226 /* clear floating flag */
227 gst_object_ref_sink (bus);
229 GST_DEBUG_OBJECT (bus, "created");
233 gst_bus_dispose (GObject * object)
235 GstBus *bus = GST_BUS (object);
237 if (bus->priv->queue) {
240 g_mutex_lock (&bus->priv->queue_lock);
242 message = gst_atomic_queue_pop (bus->priv->queue);
244 gst_message_unref (message);
245 } while (message != NULL);
246 gst_atomic_queue_unref (bus->priv->queue);
247 bus->priv->queue = NULL;
248 g_mutex_unlock (&bus->priv->queue_lock);
249 g_mutex_clear (&bus->priv->queue_lock);
252 gst_poll_free (bus->priv->poll);
253 bus->priv->poll = NULL;
256 G_OBJECT_CLASS (parent_class)->dispose (object);
260 gst_bus_finalize (GObject * object)
262 GstBus *bus = GST_BUS (object);
264 if (bus->priv->sync_handler_notify)
265 bus->priv->sync_handler_notify (bus->priv->sync_handler_data);
267 G_OBJECT_CLASS (parent_class)->finalize (object);
273 * Creates a new #GstBus instance.
275 * Returns: (transfer full): a new #GstBus instance
282 result = g_object_newv (gst_bus_get_type (), 0, NULL);
283 GST_DEBUG_OBJECT (result, "created new bus");
290 * @bus: a #GstBus to post on
291 * @message: (transfer full): the #GstMessage to post
293 * Post a message on the given bus. Ownership of the message
294 * is taken by the bus.
296 * Returns: TRUE if the message could be posted, FALSE if the bus is flushing.
301 gst_bus_post (GstBus * bus, GstMessage * message)
303 GstBusSyncReply reply = GST_BUS_PASS;
304 GstBusSyncHandler handler;
305 gboolean emit_sync_message;
306 gpointer handler_data;
308 g_return_val_if_fail (GST_IS_BUS (bus), FALSE);
309 g_return_val_if_fail (GST_IS_MESSAGE (message), FALSE);
311 GST_DEBUG_OBJECT (bus, "[msg %p] posting on bus %" GST_PTR_FORMAT, message,
314 GST_OBJECT_LOCK (bus);
315 /* check if the bus is flushing */
316 if (GST_OBJECT_FLAG_IS_SET (bus, GST_BUS_FLUSHING))
319 handler = bus->priv->sync_handler;
320 handler_data = bus->priv->sync_handler_data;
321 emit_sync_message = bus->priv->num_sync_message_emitters > 0;
322 GST_OBJECT_UNLOCK (bus);
324 /* first call the sync handler if it is installed */
326 reply = handler (bus, message, handler_data);
328 /* emit sync-message if requested to do so via
329 gst_bus_enable_sync_message_emission. terrible but effective */
330 if (emit_sync_message && reply != GST_BUS_DROP
331 && handler != gst_bus_sync_signal_handler)
332 gst_bus_sync_signal_handler (bus, message, NULL);
334 /* If this is a bus without async message delivery
335 * always drop the message */
336 if (!bus->priv->poll)
337 reply = GST_BUS_DROP;
339 /* now see what we should do with the message */
342 /* drop the message */
343 GST_DEBUG_OBJECT (bus, "[msg %p] dropped", message);
346 /* pass the message to the async queue, refcount passed in the queue */
347 GST_DEBUG_OBJECT (bus, "[msg %p] pushing on async queue", message);
348 gst_atomic_queue_push (bus->priv->queue, message);
349 gst_poll_write_control (bus->priv->poll);
350 GST_DEBUG_OBJECT (bus, "[msg %p] pushed on async queue", message);
355 /* async delivery, we need a mutex and a cond to block
357 GCond *cond = GST_MESSAGE_GET_COND (message);
358 GMutex *lock = GST_MESSAGE_GET_LOCK (message);
363 GST_DEBUG_OBJECT (bus, "[msg %p] waiting for async delivery", message);
365 /* now we lock the message mutex, send the message to the async
366 * queue. When the message is handled by the app and destroyed,
367 * the cond will be signalled and we can continue */
370 gst_atomic_queue_push (bus->priv->queue, message);
371 gst_poll_write_control (bus->priv->poll);
373 /* now block till the message is freed */
374 g_cond_wait (cond, lock);
375 g_mutex_unlock (lock);
377 GST_DEBUG_OBJECT (bus, "[msg %p] delivered asynchronously", message);
379 g_mutex_clear (lock);
384 g_warning ("invalid return from bus sync handler");
392 GST_DEBUG_OBJECT (bus, "bus is flushing");
393 gst_message_unref (message);
394 GST_OBJECT_UNLOCK (bus);
401 * gst_bus_have_pending:
402 * @bus: a #GstBus to check
404 * Check if there are pending messages on the bus that
407 * Returns: TRUE if there are messages on the bus to be handled, FALSE
413 gst_bus_have_pending (GstBus * bus)
417 g_return_val_if_fail (GST_IS_BUS (bus), FALSE);
419 /* see if there is a message on the bus */
420 result = gst_atomic_queue_length (bus->priv->queue) != 0;
426 * gst_bus_set_flushing:
428 * @flushing: whether or not to flush the bus
430 * If @flushing, flush out and unref any messages queued in the bus. Releases
431 * references to the message origin objects. Will flush future messages until
432 * gst_bus_set_flushing() sets @flushing to #FALSE.
437 gst_bus_set_flushing (GstBus * bus, gboolean flushing)
441 GST_OBJECT_LOCK (bus);
444 GST_OBJECT_FLAG_SET (bus, GST_BUS_FLUSHING);
446 GST_DEBUG_OBJECT (bus, "set bus flushing");
448 while ((message = gst_bus_pop (bus)))
449 gst_message_unref (message);
451 GST_DEBUG_OBJECT (bus, "unset bus flushing");
452 GST_OBJECT_FLAG_UNSET (bus, GST_BUS_FLUSHING);
455 GST_OBJECT_UNLOCK (bus);
459 * gst_bus_timed_pop_filtered:
460 * @bus: a #GstBus to pop from
461 * @timeout: a timeout in nanoseconds, or GST_CLOCK_TIME_NONE to wait forever
462 * @types: message types to take into account, GST_MESSAGE_ANY for any type
464 * Get a message from the bus whose type matches the message type mask @types,
465 * waiting up to the specified timeout (and discarding any messages that do not
466 * match the mask provided).
468 * If @timeout is 0, this function behaves like gst_bus_pop_filtered(). If
469 * @timeout is #GST_CLOCK_TIME_NONE, this function will block forever until a
470 * matching message was posted on the bus.
472 * Returns: (transfer full): a #GstMessage matching the filter in @types,
473 * or NULL if no matching message was found on the bus until the timeout
474 * expired. The message is taken from the bus and needs to be unreffed
475 * with gst_message_unref() after usage.
480 gst_bus_timed_pop_filtered (GstBus * bus, GstClockTime timeout,
481 GstMessageType types)
485 gboolean first_round = TRUE;
486 GstClockTime elapsed = 0;
488 g_return_val_if_fail (GST_IS_BUS (bus), NULL);
489 g_return_val_if_fail (types != 0, NULL);
490 g_return_val_if_fail (timeout == 0 || bus->priv->poll != NULL, NULL);
492 g_mutex_lock (&bus->priv->queue_lock);
497 GST_LOG_OBJECT (bus, "have %d messages",
498 gst_atomic_queue_length (bus->priv->queue));
500 while ((message = gst_atomic_queue_pop (bus->priv->queue))) {
502 gst_poll_read_control (bus->priv->poll);
504 GST_DEBUG_OBJECT (bus, "got message %p, %s from %s, type mask is %u",
505 message, GST_MESSAGE_TYPE_NAME (message),
506 GST_MESSAGE_SRC_NAME (message), (guint) types);
507 if ((GST_MESSAGE_TYPE (message) & types) != 0) {
508 /* Extra check to ensure extended types don't get matched unless
510 if ((GST_MESSAGE_TYPE_IS_EXTENDED (message) == FALSE)
511 || (types & GST_MESSAGE_EXTENDED)) {
512 /* exit the loop, we have a message */
517 GST_DEBUG_OBJECT (bus, "discarding message, does not match mask");
518 gst_message_unref (message);
522 /* no need to wait, exit loop */
526 else if (timeout != GST_CLOCK_TIME_NONE) {
528 g_get_current_time (&then);
531 g_get_current_time (&now);
533 elapsed = GST_TIMEVAL_TO_TIME (now) - GST_TIMEVAL_TO_TIME (then);
535 if (elapsed > timeout)
540 /* only here in timeout case */
541 g_assert (bus->priv->poll);
542 g_mutex_unlock (&bus->priv->queue_lock);
543 ret = gst_poll_wait (bus->priv->poll, timeout - elapsed);
544 g_mutex_lock (&bus->priv->queue_lock);
547 GST_INFO_OBJECT (bus, "timed out, breaking loop");
550 GST_INFO_OBJECT (bus, "we got woken up, recheck for message");
556 g_mutex_unlock (&bus->priv->queue_lock);
564 * @bus: a #GstBus to pop
565 * @timeout: a timeout
567 * Get a message from the bus, waiting up to the specified timeout.
569 * If @timeout is 0, this function behaves like gst_bus_pop(). If @timeout is
570 * #GST_CLOCK_TIME_NONE, this function will block forever until a message was
573 * Returns: (transfer full): the #GstMessage that is on the bus after the
574 * specified timeout or NULL if the bus is empty after the timeout expired.
575 * The message is taken from the bus and needs to be unreffed with
576 * gst_message_unref() after usage.
581 gst_bus_timed_pop (GstBus * bus, GstClockTime timeout)
583 g_return_val_if_fail (GST_IS_BUS (bus), NULL);
585 return gst_bus_timed_pop_filtered (bus, timeout, GST_MESSAGE_ANY);
589 * gst_bus_pop_filtered:
590 * @bus: a #GstBus to pop
591 * @types: message types to take into account
593 * Get a message matching @type from the bus. Will discard all messages on
594 * the bus that do not match @type and that have been posted before the first
595 * message that does match @type. If there is no message matching @type on
596 * the bus, all messages will be discarded. It is not possible to use message
597 * enums beyond #GST_MESSAGE_EXTENDED in the @events mask.
599 * Returns: (transfer full): the next #GstMessage matching @type that is on
600 * the bus, or NULL if the bus is empty or there is no message matching
601 * @type. The message is taken from the bus and needs to be unreffed with
602 * gst_message_unref() after usage.
607 gst_bus_pop_filtered (GstBus * bus, GstMessageType types)
609 g_return_val_if_fail (GST_IS_BUS (bus), NULL);
610 g_return_val_if_fail (types != 0, NULL);
612 return gst_bus_timed_pop_filtered (bus, 0, types);
617 * @bus: a #GstBus to pop
619 * Get a message from the bus.
621 * Returns: (transfer full): the #GstMessage that is on the bus, or NULL if the
622 * bus is empty. The message is taken from the bus and needs to be unreffed
623 * with gst_message_unref() after usage.
628 gst_bus_pop (GstBus * bus)
630 g_return_val_if_fail (GST_IS_BUS (bus), NULL);
632 return gst_bus_timed_pop_filtered (bus, 0, GST_MESSAGE_ANY);
639 * Peek the message on the top of the bus' queue. The message will remain
640 * on the bus' message queue. A reference is returned, and needs to be unreffed
643 * Returns: (transfer full): the #GstMessage that is on the bus, or NULL if the
649 gst_bus_peek (GstBus * bus)
653 g_return_val_if_fail (GST_IS_BUS (bus), NULL);
655 g_mutex_lock (&bus->priv->queue_lock);
656 message = gst_atomic_queue_peek (bus->priv->queue);
658 gst_message_ref (message);
659 g_mutex_unlock (&bus->priv->queue_lock);
661 GST_DEBUG_OBJECT (bus, "peek on bus, got message %p", message);
667 * gst_bus_set_sync_handler:
668 * @bus: a #GstBus to install the handler on
669 * @func: (allow-none): The handler function to install
670 * @user_data: User data that will be sent to the handler function.
671 * @notify: called when @user_data becomes unused
673 * Sets the synchronous handler on the bus. The function will be called
674 * every time a new message is posted on the bus. Note that the function
675 * will be called in the same thread context as the posting object. This
676 * function is usually only called by the creator of the bus. Applications
677 * should handle messages asynchronously using the gst_bus watch and poll
680 * You cannot replace an existing sync_handler. You can pass NULL to this
681 * function, which will clear the existing handler.
684 gst_bus_set_sync_handler (GstBus * bus, GstBusSyncHandler func,
685 gpointer user_data, GDestroyNotify notify)
687 GDestroyNotify old_notify;
689 g_return_if_fail (GST_IS_BUS (bus));
691 GST_OBJECT_LOCK (bus);
692 /* Assert if the user attempts to replace an existing sync_handler,
693 * other than to clear it */
694 if (func != NULL && bus->priv->sync_handler != NULL)
697 if ((old_notify = bus->priv->sync_handler_notify)) {
698 gpointer old_data = bus->priv->sync_handler_data;
700 bus->priv->sync_handler_data = NULL;
701 bus->priv->sync_handler_notify = NULL;
702 GST_OBJECT_UNLOCK (bus);
704 old_notify (old_data);
706 GST_OBJECT_LOCK (bus);
708 bus->priv->sync_handler = func;
709 bus->priv->sync_handler_data = user_data;
710 bus->priv->sync_handler_notify = notify;
711 GST_OBJECT_UNLOCK (bus);
717 GST_OBJECT_UNLOCK (bus);
718 g_warning ("cannot replace existing sync handler");
723 /* GSource for the bus
732 gst_bus_source_prepare (GSource * source, gint * timeout)
739 gst_bus_source_check (GSource * source)
741 GstBusSource *bsrc = (GstBusSource *) source;
743 return bsrc->bus->priv->pollfd.revents & (G_IO_IN | G_IO_HUP | G_IO_ERR);
747 gst_bus_source_dispatch (GSource * source, GSourceFunc callback,
750 GstBusFunc handler = (GstBusFunc) callback;
751 GstBusSource *bsource = (GstBusSource *) source;
756 g_return_val_if_fail (bsource != NULL, FALSE);
760 g_return_val_if_fail (GST_IS_BUS (bus), FALSE);
762 message = gst_bus_pop (bus);
764 /* The message queue might be empty if some other thread or callback set
765 * the bus to flushing between check/prepare and dispatch */
766 if (G_UNLIKELY (message == NULL))
772 GST_DEBUG_OBJECT (bus, "source %p calling dispatch with %" GST_PTR_FORMAT,
775 keep = handler (bus, message, user_data);
776 gst_message_unref (message);
778 GST_DEBUG_OBJECT (bus, "source %p handler returns %d", source, keep);
784 g_warning ("GstBus watch dispatched without callback\n"
785 "You must call g_source_set_callback().");
786 gst_message_unref (message);
792 gst_bus_source_finalize (GSource * source)
794 GstBusSource *bsource = (GstBusSource *) source;
799 GST_DEBUG_OBJECT (bus, "finalize source %p", source);
801 GST_OBJECT_LOCK (bus);
802 if (bus->priv->watch_id == source)
803 bus->priv->watch_id = NULL;
804 GST_OBJECT_UNLOCK (bus);
806 gst_object_unref (bsource->bus);
810 static GSourceFuncs gst_bus_source_funcs = {
811 gst_bus_source_prepare,
812 gst_bus_source_check,
813 gst_bus_source_dispatch,
814 gst_bus_source_finalize
818 * gst_bus_create_watch:
819 * @bus: a #GstBus to create the watch for
821 * Create watch for this bus. The GSource will be dispatched whenever
822 * a message is on the bus. After the GSource is dispatched, the
823 * message is popped off the bus and unreffed.
825 * Returns: (transfer full): a #GSource that can be added to a mainloop.
828 gst_bus_create_watch (GstBus * bus)
830 GstBusSource *source;
832 g_return_val_if_fail (GST_IS_BUS (bus), NULL);
833 g_return_val_if_fail (bus->priv->poll != NULL, NULL);
835 source = (GstBusSource *) g_source_new (&gst_bus_source_funcs,
836 sizeof (GstBusSource));
838 g_source_set_name ((GSource *) source, "GStreamer message bus watch");
840 source->bus = gst_object_ref (bus);
841 g_source_add_poll ((GSource *) source, &bus->priv->pollfd);
843 return (GSource *) source;
846 /* must be called with the bus OBJECT LOCK */
848 gst_bus_add_watch_full_unlocked (GstBus * bus, gint priority,
849 GstBusFunc func, gpointer user_data, GDestroyNotify notify)
855 if (bus->priv->watch_id) {
856 GST_ERROR_OBJECT (bus,
857 "Tried to add new watch while one was already there");
861 source = gst_bus_create_watch (bus);
863 if (priority != G_PRIORITY_DEFAULT)
864 g_source_set_priority (source, priority);
866 g_source_set_callback (source, (GSourceFunc) func, user_data, notify);
868 ctx = g_main_context_get_thread_default ();
869 id = g_source_attach (source, ctx);
870 g_source_unref (source);
873 bus->priv->watch_id = source;
876 GST_DEBUG_OBJECT (bus, "New source %p with id %u", source, id);
881 * gst_bus_add_watch_full:
882 * @bus: a #GstBus to create the watch for.
883 * @priority: The priority of the watch.
884 * @func: A function to call when a message is received.
885 * @user_data: user data passed to @func.
886 * @notify: the function to call when the source is removed.
888 * Adds a bus watch to the default main context with the given @priority (e.g.
889 * %G_PRIORITY_DEFAULT). It is also possible to use a non-default main
890 * context set up using g_main_context_push_thread_default() (before
891 * one had to create a bus watch source and attach it to the desired main
892 * context 'manually').
894 * This function is used to receive asynchronous messages in the main loop.
895 * There can only be a single bus watch per bus, you must remove it before you
898 * When @func is called, the message belongs to the caller; if you want to
899 * keep a copy of it, call gst_message_ref() before leaving @func.
901 * The watch can be removed using g_source_remove() or by returning FALSE
906 * Returns: The event source id.
907 * Rename to: gst_bus_add_watch
910 gst_bus_add_watch_full (GstBus * bus, gint priority,
911 GstBusFunc func, gpointer user_data, GDestroyNotify notify)
915 g_return_val_if_fail (GST_IS_BUS (bus), 0);
917 GST_OBJECT_LOCK (bus);
918 id = gst_bus_add_watch_full_unlocked (bus, priority, func, user_data, notify);
919 GST_OBJECT_UNLOCK (bus);
925 * gst_bus_add_watch: (skip)
926 * @bus: a #GstBus to create the watch for
927 * @func: A function to call when a message is received.
928 * @user_data: user data passed to @func.
930 * Adds a bus watch to the default main context with the default priority
931 * (%G_PRIORITY_DEFAULT). It is also possible to use a non-default main
932 * context set up using g_main_context_push_thread_default() (before
933 * one had to create a bus watch source and attach it to the desired main
934 * context 'manually').
936 * This function is used to receive asynchronous messages in the main loop.
937 * There can only be a single bus watch per bus, you must remove it before you
940 * The watch can be removed using g_source_remove() or by returning FALSE
943 * Returns: The event source id.
948 gst_bus_add_watch (GstBus * bus, GstBusFunc func, gpointer user_data)
950 return gst_bus_add_watch_full (bus, G_PRIORITY_DEFAULT, func,
958 gboolean source_running;
959 GstMessageType events;
964 poll_func (GstBus * bus, GstMessage * message, GstBusPollData * poll_data)
968 if (!g_main_loop_is_running (poll_data->loop)) {
969 GST_DEBUG ("mainloop %p not running", poll_data->loop);
973 type = GST_MESSAGE_TYPE (message);
975 if (type & poll_data->events) {
976 g_assert (poll_data->message == NULL);
977 /* keep ref to message */
978 poll_data->message = gst_message_ref (message);
979 GST_DEBUG ("mainloop %p quit", poll_data->loop);
980 g_main_loop_quit (poll_data->loop);
982 GST_DEBUG ("type %08x does not match %08x", type, poll_data->events);
987 poll_timeout (GstBusPollData * poll_data)
989 GST_DEBUG ("mainloop %p quit", poll_data->loop);
990 g_main_loop_quit (poll_data->loop);
992 /* we don't remove the GSource as this would free our poll_data,
993 * which we still need */
998 poll_destroy (GstBusPollData * poll_data, gpointer unused)
1000 poll_data->source_running = FALSE;
1001 if (!poll_data->timeout_id) {
1002 g_main_loop_unref (poll_data->loop);
1003 g_slice_free (GstBusPollData, poll_data);
1008 poll_destroy_timeout (GstBusPollData * poll_data)
1010 poll_data->timeout_id = 0;
1011 if (!poll_data->source_running) {
1012 g_main_loop_unref (poll_data->loop);
1013 g_slice_free (GstBusPollData, poll_data);
1020 * @events: a mask of #GstMessageType, representing the set of message types to
1021 * poll for (note special handling of extended message types below)
1022 * @timeout: the poll timeout, as a #GstClockTime, or #GST_CLOCK_TIME_NONE to poll
1025 * Poll the bus for messages. Will block while waiting for messages to come.
1026 * You can specify a maximum time to poll with the @timeout parameter. If
1027 * @timeout is negative, this function will block indefinitely.
1029 * All messages not in @events will be popped off the bus and will be ignored.
1030 * It is not possible to use message enums beyond #GST_MESSAGE_EXTENDED in the
1033 * Because poll is implemented using the "message" signal enabled by
1034 * gst_bus_add_signal_watch(), calling gst_bus_poll() will cause the "message"
1035 * signal to be emitted for every message that poll sees. Thus a "message"
1036 * signal handler will see the same messages that this function sees -- neither
1037 * will steal messages from the other.
1039 * This function will run a main loop from the default main context when
1042 * You should never use this function, since it is pure evil. This is
1043 * especially true for GUI applications based on Gtk+ or Qt, but also for any
1044 * other non-trivial application that uses the GLib main loop. As this function
1045 * runs a GLib main loop, any callback attached to the default GLib main
1046 * context may be invoked. This could be timeouts, GUI events, I/O events etc.;
1047 * even if gst_bus_poll() is called with a 0 timeout. Any of these callbacks
1048 * may do things you do not expect, e.g. destroy the main application window or
1049 * some other resource; change other application state; display a dialog and
1050 * run another main loop until the user clicks it away. In short, using this
1051 * function may add a lot of complexity to your code through unexpected
1052 * re-entrancy and unexpected changes to your application's state.
1054 * For 0 timeouts use gst_bus_pop_filtered() instead of this function; for
1055 * other short timeouts use gst_bus_timed_pop_filtered(); everything else is
1056 * better handled by setting up an asynchronous bus watch and doing things
1059 * Returns: (transfer full): the message that was received, or NULL if the
1060 * poll timed out. The message is taken from the bus and needs to be
1061 * unreffed with gst_message_unref() after usage.
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_id == 0);
1259 bus->priv->signal_watch_id =
1260 gst_bus_add_watch_full_unlocked (bus, priority, gst_bus_async_signal_func,
1263 if (G_UNLIKELY (bus->priv->signal_watch_id == 0))
1268 bus->priv->num_signal_watchers++;
1270 GST_OBJECT_UNLOCK (bus);
1276 g_critical ("Could not add signal watch to bus %s", GST_OBJECT_NAME (bus));
1277 GST_OBJECT_UNLOCK (bus);
1283 * gst_bus_add_signal_watch:
1284 * @bus: a #GstBus on which you want to receive the "message" signal
1286 * Adds a bus signal watch to the default main context with the default priority
1287 * (%G_PRIORITY_DEFAULT). It is also possible to use a non-default
1288 * main context set up using g_main_context_push_thread_default() (before
1289 * one had to create a bus watch source and attach it to the desired main
1290 * context 'manually').
1292 * After calling this statement, the bus will emit the "message" signal for each
1293 * message posted on the bus.
1295 * This function may be called multiple times. To clean up, the caller is
1296 * responsible for calling gst_bus_remove_signal_watch() as many times as this
1297 * function is called.
1302 gst_bus_add_signal_watch (GstBus * bus)
1304 gst_bus_add_signal_watch_full (bus, G_PRIORITY_DEFAULT);
1308 * gst_bus_remove_signal_watch:
1309 * @bus: a #GstBus you previously added a signal watch to
1311 * Removes a signal watch previously added with gst_bus_add_signal_watch().
1316 gst_bus_remove_signal_watch (GstBus * bus)
1320 g_return_if_fail (GST_IS_BUS (bus));
1322 /* I know the callees don't take this lock, so go ahead and abuse it */
1323 GST_OBJECT_LOCK (bus);
1325 if (bus->priv->num_signal_watchers == 0)
1328 bus->priv->num_signal_watchers--;
1330 if (bus->priv->num_signal_watchers > 0)
1333 id = bus->priv->signal_watch_id;
1334 bus->priv->signal_watch_id = 0;
1336 GST_DEBUG_OBJECT (bus, "removing signal watch %u", id);
1339 GST_OBJECT_UNLOCK (bus);
1342 g_source_remove (id);
1349 g_critical ("Bus %s has no signal watches attached", GST_OBJECT_NAME (bus));
1350 GST_OBJECT_UNLOCK (bus);