2 * Copyright (C) 2004 Wim Taymans <wim@fluendo.com>
4 * gstbus.c: GstBus subsystem
6 * This library is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU Library General Public
8 * License as published by the Free Software Foundation; either
9 * version 2 of the License, or (at your option) any later version.
11 * This library is distributed in the hope that it will be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14 * Library General Public License for more details.
16 * You should have received a copy of the GNU Library General Public
17 * License along with this library; if not, write to the
18 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
19 * Boston, MA 02111-1307, USA.
24 * @short_description: Asynchronous message bus subsystem
25 * @see_also: #GstMessage, #GstElement
27 * The #GstBus is an object responsible for delivering #GstMessage packets in
28 * a first-in first-out way from the streaming threads (see #GstTask) to the
31 * Since the application typically only wants to deal with delivery of these
32 * messages from one thread, the GstBus will marshall the messages between
33 * different threads. This is important since the actual streaming of media
34 * is done in another thread than the application.
36 * The GstBus provides support for #GSource based notifications. This makes it
37 * possible to handle the delivery in the glib mainloop.
39 * The #GSource callback function gst_bus_async_signal_func() can be used to
40 * convert all bus messages into signal emissions.
42 * A message is posted on the bus with the gst_bus_post() method. With the
43 * gst_bus_peek() and gst_bus_pop() methods one can look at or retrieve a
44 * previously posted message.
46 * The bus can be polled with the gst_bus_poll() method. This methods blocks
47 * up to the specified timeout value until one of the specified messages types
48 * is posted on the bus. The application can then gst_bus_pop() the messages
49 * from the bus to handle them.
50 * Alternatively the application can register an asynchronous bus function
51 * using gst_bus_add_watch_full() or gst_bus_add_watch(). This function will
52 * install a #GSource in the default glib main loop and will deliver messages
53 * a short while after they have been posted. Note that the main loop should
54 * be running for the asynchronous callbacks.
56 * It is also possible to get messages from the bus without any thread
57 * marshalling with the gst_bus_set_sync_handler() method. This makes it
58 * possible to react to a message in the same thread that posted the
59 * message on the bus. This should only be used if the application is able
60 * to deal with messages from different threads.
62 * Every #GstPipeline has one bus.
64 * Note that a #GstPipeline will set its bus into flushing state when changing
65 * from READY to NULL state.
67 * Last reviewed on 2006-03-12 (0.10.5)
70 #include "gst_private.h"
75 #include <sys/types.h>
81 #include "glib-compat-private.h"
83 #define GST_CAT_DEFAULT GST_CAT_BUS
93 #define DEFAULT_ENABLE_ASYNC (TRUE)
101 static void gst_bus_dispose (GObject * object);
103 static guint gst_bus_signals[LAST_SIGNAL] = { 0 };
105 struct _GstBusPrivate
107 guint num_sync_message_emitters;
110 gboolean enable_async;
115 #define gst_bus_parent_class parent_class
116 G_DEFINE_TYPE (GstBus, gst_bus, GST_TYPE_OBJECT);
119 gst_bus_set_property (GObject * object,
120 guint prop_id, const GValue * value, GParamSpec * pspec)
122 GstBus *bus = GST_BUS_CAST (object);
125 case PROP_ENABLE_ASYNC:
126 bus->priv->enable_async = g_value_get_boolean (value);
129 G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
135 gst_bus_constructed (GObject * object)
137 GstBus *bus = GST_BUS_CAST (object);
139 if (bus->priv->enable_async) {
140 bus->priv->poll = gst_poll_new_timer ();
141 gst_poll_get_read_gpollfd (bus->priv->poll, &bus->priv->pollfd);
146 gst_bus_class_init (GstBusClass * klass)
148 GObjectClass *gobject_class = (GObjectClass *) klass;
150 gobject_class->dispose = gst_bus_dispose;
151 gobject_class->set_property = gst_bus_set_property;
152 gobject_class->constructed = gst_bus_constructed;
154 /* GstBus:enable-async:
156 * Enable async message delivery support for bus watches,
157 * gst_bus_pop() and similar API. Without this only the
158 * synchronous message handlers are called.
160 * This property is used to create the child element buses
165 g_object_class_install_property (gobject_class, PROP_ENABLE_ASYNC,
166 g_param_spec_boolean ("enable-async", "Enable Async",
167 "Enable async message delivery for bus watches and gst_bus_pop()",
168 DEFAULT_ENABLE_ASYNC,
169 G_PARAM_CONSTRUCT_ONLY | G_PARAM_WRITABLE | G_PARAM_STATIC_STRINGS));
172 * GstBus::sync-message:
173 * @bus: the object which received the signal
174 * @message: the message that has been posted synchronously
176 * A message has been posted on the bus. This signal is emitted from the
177 * thread that posted the message so one has to be careful with locking.
179 * This signal will not be emitted by default, you have to set up
180 * gst_bus_sync_signal_handler() as a sync handler if you want this
181 * signal to be emitted when a message is posted on the bus, like this:
183 * gst_bus_set_sync_handler (bus, gst_bus_sync_signal_handler, yourdata);
186 gst_bus_signals[SYNC_MESSAGE] =
187 g_signal_new ("sync-message", G_TYPE_FROM_CLASS (klass),
188 G_SIGNAL_RUN_LAST | G_SIGNAL_DETAILED,
189 G_STRUCT_OFFSET (GstBusClass, sync_message), NULL, NULL,
190 g_cclosure_marshal_VOID__BOXED, G_TYPE_NONE, 1, GST_TYPE_MESSAGE);
194 * @bus: the object which received the signal
195 * @message: the message that has been posted asynchronously
197 * A message has been posted on the bus. This signal is emitted from a
198 * GSource added to the mainloop. this signal will only be emitted when
199 * there is a mainloop running.
201 gst_bus_signals[ASYNC_MESSAGE] =
202 g_signal_new ("message", G_TYPE_FROM_CLASS (klass),
203 G_SIGNAL_RUN_LAST | G_SIGNAL_DETAILED,
204 G_STRUCT_OFFSET (GstBusClass, message), NULL, NULL,
205 g_cclosure_marshal_VOID__BOXED, G_TYPE_NONE, 1, GST_TYPE_MESSAGE);
207 g_type_class_add_private (klass, sizeof (GstBusPrivate));
211 gst_bus_init (GstBus * bus)
213 bus->queue = gst_atomic_queue_new (32);
214 bus->queue_lock = g_mutex_new ();
216 bus->priv = G_TYPE_INSTANCE_GET_PRIVATE (bus, GST_TYPE_BUS, GstBusPrivate);
217 bus->priv->enable_async = DEFAULT_ENABLE_ASYNC;
219 GST_DEBUG_OBJECT (bus, "created");
223 gst_bus_dispose (GObject * object)
225 GstBus *bus = GST_BUS (object);
230 g_mutex_lock (bus->queue_lock);
232 message = gst_atomic_queue_pop (bus->queue);
234 gst_message_unref (message);
235 } while (message != NULL);
236 gst_atomic_queue_unref (bus->queue);
238 g_mutex_unlock (bus->queue_lock);
239 g_mutex_free (bus->queue_lock);
240 bus->queue_lock = NULL;
243 gst_poll_free (bus->priv->poll);
244 bus->priv->poll = NULL;
247 G_OBJECT_CLASS (parent_class)->dispose (object);
253 * Creates a new #GstBus instance.
255 * Returns: (transfer full): a new #GstBus instance
262 result = g_object_newv (gst_bus_get_type (), 0, NULL);
263 GST_DEBUG_OBJECT (result, "created new bus");
270 * @bus: a #GstBus to post on
271 * @message: (transfer full): the #GstMessage to post
273 * Post a message on the given bus. Ownership of the message
274 * is taken by the bus.
276 * Returns: TRUE if the message could be posted, FALSE if the bus is flushing.
281 gst_bus_post (GstBus * bus, GstMessage * message)
283 GstBusSyncReply reply = GST_BUS_PASS;
284 GstBusSyncHandler handler;
285 gboolean emit_sync_message;
286 gpointer handler_data;
288 g_return_val_if_fail (GST_IS_BUS (bus), FALSE);
289 g_return_val_if_fail (GST_IS_MESSAGE (message), FALSE);
291 GST_DEBUG_OBJECT (bus, "[msg %p] posting on bus %" GST_PTR_FORMAT, message,
294 GST_OBJECT_LOCK (bus);
295 /* check if the bus is flushing */
296 if (GST_OBJECT_FLAG_IS_SET (bus, GST_BUS_FLUSHING))
299 handler = bus->sync_handler;
300 handler_data = bus->sync_handler_data;
301 emit_sync_message = bus->priv->num_sync_message_emitters > 0;
302 GST_OBJECT_UNLOCK (bus);
304 /* first call the sync handler if it is installed */
306 reply = handler (bus, message, handler_data);
308 /* emit sync-message if requested to do so via
309 gst_bus_enable_sync_message_emission. terrible but effective */
310 if (emit_sync_message && reply != GST_BUS_DROP
311 && handler != gst_bus_sync_signal_handler)
312 gst_bus_sync_signal_handler (bus, message, NULL);
314 /* If this is a bus without async message delivery
315 * always drop the message */
316 if (!bus->priv->poll)
317 reply = GST_BUS_DROP;
319 /* now see what we should do with the message */
322 /* drop the message */
323 GST_DEBUG_OBJECT (bus, "[msg %p] dropped", message);
326 /* pass the message to the async queue, refcount passed in the queue */
327 GST_DEBUG_OBJECT (bus, "[msg %p] pushing on async queue", message);
328 gst_atomic_queue_push (bus->queue, message);
329 gst_poll_write_control (bus->priv->poll);
330 GST_DEBUG_OBJECT (bus, "[msg %p] pushed on async queue", message);
335 /* async delivery, we need a mutex and a cond to block
337 GMutex *lock = g_mutex_new ();
338 GCond *cond = g_cond_new ();
340 GST_MESSAGE_COND (message) = cond;
341 GST_MESSAGE_GET_LOCK (message) = lock;
343 GST_DEBUG_OBJECT (bus, "[msg %p] waiting for async delivery", message);
345 /* now we lock the message mutex, send the message to the async
346 * queue. When the message is handled by the app and destroyed,
347 * the cond will be signalled and we can continue */
350 gst_atomic_queue_push (bus->queue, message);
351 gst_poll_write_control (bus->priv->poll);
353 /* now block till the message is freed */
354 g_cond_wait (cond, lock);
355 g_mutex_unlock (lock);
357 GST_DEBUG_OBJECT (bus, "[msg %p] delivered asynchronously", message);
364 g_warning ("invalid return from bus sync handler");
372 GST_DEBUG_OBJECT (bus, "bus is flushing");
373 gst_message_unref (message);
374 GST_OBJECT_UNLOCK (bus);
381 * gst_bus_have_pending:
382 * @bus: a #GstBus to check
384 * Check if there are pending messages on the bus that
387 * Returns: TRUE if there are messages on the bus to be handled, FALSE
393 gst_bus_have_pending (GstBus * bus)
397 g_return_val_if_fail (GST_IS_BUS (bus), FALSE);
399 /* see if there is a message on the bus */
400 result = gst_atomic_queue_length (bus->queue) != 0;
406 * gst_bus_set_flushing:
408 * @flushing: whether or not to flush the bus
410 * If @flushing, flush out and unref any messages queued in the bus. Releases
411 * references to the message origin objects. Will flush future messages until
412 * gst_bus_set_flushing() sets @flushing to #FALSE.
417 gst_bus_set_flushing (GstBus * bus, gboolean flushing)
421 GST_OBJECT_LOCK (bus);
424 GST_OBJECT_FLAG_SET (bus, GST_BUS_FLUSHING);
426 GST_DEBUG_OBJECT (bus, "set bus flushing");
428 while ((message = gst_bus_pop (bus)))
429 gst_message_unref (message);
431 GST_DEBUG_OBJECT (bus, "unset bus flushing");
432 GST_OBJECT_FLAG_UNSET (bus, GST_BUS_FLUSHING);
435 GST_OBJECT_UNLOCK (bus);
439 * gst_bus_timed_pop_filtered:
440 * @bus: a #GstBus to pop from
441 * @timeout: a timeout in nanoseconds, or GST_CLOCK_TIME_NONE to wait forever
442 * @types: message types to take into account, GST_MESSAGE_ANY for any type
444 * Get a message from the bus whose type matches the message type mask @types,
445 * waiting up to the specified timeout (and discarding any messages that do not
446 * match the mask provided).
448 * If @timeout is 0, this function behaves like gst_bus_pop_filtered(). If
449 * @timeout is #GST_CLOCK_TIME_NONE, this function will block forever until a
450 * matching message was posted on the bus.
452 * Returns: (transfer full): a #GstMessage matching the filter in @types,
453 * or NULL if no matching message was found on the bus until the timeout
454 * expired. The message is taken from the bus and needs to be unreffed
455 * with gst_message_unref() after usage.
462 gst_bus_timed_pop_filtered (GstBus * bus, GstClockTime timeout,
463 GstMessageType types)
467 gboolean first_round = TRUE;
468 GstClockTime elapsed = 0;
470 g_return_val_if_fail (GST_IS_BUS (bus), NULL);
471 g_return_val_if_fail (types != 0, NULL);
472 g_return_val_if_fail (timeout == 0 || bus->priv->poll != NULL, NULL);
474 g_mutex_lock (bus->queue_lock);
479 GST_LOG_OBJECT (bus, "have %d messages",
480 gst_atomic_queue_length (bus->queue));
482 while ((message = gst_atomic_queue_pop (bus->queue))) {
484 gst_poll_read_control (bus->priv->poll);
486 GST_DEBUG_OBJECT (bus, "got message %p, %s from %s, type mask is %u",
487 message, GST_MESSAGE_TYPE_NAME (message),
488 GST_MESSAGE_SRC_NAME (message), (guint) types);
489 if ((GST_MESSAGE_TYPE (message) & types) != 0) {
490 /* exit the loop, we have a message */
493 GST_DEBUG_OBJECT (bus, "discarding message, does not match mask");
494 gst_message_unref (message);
499 /* no need to wait, exit loop */
503 else if (timeout != GST_CLOCK_TIME_NONE) {
505 g_get_current_time (&then);
508 g_get_current_time (&now);
510 elapsed = GST_TIMEVAL_TO_TIME (now) - GST_TIMEVAL_TO_TIME (then);
512 if (elapsed > timeout)
517 /* only here in timeout case */
518 g_assert (bus->priv->poll);
519 g_mutex_unlock (bus->queue_lock);
520 ret = gst_poll_wait (bus->priv->poll, timeout - elapsed);
521 g_mutex_lock (bus->queue_lock);
524 GST_INFO_OBJECT (bus, "timed out, breaking loop");
527 GST_INFO_OBJECT (bus, "we got woken up, recheck for message");
533 g_mutex_unlock (bus->queue_lock);
541 * @bus: a #GstBus to pop
542 * @timeout: a timeout
544 * Get a message from the bus, waiting up to the specified timeout.
546 * If @timeout is 0, this function behaves like gst_bus_pop(). If @timeout is
547 * #GST_CLOCK_TIME_NONE, this function will block forever until a message was
550 * Returns: (transfer full): the #GstMessage that is on the bus after the
551 * specified timeout or NULL if the bus is empty after the timeout expired.
552 * The message is taken from the bus and needs to be unreffed with
553 * gst_message_unref() after usage.
560 gst_bus_timed_pop (GstBus * bus, GstClockTime timeout)
562 g_return_val_if_fail (GST_IS_BUS (bus), NULL);
564 return gst_bus_timed_pop_filtered (bus, timeout, GST_MESSAGE_ANY);
568 * gst_bus_pop_filtered:
569 * @bus: a #GstBus to pop
570 * @types: message types to take into account
572 * Get a message matching @type from the bus. Will discard all messages on
573 * the bus that do not match @type and that have been posted before the first
574 * message that does match @type. If there is no message matching @type on
575 * the bus, all messages will be discarded.
577 * Returns: (transfer full): the next #GstMessage matching @type that is on
578 * the bus, or NULL if the bus is empty or there is no message matching
579 * @type. The message is taken from the bus and needs to be unreffed with
580 * gst_message_unref() after usage.
587 gst_bus_pop_filtered (GstBus * bus, GstMessageType types)
589 g_return_val_if_fail (GST_IS_BUS (bus), NULL);
590 g_return_val_if_fail (types != 0, NULL);
592 return gst_bus_timed_pop_filtered (bus, 0, types);
597 * @bus: a #GstBus to pop
599 * Get a message from the bus.
601 * Returns: (transfer full): the #GstMessage that is on the bus, or NULL if the
602 * bus is empty. The message is taken from the bus and needs to be unreffed
603 * with gst_message_unref() after usage.
608 gst_bus_pop (GstBus * bus)
610 g_return_val_if_fail (GST_IS_BUS (bus), NULL);
612 return gst_bus_timed_pop_filtered (bus, 0, GST_MESSAGE_ANY);
619 * Peek the message on the top of the bus' queue. The message will remain
620 * on the bus' message queue. A reference is returned, and needs to be unreffed
623 * Returns: (transfer full): the #GstMessage that is on the bus, or NULL if the
629 gst_bus_peek (GstBus * bus)
633 g_return_val_if_fail (GST_IS_BUS (bus), NULL);
635 g_mutex_lock (bus->queue_lock);
636 message = gst_atomic_queue_peek (bus->queue);
638 gst_message_ref (message);
639 g_mutex_unlock (bus->queue_lock);
641 GST_DEBUG_OBJECT (bus, "peek on bus, got message %p", message);
647 * gst_bus_set_sync_handler:
648 * @bus: a #GstBus to install the handler on
649 * @func: The handler function to install
650 * @data: User data that will be sent to the handler function.
652 * Sets the synchronous handler on the bus. The function will be called
653 * every time a new message is posted on the bus. Note that the function
654 * will be called in the same thread context as the posting object. This
655 * function is usually only called by the creator of the bus. Applications
656 * should handle messages asynchronously using the gst_bus watch and poll
659 * You cannot replace an existing sync_handler. You can pass NULL to this
660 * function, which will clear the existing handler.
663 gst_bus_set_sync_handler (GstBus * bus, GstBusSyncHandler func, gpointer data)
665 g_return_if_fail (GST_IS_BUS (bus));
667 GST_OBJECT_LOCK (bus);
669 /* Assert if the user attempts to replace an existing sync_handler,
670 * other than to clear it */
671 if (func != NULL && bus->sync_handler != NULL)
674 bus->sync_handler = func;
675 bus->sync_handler_data = data;
676 GST_OBJECT_UNLOCK (bus);
682 GST_OBJECT_UNLOCK (bus);
683 g_warning ("cannot replace existing sync handler");
688 /* GSource for the bus
697 gst_bus_source_prepare (GSource * source, gint * timeout)
704 gst_bus_source_check (GSource * source)
706 GstBusSource *bsrc = (GstBusSource *) source;
708 return bsrc->bus->priv->pollfd.revents & (G_IO_IN | G_IO_HUP | G_IO_ERR);
712 gst_bus_source_dispatch (GSource * source, GSourceFunc callback,
715 GstBusFunc handler = (GstBusFunc) callback;
716 GstBusSource *bsource = (GstBusSource *) source;
721 g_return_val_if_fail (bsource != NULL, FALSE);
725 g_return_val_if_fail (GST_IS_BUS (bus), FALSE);
727 message = gst_bus_pop (bus);
729 /* The message queue might be empty if some other thread or callback set
730 * the bus to flushing between check/prepare and dispatch */
731 if (G_UNLIKELY (message == NULL))
737 GST_DEBUG_OBJECT (bus, "source %p calling dispatch with %" GST_PTR_FORMAT,
740 keep = handler (bus, message, user_data);
741 gst_message_unref (message);
743 GST_DEBUG_OBJECT (bus, "source %p handler returns %d", source, keep);
749 g_warning ("GstBus watch dispatched without callback\n"
750 "You must call g_source_set_callback().");
751 gst_message_unref (message);
757 gst_bus_source_finalize (GSource * source)
759 GstBusSource *bsource = (GstBusSource *) source;
764 GST_DEBUG_OBJECT (bus, "finalize source %p", source);
766 GST_OBJECT_LOCK (bus);
767 if (bus->priv->watch_id == source)
768 bus->priv->watch_id = NULL;
769 GST_OBJECT_UNLOCK (bus);
771 gst_object_unref (bsource->bus);
775 static GSourceFuncs gst_bus_source_funcs = {
776 gst_bus_source_prepare,
777 gst_bus_source_check,
778 gst_bus_source_dispatch,
779 gst_bus_source_finalize
783 * gst_bus_create_watch:
784 * @bus: a #GstBus to create the watch for
786 * Create watch for this bus. The GSource will be dispatched whenever
787 * a message is on the bus. After the GSource is dispatched, the
788 * message is popped off the bus and unreffed.
790 * Returns: (transfer full): a #GSource that can be added to a mainloop.
793 gst_bus_create_watch (GstBus * bus)
795 GstBusSource *source;
797 g_return_val_if_fail (GST_IS_BUS (bus), NULL);
798 g_return_val_if_fail (bus->priv->poll != NULL, NULL);
800 source = (GstBusSource *) g_source_new (&gst_bus_source_funcs,
801 sizeof (GstBusSource));
803 #if GLIB_CHECK_VERSION(2,26,0)
804 g_source_set_name ((GSource *) source, "GStreamer message bus watch");
807 source->bus = gst_object_ref (bus);
808 g_source_add_poll ((GSource *) source, &bus->priv->pollfd);
810 return (GSource *) source;
813 /* must be called with the bus OBJECT LOCK */
815 gst_bus_add_watch_full_unlocked (GstBus * bus, gint priority,
816 GstBusFunc func, gpointer user_data, GDestroyNotify notify)
822 if (bus->priv->watch_id) {
823 GST_ERROR_OBJECT (bus,
824 "Tried to add new watch while one was already there");
828 source = gst_bus_create_watch (bus);
830 if (priority != G_PRIORITY_DEFAULT)
831 g_source_set_priority (source, priority);
833 g_source_set_callback (source, (GSourceFunc) func, user_data, notify);
835 ctx = g_main_context_get_thread_default ();
836 id = g_source_attach (source, ctx);
837 g_source_unref (source);
840 bus->priv->watch_id = source;
843 GST_DEBUG_OBJECT (bus, "New source %p with id %u", source, id);
848 * gst_bus_add_watch_full:
849 * @bus: a #GstBus to create the watch for.
850 * @priority: The priority of the watch.
851 * @func: A function to call when a message is received.
852 * @user_data: user data passed to @func.
853 * @notify: the function to call when the source is removed.
855 * Adds a bus watch to the default main context with the given @priority (e.g.
856 * %G_PRIORITY_DEFAULT). Since 0.10.33 it is also possible to use a non-default
857 * main context set up using g_main_context_push_thread_default() (before
858 * one had to create a bus watch source and attach it to the desired main
859 * context 'manually').
861 * This function is used to receive asynchronous messages in the main loop.
862 * There can only be a single bus watch per bus, you must remove it before you
865 * When @func is called, the message belongs to the caller; if you want to
866 * keep a copy of it, call gst_message_ref() before leaving @func.
868 * The watch can be removed using g_source_remove() or by returning FALSE
871 * Returns: The event source id.
872 * Rename to: gst_bus_add_watch
876 gst_bus_add_watch_full (GstBus * bus, gint priority,
877 GstBusFunc func, gpointer user_data, GDestroyNotify notify)
881 g_return_val_if_fail (GST_IS_BUS (bus), 0);
883 GST_OBJECT_LOCK (bus);
884 id = gst_bus_add_watch_full_unlocked (bus, priority, func, user_data, notify);
885 GST_OBJECT_UNLOCK (bus);
891 * gst_bus_add_watch: (skip)
892 * @bus: a #GstBus to create the watch for
893 * @func: A function to call when a message is received.
894 * @user_data: user data passed to @func.
896 * Adds a bus watch to the default main context with the default priority
897 * (%G_PRIORITY_DEFAULT). Since 0.10.33 it is also possible to use a non-default
898 * main context set up using g_main_context_push_thread_default() (before
899 * one had to create a bus watch source and attach it to the desired main
900 * context 'manually').
902 * This function is used to receive asynchronous messages in the main loop.
903 * There can only be a single bus watch per bus, you must remove it before you
906 * The watch can be removed using g_source_remove() or by returning FALSE
909 * Returns: The event source id.
914 gst_bus_add_watch (GstBus * bus, GstBusFunc func, gpointer user_data)
916 return gst_bus_add_watch_full (bus, G_PRIORITY_DEFAULT, func,
924 gboolean source_running;
925 GstMessageType events;
930 poll_func (GstBus * bus, GstMessage * message, GstBusPollData * poll_data)
934 if (!g_main_loop_is_running (poll_data->loop)) {
935 GST_DEBUG ("mainloop %p not running", poll_data->loop);
939 type = GST_MESSAGE_TYPE (message);
941 if (type & poll_data->events) {
942 g_assert (poll_data->message == NULL);
943 /* keep ref to message */
944 poll_data->message = gst_message_ref (message);
945 GST_DEBUG ("mainloop %p quit", poll_data->loop);
946 g_main_loop_quit (poll_data->loop);
948 GST_DEBUG ("type %08x does not match %08x", type, poll_data->events);
953 poll_timeout (GstBusPollData * poll_data)
955 GST_DEBUG ("mainloop %p quit", poll_data->loop);
956 g_main_loop_quit (poll_data->loop);
958 /* we don't remove the GSource as this would free our poll_data,
959 * which we still need */
964 poll_destroy (GstBusPollData * poll_data, gpointer unused)
966 poll_data->source_running = FALSE;
967 if (!poll_data->timeout_id) {
968 g_main_loop_unref (poll_data->loop);
969 g_slice_free (GstBusPollData, poll_data);
974 poll_destroy_timeout (GstBusPollData * poll_data)
976 poll_data->timeout_id = 0;
977 if (!poll_data->source_running) {
978 g_main_loop_unref (poll_data->loop);
979 g_slice_free (GstBusPollData, poll_data);
986 * @events: a mask of #GstMessageType, representing the set of message types to
988 * @timeout: the poll timeout, as a #GstClockTimeDiff, or -1 to poll
991 * Poll the bus for messages. Will block while waiting for messages to come.
992 * You can specify a maximum time to poll with the @timeout parameter. If
993 * @timeout is negative, this function will block indefinitely.
995 * All messages not in @events will be popped off the bus and will be ignored.
997 * Because poll is implemented using the "message" signal enabled by
998 * gst_bus_add_signal_watch(), calling gst_bus_poll() will cause the "message"
999 * signal to be emitted for every message that poll sees. Thus a "message"
1000 * signal handler will see the same messages that this function sees -- neither
1001 * will steal messages from the other.
1003 * This function will run a main loop from the default main context when
1006 * You should never use this function, since it is pure evil. This is
1007 * especially true for GUI applications based on Gtk+ or Qt, but also for any
1008 * other non-trivial application that uses the GLib main loop. As this function
1009 * runs a GLib main loop, any callback attached to the default GLib main
1010 * context may be invoked. This could be timeouts, GUI events, I/O events etc.;
1011 * even if gst_bus_poll() is called with a 0 timeout. Any of these callbacks
1012 * may do things you do not expect, e.g. destroy the main application window or
1013 * some other resource; change other application state; display a dialog and
1014 * run another main loop until the user clicks it away. In short, using this
1015 * function may add a lot of complexity to your code through unexpected
1016 * re-entrancy and unexpected changes to your application's state.
1018 * For 0 timeouts use gst_bus_pop_filtered() instead of this function; for
1019 * other short timeouts use gst_bus_timed_pop_filtered(); everything else is
1020 * better handled by setting up an asynchronous bus watch and doing things
1023 * Returns: (transfer full): the message that was received, or NULL if the
1024 * poll timed out. The message is taken from the bus and needs to be
1025 * unreffed with gst_message_unref() after usage.
1028 gst_bus_poll (GstBus * bus, GstMessageType events, GstClockTimeDiff timeout)
1030 GstBusPollData *poll_data;
1034 poll_data = g_slice_new (GstBusPollData);
1035 poll_data->source_running = TRUE;
1036 poll_data->loop = g_main_loop_new (NULL, FALSE);
1037 poll_data->events = events;
1038 poll_data->message = NULL;
1041 poll_data->timeout_id = g_timeout_add_full (G_PRIORITY_DEFAULT_IDLE,
1042 timeout / GST_MSECOND, (GSourceFunc) poll_timeout, poll_data,
1043 (GDestroyNotify) poll_destroy_timeout);
1045 poll_data->timeout_id = 0;
1047 id = g_signal_connect_data (bus, "message", G_CALLBACK (poll_func), poll_data,
1048 (GClosureNotify) poll_destroy, 0);
1050 /* these can be nested, so it's ok */
1051 gst_bus_add_signal_watch (bus);
1053 GST_DEBUG ("running mainloop %p", poll_data->loop);
1054 g_main_loop_run (poll_data->loop);
1055 GST_DEBUG ("mainloop stopped %p", poll_data->loop);
1057 gst_bus_remove_signal_watch (bus);
1060 ret = poll_data->message;
1062 if (poll_data->timeout_id)
1063 g_source_remove (poll_data->timeout_id);
1065 /* poll_data will be freed now */
1066 g_signal_handler_disconnect (bus, id);
1068 GST_DEBUG_OBJECT (bus, "finished poll with message %p", ret);
1074 * gst_bus_async_signal_func:
1076 * @message: the #GstMessage received
1079 * A helper #GstBusFunc that can be used to convert all asynchronous messages
1085 gst_bus_async_signal_func (GstBus * bus, GstMessage * message, gpointer data)
1089 g_return_val_if_fail (GST_IS_BUS (bus), TRUE);
1090 g_return_val_if_fail (message != NULL, TRUE);
1092 detail = gst_message_type_to_quark (GST_MESSAGE_TYPE (message));
1094 g_signal_emit (bus, gst_bus_signals[ASYNC_MESSAGE], detail, message);
1096 /* we never remove this source based on signal emission return values */
1101 * gst_bus_sync_signal_handler:
1103 * @message: the #GstMessage received
1106 * A helper GstBusSyncHandler that can be used to convert all synchronous
1107 * messages into signals.
1109 * Returns: GST_BUS_PASS
1112 gst_bus_sync_signal_handler (GstBus * bus, GstMessage * message, gpointer data)
1116 g_return_val_if_fail (GST_IS_BUS (bus), GST_BUS_DROP);
1117 g_return_val_if_fail (message != NULL, GST_BUS_DROP);
1119 detail = gst_message_type_to_quark (GST_MESSAGE_TYPE (message));
1121 g_signal_emit (bus, gst_bus_signals[SYNC_MESSAGE], detail, message);
1123 return GST_BUS_PASS;
1127 * gst_bus_enable_sync_message_emission:
1128 * @bus: a #GstBus on which you want to receive the "sync-message" signal
1130 * Instructs GStreamer to emit the "sync-message" signal after running the bus's
1131 * sync handler. This function is here so that code can ensure that they can
1132 * synchronously receive messages without having to affect what the bin's sync
1135 * This function may be called multiple times. To clean up, the caller is
1136 * responsible for calling gst_bus_disable_sync_message_emission() as many times
1137 * as this function is called.
1139 * While this function looks similar to gst_bus_add_signal_watch(), it is not
1140 * exactly the same -- this function enables <emphasis>synchronous</emphasis> emission of
1141 * signals when messages arrive; gst_bus_add_signal_watch() adds an idle callback
1142 * to pop messages off the bus <emphasis>asynchronously</emphasis>. The sync-message signal
1143 * comes from the thread of whatever object posted the message; the "message"
1144 * signal is marshalled to the main thread via the main loop.
1149 gst_bus_enable_sync_message_emission (GstBus * bus)
1151 g_return_if_fail (GST_IS_BUS (bus));
1153 GST_OBJECT_LOCK (bus);
1154 bus->priv->num_sync_message_emitters++;
1155 GST_OBJECT_UNLOCK (bus);
1159 * gst_bus_disable_sync_message_emission:
1160 * @bus: a #GstBus on which you previously called
1161 * gst_bus_enable_sync_message_emission()
1163 * Instructs GStreamer to stop emitting the "sync-message" signal for this bus.
1164 * See gst_bus_enable_sync_message_emission() for more information.
1166 * In the event that multiple pieces of code have called
1167 * gst_bus_enable_sync_message_emission(), the sync-message emissions will only
1168 * be stopped after all calls to gst_bus_enable_sync_message_emission() were
1169 * "cancelled" by calling this function. In this way the semantics are exactly
1170 * the same as gst_object_ref() that which calls enable should also call
1176 gst_bus_disable_sync_message_emission (GstBus * bus)
1178 g_return_if_fail (GST_IS_BUS (bus));
1179 g_return_if_fail (bus->num_signal_watchers == 0);
1181 GST_OBJECT_LOCK (bus);
1182 bus->priv->num_sync_message_emitters--;
1183 GST_OBJECT_UNLOCK (bus);
1187 * gst_bus_add_signal_watch_full:
1188 * @bus: a #GstBus on which you want to receive the "message" signal
1189 * @priority: The priority of the watch.
1191 * Adds a bus signal watch to the default main context with the given @priority
1192 * (e.g. %G_PRIORITY_DEFAULT). Since 0.10.33 it is also possible to use a
1193 * non-default main context set up using g_main_context_push_thread_default()
1194 * (before one had to create a bus watch source and attach it to the desired
1195 * main context 'manually').
1197 * After calling this statement, the bus will emit the "message" signal for each
1198 * message posted on the bus when the main loop is running.
1200 * This function may be called multiple times. To clean up, the caller is
1201 * responsible for calling gst_bus_remove_signal_watch() as many times as this
1202 * function is called.
1204 * There can only be a single bus watch per bus, you must remove any signal
1205 * watch before you can set another type of watch.
1210 gst_bus_add_signal_watch_full (GstBus * bus, gint priority)
1212 g_return_if_fail (GST_IS_BUS (bus));
1214 /* I know the callees don't take this lock, so go ahead and abuse it */
1215 GST_OBJECT_LOCK (bus);
1217 if (bus->num_signal_watchers > 0)
1220 /* this should not fail because the counter above takes care of it */
1221 g_assert (bus->signal_watch_id == 0);
1223 bus->signal_watch_id =
1224 gst_bus_add_watch_full_unlocked (bus, priority, gst_bus_async_signal_func,
1227 if (G_UNLIKELY (bus->signal_watch_id == 0))
1232 bus->num_signal_watchers++;
1234 GST_OBJECT_UNLOCK (bus);
1240 g_critical ("Could not add signal watch to bus %s", GST_OBJECT_NAME (bus));
1241 GST_OBJECT_UNLOCK (bus);
1247 * gst_bus_add_signal_watch:
1248 * @bus: a #GstBus on which you want to receive the "message" signal
1250 * Adds a bus signal watch to the default main context with the default priority
1251 * (%G_PRIORITY_DEFAULT). Since 0.10.33 it is also possible to use a non-default
1252 * main context set up using g_main_context_push_thread_default() (before
1253 * one had to create a bus watch source and attach it to the desired main
1254 * context 'manually').
1256 * After calling this statement, the bus will emit the "message" signal for each
1257 * message posted on the bus.
1259 * This function may be called multiple times. To clean up, the caller is
1260 * responsible for calling gst_bus_remove_signal_watch() as many times as this
1261 * function is called.
1266 gst_bus_add_signal_watch (GstBus * bus)
1268 gst_bus_add_signal_watch_full (bus, G_PRIORITY_DEFAULT);
1272 * gst_bus_remove_signal_watch:
1273 * @bus: a #GstBus you previously added a signal watch to
1275 * Removes a signal watch previously added with gst_bus_add_signal_watch().
1280 gst_bus_remove_signal_watch (GstBus * bus)
1284 g_return_if_fail (GST_IS_BUS (bus));
1286 /* I know the callees don't take this lock, so go ahead and abuse it */
1287 GST_OBJECT_LOCK (bus);
1289 if (bus->num_signal_watchers == 0)
1292 bus->num_signal_watchers--;
1294 if (bus->num_signal_watchers > 0)
1297 id = bus->signal_watch_id;
1298 bus->signal_watch_id = 0;
1300 GST_DEBUG_OBJECT (bus, "removing signal watch %u", id);
1303 GST_OBJECT_UNLOCK (bus);
1306 g_source_remove (id);
1313 g_critical ("Bus %s has no signal watches attached", GST_OBJECT_NAME (bus));
1314 GST_OBJECT_UNLOCK (bus);