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>
82 #define GST_CAT_DEFAULT GST_CAT_BUS
92 #define DEFAULT_ENABLE_ASYNC (TRUE)
100 static void gst_bus_dispose (GObject * object);
102 static guint gst_bus_signals[LAST_SIGNAL] = { 0 };
104 struct _GstBusPrivate
106 guint num_sync_message_emitters;
109 gboolean enable_async;
114 #define gst_bus_parent_class parent_class
115 G_DEFINE_TYPE (GstBus, gst_bus, GST_TYPE_OBJECT);
118 gst_bus_set_property (GObject * object,
119 guint prop_id, const GValue * value, GParamSpec * pspec)
121 GstBus *bus = GST_BUS_CAST (object);
124 case PROP_ENABLE_ASYNC:
125 bus->priv->enable_async = g_value_get_boolean (value);
128 G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
134 gst_bus_constructed (GObject * object)
136 GstBus *bus = GST_BUS_CAST (object);
138 if (bus->priv->enable_async) {
139 bus->priv->poll = gst_poll_new_timer ();
140 gst_poll_get_read_gpollfd (bus->priv->poll, &bus->priv->pollfd);
145 gst_bus_class_init (GstBusClass * klass)
147 GObjectClass *gobject_class = (GObjectClass *) klass;
149 gobject_class->dispose = gst_bus_dispose;
150 gobject_class->set_property = gst_bus_set_property;
151 gobject_class->constructed = gst_bus_constructed;
153 /* GstBus:enable-async:
155 * Enable async message delivery support for bus watches,
156 * gst_bus_pop() and similar API. Without this only the
157 * synchronous message handlers are called.
159 * This property is used to create the child element buses
164 g_object_class_install_property (gobject_class, PROP_ENABLE_ASYNC,
165 g_param_spec_boolean ("enable-async", "Enable Async",
166 "Enable async message delivery for bus watches and gst_bus_pop()",
167 DEFAULT_ENABLE_ASYNC,
168 G_PARAM_CONSTRUCT_ONLY | G_PARAM_WRITABLE | G_PARAM_STATIC_STRINGS));
171 * GstBus::sync-message:
172 * @bus: the object which received the signal
173 * @message: the message that has been posted synchronously
175 * A message has been posted on the bus. This signal is emitted from the
176 * thread that posted the message so one has to be careful with locking.
178 * This signal will not be emitted by default, you have to set up
179 * gst_bus_sync_signal_handler() as a sync handler if you want this
180 * signal to be emitted when a message is posted on the bus, like this:
182 * gst_bus_set_sync_handler (bus, gst_bus_sync_signal_handler, yourdata);
185 gst_bus_signals[SYNC_MESSAGE] =
186 g_signal_new ("sync-message", G_TYPE_FROM_CLASS (klass),
187 G_SIGNAL_RUN_LAST | G_SIGNAL_DETAILED,
188 G_STRUCT_OFFSET (GstBusClass, sync_message), NULL, NULL,
189 g_cclosure_marshal_VOID__BOXED, G_TYPE_NONE, 1, GST_TYPE_MESSAGE);
193 * @bus: the object which received the signal
194 * @message: the message that has been posted asynchronously
196 * A message has been posted on the bus. This signal is emitted from a
197 * GSource added to the mainloop. this signal will only be emitted when
198 * there is a mainloop running.
200 gst_bus_signals[ASYNC_MESSAGE] =
201 g_signal_new ("message", G_TYPE_FROM_CLASS (klass),
202 G_SIGNAL_RUN_LAST | G_SIGNAL_DETAILED,
203 G_STRUCT_OFFSET (GstBusClass, message), NULL, NULL,
204 g_cclosure_marshal_VOID__BOXED, G_TYPE_NONE, 1, GST_TYPE_MESSAGE);
206 g_type_class_add_private (klass, sizeof (GstBusPrivate));
210 gst_bus_init (GstBus * bus)
212 bus->queue = gst_atomic_queue_new (32);
213 bus->queue_lock = g_mutex_new ();
215 bus->priv = G_TYPE_INSTANCE_GET_PRIVATE (bus, GST_TYPE_BUS, GstBusPrivate);
216 bus->priv->enable_async = DEFAULT_ENABLE_ASYNC;
218 GST_DEBUG_OBJECT (bus, "created");
222 gst_bus_dispose (GObject * object)
224 GstBus *bus = GST_BUS (object);
229 g_mutex_lock (bus->queue_lock);
231 message = gst_atomic_queue_pop (bus->queue);
233 gst_message_unref (message);
234 } while (message != NULL);
235 gst_atomic_queue_unref (bus->queue);
237 g_mutex_unlock (bus->queue_lock);
238 g_mutex_free (bus->queue_lock);
239 bus->queue_lock = NULL;
242 gst_poll_free (bus->priv->poll);
243 bus->priv->poll = NULL;
246 G_OBJECT_CLASS (parent_class)->dispose (object);
252 * Creates a new #GstBus instance.
254 * Returns: (transfer full): a new #GstBus instance
261 result = g_object_newv (gst_bus_get_type (), 0, NULL);
262 GST_DEBUG_OBJECT (result, "created new bus");
269 * @bus: a #GstBus to post on
270 * @message: (transfer full): the #GstMessage to post
272 * Post a message on the given bus. Ownership of the message
273 * is taken by the bus.
275 * Returns: TRUE if the message could be posted, FALSE if the bus is flushing.
280 gst_bus_post (GstBus * bus, GstMessage * message)
282 GstBusSyncReply reply = GST_BUS_PASS;
283 GstBusSyncHandler handler;
284 gboolean emit_sync_message;
285 gpointer handler_data;
287 g_return_val_if_fail (GST_IS_BUS (bus), FALSE);
288 g_return_val_if_fail (GST_IS_MESSAGE (message), FALSE);
290 GST_DEBUG_OBJECT (bus, "[msg %p] posting on bus %" GST_PTR_FORMAT, message,
293 GST_OBJECT_LOCK (bus);
294 /* check if the bus is flushing */
295 if (GST_OBJECT_FLAG_IS_SET (bus, GST_BUS_FLUSHING))
298 handler = bus->sync_handler;
299 handler_data = bus->sync_handler_data;
300 emit_sync_message = bus->priv->num_sync_message_emitters > 0;
301 GST_OBJECT_UNLOCK (bus);
303 /* first call the sync handler if it is installed */
305 reply = handler (bus, message, handler_data);
307 /* emit sync-message if requested to do so via
308 gst_bus_enable_sync_message_emission. terrible but effective */
309 if (emit_sync_message && reply != GST_BUS_DROP
310 && handler != gst_bus_sync_signal_handler)
311 gst_bus_sync_signal_handler (bus, message, NULL);
313 /* If this is a bus without async message delivery
314 * always drop the message */
315 if (!bus->priv->poll)
316 reply = GST_BUS_DROP;
318 /* now see what we should do with the message */
321 /* drop the message */
322 GST_DEBUG_OBJECT (bus, "[msg %p] dropped", message);
325 /* pass the message to the async queue, refcount passed in the queue */
326 GST_DEBUG_OBJECT (bus, "[msg %p] pushing on async queue", message);
327 gst_atomic_queue_push (bus->queue, message);
328 gst_poll_write_control (bus->priv->poll);
329 GST_DEBUG_OBJECT (bus, "[msg %p] pushed on async queue", message);
334 /* async delivery, we need a mutex and a cond to block
336 GMutex *lock = g_mutex_new ();
337 GCond *cond = g_cond_new ();
339 GST_MESSAGE_COND (message) = cond;
340 GST_MESSAGE_GET_LOCK (message) = lock;
342 GST_DEBUG_OBJECT (bus, "[msg %p] waiting for async delivery", message);
344 /* now we lock the message mutex, send the message to the async
345 * queue. When the message is handled by the app and destroyed,
346 * the cond will be signalled and we can continue */
349 gst_atomic_queue_push (bus->queue, message);
350 gst_poll_write_control (bus->priv->poll);
352 /* now block till the message is freed */
353 g_cond_wait (cond, lock);
354 g_mutex_unlock (lock);
356 GST_DEBUG_OBJECT (bus, "[msg %p] delivered asynchronously", message);
363 g_warning ("invalid return from bus sync handler");
371 GST_DEBUG_OBJECT (bus, "bus is flushing");
372 gst_message_unref (message);
373 GST_OBJECT_UNLOCK (bus);
380 * gst_bus_have_pending:
381 * @bus: a #GstBus to check
383 * Check if there are pending messages on the bus that
386 * Returns: TRUE if there are messages on the bus to be handled, FALSE
392 gst_bus_have_pending (GstBus * bus)
396 g_return_val_if_fail (GST_IS_BUS (bus), FALSE);
398 /* see if there is a message on the bus */
399 result = gst_atomic_queue_length (bus->queue) != 0;
405 * gst_bus_set_flushing:
407 * @flushing: whether or not to flush the bus
409 * If @flushing, flush out and unref any messages queued in the bus. Releases
410 * references to the message origin objects. Will flush future messages until
411 * gst_bus_set_flushing() sets @flushing to #FALSE.
416 gst_bus_set_flushing (GstBus * bus, gboolean flushing)
420 GST_OBJECT_LOCK (bus);
423 GST_OBJECT_FLAG_SET (bus, GST_BUS_FLUSHING);
425 GST_DEBUG_OBJECT (bus, "set bus flushing");
427 while ((message = gst_bus_pop (bus)))
428 gst_message_unref (message);
430 GST_DEBUG_OBJECT (bus, "unset bus flushing");
431 GST_OBJECT_FLAG_UNSET (bus, GST_BUS_FLUSHING);
434 GST_OBJECT_UNLOCK (bus);
438 * gst_bus_timed_pop_filtered:
439 * @bus: a #GstBus to pop from
440 * @timeout: a timeout in nanoseconds, or GST_CLOCK_TIME_NONE to wait forever
441 * @types: message types to take into account, GST_MESSAGE_ANY for any type
443 * Get a message from the bus whose type matches the message type mask @types,
444 * waiting up to the specified timeout (and discarding any messages that do not
445 * match the mask provided).
447 * If @timeout is 0, this function behaves like gst_bus_pop_filtered(). If
448 * @timeout is #GST_CLOCK_TIME_NONE, this function will block forever until a
449 * matching message was posted on the bus.
451 * Returns: (transfer full): a #GstMessage matching the filter in @types,
452 * or NULL if no matching message was found on the bus until the timeout
453 * expired. The message is taken from the bus and needs to be unreffed
454 * with gst_message_unref() after usage.
461 gst_bus_timed_pop_filtered (GstBus * bus, GstClockTime timeout,
462 GstMessageType types)
466 gboolean first_round = TRUE;
467 GstClockTime elapsed = 0;
469 g_return_val_if_fail (GST_IS_BUS (bus), NULL);
470 g_return_val_if_fail (types != 0, NULL);
471 g_return_val_if_fail (timeout == 0 || bus->priv->poll != NULL, NULL);
473 g_mutex_lock (bus->queue_lock);
478 GST_LOG_OBJECT (bus, "have %d messages",
479 gst_atomic_queue_length (bus->queue));
481 while ((message = gst_atomic_queue_pop (bus->queue))) {
483 gst_poll_read_control (bus->priv->poll);
485 GST_DEBUG_OBJECT (bus, "got message %p, %s from %s, type mask is %u",
486 message, GST_MESSAGE_TYPE_NAME (message),
487 GST_MESSAGE_SRC (message) ?
488 GST_OBJECT_NAME (GST_MESSAGE_SRC (message)) : "NULL", (guint) types);
490 if ((GST_MESSAGE_TYPE (message) & types) != 0) {
491 /* exit the loop, we have a message */
494 GST_DEBUG_OBJECT (bus, "discarding message, does not match mask");
495 gst_message_unref (message);
500 /* no need to wait, exit loop */
504 else if (timeout != GST_CLOCK_TIME_NONE) {
506 g_get_current_time (&then);
509 g_get_current_time (&now);
511 elapsed = GST_TIMEVAL_TO_TIME (now) - GST_TIMEVAL_TO_TIME (then);
513 if (elapsed > timeout)
518 /* only here in timeout case */
519 g_assert (bus->priv->poll);
520 g_mutex_unlock (bus->queue_lock);
521 ret = gst_poll_wait (bus->priv->poll, timeout - elapsed);
522 g_mutex_lock (bus->queue_lock);
525 GST_INFO_OBJECT (bus, "timed out, breaking loop");
528 GST_INFO_OBJECT (bus, "we got woken up, recheck for message");
534 g_mutex_unlock (bus->queue_lock);
542 * @bus: a #GstBus to pop
543 * @timeout: a timeout
545 * Get a message from the bus, waiting up to the specified timeout.
547 * If @timeout is 0, this function behaves like gst_bus_pop(). If @timeout is
548 * #GST_CLOCK_TIME_NONE, this function will block forever until a message was
551 * Returns: (transfer full): the #GstMessage that is on the bus after the
552 * specified timeout or NULL if the bus is empty after the timeout expired.
553 * The message is taken from the bus and needs to be unreffed with
554 * gst_message_unref() after usage.
561 gst_bus_timed_pop (GstBus * bus, GstClockTime timeout)
563 g_return_val_if_fail (GST_IS_BUS (bus), NULL);
565 return gst_bus_timed_pop_filtered (bus, timeout, GST_MESSAGE_ANY);
569 * gst_bus_pop_filtered:
570 * @bus: a #GstBus to pop
571 * @types: message types to take into account
573 * Get a message matching @type from the bus. Will discard all messages on
574 * the bus that do not match @type and that have been posted before the first
575 * message that does match @type. If there is no message matching @type on
576 * the bus, all messages will be discarded.
578 * Returns: (transfer full): the next #GstMessage matching @type that is on
579 * the bus, or NULL if the bus is empty or there is no message matching
580 * @type. The message is taken from the bus and needs to be unreffed with
581 * gst_message_unref() after usage.
588 gst_bus_pop_filtered (GstBus * bus, GstMessageType types)
590 g_return_val_if_fail (GST_IS_BUS (bus), NULL);
591 g_return_val_if_fail (types != 0, NULL);
593 return gst_bus_timed_pop_filtered (bus, 0, types);
598 * @bus: a #GstBus to pop
600 * Get a message from the bus.
602 * Returns: (transfer full): the #GstMessage that is on the bus, or NULL if the
603 * bus is empty. The message is taken from the bus and needs to be unreffed
604 * with gst_message_unref() after usage.
609 gst_bus_pop (GstBus * bus)
611 g_return_val_if_fail (GST_IS_BUS (bus), NULL);
613 return gst_bus_timed_pop_filtered (bus, 0, GST_MESSAGE_ANY);
620 * Peek the message on the top of the bus' queue. The message will remain
621 * on the bus' message queue. A reference is returned, and needs to be unreffed
624 * Returns: (transfer full): the #GstMessage that is on the bus, or NULL if the
630 gst_bus_peek (GstBus * bus)
634 g_return_val_if_fail (GST_IS_BUS (bus), NULL);
636 g_mutex_lock (bus->queue_lock);
637 message = gst_atomic_queue_peek (bus->queue);
639 gst_message_ref (message);
640 g_mutex_unlock (bus->queue_lock);
642 GST_DEBUG_OBJECT (bus, "peek on bus, got message %p", message);
648 * gst_bus_set_sync_handler:
649 * @bus: a #GstBus to install the handler on
650 * @func: The handler function to install
651 * @data: User data that will be sent to the handler function.
653 * Sets the synchronous handler on the bus. The function will be called
654 * every time a new message is posted on the bus. Note that the function
655 * will be called in the same thread context as the posting object. This
656 * function is usually only called by the creator of the bus. Applications
657 * should handle messages asynchronously using the gst_bus watch and poll
660 * You cannot replace an existing sync_handler. You can pass NULL to this
661 * function, which will clear the existing handler.
664 gst_bus_set_sync_handler (GstBus * bus, GstBusSyncHandler func, gpointer data)
666 g_return_if_fail (GST_IS_BUS (bus));
668 GST_OBJECT_LOCK (bus);
670 /* Assert if the user attempts to replace an existing sync_handler,
671 * other than to clear it */
672 if (func != NULL && bus->sync_handler != NULL)
675 bus->sync_handler = func;
676 bus->sync_handler_data = data;
677 GST_OBJECT_UNLOCK (bus);
683 GST_OBJECT_UNLOCK (bus);
684 g_warning ("cannot replace existing sync handler");
689 /* GSource for the bus
698 gst_bus_source_prepare (GSource * source, gint * timeout)
705 gst_bus_source_check (GSource * source)
707 GstBusSource *bsrc = (GstBusSource *) source;
709 return bsrc->bus->priv->pollfd.revents & (G_IO_IN | G_IO_HUP | G_IO_ERR);
713 gst_bus_source_dispatch (GSource * source, GSourceFunc callback,
716 GstBusFunc handler = (GstBusFunc) callback;
717 GstBusSource *bsource = (GstBusSource *) source;
722 g_return_val_if_fail (bsource != NULL, FALSE);
726 g_return_val_if_fail (GST_IS_BUS (bus), FALSE);
728 message = gst_bus_pop (bus);
730 /* The message queue might be empty if some other thread or callback set
731 * the bus to flushing between check/prepare and dispatch */
732 if (G_UNLIKELY (message == NULL))
738 GST_DEBUG_OBJECT (bus, "source %p calling dispatch with %" GST_PTR_FORMAT,
741 keep = handler (bus, message, user_data);
742 gst_message_unref (message);
744 GST_DEBUG_OBJECT (bus, "source %p handler returns %d", source, keep);
750 g_warning ("GstBus watch dispatched without callback\n"
751 "You must call g_source_set_callback().");
752 gst_message_unref (message);
758 gst_bus_source_finalize (GSource * source)
760 GstBusSource *bsource = (GstBusSource *) source;
765 GST_DEBUG_OBJECT (bus, "finalize source %p", source);
767 GST_OBJECT_LOCK (bus);
768 if (bus->priv->watch_id == source)
769 bus->priv->watch_id = NULL;
770 GST_OBJECT_UNLOCK (bus);
772 gst_object_unref (bsource->bus);
776 static GSourceFuncs gst_bus_source_funcs = {
777 gst_bus_source_prepare,
778 gst_bus_source_check,
779 gst_bus_source_dispatch,
780 gst_bus_source_finalize
784 * gst_bus_create_watch:
785 * @bus: a #GstBus to create the watch for
787 * Create watch for this bus. The GSource will be dispatched whenever
788 * a message is on the bus. After the GSource is dispatched, the
789 * message is popped off the bus and unreffed.
791 * Returns: (transfer full): a #GSource that can be added to a mainloop.
794 gst_bus_create_watch (GstBus * bus)
796 GstBusSource *source;
798 g_return_val_if_fail (GST_IS_BUS (bus), NULL);
799 g_return_val_if_fail (bus->priv->poll != NULL, NULL);
801 source = (GstBusSource *) g_source_new (&gst_bus_source_funcs,
802 sizeof (GstBusSource));
804 #if GLIB_CHECK_VERSION(2,26,0)
805 g_source_set_name ((GSource *) source, "GStreamer message bus watch");
808 source->bus = gst_object_ref (bus);
809 g_source_add_poll ((GSource *) source, &bus->priv->pollfd);
811 return (GSource *) source;
814 /* must be called with the bus OBJECT LOCK */
816 gst_bus_add_watch_full_unlocked (GstBus * bus, gint priority,
817 GstBusFunc func, gpointer user_data, GDestroyNotify notify)
823 if (bus->priv->watch_id) {
824 GST_ERROR_OBJECT (bus,
825 "Tried to add new watch while one was already there");
829 source = gst_bus_create_watch (bus);
831 if (priority != G_PRIORITY_DEFAULT)
832 g_source_set_priority (source, priority);
834 g_source_set_callback (source, (GSourceFunc) func, user_data, notify);
836 ctx = g_main_context_get_thread_default ();
837 id = g_source_attach (source, ctx);
838 g_source_unref (source);
841 bus->priv->watch_id = source;
844 GST_DEBUG_OBJECT (bus, "New source %p with id %u", source, id);
849 * gst_bus_add_watch_full:
850 * @bus: a #GstBus to create the watch for.
851 * @priority: The priority of the watch.
852 * @func: A function to call when a message is received.
853 * @user_data: user data passed to @func.
854 * @notify: the function to call when the source is removed.
856 * Adds a bus watch to the default main context with the given @priority (e.g.
857 * %G_PRIORITY_DEFAULT). Since 0.10.33 it is also possible to use a non-default
858 * main context set up using g_main_context_push_thread_default() (before
859 * one had to create a bus watch source and attach it to the desired main
860 * context 'manually').
862 * This function is used to receive asynchronous messages in the main loop.
863 * There can only be a single bus watch per bus, you must remove it before you
866 * When @func is called, the message belongs to the caller; if you want to
867 * keep a copy of it, call gst_message_ref() before leaving @func.
869 * The watch can be removed using g_source_remove() or by returning FALSE
872 * Returns: The event source id.
873 * Rename to: gst_bus_add_watch
877 gst_bus_add_watch_full (GstBus * bus, gint priority,
878 GstBusFunc func, gpointer user_data, GDestroyNotify notify)
882 g_return_val_if_fail (GST_IS_BUS (bus), 0);
884 GST_OBJECT_LOCK (bus);
885 id = gst_bus_add_watch_full_unlocked (bus, priority, func, user_data, notify);
886 GST_OBJECT_UNLOCK (bus);
892 * gst_bus_add_watch: (skip)
893 * @bus: a #GstBus to create the watch for
894 * @func: A function to call when a message is received.
895 * @user_data: user data passed to @func.
897 * Adds a bus watch to the default main context with the default priority
898 * (%G_PRIORITY_DEFAULT). Since 0.10.33 it is also possible to use a non-default
899 * main context set up using g_main_context_push_thread_default() (before
900 * one had to create a bus watch source and attach it to the desired main
901 * context 'manually').
903 * This function is used to receive asynchronous messages in the main loop.
904 * There can only be a single bus watch per bus, you must remove it before you
907 * The watch can be removed using g_source_remove() or by returning FALSE
910 * Returns: The event source id.
915 gst_bus_add_watch (GstBus * bus, GstBusFunc func, gpointer user_data)
917 return gst_bus_add_watch_full (bus, G_PRIORITY_DEFAULT, func,
925 gboolean source_running;
926 GstMessageType events;
931 poll_func (GstBus * bus, GstMessage * message, GstBusPollData * poll_data)
935 if (!g_main_loop_is_running (poll_data->loop)) {
936 GST_DEBUG ("mainloop %p not running", poll_data->loop);
940 type = GST_MESSAGE_TYPE (message);
942 if (type & poll_data->events) {
943 g_assert (poll_data->message == NULL);
944 /* keep ref to message */
945 poll_data->message = gst_message_ref (message);
946 GST_DEBUG ("mainloop %p quit", poll_data->loop);
947 g_main_loop_quit (poll_data->loop);
949 GST_DEBUG ("type %08x does not match %08x", type, poll_data->events);
954 poll_timeout (GstBusPollData * poll_data)
956 GST_DEBUG ("mainloop %p quit", poll_data->loop);
957 g_main_loop_quit (poll_data->loop);
959 /* we don't remove the GSource as this would free our poll_data,
960 * which we still need */
965 poll_destroy (GstBusPollData * poll_data, gpointer unused)
967 poll_data->source_running = FALSE;
968 if (!poll_data->timeout_id) {
969 g_main_loop_unref (poll_data->loop);
970 g_slice_free (GstBusPollData, poll_data);
975 poll_destroy_timeout (GstBusPollData * poll_data)
977 poll_data->timeout_id = 0;
978 if (!poll_data->source_running) {
979 g_main_loop_unref (poll_data->loop);
980 g_slice_free (GstBusPollData, poll_data);
987 * @events: a mask of #GstMessageType, representing the set of message types to
989 * @timeout: the poll timeout, as a #GstClockTimeDiff, or -1 to poll
992 * Poll the bus for messages. Will block while waiting for messages to come.
993 * You can specify a maximum time to poll with the @timeout parameter. If
994 * @timeout is negative, this function will block indefinitely.
996 * All messages not in @events will be popped off the bus and will be ignored.
998 * Because poll is implemented using the "message" signal enabled by
999 * gst_bus_add_signal_watch(), calling gst_bus_poll() will cause the "message"
1000 * signal to be emitted for every message that poll sees. Thus a "message"
1001 * signal handler will see the same messages that this function sees -- neither
1002 * will steal messages from the other.
1004 * This function will run a main loop from the default main context when
1007 * You should never use this function, since it is pure evil. This is
1008 * especially true for GUI applications based on Gtk+ or Qt, but also for any
1009 * other non-trivial application that uses the GLib main loop. As this function
1010 * runs a GLib main loop, any callback attached to the default GLib main
1011 * context may be invoked. This could be timeouts, GUI events, I/O events etc.;
1012 * even if gst_bus_poll() is called with a 0 timeout. Any of these callbacks
1013 * may do things you do not expect, e.g. destroy the main application window or
1014 * some other resource; change other application state; display a dialog and
1015 * run another main loop until the user clicks it away. In short, using this
1016 * function may add a lot of complexity to your code through unexpected
1017 * re-entrancy and unexpected changes to your application's state.
1019 * For 0 timeouts use gst_bus_pop_filtered() instead of this function; for
1020 * other short timeouts use gst_bus_timed_pop_filtered(); everything else is
1021 * better handled by setting up an asynchronous bus watch and doing things
1024 * Returns: (transfer full): the message that was received, or NULL if the
1025 * poll timed out. The message is taken from the bus and needs to be
1026 * unreffed with gst_message_unref() after usage.
1029 gst_bus_poll (GstBus * bus, GstMessageType events, GstClockTimeDiff timeout)
1031 GstBusPollData *poll_data;
1035 poll_data = g_slice_new (GstBusPollData);
1036 poll_data->source_running = TRUE;
1037 poll_data->loop = g_main_loop_new (NULL, FALSE);
1038 poll_data->events = events;
1039 poll_data->message = NULL;
1042 poll_data->timeout_id = g_timeout_add_full (G_PRIORITY_DEFAULT_IDLE,
1043 timeout / GST_MSECOND, (GSourceFunc) poll_timeout, poll_data,
1044 (GDestroyNotify) poll_destroy_timeout);
1046 poll_data->timeout_id = 0;
1048 id = g_signal_connect_data (bus, "message", G_CALLBACK (poll_func), poll_data,
1049 (GClosureNotify) poll_destroy, 0);
1051 /* these can be nested, so it's ok */
1052 gst_bus_add_signal_watch (bus);
1054 GST_DEBUG ("running mainloop %p", poll_data->loop);
1055 g_main_loop_run (poll_data->loop);
1056 GST_DEBUG ("mainloop stopped %p", poll_data->loop);
1058 gst_bus_remove_signal_watch (bus);
1061 ret = poll_data->message;
1063 if (poll_data->timeout_id)
1064 g_source_remove (poll_data->timeout_id);
1066 /* poll_data will be freed now */
1067 g_signal_handler_disconnect (bus, id);
1069 GST_DEBUG_OBJECT (bus, "finished poll with message %p", ret);
1075 * gst_bus_async_signal_func:
1077 * @message: the #GstMessage received
1080 * A helper #GstBusFunc that can be used to convert all asynchronous messages
1086 gst_bus_async_signal_func (GstBus * bus, GstMessage * message, gpointer data)
1090 g_return_val_if_fail (GST_IS_BUS (bus), TRUE);
1091 g_return_val_if_fail (message != NULL, TRUE);
1093 detail = gst_message_type_to_quark (GST_MESSAGE_TYPE (message));
1095 g_signal_emit (bus, gst_bus_signals[ASYNC_MESSAGE], detail, message);
1097 /* we never remove this source based on signal emission return values */
1102 * gst_bus_sync_signal_handler:
1104 * @message: the #GstMessage received
1107 * A helper GstBusSyncHandler that can be used to convert all synchronous
1108 * messages into signals.
1110 * Returns: GST_BUS_PASS
1113 gst_bus_sync_signal_handler (GstBus * bus, GstMessage * message, gpointer data)
1117 g_return_val_if_fail (GST_IS_BUS (bus), GST_BUS_DROP);
1118 g_return_val_if_fail (message != NULL, GST_BUS_DROP);
1120 detail = gst_message_type_to_quark (GST_MESSAGE_TYPE (message));
1122 g_signal_emit (bus, gst_bus_signals[SYNC_MESSAGE], detail, message);
1124 return GST_BUS_PASS;
1128 * gst_bus_enable_sync_message_emission:
1129 * @bus: a #GstBus on which you want to receive the "sync-message" signal
1131 * Instructs GStreamer to emit the "sync-message" signal after running the bus's
1132 * sync handler. This function is here so that code can ensure that they can
1133 * synchronously receive messages without having to affect what the bin's sync
1136 * This function may be called multiple times. To clean up, the caller is
1137 * responsible for calling gst_bus_disable_sync_message_emission() as many times
1138 * as this function is called.
1140 * While this function looks similar to gst_bus_add_signal_watch(), it is not
1141 * exactly the same -- this function enables <emphasis>synchronous</emphasis> emission of
1142 * signals when messages arrive; gst_bus_add_signal_watch() adds an idle callback
1143 * to pop messages off the bus <emphasis>asynchronously</emphasis>. The sync-message signal
1144 * comes from the thread of whatever object posted the message; the "message"
1145 * signal is marshalled to the main thread via the main loop.
1150 gst_bus_enable_sync_message_emission (GstBus * bus)
1152 g_return_if_fail (GST_IS_BUS (bus));
1154 GST_OBJECT_LOCK (bus);
1155 bus->priv->num_sync_message_emitters++;
1156 GST_OBJECT_UNLOCK (bus);
1160 * gst_bus_disable_sync_message_emission:
1161 * @bus: a #GstBus on which you previously called
1162 * gst_bus_enable_sync_message_emission()
1164 * Instructs GStreamer to stop emitting the "sync-message" signal for this bus.
1165 * See gst_bus_enable_sync_message_emission() for more information.
1167 * In the event that multiple pieces of code have called
1168 * gst_bus_enable_sync_message_emission(), the sync-message emissions will only
1169 * be stopped after all calls to gst_bus_enable_sync_message_emission() were
1170 * "cancelled" by calling this function. In this way the semantics are exactly
1171 * the same as gst_object_ref() that which calls enable should also call
1177 gst_bus_disable_sync_message_emission (GstBus * bus)
1179 g_return_if_fail (GST_IS_BUS (bus));
1180 g_return_if_fail (bus->num_signal_watchers == 0);
1182 GST_OBJECT_LOCK (bus);
1183 bus->priv->num_sync_message_emitters--;
1184 GST_OBJECT_UNLOCK (bus);
1188 * gst_bus_add_signal_watch_full:
1189 * @bus: a #GstBus on which you want to receive the "message" signal
1190 * @priority: The priority of the watch.
1192 * Adds a bus signal watch to the default main context with the given @priority
1193 * (e.g. %G_PRIORITY_DEFAULT). Since 0.10.33 it is also possible to use a
1194 * non-default main context set up using g_main_context_push_thread_default()
1195 * (before one had to create a bus watch source and attach it to the desired
1196 * main context 'manually').
1198 * After calling this statement, the bus will emit the "message" signal for each
1199 * message posted on the bus when the main loop is running.
1201 * This function may be called multiple times. To clean up, the caller is
1202 * responsible for calling gst_bus_remove_signal_watch() as many times as this
1203 * function is called.
1205 * There can only be a single bus watch per bus, you must remove any signal
1206 * watch before you can set another type of watch.
1211 gst_bus_add_signal_watch_full (GstBus * bus, gint priority)
1213 g_return_if_fail (GST_IS_BUS (bus));
1215 /* I know the callees don't take this lock, so go ahead and abuse it */
1216 GST_OBJECT_LOCK (bus);
1218 if (bus->num_signal_watchers > 0)
1221 /* this should not fail because the counter above takes care of it */
1222 g_assert (bus->signal_watch_id == 0);
1224 bus->signal_watch_id =
1225 gst_bus_add_watch_full_unlocked (bus, priority, gst_bus_async_signal_func,
1228 if (G_UNLIKELY (bus->signal_watch_id == 0))
1233 bus->num_signal_watchers++;
1235 GST_OBJECT_UNLOCK (bus);
1241 g_critical ("Could not add signal watch to bus %s", GST_OBJECT_NAME (bus));
1242 GST_OBJECT_UNLOCK (bus);
1248 * gst_bus_add_signal_watch:
1249 * @bus: a #GstBus on which you want to receive the "message" signal
1251 * Adds a bus signal watch to the default main context with the default priority
1252 * (%G_PRIORITY_DEFAULT). Since 0.10.33 it is also possible to use a non-default
1253 * main context set up using g_main_context_push_thread_default() (before
1254 * one had to create a bus watch source and attach it to the desired main
1255 * context 'manually').
1257 * After calling this statement, the bus will emit the "message" signal for each
1258 * message posted on the bus.
1260 * This function may be called multiple times. To clean up, the caller is
1261 * responsible for calling gst_bus_remove_signal_watch() as many times as this
1262 * function is called.
1267 gst_bus_add_signal_watch (GstBus * bus)
1269 gst_bus_add_signal_watch_full (bus, G_PRIORITY_DEFAULT);
1273 * gst_bus_remove_signal_watch:
1274 * @bus: a #GstBus you previously added a signal watch to
1276 * Removes a signal watch previously added with gst_bus_add_signal_watch().
1281 gst_bus_remove_signal_watch (GstBus * bus)
1285 g_return_if_fail (GST_IS_BUS (bus));
1287 /* I know the callees don't take this lock, so go ahead and abuse it */
1288 GST_OBJECT_LOCK (bus);
1290 if (bus->num_signal_watchers == 0)
1293 bus->num_signal_watchers--;
1295 if (bus->num_signal_watchers > 0)
1298 id = bus->signal_watch_id;
1299 bus->signal_watch_id = 0;
1301 GST_DEBUG_OBJECT (bus, "removing signal watch %u", id);
1304 GST_OBJECT_UNLOCK (bus);
1307 g_source_remove (id);
1314 g_critical ("Bus %s has no signal watches attached", GST_OBJECT_NAME (bus));
1315 GST_OBJECT_UNLOCK (bus);