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>
80 #include "glib-compat-private.h"
82 #define GST_CAT_DEFAULT GST_CAT_BUS
92 static void gst_bus_dispose (GObject * object);
94 static void gst_bus_set_main_context (GstBus * bus, GMainContext * ctx);
96 static GstObjectClass *parent_class = NULL;
97 static guint gst_bus_signals[LAST_SIGNAL] = { 0 };
101 guint num_sync_message_emitters;
104 GMainContext *main_context;
107 G_DEFINE_TYPE (GstBus, gst_bus, GST_TYPE_OBJECT);
109 /* fixme: do something about this */
111 marshal_VOID__MINIOBJECT (GClosure * closure, GValue * return_value,
112 guint n_param_values, const GValue * param_values, gpointer invocation_hint,
113 gpointer marshal_data)
115 typedef void (*marshalfunc_VOID__MINIOBJECT) (gpointer obj, gpointer arg1,
117 register marshalfunc_VOID__MINIOBJECT callback;
118 register GCClosure *cc = (GCClosure *) closure;
119 register gpointer data1, data2;
121 g_return_if_fail (n_param_values == 2);
123 if (G_CCLOSURE_SWAP_DATA (closure)) {
124 data1 = closure->data;
125 data2 = g_value_peek_pointer (param_values + 0);
127 data1 = g_value_peek_pointer (param_values + 0);
128 data2 = closure->data;
131 (marshalfunc_VOID__MINIOBJECT) (marshal_data ? marshal_data :
134 callback (data1, gst_value_get_mini_object (param_values + 1), data2);
138 gst_bus_class_init (GstBusClass * klass)
140 GObjectClass *gobject_class = (GObjectClass *) klass;
142 parent_class = g_type_class_peek_parent (klass);
144 gobject_class->dispose = gst_bus_dispose;
147 * GstBus::sync-message:
148 * @bus: the object which received the signal
149 * @message: the message that has been posted synchronously
151 * A message has been posted on the bus. This signal is emitted from the
152 * thread that posted the message so one has to be careful with locking.
154 * This signal will not be emitted by default, you have to set up
155 * gst_bus_sync_signal_handler() as a sync handler if you want this
156 * signal to be emitted when a message is posted on the bus, like this:
158 * gst_bus_set_sync_handler (bus, gst_bus_sync_signal_handler, yourdata);
161 gst_bus_signals[SYNC_MESSAGE] =
162 g_signal_new ("sync-message", G_TYPE_FROM_CLASS (klass),
163 G_SIGNAL_RUN_LAST | G_SIGNAL_DETAILED,
164 G_STRUCT_OFFSET (GstBusClass, sync_message), NULL, NULL,
165 marshal_VOID__MINIOBJECT, G_TYPE_NONE, 1, GST_TYPE_MESSAGE);
169 * @bus: the object which received the signal
170 * @message: the message that has been posted asynchronously
172 * A message has been posted on the bus. This signal is emitted from a
173 * GSource added to the mainloop. this signal will only be emitted when
174 * there is a mainloop running.
176 gst_bus_signals[ASYNC_MESSAGE] =
177 g_signal_new ("message", G_TYPE_FROM_CLASS (klass),
178 G_SIGNAL_RUN_LAST | G_SIGNAL_DETAILED,
179 G_STRUCT_OFFSET (GstBusClass, message), NULL, NULL,
180 marshal_VOID__MINIOBJECT, G_TYPE_NONE, 1, GST_TYPE_MESSAGE);
182 g_type_class_add_private (klass, sizeof (GstBusPrivate));
186 gst_bus_init (GstBus * bus)
188 bus->queue = g_queue_new ();
189 bus->queue_lock = g_mutex_new ();
191 bus->priv = G_TYPE_INSTANCE_GET_PRIVATE (bus, GST_TYPE_BUS, GstBusPrivate);
192 bus->priv->queue_cond = g_cond_new ();
194 GST_DEBUG_OBJECT (bus, "created");
198 gst_bus_dispose (GObject * object)
200 GstBus *bus = GST_BUS (object);
205 g_mutex_lock (bus->queue_lock);
207 message = g_queue_pop_head (bus->queue);
209 gst_message_unref (message);
210 } while (message != NULL);
211 g_queue_free (bus->queue);
213 g_mutex_unlock (bus->queue_lock);
214 g_mutex_free (bus->queue_lock);
215 bus->queue_lock = NULL;
216 g_cond_free (bus->priv->queue_cond);
217 bus->priv->queue_cond = NULL;
220 if (bus->priv->main_context) {
221 g_main_context_unref (bus->priv->main_context);
222 bus->priv->main_context = NULL;
225 G_OBJECT_CLASS (parent_class)->dispose (object);
229 gst_bus_wakeup_main_context (GstBus * bus)
233 GST_OBJECT_LOCK (bus);
234 if ((ctx = bus->priv->main_context))
235 g_main_context_ref (ctx);
236 GST_OBJECT_UNLOCK (bus);
238 g_main_context_wakeup (ctx);
241 g_main_context_unref (ctx);
245 gst_bus_set_main_context (GstBus * bus, GMainContext * ctx)
247 GST_OBJECT_LOCK (bus);
249 if (bus->priv->main_context != NULL) {
250 g_main_context_unref (bus->priv->main_context);
251 bus->priv->main_context = NULL;
255 bus->priv->main_context = g_main_context_ref (ctx);
258 GST_DEBUG_OBJECT (bus, "setting main context to %p, GLib default context: %p",
259 ctx, g_main_context_default ());
261 GST_OBJECT_UNLOCK (bus);
267 * Creates a new #GstBus instance.
269 * Returns: (transfer full): a new #GstBus instance
276 result = g_object_newv (gst_bus_get_type (), 0, NULL);
277 GST_DEBUG_OBJECT (result, "created new bus");
284 * @bus: a #GstBus to post on
285 * @message: (transfer full): the #GstMessage to post
287 * Post a message on the given bus. Ownership of the message
288 * is taken by the bus.
290 * Returns: TRUE if the message could be posted, FALSE if the bus is flushing.
295 gst_bus_post (GstBus * bus, GstMessage * message)
297 GstBusSyncReply reply = GST_BUS_PASS;
298 GstBusSyncHandler handler;
299 gboolean emit_sync_message;
300 gpointer handler_data;
302 g_return_val_if_fail (GST_IS_BUS (bus), FALSE);
303 g_return_val_if_fail (GST_IS_MESSAGE (message), FALSE);
305 GST_DEBUG_OBJECT (bus, "[msg %p] posting on bus, type %s, %" GST_PTR_FORMAT
306 " from source %" GST_PTR_FORMAT,
307 message, GST_MESSAGE_TYPE_NAME (message), message->structure,
310 GST_OBJECT_LOCK (bus);
311 /* check if the bus is flushing */
312 if (GST_OBJECT_FLAG_IS_SET (bus, GST_BUS_FLUSHING))
315 handler = bus->sync_handler;
316 handler_data = bus->sync_handler_data;
317 emit_sync_message = bus->priv->num_sync_message_emitters > 0;
318 GST_OBJECT_UNLOCK (bus);
320 /* first call the sync handler if it is installed */
322 reply = handler (bus, message, handler_data);
324 /* emit sync-message if requested to do so via
325 gst_bus_enable_sync_message_emission. terrible but effective */
326 if (emit_sync_message && reply != GST_BUS_DROP
327 && handler != gst_bus_sync_signal_handler)
328 gst_bus_sync_signal_handler (bus, message, NULL);
330 /* now see what we should do with the message */
333 /* drop the message */
334 GST_DEBUG_OBJECT (bus, "[msg %p] dropped", message);
337 /* pass the message to the async queue, refcount passed in the queue */
338 GST_DEBUG_OBJECT (bus, "[msg %p] pushing on async queue", message);
339 g_mutex_lock (bus->queue_lock);
340 g_queue_push_tail (bus->queue, message);
341 g_cond_broadcast (bus->priv->queue_cond);
342 g_mutex_unlock (bus->queue_lock);
343 GST_DEBUG_OBJECT (bus, "[msg %p] pushed on async queue", message);
345 gst_bus_wakeup_main_context (bus);
350 /* async delivery, we need a mutex and a cond to block
352 GMutex *lock = g_mutex_new ();
353 GCond *cond = g_cond_new ();
355 GST_MESSAGE_COND (message) = cond;
356 GST_MESSAGE_GET_LOCK (message) = lock;
358 GST_DEBUG_OBJECT (bus, "[msg %p] waiting for async delivery", message);
360 /* now we lock the message mutex, send the message to the async
361 * queue. When the message is handled by the app and destroyed,
362 * the cond will be signalled and we can continue */
364 g_mutex_lock (bus->queue_lock);
365 g_queue_push_tail (bus->queue, message);
366 g_cond_broadcast (bus->priv->queue_cond);
367 g_mutex_unlock (bus->queue_lock);
369 gst_bus_wakeup_main_context (bus);
371 /* now block till the message is freed */
372 g_cond_wait (cond, lock);
373 g_mutex_unlock (lock);
375 GST_DEBUG_OBJECT (bus, "[msg %p] delivered asynchronously", message);
382 g_warning ("invalid return from bus sync handler");
390 GST_DEBUG_OBJECT (bus, "bus is flushing");
391 gst_message_unref (message);
392 GST_OBJECT_UNLOCK (bus);
399 * gst_bus_have_pending:
400 * @bus: a #GstBus to check
402 * Check if there are pending messages on the bus that
405 * Returns: TRUE if there are messages on the bus to be handled, FALSE
411 gst_bus_have_pending (GstBus * bus)
415 g_return_val_if_fail (GST_IS_BUS (bus), FALSE);
417 g_mutex_lock (bus->queue_lock);
418 /* see if there is a message on the bus */
419 result = !g_queue_is_empty (bus->queue);
420 g_mutex_unlock (bus->queue_lock);
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.
482 gst_bus_timed_pop_filtered (GstBus * bus, GstClockTime timeout,
483 GstMessageType types)
486 GTimeVal *timeval, abstimeout;
487 gboolean first_round = TRUE;
489 g_return_val_if_fail (GST_IS_BUS (bus), NULL);
490 g_return_val_if_fail (types != 0, NULL);
492 g_mutex_lock (bus->queue_lock);
495 GST_LOG_OBJECT (bus, "have %d messages", g_queue_get_length (bus->queue));
497 while ((message = g_queue_pop_head (bus->queue))) {
498 GST_DEBUG_OBJECT (bus, "got message %p, %s from %s, type mask is %u",
499 message, GST_MESSAGE_TYPE_NAME (message),
500 GST_MESSAGE_SRC_NAME (message), (guint) types);
501 if ((GST_MESSAGE_TYPE (message) & types) != 0) {
502 /* exit the loop, we have a message */
505 GST_DEBUG_OBJECT (bus, "discarding message, does not match mask");
506 gst_message_unref (message);
511 /* no need to wait, exit loop */
515 if (timeout == GST_CLOCK_TIME_NONE) {
518 } else if (first_round) {
519 glong add = timeout / 1000;
522 /* no need to wait */
525 /* make timeout absolute */
526 g_get_current_time (&abstimeout);
527 g_time_val_add (&abstimeout, add);
528 timeval = &abstimeout;
530 GST_DEBUG_OBJECT (bus, "blocking for message, timeout %ld", add);
532 /* calculated the absolute end time already, no need to do it again */
533 GST_DEBUG_OBJECT (bus, "blocking for message, again");
534 timeval = &abstimeout; /* fool compiler */
536 if (!g_cond_timed_wait (bus->priv->queue_cond, bus->queue_lock, timeval)) {
537 GST_INFO_OBJECT (bus, "timed out, breaking loop");
540 GST_INFO_OBJECT (bus, "we got woken up, recheck for message");
546 g_mutex_unlock (bus->queue_lock);
554 * @bus: a #GstBus to pop
555 * @timeout: a timeout
557 * Get a message from the bus, waiting up to the specified timeout.
559 * If @timeout is 0, this function behaves like gst_bus_pop(). If @timeout is
560 * #GST_CLOCK_TIME_NONE, this function will block forever until a message was
563 * Returns: (transfer full): the #GstMessage that is on the bus after the
564 * specified timeout or NULL if the bus is empty after the timeout expired.
565 * The message is taken from the bus and needs to be unreffed with
566 * gst_message_unref() after usage.
573 gst_bus_timed_pop (GstBus * bus, GstClockTime timeout)
575 g_return_val_if_fail (GST_IS_BUS (bus), NULL);
577 return gst_bus_timed_pop_filtered (bus, timeout, GST_MESSAGE_ANY);
581 * gst_bus_pop_filtered:
582 * @bus: a #GstBus to pop
583 * @types: message types to take into account
585 * Get a message matching @type from the bus. Will discard all messages on
586 * the bus that do not match @type and that have been posted before the first
587 * message that does match @type. If there is no message matching @type on
588 * the bus, all messages will be discarded.
590 * Returns: (transfer full): the next #GstMessage matching @type that is on
591 * the bus, or NULL if the bus is empty or there is no message matching
592 * @type. The message is taken from the bus and needs to be unreffed with
593 * gst_message_unref() after usage.
600 gst_bus_pop_filtered (GstBus * bus, GstMessageType types)
602 g_return_val_if_fail (GST_IS_BUS (bus), NULL);
603 g_return_val_if_fail (types != 0, NULL);
605 return gst_bus_timed_pop_filtered (bus, 0, types);
610 * @bus: a #GstBus to pop
612 * Get a message from the bus.
614 * Returns: (transfer full): the #GstMessage that is on the bus, or NULL if the
615 * bus is empty. The message is taken from the bus and needs to be unreffed
616 * with gst_message_unref() after usage.
621 gst_bus_pop (GstBus * bus)
623 g_return_val_if_fail (GST_IS_BUS (bus), NULL);
625 return gst_bus_timed_pop_filtered (bus, 0, GST_MESSAGE_ANY);
632 * Peek the message on the top of the bus' queue. The message will remain
633 * on the bus' message queue. A reference is returned, and needs to be unreffed
636 * Returns: (transfer full): the #GstMessage that is on the bus, or NULL if the
642 gst_bus_peek (GstBus * bus)
646 g_return_val_if_fail (GST_IS_BUS (bus), NULL);
648 g_mutex_lock (bus->queue_lock);
649 message = g_queue_peek_head (bus->queue);
651 gst_message_ref (message);
652 g_mutex_unlock (bus->queue_lock);
654 GST_DEBUG_OBJECT (bus, "peek on bus, got message %p", message);
660 * gst_bus_set_sync_handler:
661 * @bus: a #GstBus to install the handler on
662 * @func: The handler function to install
663 * @data: User data that will be sent to the handler function.
665 * Sets the synchronous handler on the bus. The function will be called
666 * every time a new message is posted on the bus. Note that the function
667 * will be called in the same thread context as the posting object. This
668 * function is usually only called by the creator of the bus. Applications
669 * should handle messages asynchronously using the gst_bus watch and poll
672 * You cannot replace an existing sync_handler. You can pass NULL to this
673 * function, which will clear the existing handler.
676 gst_bus_set_sync_handler (GstBus * bus, GstBusSyncHandler func, gpointer data)
678 g_return_if_fail (GST_IS_BUS (bus));
680 GST_OBJECT_LOCK (bus);
682 /* Assert if the user attempts to replace an existing sync_handler,
683 * other than to clear it */
684 if (func != NULL && bus->sync_handler != NULL)
687 bus->sync_handler = func;
688 bus->sync_handler_data = data;
689 GST_OBJECT_UNLOCK (bus);
695 GST_OBJECT_UNLOCK (bus);
696 g_warning ("cannot replace existing sync handler");
701 /* GSource for the bus
711 gst_bus_source_prepare (GSource * source, gint * timeout)
713 GstBusSource *bsrc = (GstBusSource *) source;
715 /* we do this here now that we know that we're attached to a main context
716 * (we don't support detaching a source from a main context and then
717 * re-attaching it to a different main context) */
718 if (G_UNLIKELY (!bsrc->inited)) {
719 gst_bus_set_main_context (bsrc->bus, g_source_get_context (source));
724 return gst_bus_have_pending (bsrc->bus);
728 gst_bus_source_check (GSource * source)
730 GstBusSource *bsrc = (GstBusSource *) source;
732 return gst_bus_have_pending (bsrc->bus);
736 gst_bus_source_dispatch (GSource * source, GSourceFunc callback,
739 GstBusFunc handler = (GstBusFunc) callback;
740 GstBusSource *bsource = (GstBusSource *) source;
745 g_return_val_if_fail (bsource != NULL, FALSE);
749 g_return_val_if_fail (GST_IS_BUS (bus), FALSE);
751 message = gst_bus_pop (bus);
753 /* The message queue might be empty if some other thread or callback set
754 * the bus to flushing between check/prepare and dispatch */
755 if (G_UNLIKELY (message == NULL))
761 GST_DEBUG_OBJECT (bus, "source %p calling dispatch with %" GST_PTR_FORMAT,
764 keep = handler (bus, message, user_data);
765 gst_message_unref (message);
767 GST_DEBUG_OBJECT (bus, "source %p handler returns %d", source, keep);
773 g_warning ("GstBus watch dispatched without callback\n"
774 "You must call g_source_set_callback().");
775 gst_message_unref (message);
781 gst_bus_source_finalize (GSource * source)
783 GstBusSource *bsource = (GstBusSource *) source;
788 GST_DEBUG_OBJECT (bus, "finalize source %p", source);
790 GST_OBJECT_LOCK (bus);
791 if (bus->priv->watch_id == source)
792 bus->priv->watch_id = NULL;
793 GST_OBJECT_UNLOCK (bus);
795 gst_bus_set_main_context (bsource->bus, NULL);
796 gst_object_unref (bsource->bus);
800 static GSourceFuncs gst_bus_source_funcs = {
801 gst_bus_source_prepare,
802 gst_bus_source_check,
803 gst_bus_source_dispatch,
804 gst_bus_source_finalize
808 * gst_bus_create_watch:
809 * @bus: a #GstBus to create the watch for
811 * Create watch for this bus. The GSource will be dispatched whenever
812 * a message is on the bus. After the GSource is dispatched, the
813 * message is popped off the bus and unreffed.
815 * Returns: (transfer full): a #GSource that can be added to a mainloop.
818 gst_bus_create_watch (GstBus * bus)
820 GstBusSource *source;
822 g_return_val_if_fail (GST_IS_BUS (bus), NULL);
824 source = (GstBusSource *) g_source_new (&gst_bus_source_funcs,
825 sizeof (GstBusSource));
827 #if GLIB_CHECK_VERSION(2,26,0)
828 g_source_set_name ((GSource *) source, "GStreamer message bus watch");
831 source->bus = gst_object_ref (bus);
832 source->inited = FALSE;
834 return (GSource *) source;
837 /* must be called with the bus OBJECT LOCK */
839 gst_bus_add_watch_full_unlocked (GstBus * bus, gint priority,
840 GstBusFunc func, gpointer user_data, GDestroyNotify notify)
846 if (bus->priv->watch_id) {
847 GST_ERROR_OBJECT (bus,
848 "Tried to add new watch while one was already there");
852 source = gst_bus_create_watch (bus);
854 if (priority != G_PRIORITY_DEFAULT)
855 g_source_set_priority (source, priority);
857 g_source_set_callback (source, (GSourceFunc) func, user_data, notify);
859 ctx = g_main_context_get_thread_default ();
860 id = g_source_attach (source, ctx);
861 g_source_unref (source);
864 bus->priv->watch_id = source;
867 GST_DEBUG_OBJECT (bus, "New source %p with id %u", source, id);
872 * gst_bus_add_watch_full:
873 * @bus: a #GstBus to create the watch for.
874 * @priority: The priority of the watch.
875 * @func: A function to call when a message is received.
876 * @user_data: user data passed to @func.
877 * @notify: the function to call when the source is removed.
879 * Adds a bus watch to the default main context with the given @priority (e.g.
880 * %G_PRIORITY_DEFAULT). Since 0.10.33 it is also possible to use a non-default
881 * main context set up using g_main_context_push_thread_default() (before
882 * one had to create a bus watch source and attach it to the desired main
883 * context 'manually').
885 * This function is used to receive asynchronous messages in the main loop.
886 * There can only be a single bus watch per bus, you must remove it before you
889 * When @func is called, the message belongs to the caller; if you want to
890 * keep a copy of it, call gst_message_ref() before leaving @func.
892 * The watch can be removed using g_source_remove() or by returning FALSE
895 * Returns: The event source id.
900 gst_bus_add_watch_full (GstBus * bus, gint priority,
901 GstBusFunc func, gpointer user_data, GDestroyNotify notify)
905 g_return_val_if_fail (GST_IS_BUS (bus), 0);
907 GST_OBJECT_LOCK (bus);
908 id = gst_bus_add_watch_full_unlocked (bus, priority, func, user_data, notify);
909 GST_OBJECT_UNLOCK (bus);
916 * @bus: a #GstBus to create the watch for
917 * @func: A function to call when a message is received.
918 * @user_data: user data passed to @func.
920 * Adds a bus watch to the default main context with the default priority
921 * (%G_PRIORITY_DEFAULT). Since 0.10.33 it is also possible to use a non-default
922 * main context set up using g_main_context_push_thread_default() (before
923 * one had to create a bus watch source and attach it to the desired main
924 * context 'manually').
926 * This function is used to receive asynchronous messages in the main loop.
927 * There can only be a single bus watch per bus, you must remove it before you
930 * The watch can be removed using g_source_remove() or by returning FALSE
933 * Returns: The event source id.
938 gst_bus_add_watch (GstBus * bus, GstBusFunc func, gpointer user_data)
940 return gst_bus_add_watch_full (bus, G_PRIORITY_DEFAULT, func,
948 gboolean source_running;
949 GstMessageType events;
954 poll_func (GstBus * bus, GstMessage * message, GstBusPollData * poll_data)
958 if (!g_main_loop_is_running (poll_data->loop)) {
959 GST_DEBUG ("mainloop %p not running", poll_data->loop);
963 type = GST_MESSAGE_TYPE (message);
965 if (type & poll_data->events) {
966 g_assert (poll_data->message == NULL);
967 /* keep ref to message */
968 poll_data->message = gst_message_ref (message);
969 GST_DEBUG ("mainloop %p quit", poll_data->loop);
970 g_main_loop_quit (poll_data->loop);
972 GST_DEBUG ("type %08x does not match %08x", type, poll_data->events);
977 poll_timeout (GstBusPollData * poll_data)
979 GST_DEBUG ("mainloop %p quit", poll_data->loop);
980 g_main_loop_quit (poll_data->loop);
982 /* we don't remove the GSource as this would free our poll_data,
983 * which we still need */
988 poll_destroy (GstBusPollData * poll_data, gpointer unused)
990 poll_data->source_running = FALSE;
991 if (!poll_data->timeout_id) {
992 g_main_loop_unref (poll_data->loop);
993 g_slice_free (GstBusPollData, poll_data);
998 poll_destroy_timeout (GstBusPollData * poll_data)
1000 poll_data->timeout_id = 0;
1001 if (!poll_data->source_running) {
1002 g_main_loop_unref (poll_data->loop);
1003 g_slice_free (GstBusPollData, poll_data);
1010 * @events: a mask of #GstMessageType, representing the set of message types to
1012 * @timeout: the poll timeout, as a #GstClockTimeDiff, or -1 to poll
1015 * Poll the bus for messages. Will block while waiting for messages to come.
1016 * You can specify a maximum time to poll with the @timeout parameter. If
1017 * @timeout is negative, this function will block indefinitely.
1019 * All messages not in @events will be popped off the bus and will be ignored.
1021 * Because poll is implemented using the "message" signal enabled by
1022 * gst_bus_add_signal_watch(), calling gst_bus_poll() will cause the "message"
1023 * signal to be emitted for every message that poll sees. Thus a "message"
1024 * signal handler will see the same messages that this function sees -- neither
1025 * will steal messages from the other.
1027 * This function will run a main loop from the default main context when
1030 * You should never use this function, since it is pure evil. This is
1031 * especially true for GUI applications based on Gtk+ or Qt, but also for any
1032 * other non-trivial application that uses the GLib main loop. As this function
1033 * runs a GLib main loop, any callback attached to the default GLib main
1034 * context may be invoked. This could be timeouts, GUI events, I/O events etc.;
1035 * even if gst_bus_poll() is called with a 0 timeout. Any of these callbacks
1036 * may do things you do not expect, e.g. destroy the main application window or
1037 * some other resource; change other application state; display a dialog and
1038 * run another main loop until the user clicks it away. In short, using this
1039 * function may add a lot of complexity to your code through unexpected
1040 * re-entrancy and unexpected changes to your application's state.
1042 * For 0 timeouts use gst_bus_pop_filtered() instead of this function; for
1043 * other short timeouts use gst_bus_timed_pop_filtered(); everything else is
1044 * better handled by setting up an asynchronous bus watch and doing things
1047 * Returns: (transfer full): the message that was received, or NULL if the
1048 * poll timed out. The message is taken from the bus and needs to be
1049 * unreffed with gst_message_unref() after usage.
1052 gst_bus_poll (GstBus * bus, GstMessageType events, GstClockTimeDiff timeout)
1054 GstBusPollData *poll_data;
1058 poll_data = g_slice_new (GstBusPollData);
1059 poll_data->source_running = TRUE;
1060 poll_data->loop = g_main_loop_new (NULL, FALSE);
1061 poll_data->events = events;
1062 poll_data->message = NULL;
1065 poll_data->timeout_id = g_timeout_add_full (G_PRIORITY_DEFAULT_IDLE,
1066 timeout / GST_MSECOND, (GSourceFunc) poll_timeout, poll_data,
1067 (GDestroyNotify) poll_destroy_timeout);
1069 poll_data->timeout_id = 0;
1071 id = g_signal_connect_data (bus, "message", G_CALLBACK (poll_func), poll_data,
1072 (GClosureNotify) poll_destroy, 0);
1074 /* these can be nested, so it's ok */
1075 gst_bus_add_signal_watch (bus);
1077 GST_DEBUG ("running mainloop %p", poll_data->loop);
1078 g_main_loop_run (poll_data->loop);
1079 GST_DEBUG ("mainloop stopped %p", poll_data->loop);
1081 gst_bus_remove_signal_watch (bus);
1084 ret = poll_data->message;
1086 if (poll_data->timeout_id)
1087 g_source_remove (poll_data->timeout_id);
1089 /* poll_data will be freed now */
1090 g_signal_handler_disconnect (bus, id);
1092 GST_DEBUG_OBJECT (bus, "finished poll with message %p", ret);
1098 * gst_bus_async_signal_func:
1100 * @message: the #GstMessage received
1103 * A helper #GstBusFunc that can be used to convert all asynchronous messages
1109 gst_bus_async_signal_func (GstBus * bus, GstMessage * message, gpointer data)
1113 g_return_val_if_fail (GST_IS_BUS (bus), TRUE);
1114 g_return_val_if_fail (message != NULL, TRUE);
1116 detail = gst_message_type_to_quark (GST_MESSAGE_TYPE (message));
1118 g_signal_emit (bus, gst_bus_signals[ASYNC_MESSAGE], detail, message);
1120 /* we never remove this source based on signal emission return values */
1125 * gst_bus_sync_signal_handler:
1127 * @message: the #GstMessage received
1130 * A helper GstBusSyncHandler that can be used to convert all synchronous
1131 * messages into signals.
1133 * Returns: GST_BUS_PASS
1136 gst_bus_sync_signal_handler (GstBus * bus, GstMessage * message, gpointer data)
1140 g_return_val_if_fail (GST_IS_BUS (bus), GST_BUS_DROP);
1141 g_return_val_if_fail (message != NULL, GST_BUS_DROP);
1143 detail = gst_message_type_to_quark (GST_MESSAGE_TYPE (message));
1145 g_signal_emit (bus, gst_bus_signals[SYNC_MESSAGE], detail, message);
1147 return GST_BUS_PASS;
1151 * gst_bus_enable_sync_message_emission:
1152 * @bus: a #GstBus on which you want to receive the "sync-message" signal
1154 * Instructs GStreamer to emit the "sync-message" signal after running the bus's
1155 * sync handler. This function is here so that code can ensure that they can
1156 * synchronously receive messages without having to affect what the bin's sync
1159 * This function may be called multiple times. To clean up, the caller is
1160 * responsible for calling gst_bus_disable_sync_message_emission() as many times
1161 * as this function is called.
1163 * While this function looks similar to gst_bus_add_signal_watch(), it is not
1164 * exactly the same -- this function enables <emphasis>synchronous</emphasis> emission of
1165 * signals when messages arrive; gst_bus_add_signal_watch() adds an idle callback
1166 * to pop messages off the bus <emphasis>asynchronously</emphasis>. The sync-message signal
1167 * comes from the thread of whatever object posted the message; the "message"
1168 * signal is marshalled to the main thread via the main loop.
1173 gst_bus_enable_sync_message_emission (GstBus * bus)
1175 g_return_if_fail (GST_IS_BUS (bus));
1177 GST_OBJECT_LOCK (bus);
1178 bus->priv->num_sync_message_emitters++;
1179 GST_OBJECT_UNLOCK (bus);
1183 * gst_bus_disable_sync_message_emission:
1184 * @bus: a #GstBus on which you previously called
1185 * gst_bus_enable_sync_message_emission()
1187 * Instructs GStreamer to stop emitting the "sync-message" signal for this bus.
1188 * See gst_bus_enable_sync_message_emission() for more information.
1190 * In the event that multiple pieces of code have called
1191 * gst_bus_enable_sync_message_emission(), the sync-message emissions will only
1192 * be stopped after all calls to gst_bus_enable_sync_message_emission() were
1193 * "cancelled" by calling this function. In this way the semantics are exactly
1194 * the same as gst_object_ref() that which calls enable should also call
1200 gst_bus_disable_sync_message_emission (GstBus * bus)
1202 g_return_if_fail (GST_IS_BUS (bus));
1203 g_return_if_fail (bus->num_signal_watchers == 0);
1205 GST_OBJECT_LOCK (bus);
1206 bus->priv->num_sync_message_emitters--;
1207 GST_OBJECT_UNLOCK (bus);
1211 * gst_bus_add_signal_watch_full:
1212 * @bus: a #GstBus on which you want to receive the "message" signal
1213 * @priority: The priority of the watch.
1215 * Adds a bus signal watch to the default main context with the given @priority
1216 * (e.g. %G_PRIORITY_DEFAULT). Since 0.10.33 it is also possible to use a
1217 * non-default main context set up using g_main_context_push_thread_default()
1218 * (before one had to create a bus watch source and attach it to the desired
1219 * main context 'manually').
1221 * After calling this statement, the bus will emit the "message" signal for each
1222 * message posted on the bus when the main loop is running.
1224 * This function may be called multiple times. To clean up, the caller is
1225 * responsible for calling gst_bus_remove_signal_watch() as many times as this
1226 * function is called.
1228 * There can only be a single bus watch per bus, you must remove any signal
1229 * watch before you can set another type of watch.
1234 gst_bus_add_signal_watch_full (GstBus * bus, gint priority)
1236 g_return_if_fail (GST_IS_BUS (bus));
1238 /* I know the callees don't take this lock, so go ahead and abuse it */
1239 GST_OBJECT_LOCK (bus);
1241 if (bus->num_signal_watchers > 0)
1244 /* this should not fail because the counter above takes care of it */
1245 g_assert (bus->signal_watch_id == 0);
1247 bus->signal_watch_id =
1248 gst_bus_add_watch_full_unlocked (bus, priority, gst_bus_async_signal_func,
1251 if (G_UNLIKELY (bus->signal_watch_id == 0))
1256 bus->num_signal_watchers++;
1258 GST_OBJECT_UNLOCK (bus);
1264 g_critical ("Could not add signal watch to bus %s", GST_OBJECT_NAME (bus));
1265 GST_OBJECT_UNLOCK (bus);
1271 * gst_bus_add_signal_watch:
1272 * @bus: a #GstBus on which you want to receive the "message" signal
1274 * Adds a bus signal watch to the default main context with the default priority
1275 * (%G_PRIORITY_DEFAULT). Since 0.10.33 it is also possible to use a non-default
1276 * main context set up using g_main_context_push_thread_default() (before
1277 * one had to create a bus watch source and attach it to the desired main
1278 * context 'manually').
1280 * After calling this statement, the bus will emit the "message" signal for each
1281 * message posted on the bus.
1283 * This function may be called multiple times. To clean up, the caller is
1284 * responsible for calling gst_bus_remove_signal_watch() as many times as this
1285 * function is called.
1290 gst_bus_add_signal_watch (GstBus * bus)
1292 gst_bus_add_signal_watch_full (bus, G_PRIORITY_DEFAULT);
1296 * gst_bus_remove_signal_watch:
1297 * @bus: a #GstBus you previously added a signal watch to
1299 * Removes a signal watch previously added with gst_bus_add_signal_watch().
1304 gst_bus_remove_signal_watch (GstBus * bus)
1308 g_return_if_fail (GST_IS_BUS (bus));
1310 /* I know the callees don't take this lock, so go ahead and abuse it */
1311 GST_OBJECT_LOCK (bus);
1313 if (bus->num_signal_watchers == 0)
1316 bus->num_signal_watchers--;
1318 if (bus->num_signal_watchers > 0)
1321 id = bus->signal_watch_id;
1322 bus->signal_watch_id = 0;
1324 GST_DEBUG_OBJECT (bus, "removing signal watch %u", id);
1327 GST_OBJECT_UNLOCK (bus);
1330 g_source_remove (id);
1337 g_critical ("Bus %s has no signal watches attached", GST_OBJECT_NAME (bus));
1338 GST_OBJECT_UNLOCK (bus);