Struct gstreamer::Bus

pub struct Bus(_, _);

The Bus is an object responsible for delivering Message packets in a first-in first-out way from the streaming threads (see Task) to the application.

Since the application typically only wants to deal with delivery of these messages from one thread, the GstBus will marshall the messages between different threads. This is important since the actual streaming of media is done in another thread than the application.

The GstBus provides support for glib::Source based notifications. This makes it possible to handle the delivery in the glib mainloop.

The glib::Source callback function Bus::async_signal_func can be used to convert all bus messages into signal emissions.

A message is posted on the bus with the Bus::post method. With the Bus::peek and Bus::pop methods one can look at or retrieve a previously posted message.

The bus can be polled with the Bus::poll method. This methods blocks up to the specified timeout value until one of the specified messages types is posted on the bus. The application can then Bus::pop the messages from the bus to handle them. Alternatively the application can register an asynchronous bus function using Bus::add_watch_full or Bus::add_watch. This function will install a glib::Source in the default glib main loop and will deliver messages a short while after they have been posted. Note that the main loop should be running for the asynchronous callbacks.

It is also possible to get messages from the bus without any thread marshalling with the Bus::set_sync_handler method. This makes it possible to react to a message in the same thread that posted the message on the bus. This should only be used if the application is able to deal with messages from different threads.

Every Pipeline has one bus.

Note that a Pipeline will set its bus into flushing state when changing from READY to NULL state.

Implements

GstObjectExt, glib::object::ObjectExt

Implementations

impl Bus

pub fn new() -> Bus

Creates a new Bus instance.

Returns

a new Bus instance

pub fn add_signal_watch(&self)

Adds a bus signal watch to the default main context with the default priority (G_PRIORITY_DEFAULT). It is also possible to use a non-default main context set up using glib::MainContext::push_thread_default (before one had to create a bus watch source and attach it to the desired main context 'manually').

After calling this statement, the bus will emit the "message" signal for each message posted on the bus.

This function may be called multiple times. To clean up, the caller is responsible for calling Bus::remove_signal_watch as many times as this function is called.

MT safe.

pub fn disable_sync_message_emission(&self)

Instructs GStreamer to stop emitting the "sync-message" signal for this bus. See Bus::enable_sync_message_emission for more information.

In the event that multiple pieces of code have called Bus::enable_sync_message_emission, the sync-message emissions will only be stopped after all calls to Bus::enable_sync_message_emission were "cancelled" by calling this function. In this way the semantics are exactly the same as GstObjectExt::ref that which calls enable should also call disable.

MT safe.

pub fn enable_sync_message_emission(&self)

Instructs GStreamer to emit the "sync-message" signal after running the bus's sync handler. This function is here so that code can ensure that they can synchronously receive messages without having to affect what the bin's sync handler is.

This function may be called multiple times. To clean up, the caller is responsible for calling Bus::disable_sync_message_emission as many times as this function is called.

While this function looks similar to Bus::add_signal_watch, it is not exactly the same -- this function enables synchronous emission of signals when messages arrive; Bus::add_signal_watch adds an idle callback to pop messages off the bus asynchronously. The sync-message signal comes from the thread of whatever object posted the message; the "message" signal is marshalled to the main thread via the main loop.

MT safe.

pub fn have_pending(&self) -> bool

Check if there are pending messages on the bus that should be handled.

Returns

true if there are messages on the bus to be handled, false otherwise.

MT safe.

pub fn peek(&self) -> Option<Message>

Peek the message on the top of the bus' queue. The message will remain on the bus' message queue. A reference is returned, and needs to be unreffed by the caller.

Returns

the Message that is on the bus, or None if the bus is empty.

MT safe.

pub fn pop(&self) -> Option<Message>

Get a message from the bus.

Returns

the Message that is on the bus, or None if the bus is empty. The message is taken from the bus and needs to be unreffed with Message::unref after usage.

MT safe.

pub fn post(&self, message: &Message) -> Result<(), BoolError>

Post a message on the given bus. Ownership of the message is taken by the bus.

message

the Message to post

Returns

true if the message could be posted, false if the bus is flushing.

MT safe.

pub fn remove_signal_watch(&self)

Removes a signal watch previously added with Bus::add_signal_watch.

MT safe.

pub fn remove_watch(&self) -> Result<(), BoolError>

Removes an installed bus watch from self.

Returns

true on success or false if self has no event source.

pub fn set_flushing(&self, flushing: bool)

If flushing, flush out and unref any messages queued in the bus. Releases references to the message origin objects. Will flush future messages until Bus::set_flushing sets flushing to false.

MT safe.

flushing

whether or not to flush the bus

pub fn timed_pop(&self, timeout: ClockTime) -> Option<Message>

Get a message from the bus, waiting up to the specified timeout.

If timeout is 0, this function behaves like Bus::pop. If timeout is GST_CLOCK_TIME_NONE, this function will block forever until a message was posted on the bus.

timeout

a timeout

Returns

the Message that is on the bus after the specified timeout or None if the bus is empty after the timeout expired. The message is taken from the bus and needs to be unreffed with Message::unref after usage.

MT safe.

pub fn connect_message<F: Fn(&Bus, &Message) + Send + 'static>(
    &self,
    f: F
) -> SignalHandlerId

A message has been posted on the bus. This signal is emitted from a GSource added to the mainloop. this signal will only be emitted when there is a mainloop running.

message

the message that has been posted asynchronously

pub fn connect_sync_message<F: Fn(&Bus, &Message) + Send + Sync + 'static>(
    &self,
    f: F
) -> SignalHandlerId

A message has been posted on the bus. This signal is emitted from the thread that posted the message so one has to be careful with locking.

This signal will not be emitted by default, you have to call Bus::enable_sync_message_emission before.

message

the message that has been posted synchronously

impl Bus

pub fn add_signal_watch_full(&self, priority: Priority)

Adds a bus signal watch to the default main context with the given priority (e.g. G_PRIORITY_DEFAULT). It is also possible to use a non-default main context set up using glib::MainContext::push_thread_default (before one had to create a bus watch source and attach it to the desired main context 'manually').

After calling this statement, the bus will emit the "message" signal for each message posted on the bus when the main loop is running.

This function may be called multiple times. To clean up, the caller is responsible for calling Bus::remove_signal_watch as many times as this function is called.

There can only be a single bus watch per bus, you must remove any signal watch before you can set another type of watch.

MT safe.

priority

The priority of the watch.

pub fn create_watch<F>(
    &self,
    name: Option<&str>,
    priority: Priority,
    func: F
) -> Source where
    F: FnMut(&Bus, &Message) -> Continue + Send + 'static, 

Create watch for this bus. The GSource will be dispatched whenever a message is on the bus. After the GSource is dispatched, the message is popped off the bus and unreffed.

Returns

a glib::Source that can be added to a mainloop.

pub fn add_watch<F>(&self, func: F) -> Result<SourceId, BoolError> where
    F: FnMut(&Bus, &Message) -> Continue + Send + 'static, 

Adds a bus watch to the default main context with the default priority (G_PRIORITY_DEFAULT). It is also possible to use a non-default main context set up using glib::MainContext::push_thread_default (before one had to create a bus watch source and attach it to the desired main context 'manually').

This function is used to receive asynchronous messages in the main loop. There can only be a single bus watch per bus, you must remove it before you can set a new one.

The bus watch will only work if a GLib main loop is being run.

The watch can be removed using Bus::remove_watch or by returning false from func. If the watch was added to the default main context it is also possible to remove the watch using glib::Source::remove.

The bus watch will take its own reference to the self, so it is safe to unref self using GstObjectExt::unref after setting the bus watch.

MT safe.

func

A function to call when a message is received.

user_data

user data passed to func.

Returns

The event source id or 0 if self already got an event source.

pub fn add_watch_local<F>(&self, func: F) -> Result<SourceId, BoolError> where
    F: FnMut(&Bus, &Message) -> Continue + 'static, 

pub fn set_sync_handler<F>(&self, func: F) where
    F: Fn(&Bus, &Message) -> BusSyncReply + Send + Sync + 'static, 

Sets the synchronous handler on the bus. The function will be called every time a new message is posted on the bus. Note that the function will be called in the same thread context as the posting object. This function is usually only called by the creator of the bus. Applications should handle messages asynchronously using the gst_bus watch and poll functions.

Before 1.16.3 it was not possible to replace an existing handler and clearing an existing handler with None was not thread-safe.

func

The handler function to install

user_data

User data that will be sent to the handler function.

notify

called when user_data becomes unused

pub fn unset_sync_handler(&self)

pub fn iter(&self) -> Iter<'_>

pub fn iter_timed(&self, timeout: ClockTime) -> Iter<'_>

pub fn iter_filtered<'a>(
    &'a self,
    msg_types: &'a [MessageType]
) -> impl Iterator<Item = Message> + 'a

pub fn iter_timed_filtered<'a>(
    &'a self,
    timeout: ClockTime,
    msg_types: &'a [MessageType]
) -> impl Iterator<Item = Message> + 'a

pub fn timed_pop_filtered(
    &self,
    timeout: ClockTime,
    msg_types: &[MessageType]
) -> Option<Message>

Get a message from the bus whose type matches the message type mask types, waiting up to the specified timeout (and discarding any messages that do not match the mask provided).

If timeout is 0, this function behaves like Bus::pop_filtered. If timeout is GST_CLOCK_TIME_NONE, this function will block forever until a matching message was posted on the bus.

timeout

a timeout in nanoseconds, or GST_CLOCK_TIME_NONE to wait forever

types

message types to take into account, GST_MESSAGE_ANY for any type

Returns

a Message matching the filter in types, or None if no matching message was found on the bus until the timeout expired. The message is taken from the bus and needs to be unreffed with Message::unref after usage.

MT safe.

pub fn pop_filtered(&self, msg_types: &[MessageType]) -> Option<Message>

Get a message matching type_ from the bus. Will discard all messages on the bus that do not match type_ and that have been posted before the first message that does match type_. If there is no message matching type_ on the bus, all messages will be discarded. It is not possible to use message enums beyond MessageType::Extended in the events mask.

types

message types to take into account

Returns

the next Message matching type_ that is on the bus, or None if the bus is empty or there is no message matching type_. The message is taken from the bus and needs to be unreffed with Message::unref after usage.

MT safe.

pub fn stream(&self) -> BusStream

pub fn stream_filtered<'a>(
    &self,
    message_types: &'a [MessageType]
) -> impl Stream<Item = Message> + Unpin + Send + 'a

Trait Implementations

impl Clone for Bus

fn clone(&self) -> Bus

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for Bus

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for Bus

fn default() -> Self

Returns the "default value" for a type.

impl Eq for Bus

impl Hash for Bus

fn hash<__H: Hasher>(&self, state: &mut __H)

Feeds this value into the given Hasher.

fn hash_slice<H>(data: &[Self], state: &mut H) where
    H: Hasher, 

Feeds a slice of this type into the given Hasher.

impl IsA<Object> for Bus

impl Ord for Bus

fn cmp(&self, other: &Bus) -> Ordering

This method returns an Ordering between self and other.

#[must_use]fn max(self, other: Self) -> Self

Compares and returns the maximum of two values.

#[must_use]fn min(self, other: Self) -> Self

Compares and returns the minimum of two values.

#[must_use]fn clamp(self, min: Self, max: Self) -> Self

🔬 This is a nightly-only experimental API. (clamp)

Restrict a value to a certain interval.

impl<T: ObjectType> PartialEq<T> for Bus

fn eq(&self, other: &T) -> bool

This method tests for self and other values to be equal, and is used by ==.

#[must_use]fn ne(&self, other: &Rhs) -> bool

This method tests for !=.

impl<T: ObjectType> PartialOrd<T> for Bus

fn partial_cmp(&self, other: &T) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

#[must_use]fn lt(&self, other: &Rhs) -> bool

This method tests less than (for self and other) and is used by the < operator.

#[must_use]fn le(&self, other: &Rhs) -> bool

This method tests less than or equal to (for self and other) and is used by the <= operator.

#[must_use]fn gt(&self, other: &Rhs) -> bool

This method tests greater than (for self and other) and is used by the > operator.

#[must_use]fn ge(&self, other: &Rhs) -> bool

This method tests greater than or equal to (for self and other) and is used by the >= operator.

impl Send for Bus

impl StaticType for Bus

fn static_type() -> Type

Returns the type identifier of Self.

impl Sync for Bus

impl UnixBusExtManual for Bus

fn get_pollfd(&self) -> RawFd

impl WindowsBusExtManual for Bus

fn get_pollfd(&self) -> RawHandle