Method

GioDBusConnectionsignal_subscribe

since: 2.26

Declaration 

guint
g_dbus_connection_signal_subscribe (
  GDBusConnection* connection,
  const gchar* sender,
  const gchar* interface_name,
  const gchar* member,
  const gchar* object_path,
  const gchar* arg0,
  GDBusSignalFlags flags,
  GDBusSignalCallback callback,
  gpointer user_data,
  GDestroyNotify user_data_free_func
)

Description

Subscribes to signals on connection and invokes callback whenever the signal is received. Note that callback will be invoked in the [thread-default main context][g-main-context-push-thread-default] of the thread you are calling this method from.

If connection is not a message bus connection, sender must be NULL.

If sender is a well-known name note that callback is invoked with the unique name for the owner of sender, not the well-known name as one would expect. This is because the message bus rewrites the name. As such, to avoid certain race conditions, users should be tracking the name owner of the well-known name and use that when processing the received signal.

If one of G_DBUS_SIGNAL_FLAGS_MATCH_ARG0_NAMESPACE or G_DBUS_SIGNAL_FLAGS_MATCH_ARG0_PATH are given, arg0 is interpreted as part of a namespace or path. The first argument of a signal is matched against that part as specified by D-Bus.

If user_data_free_func is non-NULL, it will be called (in the thread-default main context of the thread you are calling this method from) at some point after user_data is no longer needed. (It is not guaranteed to be called synchronously when the signal is unsubscribed from, and may be called after connection has been destroyed.)

As callback is potentially invoked in a different thread from where it’s emitted, it’s possible for this to happen after g_dbus_connection_signal_unsubscribe() has been called in another thread. Due to this, user_data should have a strong reference which is freed with user_data_free_func, rather than pointing to data whose lifecycle is tied to the signal subscription. For example, if a GObject is used to store the subscription ID from g_dbus_connection_signal_subscribe(), a strong reference to that GObject must be passed to user_data, and g_object_unref() passed to user_data_free_func. You are responsible for breaking the resulting reference count cycle by explicitly unsubscribing from the signal when dropping the last external reference to the GObject. Alternatively, a weak reference may be used.

It is guaranteed that if you unsubscribe from a signal using g_dbus_connection_signal_unsubscribe() from the same thread which made the corresponding g_dbus_connection_signal_subscribe() call, callback will not be invoked after g_dbus_connection_signal_unsubscribe() returns.

The returned subscription identifier is an opaque value which is guaranteed to never be zero.

This function can never fail.

Available since: 2.26

Parameters

sender

Type: const gchar*

Sender name to match on (unique or well-known name) or NULL to listen from all senders.

The argument can be NULL.
The data is owned by the caller of the function.
The value is a NUL terminated UTF-8 string.
interface_name

Type: const gchar*

D-Bus interface name to match on or NULL to match on all interfaces.

The argument can be NULL.
The data is owned by the caller of the function.
The value is a NUL terminated UTF-8 string.
member

Type: const gchar*

D-Bus signal name to match on or NULL to match on all signals.

The argument can be NULL.
The data is owned by the caller of the function.
The value is a NUL terminated UTF-8 string.
object_path

Type: const gchar*

Object path to match on or NULL to match on all object paths.

The argument can be NULL.
The data is owned by the caller of the function.
The value is a NUL terminated UTF-8 string.
arg0

Type: const gchar*

Contents of first string argument to match on or NULL to match on all kinds of arguments.

The argument can be NULL.
The data is owned by the caller of the function.
The value is a NUL terminated UTF-8 string.
flags

Type: GDBusSignalFlags

GDBusSignalFlags describing how arg0 is used in subscribing to the signal.

callback

Type: GDBusSignalCallback

Callback to invoke when there is a signal matching the requested data.

user_data

Type: gpointer

User data to pass to callback.

The argument can be NULL.
The data is owned by the caller of the function.
user_data_free_func

Type: GDestroyNotify

Function to free user_data with when subscription is removed or NULL.

The argument can be NULL.

Return value

Type: guint

A subscription identifier that can be used with g_dbus_connection_signal_unsubscribe()