GioDBusObjectManagerClient

GDBusObjectManagerClient is used to create, monitor and delete object proxies for remote objects exported by a GDBusObjectManagerServer (or any code implementing the org.freedesktop.DBus.ObjectManager interface).

Once an instance of this type has been created, you can connect to the GDBusObjectManager::object-added and [signal@Gio.DBusObjectManager::object-removed signals] and inspect the GDBusObjectProxy objects returned by g_dbus_object_manager_get_objects().

If the name for a GDBusObjectManagerClient is not owned by anyone at object construction time, the default behavior is to request the message bus to launch an owner for the name. This behavior can be disabled using the G_DBUS_OBJECT_MANAGER_CLIENT_FLAGS_DO_NOT_AUTO_START flag. It’s also worth noting that this only works if the name of interest is activatable in the first place. E.g. in some cases it is not possible to launch an owner for the requested name. In this case, GDBusObjectManagerClient object construction still succeeds but there will be no object proxies (e.g. g_dbus_object_manager_get_objects() returns the empty list) and the GDBusObjectManagerClient:name-owner property is NULL.

The owner of the requested name can come and go (for example consider a system service being restarted) – GDBusObjectManagerClient handles this case too; simply connect to the GObject::notify signal to watch for changes on the GDBusObjectManagerClient:name-owner property. When the name owner vanishes, the behavior is that GDBusObjectManagerClient:name-owner is set to NULL (this includes emission of the GObject::notify signal) and then GDBusObjectManager::object-removed signals are synthesized for all currently existing object proxies. Since GDBusObjectManagerClient:name-owner is NULL when this happens, you can use this information to disambiguate a synthesized signal from a genuine signal caused by object removal on the remote GDBusObjectManager. Similarly, when a new name owner appears, GDBusObjectManager::object-added signals are synthesized while GDBusObjectManagerClient:name-owner is still NULL. Only when all object proxies have been added, the GDBusObjectManagerClient:name-owner is set to the new name owner (this includes emission of the GObject::notify signal). Furthermore, you are guaranteed that GDBusObjectManagerClient:name-owner will alternate between a name owner (e.g. :1.42) and NULL even in the case where the name of interest is atomically replaced

Ultimately, GDBusObjectManagerClient is used to obtain GDBusProxy instances. All signals (including the org.freedesktop.DBus.Properties::PropertiesChanged signal) delivered to GDBusProxy instances are guaranteed to originate from the name owner. This guarantee along with the behavior described above, means that certain race conditions including the “half the proxy is from the old owner and the other half is from the new owner” problem cannot happen.

To avoid having the application connect to signals on the returned GDBusObjectProxy and GDBusProxy objects, the GDBusObject::interface-added, GDBusObject::interface-removed, GDBusProxy::g-properties-changed and GDBusProxy::g-signal signals are also emitted on the GDBusObjectManagerClient instance managing these objects. The signals emitted are GDBusObjectManager::interface-added, GDBusObjectManager::interface-removed, GDBusObjectManagerClient::interface-proxy-properties-changed and GDBusObjectManagerClient::interface-proxy-signal.

Note that all callbacks and signals are emitted in the thread-default main context (see g_main_context_push_thread_default()) that the GDBusObjectManagerClient object was constructed in. Additionally, the GDBusObjectProxy and GDBusProxy objects originating from the GDBusObjectManagerClient object will be created in the same context and, consequently, will deliver signals in the same main loop.

Available since: 2.30