Commands and Messages

libunique lets you send messages with commands to a running instance using unique_app_send_message(). GApplication does not have a direct equivalent for this feature at this time, but some of the predefined libunique commands have equivalents in GApplication. Instead of sending the UNIQUE_ACTIVATE command, call g_application_activate(), instead of sending the UNIQUE_OPEN command, call g_application_open(). The UNIQUE_NEW and UNIQUE_CLOSE and user-defined commands don't have direct replacement at this time.

On the other hand, GApplication supports passing entire commandlines to the running instance, which reduces the need for user-defined commands. And GDBus makes it very easy to implement D-Bus interfaces for communication between application instances, see e.g. g_dbus_connection_register_object().