music_track_listener: recognize playing song

when listener is enabled

gajim/gui_interface.py

@@ -2099,11 +2099,13 @@ class Interface:
         if not self.music_track_changed_signal:
             self.music_track_changed_signal = listener.connect(
                 'music-track-changed', self.music_track_changed)
+            listener.start()
 
     def disable_music_listener(self):
         listener = MusicTrackListener.get()
         listener.disconnect(self.music_track_changed_signal)
         self.music_track_changed_signal = None
+        listener.stop()
 
     @staticmethod
     def music_track_changed(unused_listener, music_track_info, account=None):

gajim/music_track_listener.py

@@ -55,6 +55,7 @@ class MusicTrackListener(GObject.GObject):
         super().__init__()
         self.players = {}
 
+    def start(self):
         proxy = Gio.DBusProxy.new_for_bus_sync(
             Gio.BusType.SESSION,
             Gio.DBusProxyFlags.NONE,
@@ -92,6 +93,11 @@ class MusicTrackListener(GObject.GObject):
             if name.startswith(MPRIS_PLAYER_PREFIX):
                 self._add_player(name)
 
+    def stop(self):
+        for name in list(self.players):
+            if name.startswith(MPRIS_PLAYER_PREFIX):
+                self._remove_player(name)
+
     def _signal_name_owner_changed(self, connection, sender_name, object_path,
                          interface_name, signal_name, parameters, *user_data):
         name, oldOwner, newOwner = parameters
@@ -204,4 +210,5 @@ if __name__ == '__main__':
             print(music_track_info.title)
     listener = MusicTrackListener.get()
     listener.connect('music-track-changed', music_track_change_cb)
+    listener.start()
     GLib.MainLoop().run()