audio: Expand audio state changed with target state

mopidy/audio/actor.py

@@ -23,6 +23,10 @@ mixers.register_mixers()
 playlists.register_typefinders()
 playlists.register_elements()
 
+_GST_STATE_MAPPING = {
+    gst.STATE_PLAYING: PlaybackState.PLAYING,
+    gst.STATE_PAUSED: PlaybackState.PAUSED,
+    gst.STATE_NULL: PlaybackState.STOPPED}
 
 MB = 1 << 20
 
@@ -321,20 +325,18 @@ class Audio(pykka.ThreadingActor):
         if new_state == gst.STATE_READY:
             return  # Ignore READY state as it's GStreamer specific
 
-        if new_state == gst.STATE_PLAYING:
-            new_state = PlaybackState.PLAYING
-        elif new_state == gst.STATE_PAUSED:
-            new_state = PlaybackState.PAUSED
-        elif new_state == gst.STATE_NULL:
-            new_state = PlaybackState.STOPPED
-
+        new_state = _GST_STATE_MAPPING[new_state]
         old_state, self.state = self.state, new_state
 
+        target_state = _GST_STATE_MAPPING[self._target_state]
+        if target_state == new_state:
+            target_state = None
+
         logger.debug(
-            'Triggering event: state_changed(old_state=%s, new_state=%s)',
-            old_state, new_state)
-        AudioListener.send(
-            'state_changed', old_state=old_state, new_state=new_state)
+            'Triggering event: state_changed(old_state=%s, new_state=%s, '
+            'target_state=%s)', old_state, new_state, target_state)
+        AudioListener.send('state_changed', old_state=old_state,
+                           new_state=new_state, target_state=target_state)
 
     def _on_buffering(self, percent):
         if percent < 10 and not self._buffering:

mopidy/audio/listener.py

@@ -27,17 +27,31 @@ class AudioListener(listener.Listener):
         """
         pass
 
-    def state_changed(self, old_state, new_state):
+    def state_changed(self, old_state, new_state, target_state):
         """
         Called after the playback state have changed.
 
         Will be called for both immediate and async state changes in GStreamer.
 
+        Target state is used to when we should be in the target state, but
+        temporarily need to switch to an other state. A typical example of this
+        is buffering. When this happens an event with
+        `old=PLAYING, new=PAUSED, target=PLAYING` will be emitted. Once we have
+        caught up a `old=PAUSED, new=PLAYING, target=None` event will be
+        be generated.
+
+        Regular state changes will not have target state set as they are final
+        states which should be stable.
+
         *MAY* be implemented by actor.
 
         :param old_state: the state before the change
         :type old_state: string from :class:`mopidy.core.PlaybackState` field
         :param new_state: the state after the change
+        :type new_state: A :class:`mopidy.core.PlaybackState` field
         :type new_state: string from :class:`mopidy.core.PlaybackState` field
+        :param target_state: the intended state
+        :type target_state: string from :class:`mopidy.core.PlaybackState`
+            field or :class:`None` if this is a final state.
         """
         pass

mopidy/core/actor.py

@@ -65,7 +65,7 @@ class Core(pykka.ThreadingActor, audio.AudioListener, backend.BackendListener):
     def reached_end_of_stream(self):
         self.playback.on_end_of_track()
 
-    def state_changed(self, old_state, new_state):
+    def state_changed(self, old_state, new_state, target_state):
         # XXX: This is a temporary fix for issue #232 while we wait for a more
         # permanent solution with the implementation of issue #234. When the
         # Spotify play token is lost, the Spotify backend pauses audio

tests/audio/test_listener.py

@@ -15,13 +15,14 @@ class AudioListenerTest(unittest.TestCase):
         self.listener.state_changed = mock.Mock()
 
         self.listener.on_event(
-            'state_changed', old_state='stopped', new_state='playing')
+            'state_changed', old_state='stopped', new_state='playing',
+            target_state=None)
 
         self.listener.state_changed.assert_called_with(
-            old_state='stopped', new_state='playing')
+            old_state='stopped', new_state='playing', target_state=None)
 
     def test_listener_has_default_impl_for_reached_end_of_stream(self):
         self.listener.reached_end_of_stream()
 
     def test_listener_has_default_impl_for_state_changed(self):
-        self.listener.state_changed(None, None)
+        self.listener.state_changed(None, None, None)