listeners: Make listeners async

- Add a common Listener base class
- Make send helper for sending out events with pykka
- Make send async helper for avoiding blocking events

This change ensures all the events now get sent out via the MainThread instead
of blocking the actors.

mopidy/audio/listener.py

@@ -1,9 +1,9 @@
 from __future__ import unicode_literals
 
-import pykka
+from mopidy import listener
 
 
-class AudioListener(object):
+class AudioListener(listener.Listener):
     """
     Marker interface for recipients of events sent by the audio actor.
 
@@ -17,25 +17,7 @@ class AudioListener(object):
     @staticmethod
     def send(event, **kwargs):
         """Helper to allow calling of audio listener events"""
-        listeners = pykka.ActorRegistry.get_by_class(AudioListener)
-        for listener in listeners:
-            listener.proxy().on_event(event, **kwargs)
-
-    def on_event(self, event, **kwargs):
-        """
-        Called on all events.
-
-        *MAY* be implemented by actor. By default, this method forwards the
-        event to the specific event methods.
-
-        For a list of what event names to expect, see the names of the other
-        methods in :class:`AudioListener`.
-
-        :param event: the event name
-        :type event: string
-        :param kwargs: any other arguments to the specific event handlers
-        """
-        getattr(self, event)(**kwargs)
+        listener.send_async(AudioListener, event, **kwargs)
 
     def reached_end_of_stream(self):
         """

mopidy/backends/listener.py

@@ -1,9 +1,9 @@
 from __future__ import unicode_literals
 
-import pykka
+from mopidy import listener
 
 
-class BackendListener(object):
+class BackendListener(listener.Listener):
     """
     Marker interface for recipients of events sent by the backend actors.
 
@@ -19,22 +19,7 @@ class BackendListener(object):
     @staticmethod
     def send(event, **kwargs):
         """Helper to allow calling of backend listener events"""
-        listeners = pykka.ActorRegistry.get_by_class(BackendListener)
-        for listener in listeners:
-            listener.proxy().on_event(event, **kwargs)
-
-    def on_event(self, event, **kwargs):
-        """
-        Called on all events.
-
-        *MAY* be implemented by actor. By default, this method forwards the
-        event to the specific event methods.
-
-        :param event: the event name
-        :type event: string
-        :param kwargs: any other arguments to the specific event handlers
-        """
-        getattr(self, event)(**kwargs)
+        listener.send_async(BackendListener, event, **kwargs)
 
     def playlists_loaded(self):
         """

mopidy/core/listener.py

@@ -1,9 +1,9 @@
 from __future__ import unicode_literals
 
-import pykka
+from mopidy import listener
 
 
-class CoreListener(object):
+class CoreListener(listener.Listener):
     """
     Marker interface for recipients of events sent by the core actor.
 
@@ -17,9 +17,7 @@ class CoreListener(object):
     @staticmethod
     def send(event, **kwargs):
         """Helper to allow calling of core listener events"""
-        listeners = pykka.ActorRegistry.get_by_class(CoreListener)
-        for listener in listeners:
-            listener.proxy().on_event(event, **kwargs)
+        listener.send_async(CoreListener, event, **kwargs)
 
     def on_event(self, event, **kwargs):
         """

mopidy/listener.py

@@ -0,0 +1,33 @@
+from __future__ import unicode_literals
+
+import gobject
+import logging
+import pykka
+
+logger = logging.getLogger('mopidy.listener')
+
+
+def send_async(cls, event, **kwargs):
+    gobject.idle_add(lambda: send(cls, event, **kwargs))
+
+
+def send(cls, event, **kwargs):
+    listeners = pykka.ActorRegistry.get_by_class(cls)
+    logger.debug('Sending %s to %s: %s', event, cls.__name__, kwargs)
+    for listener in listeners:
+        listener.proxy().on_event(event, **kwargs)
+
+
+class Listener(object):
+    def on_event(self, event, **kwargs):
+        """
+        Called on all events.
+
+        *MAY* be implemented by actor. By default, this method forwards the
+        event to the specific event methods.
+
+        :param event: the event name
+        :type event: string
+        :param kwargs: any other arguments to the specific event handlers
+        """
+        getattr(self, event)(**kwargs)