[gnome-music/wip/mschraal/grilo-writeback-sync-fix: 1/2] grilo: Use idle_add for writeback functions

[Marinus Schraal <mschraal src gnome org>]

commit c61964a5ed4d1541bba9a94c3a218c187462ac03
Author: Marinus Schraal <mschraal gnome org>
Date:   Wed Aug 29 23:11:10 2018 +0200

    grilo: Use idle_add for writeback functions
    
    The GStreamer clock stops ticking as soon as a Grilo writeback is
    triggered. This does not pose as an immediate problem, as it is currently
    only relied upon for scrobbling, triggering Tracker writeback and passing
    on the clock-tick. However, the former two are one-time events per song and
    the latter is also provided by other means.
    
    It will be a problem as soon as the pipeline and clock do not reset between
    songs when gapless playback is introduced. The exact core of the problem is
    unknown, but might be related to Grilo async handling: grilo#81.
    
    Calling the Grilo writeback function in an idle_add seems to resolve the
    issue until it is fixed upstream.

 gnomemusic/grilo.py | 86 ++++++++++++++++++++++++++++++-----------------------
 1 file changed, 48 insertions(+), 38 deletions(-)
---
diff --git a/gnomemusic/grilo.py b/gnomemusic/grilo.py
index 6a90dec7..1d811c73 100644
--- a/gnomemusic/grilo.py
+++ b/gnomemusic/grilo.py
@@ -346,29 +346,6 @@ class Grilo(GObject.GObject):
             callback(source, param, item, remaining, data)
         self.tracker.query(query, self.METADATA_KEYS, options, _callback, data)
 
-    @log
-    def toggle_favorite(self, song_item):
-        """Toggles favorite status for media item
-
-        Toggles favorite status and writes it back to the tracker store
-        :param song_item: A Grilo media item
-        """
-        if song_item.get_favourite():
-            # For now keep unsetting the lyrics to deal with how
-            # previous versions dealt with favorites.
-            song_item.set_lyrics("")
-            song_item.set_favourite(False)
-        else:
-            song_item.set_favourite(True)
-
-        # FIXME: We assume this is the tracker plugin.
-        # FIXME: Doing this async crashes
-        try:
-            self.tracker.store_metadata_sync(
-                song_item, [Grl.METADATA_KEY_FAVOURITE], Grl.WriteFlags.NORMAL)
-        except GLib.Error as error:
-            logger.warning("Error {}: {}".format(error.domain, error.message))
-
     @log
     def set_favorite(self, song_item, favorite):
         """Set the favorite status of a media item
@@ -443,6 +420,25 @@ class Grilo(GObject.GObject):
 
         self.tracker.query(query, self.METADATA_KEYS, options, callback, None)
 
+    @log
+    def _store_metadata(self, media, key):
+        """Convenience function to store metadata
+
+        Wrap the metadata store call in a idle_add compatible form.
+        :param media: A Grilo media item
+        :param key: A Grilo metadata key
+        """
+        # FIXME: We assume this is the tracker plugin.
+        # FIXME: Doing this async crashes.
+        try:
+            self.tracker.store_metadata_sync(
+                media, [key], Grl.WriteFlags.NORMAL)
+        except GLib.Error as error:
+            logger.warning(
+                "Error {}: {}".format(error.domain, error.message))
+
+        return GLib.SOURCE_REMOVE
+
     @log
     def bump_play_count(self, media):
         """Bumps the play count of a song
@@ -452,14 +448,10 @@ class Grilo(GObject.GObject):
         """
         count = media.get_play_count()
         media.set_play_count(count + 1)
-
-        # FIXME: We assume this is the tracker plugin.
-        # FIXME: Doing this async crashes
-        try:
-            self.tracker.store_metadata_sync(
-                media, [Grl.METADATA_KEY_PLAY_COUNT], Grl.WriteFlags.NORMAL)
-        except GLib.Error as error:
-            logger.warning("Error {}: {}".format(error.domain, error.message))
+        # FIXME: Do this as an idle call, otherwise it may not return
+        # and block other sources. This seems to point to a problem in
+        # Grilo (gnomemusic!411).
+        GLib.idle_add(self._store_metadata, media, Grl.METADATA_KEY_PLAY_COUNT)
 
     @log
     def set_last_played(self, media):
@@ -469,13 +461,31 @@ class Grilo(GObject.GObject):
         :param media: A Grilo media item
         """
         media.set_last_played(GLib.DateTime.new_now_utc())
-        # FIXME: We assume this is the tracker plugin.
-        # FIXME: Doing this async crashes
-        try:
-            self.tracker.store_metadata_sync(
-                media, [Grl.METADATA_KEY_LAST_PLAYED], Grl.WriteFlags.NORMAL)
-        except GLib.Error as error:
-            logger.warning("Error {}: {}".format(error.domain, error.message))
+        # FIXME: Do this as an idle call, otherwise it may not return
+        # and block other sources. This seems to point to a problem in
+        # Grilo (gnomemusic!411).
+        GLib.idle_add(
+            self._store_metadata, media, Grl.METADATA_KEY_LAST_PLAYED)
+
+    @log
+    def toggle_favorite(self, media):
+        """Toggles favorite status for media item
+
+        Toggles favorite status and writes it back to the tracker store
+        :param media: A Grilo media item
+        """
+        if media.get_favourite():
+            # For now keep unsetting the lyrics to deal with how
+            # previous versions dealt with favorites.
+            media.set_lyrics("")
+            media.set_favourite(False)
+        else:
+            media.set_favourite(True)
+
+        # FIXME: Do this as an idle call, otherwise it may not return
+        # and block other sources. This seems to point to a problem in
+        # Grilo (gnomemusic!411).
+        GLib.idle_add(self._store_metadata, media, Grl.METADATA_KEY_FAVOURITE)
 
     @log
     def songs_available(self, callback):