playlist: Use a bus for TrackAdded and TrackRemoved

This helps keep us from sending the items_changed() signal too soon,
before the track finishes initializing.

Signed-off-by: Anna Schumaker <Anna@NoWheyCreamery.com>

playlist/model.py

@@ -1,9 +1,11 @@
 # Copyright 2021 (c) Anna Schumaker.
+from lib import bus
 from gi.repository import GObject, Gio
 
 class TagModel(GObject.GObject, Gio.ListModel):
     def __init__(self, tag=None):
         GObject.GObject.__init__(self)
+        self.bus = bus.Bus(1)
         self.items = [ ]
         self.__set_tag__(tag)
 
@@ -34,13 +36,20 @@ class TagModel(GObject.GObject, Gio.ListModel):
             return self.items[n]
 
     def switch_tag(self, tag):
-        self.items_changed(0, self.__unset_tag__(),
-                              self.__set_tag__(tag))
+        removed = self.__unset_tag__()
+        added = self.__set_tag__(tag)
+        self.items_changed(0, removed, added)
 
-    def track_added(self, tag, track, pos):
+    def do_track_added(self, tag, track, pos):
         self.items.insert(pos, track)
         self.items_changed(pos, 0, 1)
 
-    def track_removed(self, tag, track, pos):
+    def track_added(self, tag, track, pos):
+        self.bus.board(self.do_track_added, tag, track, pos)
+
+    def do_track_removed(self, tag, track, pos):
         self.items.remove(track)
         return self.items_changed(pos, 1, 0)
+
+    def track_removed(self, tag, track, pos):
+        self.bus.board(self.do_track_removed, tag, track, pos)

playlist/test_model.py

@@ -1,5 +1,6 @@
 # Copyright 2021 (c) Anna Schumaker.
 from . import model
+from lib import bus
 from lib import fake
 from lib import tag
 from gi.repository import GObject, Gio
@@ -19,6 +20,7 @@ class TestTagModel(unittest.TestCase):
 
         self.assertIsInstance(m, GObject.Object)
         self.assertIsInstance(m, Gio.ListModel)
+        self.assertIsInstance(m.bus, bus.Bus)
 
         self.assertEqual(m.tag, t)
         self.assertEqual(m.items, [ ])
@@ -33,11 +35,13 @@ class TestTagModel(unittest.TestCase):
         track = fake.Track(1)
 
         t.add_track(track)
+        m.bus.complete()
         self.assertEqual(m.items, [ track ])
         self.assertEqual(m.get_n_items(), 1)
         self.assertEqual(m.get_item(0), fake.Track(1))
 
         t.remove_track(track)
+        m.bus.complete()
         self.assertEqual(m.items, [ ])
         self.assertEqual(m.get_n_items(), 0)
         self.assertIsNone(m.get_item(0))