playlist: Scroll to the current track when tracks change

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

playlist/__init__.py

@@ -46,6 +46,19 @@ View.append_column(column.Column("Last Played", "lastplayed", width=150))
 Scroll = Gtk.ScrolledWindow()
 Scroll.set_child(View)
 
+def scroll_to_track(track):
+    adj = Scroll.get_vadjustment()
+    for i in range(FilterModel.get_n_items()):
+        if FilterModel.get_item(i) == track:
+            Selection.select_item(i, True)
+            pos = (max(i - 5, 0) / FilterModel.get_n_items())
+            adj.set_value(pos * adj.get_upper())
+            return
+
+def on_tracks_changed(prev, new):
+    scroll_to_track(new)
+audio.Player.TrackChanged.register(on_tracks_changed)
+
 Box = Gtk.Box.new(Gtk.Orientation.VERTICAL, 0)
 Box.append(Model.Controls)
 Box.append(Scroll)