PICARD-2071: Fix tracks sometimes sorted in reverse order

When tracks got loaded while sorting was disabled the tracks ended up in reverse order. Unify the behavior by always disabling sorting while inserting tracks.

Author: phw

picard/ui/itemviews.py

@@ -969,11 +969,18 @@ def update(self, update_tracks=True, update_selection=True):
                 item.update(update_album=False)
             if newnum > oldnum:  # add new items
                 items = []
-                for i in range(newnum - 1, oldnum - 1, -1):  # insertChildren is backwards
+                for i in range(oldnum, newnum):
                     item = TrackItem(album.tracks[i], False)
                     item.setHidden(False)  # Workaround to make sure the parent state gets updated
                     items.append(item)
+                # insertChildren behaves differently if sorting is disabled / enabled, which results
+                # in different sort order of tracks in unsorted state. As we sort the tracks later
+                # anyway make sure sorting is disabled here.
+                tree_view = self.treeWidget()
+                sorting_enabled = tree_view.isSortingEnabled()
+                tree_view.setSortingEnabled(False)
                 self.insertChildren(oldnum, items)
+                tree_view.setSortingEnabled(sorting_enabled)
                 for item in items:  # Update after insertChildren so that setExpanded works
                     item.update(update_album=False)
         if album.errors: