playlists now emit PlaylistChanged also when their ordering changes (Updates issue #374)

src/playlist/playlist.cpp

@@ -989,6 +989,7 @@ void Playlist::sort(int column, Qt::SortOrder order) {
   // TODO
   undo_stack_->clear();
 
+  emit PlaylistChanged();
   Save();
 }
 
@@ -1285,6 +1286,7 @@ void Playlist::Shuffle() {
   // TODO
   undo_stack_->clear();
 
+  emit PlaylistChanged();
   Save();
 }
 

src/playlist/playlist.h

@@ -198,6 +198,8 @@ class Playlist : public QAbstractListModel {
   void EditingFinished(const QModelIndex& index);
   void PlayRequested(const QModelIndex& index);
 
+  // Signals that the underlying list of items was changed, meaning that
+  // something was added to it, removed from it or the ordering changed.
   void PlaylistChanged();
   void DynamicModeChanged(bool dynamic);
 

src/playlist/playlistmanager.h

@@ -102,6 +102,9 @@ signals:
 
   // Forwarded from individual playlists
   void CurrentSongChanged(const Song& song);
+  
+  // Signals that one of manager's playlists has changed (new items, new
+  // ordering etc.) - the argument shows which.
   void PlaylistChanged(Playlist* playlist);
   void EditingFinished(const QModelIndex& index);
   void PlayRequested(const QModelIndex& index);