class MixerItems;
class MixerViewer;
class TileMixers;
+class TileMixersDragBox;
class AlignMixers;
class AlignTimecodes;
class AddAudioTrack;
class DefaultVTransition;
class AddSubttlTrack;
class PasteSubttl;
-class MoveTracksUp;
-class MoveTracksDown;
+class RollTracksUp;
+class RollTracksDown;
class DeleteTracks;
class ConcatenateTracks;
class DeleteFirstTrack;