@Override
    public boolean update(DnDEvent aEvent) {
      setHoverIndex(-1);
      if (aEvent.getAttachedObject() instanceof PaletteItem) {
        setDropTargetIndex(locationToTargetIndex(aEvent.getPoint()));
        aEvent.setDropPossible(true);
      }
      else {
        setDropTargetIndex(-1);
        aEvent.setDropPossible(false);
      }
      return false;
    }
@Override
    public boolean update(DnDEvent aEvent)