oldNode = (DefaultMutableTreeNode) path.getLastPathComponent();
ISweaveTag swt = ((IViewport) oldNode.getUserObject()).getSweaveTag();
transferable = new TransferableSweaveTag(swt);
source.startDrag(dge, DragSource.DefaultMoveNoDrop, transferable, this);
// If you support dropping the node anywhere, you should probably
// start with a valid move cursor:
// source.startDrag(dge, DragSource.DefaultMoveDrop, transferable,