final List<ElementData> droppedElements = (List<ElementData>) event.data;
final TreeItem dropTargetItem = (TreeItem) event.item;
final MasterDetailsContentNodePart dropTargetNode = (MasterDetailsContentNodePart) dropTargetItem.getData();
final MasterDetailsContentNodePart parentNode = dropTargetNode.getParentNode();
final List<MasterDetailsContentNodePart> siblingNodes = parentNode.nodes().visible();
final Point pt = tree.getDisplay().map( null, tree, event.x, event.y );
final Rectangle bounds = dropTargetItem.getBounds();
MasterDetailsContentNodePart precedingNode = null;