t oldskips = myDiagram.skipsUndoManager;
      myDiagram.skipsUndoManager = true;
      myDiagram.startTransaction('highlight');
      if (part !== null) {
        myDiagram.highlight(part);
      } else {
        myDiagram.clearHighlighteds();
      }
      myDiagram.commitTransaction('highlight');
      myDiagram.skipsUndoManager = oldskips;
    }

    // this is called upon an external drop in this diagram,
    // after a new node has been created and selected
    function onDrop(newNode, point) {
      