/** A mouse-pressed event. Analyse what we should do with it. */
  public void mousePressed(MouseEvent evt) {
    graphEditor.requestFocus();
    int clickX = evt.getX();
    int clickY = evt.getY();

    SelectableGraphElement clickedElement = graph.findGraphElement(clickX, clickY);
    notifyPackage(clickedElement);

    if (clickedElement == null) { // nothing hit
      if (!isMultiselectionKeyDown(evt)) {
        selection.clear();
      }
      if (isButtonOne(evt)) marquee.start(clickX, clickY);
    } else if (isButtonOne(evt)) { // clicked on something
      if (isMultiselectionKeyDown(evt)) {
        // a class was clicked, while multiselectionKey was down.
        if (clickedElement.isSelected()) {
          selection.remove(clickedElement);
        } else {
          selection.add(clickedElement);
        }
      } else {
        // a class was clicked without multiselection
        if (!clickedElement.isSelected()) {
          selection.selectOnly(clickedElement);
        }
      }

      if (isDrawingDependency()) {
        if (clickedElement instanceof Target)
          rubberBand = new RubberBand(clickX, clickY, clickX, clickY);
      } else {
        dragStartX = clickX;
        dragStartY = clickY;

        if (clickedElement.isHandle(clickX, clickY)) {
          resizing = true;
        } else {
          moving = true;
        }
      }
    }
  }
 /** Clear the current selection. */
 public void clearSelection() {
   selection.clear();
 }