public ContraintComboBox() {
    super();

    // add unspecified event
    fIsReverting = false;
    addItem(Event.getConstraintDefault());
    setSelectedIndex(0);

    // 12 X characters wide
    setPrototypeDisplayValue("XXXXXXXXXXXX");
  }
  // add scope or pattern events (to distinguisj between available events)
  public void updateEvents() {
    if (fPSPController != null) {
      // save selected events
      Event lCurrent = (Event) getSelectedItem();

      removeAllItems();

      // add unspecified event
      addItem(Event.getConstraintDefault());

      for (Event e : fPSPController) addItem(e);

      setSelectedItem(lCurrent);
    }
  }