code: public final void show(final UI ui, final Listener listener,
              final boolean modal) {
          confirmListener = listener;
          center();
          setModal(modal);
          ui.addWindow(this);
      }
docs: Show confirm dialog.
  
  @param ui the UI in which the dialog should be shown
  @param listener the listener to be notified
  @param modal true if the dialog should be modal