public BookmarkDialog getBookmarkDialog(final Window owner) {
    if (dialog == null) {
      dialog = new BookmarkDialog(owner, serviceRegistrar);
      dialog.addWindowListener(
          new WindowAdapter() {
            @Override
            public void windowClosed(WindowEvent e) {
              dialog = null;
            }
          });
    }

    return dialog;
  }
 public boolean isDialogVisible() {
   return dialog != null && dialog.isVisible();
 }