// undo-redo buttons
  private void addUndoPanel() {
    PerspectiveResources pr =
        ((ImageFactory) GWT.create(ImageFactory.class)).getPerspectiveResources();
    // Image redoImage = new Image(GuiResources.INSTANCE.button_redo());
    // redoButton = new StandardButton(pr.button_redo(), null, 32);
    // redoButton.getElement().appendChild(redoImage.getElement());
    // redoButton.addFastClickHandler(new FastClickHandler(){
    // @Override
    // public void onClick(Widget source) {
    // app.getGuiManager().redo();
    // app.hideKeyboard();
    // }
    // });

    redoButton = new StandardButton(pr.menu_header_redo(), null, 32);
    redoButton.getUpHoveringFace().setImage(getImage(pr.menu_header_redo_hover(), 32));

    redoButton.addFastClickHandler(
        new FastClickHandler() {
          @Override
          public void onClick(Widget source) {
            app.getGuiManager().redo();
            app.hideKeyboard();
          }
        });

    redoButton.addStyleName("redoButton");
    // redoButton.getElement().addClassName("button");

    redoButton.getElement().getStyle().setOverflow(Overflow.HIDDEN);

    // Image undoImage = new Image(GuiResources.INSTANCE.button_undo());
    // undoButton = new StandardButton(pr.button_undo(), null, 32);
    // undoButton.getElement().appendChild(undoImage.getElement());
    // undoButton.addFastClickHandler(new FastClickHandler(){
    // @Override
    // public void onClick(Widget source) {
    // app.getGuiManager().undo();
    // app.hideKeyboard();
    // }
    // });

    undoButton = new StandardButton(pr.menu_header_undo(), null, 32);
    undoButton.getUpHoveringFace().setImage(getImage(pr.menu_header_undo_hover(), 32));

    undoButton.addFastClickHandler(
        new FastClickHandler() {
          @Override
          public void onClick(Widget source) {
            app.getGuiManager().undo();
            app.hideKeyboard();
          }
        });

    undoButton.addStyleName("undoButton");
    // undoButton.getElement().addClassName("button");

    // toolBarPanel.add(redoButton);
    updateUndoActions();
    rightButtonPanel.add(undoButton);
    rightButtonPanel.add(redoButton);
    setLabels();
  }