code: public void openMenu() {
  
          m_isOpen = true;
          setButtonDown();
  
          m_popup.show();
          m_popup.position();
          m_resizeRegistration = Window.addResizeHandler(new ResizeHandler() {
  
              public void onResize(ResizeEvent event) {
  
                  m_popup.position();
              }
          });
      }
docs: Opens the menu and fires the on toggle event.<p>