docs: public void initActionHandler(final Window window) {
  
          if (m_actionHandler != null) {
              window.addActionHandler(m_actionHandler);
              window.addCloseListener(new CloseListener() {
  
                  private static final long serialVersionUID = 1L;
  
                  public void windowClose(CloseEvent e) {
  
                      clearActionHandler(window);
                  }
              });
          }
      }