code: private void showVersionInfo(String json) {
          DefaultWindow window = new DefaultWindow("Management Model Versions");
          window.setWidth(480);
          window.setHeight(360);
          window.addCloseHandler(new CloseHandler<PopupPanel>() {
              @Override
              public void onClose(CloseEvent<PopupPanel> event) {
  
              }
          });
  
          TextArea textArea = new TextArea();
          textArea.setStyleName("fill-layout");
          textArea.setText(json);
  
          window.setWidget(textArea);
  
          window.setGlassEnabled(true);
          window.center();
      }
docs: ------------------------------------------------------ helper methods