code: public void okToUseGui() {
          if (_mayUseGui) return;
  
          _mayUseGui = true;
  
          for (Object o : _children.keySet()) {
              if (o instanceof Visibility) {
                  ((Visibility) o).okToUseGui();
              }
          }
      }
docs: This method instructs the bean that it is OK to use the Gui.