code: private void installLayout(JRootPane root) {
          if (layoutManager == null) {
              layoutManager = createLayoutManager();
          }
  
          savedOldLayout = root.getLayout();
          root.setLayout(layoutManager);
      }
docs: Installs the appropriate LayoutManager on the <code>JRootPane</code> to
  render the window decorations.
  
  @param root the JRootPane.