docs: private void updateToolTip() {
          // Try to set tool tip on frame. On Mac OS X 10.5,
          // the number of components is different, so try to be safe.
          int n = getComponentCount() - 1;
          if (n > 1) {
              n = 1;
          } else if (n < 0) {
              return;
          }
          Component c = getComponent(n);
          // this will work at least for Metal L&F
          if (c != null && c instanceof JComponent) {
              ((JComponent)c).setToolTipText(getUrl());
          }
      }