       const r = mf.getBoundingClientRect();
        kbdPanel.style.display = 'block';
        const w = kbdPanel.offsetWidth;
        kbdPanel.style.top = `${r.bottom + 16}px`;
        kbdPanel.style.left = `${r.left + r.width / 2 - w / 2}px`;
        mathVirtualKeyboard.show();
      }
    </script>
  </body>
</html>
