protected function normalizeCharForKeyEvent($char) {
    if (!is_int($char) && !is_string($char)) {
      throw new DriverException("Unsupported key type, can only be integer or string");
    }

    if (is_string($char) && strlen($char) !== 1) {
      throw new DriverException("Key can only have ONE character");
    }

    $key = $char;
    if (is_int($char)) {
      $key = chr($char);
    }
    return $key;
  }