Function moveLogically

src/codemirror.js:8741–8745

(line, start, dir, byUnit)

  }

  function moveLogically(line, start, dir, byUnit) {
    var target = start + dir;
    if (byUnit) while (target > 0 && isExtendingChar(line.text.charAt(target))) target += dir;
    return target < 0 || target > line.text.length ? null : target;
  }

  // Bidirectional ordering algorithm
  // See http://unicode.org/reports/tr9/tr9-13.html for the algorithm