Function offsetCursor

src/codemirror.js:11982–11988

(cur, offsetLine, offsetCh)

      return ret;
    }
    function offsetCursor(cur, offsetLine, offsetCh) {
      if (typeof offsetLine === 'object') {
        offsetCh = offsetLine.ch;
        offsetLine = offsetLine.line;
      }
      return Pos(cur.line + offsetLine, cur.ch + offsetCh);
    }
    function getOffset(anchor, head) {
      return {
        line: head.line - anchor.line,