Function update

static/editor.md/lib/codemirror/lib/codemirror.js:6947–6950

(line, text, spans)

  function updateDoc(doc, change, markedSpans, estimateHeight) {
    function spansFor(n) {return markedSpans ? markedSpans[n] : null;}
    function update(line, text, spans) {
      updateLine(line, text, spans, estimateHeight);
      signalLater(line, "change", line, change);
    }
    function linesFor(start, end) {
      for (var i = start, result = []; i < end; ++i)
        result.push(new Line(text[i], spansFor(i), estimateHeight));