Function makeChangeSingleDoc

static/editor.md/lib/codemirror/lib/codemirror.js:4301–4330

(doc, change, selAfter, spans)

  // More lower-level change function, handling only a single document
  // (not linked ones).
  function makeChangeSingleDoc(doc, change, selAfter, spans) {
    if (doc.cm && !doc.cm.curOp)
      return operation(doc.cm, makeChangeSingleDoc)(doc, change, selAfter, spans);

    if (change.to.line < doc.first) {
      shiftDoc(doc, change.text.length - 1 - (change.to.line - change.from.line));
      return;
    }
    if (change.from.line > doc.lastLine()) return;

    // Clip the change to the size of this doc
    if (change.from.line < doc.first) {
      var shift = change.text.length - 1 - (doc.first - change.from.line);
      shiftDoc(doc, shift);
      change = {from: Pos(doc.first, 0), to: Pos(change.to.line + shift, change.to.ch),
                text: [lst(change.text)], origin: change.origin};
    }
    var last = doc.lastLine();
    if (change.to.line > last) {
      change = {from: change.from, to: Pos(last, getLine(doc, last).text.length),
                text: [change.text[0]], origin: change.origin};
    }

    change.removed = getBetween(doc, change.from, change.to);

    if (!selAfter) selAfter = computeSelAfterChange(doc, change);
    if (doc.cm) makeChangeSingleDocInEditor(doc.cm, change, spans);
    else updateDoc(doc, change, spans);
    setSelectionNoUndo(doc, selAfter, sel_dontScroll);
  }

  // Handle the interaction of a change to a document with the editor
  // that this document is part of.