Function regLineChange

static/editor.md/lib/codemirror/lib/codemirror.js:3197–3208

(cm, line, type)

  // Register a change to a single line. Type must be one of "text",
  // "gutter", "class", "widget"
  function regLineChange(cm, line, type) {
    cm.curOp.viewChanged = true;
    var display = cm.display, ext = cm.display.externalMeasured;
    if (ext && line >= ext.lineN && line < ext.lineN + ext.size)
      display.externalMeasured = null;

    if (line < display.viewFrom || line >= display.viewTo) return;
    var lineView = display.view[findViewIndex(cm, line)];
    if (lineView.node == null) return;
    var arr = lineView.changes || (lineView.changes = []);
    if (indexOf(arr, type) == -1) arr.push(type);
  }

  // Clear the view.
  function resetView(cm) {