Function isWholeLineUpdate

static/editor.md/lib/codemirror/lib/codemirror.js:6939–6942

(doc, change)

  // are treated specially, in order to make the association of line
  // widgets and marker elements with the text behave more intuitive.
  function isWholeLineUpdate(doc, change) {
    return change.from.ch == 0 && change.to.ch == 0 && lst(change.text) == "" &&
      (!doc.cm || doc.cm.options.wholeLineUpdateBefore);
  }

  // Perform a change on the document data structure.
  function updateDoc(doc, change, markedSpans, estimateHeight) {