Function makeChangeFromHistory

external/.scrollLibs.js:7188–7272

(doc, type, allowSelectionOnly)

  // Revert a change stored in a document's history.
  function makeChangeFromHistory(doc, type, allowSelectionOnly) {
    var suppress = doc.cm && doc.cm.state.suppressEdits
    if (suppress && !allowSelectionOnly) {
      return
    }

    var hist = doc.history,
      event,
      selAfter = doc.sel
    var source = type == "undo" ? hist.done : hist.undone,
      dest = type == "undo" ? hist.undone : hist.done

    // Verify that there is a useable event (so that ctrl-z won't
    // needlessly clear selection events)
    var i = 0
    for (; i < source.length; i++) {
      event = source[i]
      if (allowSelectionOnly ? event.ranges && !event.equals(doc.sel) : !event.ranges) {
        break
      }
    }
    if (i == source.length) {
      return
    }
    hist.lastOrigin = hist.lastSelOrigin = null

    for (;;) {
      event = source.pop()
      if (event.ranges) {
        pushSelectionToHistory(event, dest)
        if (allowSelectionOnly && !event.equals(doc.sel)) {
          setSelection(doc, event, { clearRedo: false })
          return
        }
        selAfter = event
      } else if (suppress) {
        source.push(event)
        return
      } else {
        break
      }
    }

    // Build up a reverse change object to add to the opposite history
    // stack (redo when undoing, and vice versa).
    var antiChanges = []
    pushSelectionToHistory(selAfter, dest)
    dest.push({ changes: antiChanges, generation: hist.generation })
    hist.generation = event.generation || ++hist.maxGeneration

    var filter = hasHandler(doc, "beforeChange") || (doc.cm && hasHandler(doc.cm, "beforeChange"))

    var loop = function (i) {
      var change = event.changes[i]
      change.origin = type
      if (filter && !filterChange(doc, change, false)) {
        source.length = 0
        return {}