Function extendSelection

static/js/codemirror/codemirror.js:2296–2313

(doc, pos, other, bias)

  // If shift is held, this will move the selection anchor. Otherwise,
  // it'll set the whole selection.
  function extendSelection(doc, pos, other, bias) {
    if (doc.sel.shift || doc.sel.extend) {
      var anchor = doc.sel.anchor;
      if (other) {
        var posBefore = posLess(pos, anchor);
        if (posBefore != posLess(other, anchor)) {
          anchor = pos;
          pos = other;
        } else if (posBefore != posLess(pos, other)) {
          pos = other;
        }
      }
      setSelection(doc, anchor, pos, bias);
    } else {
      setSelection(doc, pos, other || pos, bias);
    }
    if (doc.cm) doc.cm.curOp.userSelChange = true;
  }

  function filterSelectionChange(doc, anchor, head) {
    var obj = {anchor: anchor, head: head};