Function extendSelection

external/.scrollLibs.js:6888–6893

(doc, head, other, options, extend)

  // Extend the primary selection range, discard the rest.
  function extendSelection(doc, head, other, options, extend) {
    if (extend == null) {
      extend = doc.cm && (doc.cm.display.shift || doc.extend)
    }
    setSelection(doc, new Selection([extendRange(doc.sel.primary(), head, other, extend)], 0), options)
  }

  // Extend all selections (pos is an array of selections with length
  // equal the number of selections)