private function writeWindow1()
    {
        $record = 0x003D; // Record identifier
        $length = 0x0012; // Number of bytes to follow

        $xWn = 0x0000; // Horizontal position of window
        $yWn = 0x0000; // Vertical position of window
        $dxWn = 0x25BC; // Width of window
        $dyWn = 0x1572; // Height of window

        $grbit = 0x0038; // Option flags

        // not supported by PhpSpreadsheet, so there is only one selected sheet, the active
        $ctabsel = 1; // Number of workbook tabs selected

        $wTabRatio = 0x0258; // Tab to scrollbar ratio

        // not supported by PhpSpreadsheet, set to 0
        $itabFirst = 0; // 1st displayed worksheet
        $itabCur = $this->spreadsheet->getActiveSheetIndex(); // Active worksheet

        $header = pack('vv', $record, $length);
        $data = pack('vvvvvvvvv', $xWn, $yWn, $dxWn, $dyWn, $grbit, $itabCur, $itabFirst, $ctabsel, $wTabRatio);
        $this->append($header . $data);
    }