private function writeLegend(XMLWriter $objWriter, Legend $legend = null)
    {
        if ($legend === null) {
            return;
        }

        $objWriter->startElement('c:legend');

        $objWriter->startElement('c:legendPos');
        $objWriter->writeAttribute('val', $legend->getPosition());
        $objWriter->endElement();

        $this->writeLayout($objWriter, $legend->getLayout());

        $objWriter->startElement('c:overlay');
        $objWriter->writeAttribute('val', ($legend->getOverlay()) ? '1' : '0');
        $objWriter->endElement();

        $objWriter->startElement('c:txPr');
        $objWriter->startElement('a:bodyPr');
        $objWriter->endElement();

        $objWriter->startElement('a:lstStyle');
        $objWriter->endElement();

        $objWriter->startElement('a:p');
        $objWriter->startElement('a:pPr');
        $objWriter->writeAttribute('rtl', 0);

        $objWriter->startElement('a:defRPr');
        $objWriter->endElement();
        $objWriter->endElement();

        $objWriter->startElement('a:endParaRPr');
        $objWriter->writeAttribute('lang', 'en-US');
        $objWriter->endElement();

        $objWriter->endElement();
        $objWriter->endElement();

        $objWriter->endElement();
    }