protected function writeGridline($oGridlines, $styleName, $chartClass)
{
if (!$oGridlines instanceof Chart\Gridlines) {
return;
}
$this->xmlContent->startElement('chart:grid');
$this->xmlContent->writeAttribute('chart:style-name', $styleName);
$this->xmlContent->writeAttribute('chart:class', $chartClass);
$this->xmlContent->endElement();
}