protected function registerStyleSheet()
{
$url = $this->getCssUrl();
if ($url === '') {
return;
}
if ($url === 'default') {
$url = $this->getApplication()->getAssetManager()->publishFilePath(dirname(__FILE__) . DIRECTORY_SEPARATOR . 'assets' . DIRECTORY_SEPARATOR . 'tabpanel.css');
}
if ($url !== '') {
$this->getPage()->getClientScript()->registerStyleSheetFile($url, $url);
}
}