core-bundle/src/Resources/contao/dca/tl_layout.php
public function styleSheetLink(Contao\DataContainer $dc)
	{
		return ' <a href="contao/main.php?do=themes&amp;table=tl_style_sheet&amp;id=' . $dc->activeRecord->pid . '&amp;popup=1&amp;nb=1&amp;rt=' . REQUEST_TOKEN . '" title="' . Contao\StringUtil::specialchars($GLOBALS['TL_LANG']['tl_layout']['edit_styles']) . '" onclick="Backend.openModalIframe({\'title\':\''.Contao\StringUtil::specialchars(str_replace("'", "\\'", $GLOBALS['TL_LANG']['tl_layout']['edit_styles'])).'\',\'url\':this.href});return false">' . Contao\Image::getHtml('edit.svg') . '</a>';
	}
public function styleSheetLink(Contao\DataContainer $dc)
	{
		return ' <a href="contao/main.php?do=themes&amp;table=tl_style_sheet&amp;id=' . $dc->activeRecord->pid . '&amp;popup=1&amp;nb=1&amp;rt=' . REQUEST_TOKEN . '" title="' . Contao\StringUtil::specialchars($GLOBALS['TL_LANG']['tl_layout']['edit_styles']) . '" onclick="Backend.openModalIframe({\'title\':\''.Contao\StringUtil::specialchars(str_replace("'", "\\'", $GLOBALS['TL_LANG']['tl_layout']['edit_styles'])).'\',\'url\':this.href});return false">' . Contao\Image::getHtml('edit.svg') . '</a>';
	}
Add a link to edit the stylesheets of the theme

@param Contao\DataContainer $dc

@return string