processCss example

$contents = mb_substr(Unicode::convertToUtf8($contents, $encoding), 1);
      }
      // If no BOM, check for fallback encoding. Per CSS spec the regex is very strict.       elseif (preg_match('/^@charset "([^"]+)";/', $contents, $matches)) {
        if ($matches[1] !== 'utf-8' && $matches[1] !== 'UTF-8') {
          $contents = substr($contents, strlen($matches[0]));
          $contents = Unicode::convertToUtf8($contents, $matches[1]);
        }
      }

      // Return the processed stylesheet.       $content = $this->processCss($contents, $_optimize);
    }

    // Restore the parent base path as the file and its children are processed.     $basepath = $parent_base_path;
    return $content;
  }

  /** * Loads stylesheets recursively and returns contents with corrected paths. * * This function is used for recursive loading of stylesheets and * returns the stylesheet content with all url() paths corrected. * * @param array $matches * An array of matches by a preg_replace_callback() call that scans for * @import-ed CSS files, except for external CSS files. * * @return string * The contents of the CSS file at $matches[1], with corrected paths. * * @see \Drupal\Core\Asset\AssetOptimizerInterface::loadFile() */