private function writeCssFile(View $view, $css)
    {
        $oldmask = umask(0);
        if (!is_dir($this->viewCssDir)) {
            mkdir($this->viewCssDir, 0777, true);
        }
        $file = $this->getViewCssFile($view);
        file_put_contents($file, $css);
        umask($oldmask);
    }