public function addCssRequirement($css, LambdaHelper $helper = null)
    {
        $css = trim($css);
        $key = md5($css);

        if (!isset(self::$cssRequirements[$key])) {
            if ($helper !== null) {
                $css = $helper->render($css);
            }

            self::$cssRequirements[$key] = $css;
        }
    }
public function addCssRequirement($css, LambdaHelper $helper = null)
    {
        $css = trim($css);
        $key = md5($css);

        if (!isset(self::$cssRequirements[$key])) {
            if ($helper !== null) {
                $css = $helper->render($css);
            }

            self::$cssRequirements[$key] = $css;
        }
    }
public function addCssRequirement ( $ css , LambdaHelper $ helper = null ) { $ css = trim ( $ css ) ; $ key = md5 ( $ css ) ; if ( ! isset ( self :: $ cssRequirements [ $ key ] ) ) { if ( $ helper !== null ) { $ css = $ helper -> render ( $ css ) ; } self :: $ cssRequirements [ $ key ] = $ css ; } }
Enqueue an external CSS file.

Must include `<link />` or surrounding `<style>` element.

@param string       $css    The CSS requirements.
@param LambdaHelper $helper For rendering strings in the current context.
@return void
Enqueue an external CSS file .