public function CssCollectionRenderer::render in HTTP/2 Server Push 8

Renders an asset collection.

Parameters

array $assets: An asset collection.

Return value

array A render array to render the asset collection.

Overrides AssetCollectionRendererInterface::render

File

src/Asset/CssCollectionRenderer.php, line 48

Class

CssCollectionRenderer

Decorates the CSS collection renderer service, adds Server Push.

Namespace

Drupal\http2_server_push\Asset

Code

public function render(array $css_assets) {
  $elements = $this->cssCollectionRenderer
    ->render($css_assets);
  $request = $this->requestStack
    ->getCurrentRequest();
  $link_headers = $request->attributes
    ->get('http2_server_push_link_headers', []);
  foreach ($elements as &$element) {
    if (!static::isLinkRelStylesheet($element)) {
      continue;
    }

    // Locally served CSS files that are sent to all browsers can be pushed.
    if (isset($element['#attributes']['href']) && static::hasRootRelativeUrl($element, 'href') && static::isUnconditional($element)) {
      $link_header_value = '<' . $element['#attributes']['href'] . '>; rel=preload; as=style';
      $link_headers[] = $link_header_value;

      // @todo When this is moved into Drupal core, consider allowing bubbling
      // of bubbleable metadata from the return value of
      // \Drupal\Core\Render\HtmlResponseAttachmentsProcessor::processAssetLibraries
      // so this line of code can work, which would mean we would no longer
      // need to use request attributes. (The problem is that a key assumption
      // is that rendering set of asset libraries to HTML that loads CSS/JS,
      // no further attachment bubbling happens. That's a fine assumption, but
      // this module is the first and sole exception.)

      /*
              $element['#attached']['http_header'][] = ['Link', $link_header_value];
      */
    }
  }
  $request->attributes
    ->set('http2_server_push_link_headers', $link_headers);
  return $elements;
}