system_page_attachments

system_page_attachments(array &$page)

function system_page_attachments(array &$page) {
  // Ensure the same CSS is loaded in template_preprocess_maintenance_page().
  $page['#attached']['library'][] = 'system/base';
  if (\Drupal::service('router.admin_context')->isAdminRoute()) {
    $page['#attached']['library'][] = 'system/admin';
  }

  // Attach libraries used by this theme.
  $active_theme = \Drupal::theme()->getActiveTheme();
  foreach ($active_theme->getLibraries() as $library) {
    $page['#attached']['library'][] = $library;
  }

  // Attach favicon.
  if (theme_get_setting('features.favicon')) {
    $favicon = theme_get_setting('favicon.url');
    $type = theme_get_setting('favicon.mimetype');
    $page['#attached']['html_head_link'][][] = array(
      'rel' => 'shortcut icon',
      'href' => UrlHelper::stripDangerousProtocols($favicon),
      'type' => $type,
    );
  }

  // Get the major Drupal version.
  list($version, ) = explode('.', \Drupal::VERSION);

  // Attach default meta tags.
  $meta_default = array(
    // Make sure the Content-Type comes first because the IE browser may be
    // vulnerable to XSS via encoding attacks from any content that comes
    // before this META tag, such as a TITLE tag.
    'system_meta_content_type' => array(
      '#tag' => 'meta',
      '#attributes' => array(
        'charset' => 'utf-8',
      ),
      // Security: This always has to be output first.
      '#weight' => -1000,
    ),
    // Show Drupal and the major version number in the META GENERATOR tag.
    'system_meta_generator' => array(
      '#type' => 'html_tag',
      '#tag' => 'meta',
      '#attributes' => array(
        'name' => 'Generator',
        'content' => 'Drupal ' . $version . ' (https://www.drupal.org)',
      ),
    ),
    // Attach default mobile meta tags for responsive design.
    'MobileOptimized' => array(
      '#tag' => 'meta',
      '#attributes' => array(
        'name' => 'MobileOptimized',
        'content' => 'width',
      ),
    ),
    'HandheldFriendly' => array(
      '#tag' => 'meta',
      '#attributes' => array(
        'name' => 'HandheldFriendly',
        'content' => 'true',
      ),
    ),
    'viewport' => array(
      '#tag' => 'meta',
      '#attributes' => array(
        'name' => 'viewport',
        'content' => 'width=device-width, initial-scale=1.0',
      ),
    ),
  );
  foreach ($meta_default as $key => $value) {
    $page['#attached']['html_head'][] = [$value, $key];
  }

  // Handle setting the "active" class on links by:
  // - loading the active-link library if the current user is authenticated;
  // - applying a response filter if the current user is anonymous.
  // @see \Drupal\Core\Link
  // @see \Drupal\Core\Utility\LinkGenerator::generate()
  // @see template_preprocess_links()
  // @see \Drupal\Core\EventSubscriber\ActiveLinkResponseFilter
  if (\Drupal::currentUser()->isAuthenticated()) {
    $page['#attached']['library'][] = 'core/drupal.active-link';
  }
}