function template_preprocess_book_navigation

Prepares variables for book navigation templates.

Default template: book-navigation.html.twig.

Parameters

array $variables: An associative array containing the following key:

• book_link: An associative array of book link properties. Properties used: bid, link_title, depth, pid, nid.

File

core/modules/book/book.module, line 389

Allows users to create and organize related content in an outline.

Code

function template_preprocess_book_navigation(&$variables) {
  $book_link = $variables['book_link'];

  // Provide extra variables for themers. Not needed by default.
  $variables['book_id'] = $book_link['bid'];
  $variables['book_title'] = $book_link['link_title'];
  $variables['book_url'] = Url::fromRoute('entity.node.canonical', [
    'node' => $book_link['bid'],
  ])
    ->toString();
  $variables['current_depth'] = $book_link['depth'];
  $variables['tree'] = '';

  /** @var \Drupal\book\BookOutline $book_outline */
  $book_outline = \Drupal::service('book.outline');
  if ($book_link['nid']) {
    $variables['tree'] = $book_outline
      ->childrenLinks($book_link);
    $build = [];
    if ($prev = $book_outline
      ->prevLink($book_link)) {
      $prev_href = Url::fromRoute('entity.node.canonical', [
        'node' => $prev['nid'],
      ])
        ->toString();
      $build['#attached']['html_head_link'][][] = [
        'rel' => 'prev',
        'href' => $prev_href,
      ];
      $variables['prev_url'] = $prev_href;
      $variables['prev_title'] = $prev['title'];
    }

    /** @var \Drupal\book\BookManagerInterface $book_manager */
    $book_manager = \Drupal::service('book.manager');
    if ($book_link['pid'] && ($parent = $book_manager
      ->loadBookLink($book_link['pid']))) {
      $parent_href = Url::fromRoute('entity.node.canonical', [
        'node' => $book_link['pid'],
      ])
        ->toString();
      $build['#attached']['html_head_link'][][] = [
        'rel' => 'up',
        'href' => $parent_href,
      ];
      $variables['parent_url'] = $parent_href;
      $variables['parent_title'] = $parent['title'];
    }
    if ($next = $book_outline
      ->nextLink($book_link)) {
      $next_href = Url::fromRoute('entity.node.canonical', [
        'node' => $next['nid'],
      ])
        ->toString();
      $build['#attached']['html_head_link'][][] = [
        'rel' => 'next',
        'href' => $next_href,
      ];
      $variables['next_url'] = $next_href;
      $variables['next_title'] = $next['title'];
    }
  }
  if (!empty($build)) {
    \Drupal::service('renderer')
      ->render($build);
  }
  $variables['has_links'] = FALSE;

  // Link variables to filter for values and set state of the flag variable.
  $links = [
    'prev_url',
    'prev_title',
    'parent_url',
    'parent_title',
    'next_url',
    'next_title',
  ];
  foreach ($links as $link) {
    if (isset($variables[$link])) {

      // Flag when there is a value.
      $variables['has_links'] = TRUE;
    }
    else {

      // Set empty to prevent notices.
      $variables[$link] = '';
    }
  }
}