elements corresponding to depth 0 and depth 1. * This is intended to support WYSIWYG output; for instance, level 3 sections * always look like level 3 sections, no matter their depth relative to the * node selected to be exported as printer-friendly HTML. * * @param \Drupal\node\NodeInterface $node * The node to export. * * @return array * A render array representing the HTML for a node and its children in the * book hierarchy. * * @throws \Exception * Thrown when the node was not attached to a book. */ public function bookExportHtml(NodeInterface $node) { if (!isset($node->book)) { throw new \Exception(); } $tree = $this->bookManager->bookSubtreeData($node->book); $contents = $this->exportTraverse($tree, array($this, 'bookNodeExport')); return array( '#theme' => 'book_export_html', '#title' => $node->label(), '#contents' => $contents, '#depth' => $node->book['depth'], '#cache' => [ 'tags' => $node->getEntityType()->getListCacheTags(), ], ); } /** * Traverses the book tree to build printable or exportable output. * * During the traversal, the callback is applied to each node and is called * recursively for each child of the node (in weight, title order). * * @param array $tree * A subtree of the book menu hierarchy, rooted at the current page. * @param callable $callable * A callback to be called upon visiting a node in the tree. * * @return string * The output generated in visiting each node. */ protected function exportTraverse(array $tree, $callable) { // If there is no valid callable, use the default callback. $callable = !empty($callable) ? $callable : array($this, 'bookNodeExport'); $build = array(); foreach ($tree as $data) { // Note- access checking is already performed when building the tree. if ($node = $this->nodeStorage->load($data['link']['nid'])) { $children = $data['below'] ? $this->exportTraverse($data['below'], $callable) : ''; $build[] = call_user_func($callable, $node, $children); } } return $build; } /** * Generates printer-friendly HTML for a node. * * @param \Drupal\node\NodeInterface $node * The node that will be output. * @param string $children * (optional) All the rendered child nodes within the current node. Defaults * to an empty string. * * @return array * A render array for the exported HTML of a given node. * * @see \Drupal\book\BookExport::exportTraverse() */ protected function bookNodeExport(NodeInterface $node, $children = '') { $build = $this->viewBuilder->view($node, 'print', NULL); unset($build['#theme']); return array( '#theme' => 'book_node_export_html', '#content' => $build, '#node' => $node, '#children' => $children, ); } }