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function render_example_preprocess_page in Examples for Developers 8

Same name and namespace in other branches
  1. 3.x modules/render_example/render_example.module \render_example_preprocess_page()

Implements hook_preprocess_page().

Demonstrates using a preprocess function to alter the renderable array that represents the page currently being viewed.

Related topics

Example: Render API
The Render API consists of two parts: one, structured arrays that provide data, and hints about how that data should be rendered, and two, a rendering pipeline that can be used to render these arrays into various output formats. This example module…

File

render_example/render_example.module, line 95
Demonstrates using Drupal's Render API.

Code

function render_example_preprocess_page(&$variables) {

  // Only modify the 'altering' page.
  if (\Drupal::routeMatch()
    ->getRouteName() !== 'render_example.altering') {
    return;
  }
  $config = \Drupal::config('render_example.settings');

  // Preprocess hooks are invoked by the theme layer, and are used to give
  // modules a chance to manipulate the variables that are going to be made
  // available to a specific template file. Since content is still defined as
  // renderable arrays at this point you can do quite a bit to manipulate the
  // eventual output by altering these arrays.
  //
  // The $page variable in this case contains the complete content of the page
  // including all regions, and the blocks placed within each region.
  //
  // The actual process of converting a renderable array to HTML is started when
  // this variable is printed out within a Twig template. Drupal's Twig
  // extension provides a wrapper around the Twig code that prints out variables
  // which checks to see if the variable being printed is a renderable array and
  // passes it through \Drupal\Core\Render\RendererInterface::render() before
  // printing it to the screen.
  $page =& $variables['page'];

  // Move the breadcrumbs into the content area.
  if ($config
    ->get('move_breadcrumbs') && !empty($page['breadcrumb']) && !empty($page['content'])) {
    $page['content']['breadcrumb'] = $page['breadcrumb'];
    unset($page['breadcrumb']);
    $page['content']['breadcrumb']['#weight'] = -99999;

    // Force the content to be re-sorted.
    $page['content']['#sorted'] = FALSE;
  }

  // Re-sort the contents of the sidebar in reverse order.
  if ($config
    ->get('reverse_sidebar') && !empty($page['sidebar_first'])) {
    $page['sidebar_first'] = array_reverse($page['sidebar_first']);
    foreach (Element::children($page['sidebar_first']) as $element) {

      // Reverse the weights if they exist.
      if (!empty($page['sidebar_first'][$element]['#weight'])) {
        $page['sidebar_first'][$element]['#weight'] *= -1;
      }
    }

    // This forces the sidebar to be re-sorted.
    $page['sidebar_first']['#sorted'] = FALSE;
  }

  // Show the render array used to build the current page.
  // This relies on the Devel module's variable dumper service.
  // https://wwww.drupal.org/project/devel
  if (Drupal::moduleHandler()
    ->moduleExists('devel') && $config
    ->get('show_page')) {
    $page['content']['page_render_array'] = [
      '#type' => 'markup',
      '#prefix' => '<h2>' . t('The page render array') . '</h2>',
      // The devel.dumper service is provided by the devel module and makes for
      // and easier to read var_dump(). Especially if the companion Kint module
      // is enabled.
      'dump' => \Drupal::service('devel.dumper')
        ->exportAsRenderable($page, '$page'),
      '#weight' => -99999,
    ];
    $page['content']['#sorted'] = FALSE;
  }
}