renderArea example

  public function elementPreRender(array $element) {
    $view = $element['#view'];
    $empty = empty($view->result);

    // Force a render array so CSS/JS can be attached.     if (!is_array($element['#rows'])) {
      $element['#rows'] = ['#markup' => $element['#rows']];
    }

    $element['#header'] = $view->display_handler->renderArea('header', $empty);
    $element['#footer'] = $view->display_handler->renderArea('footer', $empty);
    $element['#empty'] = $empty ? $view->display_handler->renderArea('empty', $empty) : [];
    $element['#exposed'] = !empty($view->exposed_widgets) ? $view->exposed_widgets : [];
    $element['#more'] = $view->display_handler->renderMoreLink();
    $element['#feed_icons'] = !empty($view->feedIcons) ? $view->feedIcons : [];

    if ($view->display_handler->renderPager()) {
      $exposed_input = $view->getExposedInput();
      $element['#pager'] = $view->renderPager($exposed_input);
    }