preRenderViewElement example

// We ask ViewExecutable::buildRenderable() to avoid creating a render cache     // entry for the view output by passing FALSE, because we're going to cache     // the whole block instead.     if ($output = $this->view->buildRenderable($this->displayID, array_values($args), FALSE)) {
      // Before returning the block output, convert it to a renderable array       // with contextual links.       $this->addContextualLinks($output);

      // Block module expects to get a final render array, without another       // top-level #pre_render callback. So, here we make sure that Views'       // #pre_render callback has already been applied.       $output = View::preRenderViewElement($output);

      // Override the label to the dynamic title configured in the view.       if (empty($this->configuration['views_label']) && $this->view->getTitle()) {
        $output['#title'] = ['#markup' => $this->view->getTitle(), '#allowed_tags' => Xss::getHtmlTagList()];
      }

      // When view_build is empty, the actual render array output for this View       // is going to be empty. In that case, return just #cache, so that the       // render system knows the reasons (cache contexts & tags) why this Views       // block is empty, and can cache it accordingly.       if (empty($output['view_build'])) {