Render popup content via AJAX

Instead of a sandbox, please do a merge request

I think the saner approach is something like:

$rowPlugin = $this->view->rowPlugin;
    foreach ($data_provider->getPositionsFromViewsRow($row, $this->view->field[$this->options['geolocation_field']]) as $position) {
      if (
        $rowPlugin instanceof EntityRow
        && !empty($row->_entity)
        && $row->_entity instanceof EntityInterface
      ) {
   // Prepare Ajax Command Link
              $row->_entity->id(),
              $rowPlugin->getEntityTypeId(),
              $rowPlugin->options['view_mode'],

and then later something like

  public function ajaxLinkCallback($nojs = 'nojs') {
    // Determine whether the request is coming from AJAX or not.
    if ($nojs == 'ajax') {
      $output = $this->t("This is some content delivered via AJAX");
      $response = new AjaxResponse();
      $response->addCommand(new AppendCommand('#ajax-example-destination-div', $output));

      // See ajax_example_advanced.inc for more details on the available
      // commands and how to use them.
      // $page = array('#type' => 'ajax', '#commands' => $commands);
      // ajax_deliver($response);
      return $response;
    }
    $response = new Response($this->t("This is some content delivered via a page load."));
    return $response;
  }

Based on this an option could be added, if the row plugin is an entity (so not fields), it can be reproducibly loaded by ajax.

When using fields, this does not work.

This is best solved via a custom "MapFeature" plugin.