ppi_preview.module

<?php

use Drupal\Core\Form\FormStateInterface;
use Drupal\Core\Entity\EntityInterface;
use Drupal\Core\Routing\RouteMatchInterface;
use Drupal\system\MenuInterface;
use Drupal\language\ConfigurableLanguageInterface;
use Drupal\Core\Access\AccessResult;

function ppi_preview_help($route_name, RouteMatchInterface $route_match) {
    switch ($route_name) {
        case 'help.page.ppi_preview':
            $output = '';
            $output .= '<h3>' . t('About') . '</h3>';
            $output .= '<p>' . t('Displays previews generated by an InDesign server') . '</p>';
            return  $output;

        default:
    }
}


function ppi_preview_form_alter(&$form, FormStateInterface $form_state, $form_id) {
  $form_object = $form_state->getFormObject();
  if ($form_object && method_exists($form_object, 'getEntity')) {
    $entity = $form_object->getEntity();

    if ($entity->getEntityTypeId() == 'node') {
      if ($entity->getType() == 'article' || $entity->getType() == "landing_page") { // type "landing_page" -> Acquia Lightning
        $config_factory = \Drupal::configFactory();
        $config = $config_factory->getEditable('ppi_preview.settings');
        $idWrapperBaseUrl = $config->get('preview_url');
        $apiKey = $config->get('api_key');
        //\Drupal::logger('ppi_preview')->notice($idWrapperBaseUrl);

        $form['ppi_preview'] = [
            '#type' => 'details',
            '#group' => isset($form['additional_settings']) ? 'additional_settings' : 'advanced',
            '#title' => t('Print Preview'),
            '#description' => t('Displays a print preview'),
            '#weight' => -10,
            '#open' => 1
        ];
        $form['ppi_preview']['preview'] = [
            '#theme' => 'image',
            '#uri' => $idWrapperBaseUrl . '?id=' . $entity->uuid() . '&key=' . $apiKey,
            '#style_name' => 'large',
            '#title' => t('ppi print preview'),
            '#attributes' => [ 'id' => 'ppi-preview-id' ],
            '#attached' => [
              'library' => [ 'ppi_preview/ppi_preview_expand' ]
            ]
        ];
      }
    }
  }
}

function ppi_preview_entity_create_access(\Drupal\Core\Session\AccountInterface $account, array $context, $entity_bundle) {
  // $account: Drupal\Core\Session\AccountProxy, account:Drupal\user\Entity\User, id:"1", initialAccountId:null, _serviceId:"current_user"
  // $context: [entity_type_id:"paragraph", langcode:"x-default"]
  // $entity_bundle: "text"
  // \Drupal::logger('ppi_preview')->notice("---------------- hook_entity_create_access() called");
  return AccessResult::allowed();
}