_content_translation_form_language_content_settings_form_alter

_content_translation_form_language_content_settings_form_alter(array &$form, FormStateInterface $form_state)

function _content_translation_form_language_content_settings_form_alter(array &$form, FormStateInterface $form_state) {
  // Inject into the content language settings the translation settings if the
  // user has the required permission.
  if (!\Drupal::currentUser()->hasPermission('administer content translation')) {
    return;
  }

  $content_translation_manager = \Drupal::service('content_translation.manager');
  $default = $form['entity_types']['#default_value'];
  foreach ($default as $entity_type_id => $enabled) {
    $default[$entity_type_id] = $enabled || $content_translation_manager->isEnabled($entity_type_id) ? $entity_type_id : FALSE;
  }
  $form['entity_types']['#default_value'] = $default;

  $form['#attached']['library'][] = 'content_translation/drupal.content_translation.admin';

  $entity_manager = Drupal::entityManager();
  $bundle_info_service = \Drupal::service('entity_type.bundle.info');
  foreach ($form['#labels'] as $entity_type_id => $label) {
    $entity_type = $entity_manager->getDefinition($entity_type_id);
    $storage_definitions = $entity_type instanceof ContentEntityTypeInterface ? $entity_manager->getFieldStorageDefinitions($entity_type_id) : array();

    $entity_type_translatable = $content_translation_manager->isSupported($entity_type_id);
    foreach ($bundle_info_service->getBundleInfo($entity_type_id) as $bundle => $bundle_info) {
      // Here we do not want the widget to be altered and hold also the "Enable
      // translation" checkbox, which would be redundant. Hence we add this key
      // to be able to skip alterations. Alter the title and display the message
      // about UI integration.
      $form['settings'][$entity_type_id][$bundle]['settings']['language']['#content_translation_skip_alter'] = TRUE;
      if (!$entity_type_translatable) {
        $form['settings'][$entity_type_id]['#title'] = t('@label (Translation is not supported).', array('@label' => $entity_type->getLabel()));
        continue;
      }

      $fields = $entity_manager->getFieldDefinitions($entity_type_id, $bundle);
      if ($fields) {
        foreach ($fields as $field_name => $definition) {
          if ($definition->isComputed() || (!empty($storage_definitions[$field_name]) && _content_translation_is_field_translatability_configurable($entity_type, $storage_definitions[$field_name]))) {
            $form['settings'][$entity_type_id][$bundle]['fields'][$field_name] = array(
              '#label' => $definition->getLabel(),
              '#type' => 'checkbox',
              '#default_value' => $definition->isTranslatable(),
            );
            // Display the column translatability configuration widget.
            $column_element = content_translation_field_sync_widget($definition, "settings[{$entity_type_id}][{$bundle}][columns][{$field_name}]");
            if ($column_element) {
              $form['settings'][$entity_type_id][$bundle]['columns'][$field_name] = $column_element;
            }
          }
        }
        if (!empty($form['settings'][$entity_type_id][$bundle]['fields'])) {
          // Only show the checkbox to enable translation if the bundles in the
          // entity might have fields and if there are fields to translate.
          $form['settings'][$entity_type_id][$bundle]['translatable'] = array(
            '#type' => 'checkbox',
            '#default_value' => $content_translation_manager->isEnabled($entity_type_id, $bundle),
          );
        }
      }
    }
  }

  $form['#validate'][] = 'content_translation_form_language_content_settings_validate';
  $form['#submit'][] = 'content_translation_form_language_content_settings_submit';
}