fallback_formatter.module

<?php

/**
 * @file
 * Hook implementations for the Fallback formatter module.
 */

use Drupal\Core\Render\Element;

/**
 * Implements hook_theme().
 */
function fallback_formatter_theme() {
  return [
    'fallback_formatter_settings_order' => [
      'render element' => 'element',
      'function' => 'theme_fallback_formatter_settings_order',
    ],
  ];
}

/**
 * Implements hook_field_formatter_info_alter().
 */
function fallback_formatter_field_formatter_info_alter(&$info) {
  // Only enable the fallback formatter for field_types that already have one
  // or more formatters.
  $field_types = [];
  foreach ($info as $formatter) {
    $field_types = array_merge($field_types, $formatter['field_types']);
  }
  $counts = array_count_values($field_types);
  foreach ($counts as $field_type => $count) {
    if ($count > 1) {
      $info['fallback']['field_types'][] = $field_type;
    }
  }
}

/**
 * Themes the formatter settings form.
 *
 * @param array $variables
 *   Theme variables.
 *
 * @return string
 *   Rendered HTML of the settings form part.
 */
function theme_fallback_formatter_settings_order($variables) {
  $element = $variables['element'];

  // Fallback formatter order (tabledrag).
  $rows = [];
  foreach (Element::children($element, TRUE) as $name) {
    $element[$name]['weight']['#attributes']['class'][] = 'fallback-formatter-order-weight';
    $rows[] = [
      'data' => [
        \Drupal::service('renderer')->render($element[$name]['label']),
        \Drupal::service('renderer')->render($element[$name]['weight']),
      ],
      'class' => ['draggable'],
    ];
  }

  $table = &$element[];

  $table = [
    '#theme' => 'table',
    '#rows' => $rows,
    '#attributes' => ['id' => 'fallback-formatter-order'],
  ];

  drupal_attach_tabledrag($table, [
    'table_id' => 'fallback-formatter-order',
    'action' => 'order',
    'relationship' => 'sibling',
    'group' => 'fallback-formatter-order-weight',
  ]);

  return \Drupal::service('renderer')->render($element);
}

/**
 * Implements hook_entity_embed_display_plugins_alter().
 *
 * Do not allow the fallback formatter to be used as an entity embed display
 * plugin.
 */
function fallback_formatter_entity_embed_display_plugins_alter(array &$plugins) {
  foreach ($plugins as $id => $plugin) {
    if (!empty($plugin['field_type']) && substr($id, -9) === ':fallback') {
      unset($plugins[$id]);
    }
  }
}