LanguageConfiguration::processLanguageConfiguration

public static LanguageConfiguration::processLanguageConfiguration(&$element, FormStateInterface $form_state, &$form)

public static function processLanguageConfiguration(&$element, FormStateInterface $form_state, &$form) {
  $options = isset($element['#options']) ? $element['#options'] : array();
  // Avoid validation failure since we are moving the '#options' key in the
  // nested 'language' select element.
  unset($element['#options']);
  /** @var \Drupal\language\Entity\ContentLanguageSettings $default_config */
  $default_config = $element['#default_value'];
  $element['langcode'] = array(
    '#type' => 'select',
    '#title' => t('Default language'),
    '#options' => $options + static::getDefaultOptions(),
    '#description' => t('Explanation of the language options is found on the <a href=":languages_list_page">languages list page</a>.', array(':languages_list_page' => \Drupal::url('entity.configurable_language.collection'))),
    '#default_value' => ($default_config != NULL) ? $default_config->getDefaultLangcode() : LanguageInterface::LANGCODE_SITE_DEFAULT,
  );

  $element['language_alterable'] = array(
    '#type' => 'checkbox',
    '#title' => t('Show language selector on create and edit pages'),
    '#default_value' => ($default_config != NULL) ? $default_config->isLanguageAlterable() : FALSE,
  );

  // Add the entity type and bundle information to the form if they are set.
  // They will be used, in the submit handler, to generate the names of the
  // configuration entities that will store the settings and are a way to uniquely
  // identify the entity.
  $language = $form_state->get('language') ? : [];
  $language += array(
    $element['#name'] => array(
      'entity_type' => $element['#entity_information']['entity_type'],
      'bundle' => $element['#entity_information']['bundle'],
    ),
  );
  $form_state->set('language', $language);

  // Do not add the submit callback for the language content settings page,
  // which is handled separately.
  if ($form['#form_id'] != 'language_content_settings_form') {
    // Determine where to attach the language_configuration element submit
    // handler.
    // @todo Form API: Allow form widgets/sections to declare #submit
    //   handlers.
    $submit_name = isset($form['actions']['save_continue']) ? 'save_continue' : 'submit';
    if (isset($form['actions'][$submit_name]['#submit']) && array_search('language_configuration_element_submit', $form['actions'][$submit_name]['#submit']) === FALSE) {
      $form['actions'][$submit_name]['#submit'][] = 'language_configuration_element_submit';
    }
    elseif (array_search('language_configuration_element_submit', $form['#submit']) === FALSE) {
      $form['#submit'][] = 'language_configuration_element_submit';
    }
  }
  return $element;
}