VerticalTabs::processVerticalTabs

public static VerticalTabs::processVerticalTabs(&$element, FormStateInterface $form_state, &$complete_form)

public static function processVerticalTabs(&$element, FormStateInterface $form_state, &$complete_form) {
  if (isset($element['#access']) && !$element['#access']) {
    return $element;
  }

  // Inject a new details as child, so that form_process_details() processes
  // this details element like any other details.
  $element['group'] = array(
    '#type' => 'details',
    '#theme_wrappers' => array(),
    '#parents' => $element['#parents'],
  );

  // Add an invisible label for accessibility.
  if (!isset($element['#title'])) {
    $element['#title'] = t('Vertical Tabs');
    $element['#title_display'] = 'invisible';
  }

  $element['#attached']['library'][] = 'core/drupal.vertical-tabs';

  // The JavaScript stores the currently selected tab in this hidden
  // field so that the active tab can be restored the next time the
  // form is rendered, e.g. on preview pages or when form validation
  // fails.
  $name = implode('__', $element['#parents']);
  if ($form_state->hasValue($name . '__active_tab')) {
    $element['#default_tab'] = $form_state->getValue($name . '__active_tab');
  }
  $element[$name . '__active_tab'] = array(
    '#type' => 'hidden',
    '#default_value' => $element['#default_tab'],
    '#attributes' => array('class' => array('vertical-tabs__active-tab')),
  );
  // Clean up the active tab value so it's not accidentally stored in
  // settings forms.
  $form_state->addCleanValueKey($name . '__active_tab');

  return $element;
}