Rearrange::submitForm

public Rearrange::submitForm(array &$form, FormStateInterface $form_state)

public function submitForm(array &$form, FormStateInterface $form_state) {
  $view = $form_state->get('view');
  $display_id = $form_state->get('display_id');
  $type = $form_state->get('type');

  $types = ViewExecutable::getHandlerTypes();
  $display = &$view->getExecutable()->displayHandlers->get($display_id);

  $old_fields = $display->getOption($types[$type]['plural']);
  $new_fields = $order = array();

  // Make an array with the weights
  foreach ($form_state->getValue('fields') as $field => $info) {
    // add each value that is a field with a weight to our list, but only if
    // it has had its 'removed' checkbox checked.
    if (is_array($info) && isset($info['weight']) && empty($info['removed'])) {
      $order[$field] = $info['weight'];
    }
  }

  // Sort the array
  asort($order);

  // Create a new list of fields in the new order.
  foreach (array_keys($order) as $field) {
    $new_fields[$field] = $old_fields[$field];
  }
  $display->setOption($types[$type]['plural'], $new_fields);

  // Store in cache
  $view->cacheSet();
}