QuickEditFieldForm::init

protected QuickEditFieldForm::init(FormStateInterface $form_state, EntityInterface $entity, $field_name)

protected function init(FormStateInterface $form_state, EntityInterface $entity, $field_name) {
  // @todo Rather than special-casing $node->revision, invoke prepareEdit()
  //   once https://www.drupal.org/node/1863258 lands.
  if ($entity->getEntityTypeId() == 'node') {
    $node_type = $this->nodeTypeStorage->load($entity->bundle());
    $entity->setNewRevision($node_type->isNewRevision());
    $entity->revision_log = NULL;
  }

  $form_state->set('entity', $entity);
  $form_state->set('field_name', $field_name);

  // Fetch the display used by the form. It is the display for the 'default'
  // form mode, with only the current field visible.
  $display = EntityFormDisplay::collectRenderDisplay($entity, 'default');
  foreach ($display->getComponents() as $name => $options) {
    if ($name != $field_name) {
      $display->removeComponent($name);
    }
  }
  $form_state->set('form_display', $display);
}