RenderElement::preRenderAjaxForm

public static RenderElement::preRenderAjaxForm($element)

public static function preRenderAjaxForm($element) {
  // Skip already processed elements.
  if (isset($element['#ajax_processed'])) {
    return $element;
  }
  // Initialize #ajax_processed, so we do not process this element again.
  $element['#ajax_processed'] = FALSE;

  // Nothing to do if there are no Ajax settings.
  if (empty($element['#ajax'])) {
    return $element;
  }

  // Add a data attribute to disable automatic refocus after ajax call.
  if (!empty($element['#ajax']['disable-refocus'])) {
    $element['#attributes']['data-disable-refocus'] = "true";
  }

  // Add a reasonable default event handler if none was specified.
  if (isset($element['#ajax']) && !isset($element['#ajax']['event'])) {
    switch ($element['#type']) {
      case 'submit':
      case 'button':
      case 'image_button':
        // Pressing the ENTER key within a textfield triggers the click event of
        // the form's first submit button. Triggering Ajax in this situation
        // leads to problems, like breaking autocomplete textfields, so we bind
        // to mousedown instead of click.
        // @see https://www.drupal.org/node/216059
        $element['#ajax']['event'] = 'mousedown';
        // Retain keyboard accessibility by setting 'keypress'. This causes
        // ajax.js to trigger 'event' when SPACE or ENTER are pressed while the
        // button has focus.
        $element['#ajax']['keypress'] = TRUE;
        // Binding to mousedown rather than click means that it is possible to
        // trigger a click by pressing the mouse, holding the mouse button down
        // until the Ajax request is complete and the button is re-enabled, and
        // then releasing the mouse button. Set 'prevent' so that ajax.js binds
        // an additional handler to prevent such a click from triggering a
        // non-Ajax form submission. This also prevents a textfield's ENTER
        // press triggering this button's non-Ajax form submission behavior.
        if (!isset($element['#ajax']['prevent'])) {
          $element['#ajax']['prevent'] = 'click';
        }
        break;

      case 'password':
      case 'textfield':
      case 'number':
      case 'tel':
      case 'textarea':
        $element['#ajax']['event'] = 'blur';
        break;

      case 'radio':
      case 'checkbox':
      case 'select':
        $element['#ajax']['event'] = 'change';
        break;

      case 'link':
        $element['#ajax']['event'] = 'click';
        break;

      default:
        return $element;
    }
  }

  // Attach JavaScript settings to the element.
  if (isset($element['#ajax']['event'])) {
    $element['#attached']['library'][] = 'core/jquery.form';
    $element['#attached']['library'][] = 'core/drupal.ajax';

    $settings = $element['#ajax'];

    // Assign default settings. When 'url' is set to NULL, ajax.js submits the
    // Ajax request to the same URL as the form or link destination is for
    // someone with JavaScript disabled. This is generally preferred as a way to
    // ensure consistent server processing for js and no-js users, and Drupal's
    // content negotiation takes care of formatting the response appropriately.
    // However, 'url' and 'options' may be set when wanting server processing
    // to be substantially different for a JavaScript triggered submission.
    $settings += [
      'url' => NULL,
      'options' => ['query' => []],
      'dialogType' => 'ajax',
    ];
    if (array_key_exists('callback', $settings) && !isset($settings['url'])) {
      $settings['url'] = Url::fromRoute('<current>');
      // Add all the current query parameters in order to ensure that we build
      // the same form on the AJAX POST requests. For example,
      // \Drupal\user\AccountForm takes query parameters into account in order
      // to hide the password field dynamically.
      $settings['options']['query'] += \Drupal::request()->query->all();
      $settings['options']['query'][FormBuilderInterface::AJAX_FORM_REQUEST] = TRUE;
    }

    // @todo Legacy support. Remove in Drupal 8.
    if (isset($settings['method']) && $settings['method'] == 'replace') {
      $settings['method'] = 'replaceWith';
    }

    // Convert \Drupal\Core\Url object to string.
    if (isset($settings['url']) && $settings['url'] instanceof Url) {
      $url = $settings['url']->setOptions($settings['options'])->toString(TRUE);
      BubbleableMetadata::createFromRenderArray($element)
        ->merge($url)
        ->applyTo($element);
      $settings['url'] = $url->getGeneratedUrl();
    }
    else {
      $settings['url'] = NULL;
    }
    unset($settings['options']);

    // Add special data to $settings['submit'] so that when this element
    // triggers an Ajax submission, Drupal's form processing can determine which
    // element triggered it.
    // @see _form_element_triggered_scripted_submission()
    if (isset($settings['trigger_as'])) {
      // An element can add a 'trigger_as' key within #ajax to make the element
      // submit as though another one (for example, a non-button can use this
      // to submit the form as though a button were clicked). When using this,
      // the 'name' key is always required to identify the element to trigger
      // as. The 'value' key is optional, and only needed when multiple elements
      // share the same name, which is commonly the case for buttons.
      $settings['submit']['_triggering_element_name'] = $settings['trigger_as']['name'];
      if (isset($settings['trigger_as']['value'])) {
        $settings['submit']['_triggering_element_value'] = $settings['trigger_as']['value'];
      }
      unset($settings['trigger_as']);
    }
    elseif (isset($element['#name'])) {
      // Most of the time, elements can submit as themselves, in which case the
      // 'trigger_as' key isn't needed, and the element's name is used.
      $settings['submit']['_triggering_element_name'] = $element['#name'];
      // If the element is a (non-image) button, its name may not identify it
      // uniquely, in which case a match on value is also needed.
      // @see _form_button_was_clicked()
      if (!empty($element['#is_button']) && empty($element['#has_garbage_value'])) {
        $settings['submit']['_triggering_element_value'] = $element['#value'];
      }
    }

    // Convert a simple #ajax['progress'] string into an array.
    if (isset($settings['progress']) && is_string($settings['progress'])) {
      $settings['progress'] = array('type' => $settings['progress']);
    }
    // Change progress path to a full URL.
    if (isset($settings['progress']['url']) && $settings['progress']['url'] instanceof Url) {
      $settings['progress']['url'] = $settings['progress']['url']->toString();
    }

    $element['#attached']['drupalSettings']['ajax'][$element['#id']] = $settings;
    $element['#attached']['drupalSettings']['ajaxTrustedUrl'][$settings['url']] = TRUE;

    // Indicate that Ajax processing was successful.
    $element['#ajax_processed'] = TRUE;
  }
  return $element;
}