class TextCustom

class TextCustom extends TokenizeAreaPluginBase {
  
  /**
   * {@inheritdoc}
   */
  protected function defineOptions() {
    $options = parent::defineOptions();
    $options['content'] = [
      'default' => '',
    ];
    return $options;
  }
  
  /**
   * {@inheritdoc}
   */
  public function buildOptionsForm(&$form, FormStateInterface $form_state) {
    parent::buildOptionsForm($form, $form_state);
    $form['content'] = [
      '#title' => $this->t('Content'),
      '#type' => 'textarea',
      '#description' => $this->t('You may enter data from this view as per the "Available global token replacements" above. You may include the following allowed HTML tags: <code>@tags</code>', [
        '@tags' => '<' . implode('> <', Xss::getAdminTagList()) . '>',
      ]),
      '#default_value' => $this->options['content'],
      '#rows' => 6,
    ];
  }
  
  /**
   * {@inheritdoc}
   */
  public function render($empty = FALSE) {
    if (!$empty || !empty($this->options['empty'])) {
      return [
        '#markup' => $this->renderTextarea($this->options['content']),
      ];
    }
    return [];
  }
  
  /**
   * Render a text area with \Drupal\Component\Utility\Xss::filterAdmin().
   */
  public function renderTextarea($value) {
    if ($value) {
      return $this->sanitizeValue($this->tokenizeValue($value), 'xss_admin');
    }
  }

}