class ToolbarSettingsForm

class ToolbarSettingsForm extends ConfigFormBase {
  
  /**
   * The menu link tree service.
   *
   * @var \Drupal\Core\Menu\MenuLinkTree
   */
  protected $menuLinkTree;
  
  /**
   * ToolbarSettingsForm constructor.
   *
   * @param \Drupal\Core\Config\ConfigFactoryInterface $config_factory
   *   The config factory.
   * @param \Drupal\Core\Menu\MenuLinkTreeInterface $menu_link_tree
   *   The menu link tree service.
   */
  public function __construct(ConfigFactoryInterface $config_factory, MenuLinkTreeInterface $menu_link_tree) {
    parent::__construct($config_factory);
    $this->menuLinkTree = $menu_link_tree;
  }
  
  /**
   * {@inheritdoc}
   */
  public static function create(ContainerInterface $container) {
    return new static($container->get('config.factory'), $container->get('menu.link_tree'));
  }
  
  /**
   * {@inheritdoc}
   */
  public function getFormId() {
    return 'devel_toolbar_settings_form';
  }
  
  /**
   * {@inheritdoc}
   */
  protected function getEditableConfigNames() {
    return [
      'devel.toolbar.settings',
    ];
  }
  
  /**
   * {@inheritdoc}
   */
  public function buildForm(array $form, FormStateInterface $form_state) {
    $config = $this->config('devel.toolbar.settings');
    $form['toolbar_items'] = [
      '#type' => 'checkboxes',
      '#title' => $this->t('Menu items always visible'),
      '#options' => $this->getLinkLabels(),
      '#default_value' => $config->get('toolbar_items') ?: [],
      '#required' => TRUE,
      '#description' => $this->t('Select the menu items always visible in devel toolbar tray. All the items not selected in this list will be visible only when the toolbar orientation is vertical.'),
    ];
    return parent::buildForm($form, $form_state);
  }
  
  /**
   * {@inheritdoc}
   */
  public function submitForm(array &$form, FormStateInterface $form_state) {
    $values = $form_state->getValues();
    $toolbar_items = array_keys(array_filter($values['toolbar_items']));
    $this->config('devel.toolbar.settings')
      ->set('toolbar_items', $toolbar_items)
      ->save();
    parent::submitForm($form, $form_state);
  }
  
  /**
   * Provides an array of available menu items.
   *
   * @return array
   *   Associative array of devel menu item labels keyed by plugin ID.
   */
  protected function getLinkLabels() {
    $options = [];
    $parameters = new MenuTreeParameters();
    $parameters->onlyEnabledLinks()
      ->setTopLevelOnly();
    $tree = $this->menuLinkTree
      ->load('devel', $parameters);
    foreach ($tree as $element) {
      $link = $element->link;
      $options[$link->getPluginId()] = $link->getTitle();
    }
    asort($options);
    return $options;
  }

}