public Client next_client_same_class (Client from, boolean reverse) {
    Client next = next_client_normal (from, reverse);
    if (next == null) return null; // prevent looping

    if (focus_base.class_hint != null
      && next.class_hint != null
      && focus_base.class_hint.class_equals (next.class_hint))

      return next;

    return next_client_same_class (next, reverse); // recursive
  }