+ optional<struct LayoutState*> get_layout_state(int surface_id) {
+ int layer_id = *this->get_layer_id(surface_id);
+ auto i = std::find_if(
+ std::begin(this->mapping), std::end(this->mapping),
+ [layer_id](struct layer const &l) { return layer_id == l.layer_id; });
+ return i == this->mapping.end() ? nullopt : optional<struct LayoutState *>(&i->state);
+ }