+void Panel::on_child_removed(Widget &wdg)
+{
+ auto i = std::remove(nav_order.begin(), nav_order.end(), &wdg);
+ if(i!=nav_order.end())
+ nav_order.erase(i, nav_order.end());
+
+ if(layout)
+ {
+ layout->remove_widget(wdg);
+ signal_autosize_changed.emit();
+ }
+}
+
+
+Panel::Loader::Loader(Panel &p, map<string, Widget *> &m):
+ DataFile::DerivedObjectLoader<Panel, Widget::Loader>(p),
+ wdg_map(m),
+ last_widget(nullptr)
+{
+ if(!widget_registry_init_done)
+ {
+ widget_registry_init_done = true;
+ register_child_type<Button>("button");
+ register_child_type<DragHandle>("draghandle");
+ register_child_type<Dropdown>("dropdown");
+ register_child_type<Entry>("entry");
+ register_child_type<HSlider>("hslider");
+ register_child_type<Image>("image");
+ register_child_type<Indicator>("indicator");
+ register_child_type<Label>("label");
+ register_child_type<List>("list");
+ register_child_type<Panel>("panel");
+ register_child_type<ProgressBar>("progressbar");
+ register_child_type<Toggle>("toggle");
+ register_child_type<VSlider>("vslider");
+ }
+
+ add("column", &Loader::arrangement<Column>);
+ add("constraint",&Loader::constraint);
+ add("expand", &Loader::expand);
+ add("ghost", &Loader::ghost);
+ add("gravity", &Loader::gravity);
+ add("grid", &Loader::grid);
+ add("layout", &Loader::layout);
+ add("row", &Loader::arrangement<Row>);
+ add("stack", &Loader::arrangement<Stack>);
+ widget_registry.invoke_all(*this);
+}
+
+Widget &Panel::Loader::get_last_widget()
+{
+ if(!last_widget)
+ throw logic_error("no widget loaded");
+
+ return *last_widget;
+}
+
+template<typename T>
+void Panel::Loader::arrangement()
+{
+ T arr(obj.get_or_create_layout());
+ ArrangedLoader<T> ldr(*this, arr);
+ load_sub_with(ldr);
+}
+
+void Panel::Loader::constraint(Layout::ConstraintType type, const string &n)
+{
+ Widget &src = get_last_widget();
+ Widget &tgt = *get_item(wdg_map, n);
+ obj.get_or_create_layout().add_constraint(src, type, tgt);
+}
+
+void Panel::Loader::expand(bool h, bool v)
+{
+ obj.get_or_create_layout().set_expand(get_last_widget(), h, v);
+}
+
+void Panel::Loader::ghost(bool g)
+{
+ obj.get_or_create_layout().set_ghost(get_last_widget(), g);
+}
+
+void Panel::Loader::gravity(int h, int v)
+{
+ obj.get_or_create_layout().set_gravity(get_last_widget(), h, v);
+}
+
+void Panel::Loader::grid(size_t cols)
+{
+ Grid grd(obj.get_or_create_layout(), cols);
+ ArrangedLoader<Grid> ldr(*this, grd);
+ load_sub_with(ldr);
+}
+
+void Panel::Loader::layout()
+{
+ Layout::Loader ldr(obj.get_or_create_layout(), wdg_map);
+ load_sub_with(ldr);
+}
+
+template<>
+void Panel::Loader::unnamed_child<Panel>()
+{
+ unique_ptr<Panel> pnl = make_unique<Panel>();
+ load_sub(*pnl, wdg_map);
+ Widget *wdg = pnl.get();
+ obj.add(move(pnl));
+ last_widget = wdg;
+}
+
+
+template<typename T>
+Panel::ArrangedLoader<T>::ArrangedLoader(Loader &ldr, T &arr):
+ arr_loader(arr)