NavigationBar

NavigationBar presents a controlled set of primary destinations. The owner supplies the selected index and handles requested changes.

Declare destinations

NavigationBar(
    {
      NavigationItem(images::home, "Home"),
      NavigationItem(images::library, "Library"),
      NavigationItem(images::settings, "Settings"),
    },
    selected
).OnChanged([selected](std::size_t index) {
  selected = index;
})

NavigationItem accepts a label alone or an ImageResource, ImageAsset, or VectorAsset plus label. .SelectedIcon(...) supplies an alternate selected icon and .Enabled(false) disables a destination.

Control selection

The bar does not own selection. Pass std::size_t or State<std::size_t> and publish the new value after NavigationEvents::Changed. NavigationBarStyle controls height, icon and label treatment, selection indicator, indication, and animation.

Theme and semantics

The component exposes collection and selected-item semantics. Labels remain important even when a theme hides unselected labels.

API

NavigationBar(items, selected_index) with initializer-list/vector and value/state overloads.
OnChanged(handler) receives the requested index.
NavigationItem(label) and icon-plus-label constructors.
NavigationItem::SelectedIcon(...) and Enabled(bool).
NavigationBarStyle configures themed appearance.