NavigationPane

NavigationPane uses the same controlled NavigationItem model as NavigationBar, but lays destinations out vertically.

Choose compact or expanded presentation

const bool expanded = UseViewportClass() == ViewportClass::Expanded;

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

The third constructor argument is expanded and defaults to false. Compact mode behaves like a navigation rail; expanded mode exposes a wider label-oriented pane. Responsiveness remains explicit application composition rather than a hidden component rewrite.

Control selection

Selection is controlled and updates through NavigationEvents::Changed. NavigationPaneStyle owns compact and expanded widths, item geometry, content colors, indication, and selection animation.

Preserve destination semantics

Both visual modes publish the same Navigation collection. Each destination is a labelled semantic button with stable selected and disabled state, so changing expanded does not replace its accessible identity.

API

• NavigationPane(items, selected_index, bool expanded = false) with initializer-list/vector and value/state overloads.
• OnChanged(handler) receives the requested index.
• Uses NavigationBar’s NavigationItem values.

See also DrawerLayout and responsive interfaces.