Module widget_tree 

Arena-based widget tree.

WidgetTree owns every node in the UI hierarchy via a generational arena (SlotMap<NodeId, WidgetNode>). Widgets become behavior-only; all structural concerns (parent/child links, CSS classes, display state, layout rects) live here, owned by the runtime.

This is the Pillar 1 foundation that Pillars 2–4 build on.

Structs

WidgetNode

A single node in the arena-based widget tree.

WidgetTree

Runtime-owned arena that holds the entire widget hierarchy.

Enums

LifecycleEvent

Events emitted during tree mutations (mount / remove).

QueryError

Errors returned by WidgetTree::query* methods.