struct ComposedOverlayView

A base view with content drawn over it, taking no layout space.

Distinct from overlay(isPresented:), which is a popup: that one detaches its subtree, emits it after the whole tree walk to escape clipping, takes input priority, and dismisses on an outside click. Those semantics are right for a menu and wrong for anything permanent — an always-present button presented that way makes the window behave like an open menu, swallowing clicks that land anywhere else.

This is the composition variant: a floating action button, a badge on a corner, a control that belongs on a canvas rather than beside it. It is an absolutely positioned Yoga child, which buys all four required behaviours from the layout engine rather than from special cases:

• No layout contribution. An absolute child is not part of its parent's flex flow, so the base view measures exactly as it did without the overlay.
• Painted above. Emission is in childNodes order and the overlay is declared second, so it lands on top of the base.
• Ordinary hit testing. It is a real node with real geometry; the hit walk visits children in reverse, so the overlay is tested before the base and everything else behaves normally. No priority, no dismissal.
• Anchored. Yoga edge insets do the placement, so it survives resizes without a re-layout pass of its own.