# LayoutParams

The reactive parameters and nested content supplied to a layout.

## Signatures

```ts
export type LayoutParams<Params, A, E, R> = {
    readonly params: RefSubject.RefSubject<Params>;
    readonly content: Fx.Fx<A, E, R>;
};
```

## Why

Parameter-only route updates can reach a retained layout without remounting its content.

## Ownership and lifetime

The executor owns both RefSubjects for the active layout child Scope. Reading them does not transfer ownership; retaining them beyond that Scope observes finalized state.

## Property: content

Reactive output nested immediately inside this layout.

## Property: content: Why

A retained outer layout can observe replacement of an inner layout or route handler.

## Property: content: Ownership and lifetime

The layout manager owns the backing content RefSubject in the same child Scope. Inner layouts
are acquired first, so this Fx represents the already-wrapped inner subtree.

## Property: params

Reactive decoded parameters for the currently selected route.

## Property: params: Why

Parameter-only navigation updates a retained layout without reconstructing it.

## Property: params: Ownership and lifetime

The layout manager owns this RefSubject in the layout's child Scope and updates it before the
retained layout renders the next value.