Struct LayoutContext 

pub struct LayoutContext { /* private fields */ }

A per-surface layout tree: the taffy engine plus the node→rect-signal registry. The layout tree is a per-surface world so nodes can be created and laid out from anywhere — including reactive effects (reactive lists) that fire from an effect body. Under M3 several surfaces share one UI thread, so the runner activates each surface’s LayoutContext around its build/event/frame; app code just calls the free functions, which operate on whichever surface is currently active.

Implementations

impl LayoutContext

pub fn new() -> Self

Allocates a fresh, inactive per-surface instance.

pub fn enter(&self) -> LayoutGuard

Makes this instance the live one until the returned guard drops, which restores the previously-active instance. Nest by keeping guards in scope; they restore in reverse order.

pub fn enter_ambient() -> LayoutGuard

Makes the ambient instance — the one that exists before any surface is built, and the only world a single-surface app ever has — live until the returned guard drops.

What the reactive flush needs for an effect owned by SurfaceHandle::NONE: it was registered outside any surface, so its world is this one, and running it against whichever surface happened to be entered when the signal fired would resolve its layout, overlays and focus in somebody else’s. Reachable as soon as one app has both — a window tree that never built a surface and a second tree that did.

Trait Implementations

impl Default for LayoutContext

fn default() -> Self

Returns the “default value” for a type.

impl Drop for LayoutContext

fn drop(&mut self)

Executes the destructor for this type.

fn pin_drop(self: Pin<&mut Self>)

🔬This is a nightly-only experimental API. (pin_ergonomics)

Execute the destructor for this type, but different to Drop::drop, it requires self to be pinned.