Trait Flow 

pub trait Flow: Send + Sync {
    type View: Any + Send + Sync + Clone + 'static;

    const DOMAIN: SemanticDomain;
    const NAME: &'static str;

    // Required method
    fn project(
        &self,
        world: &World,
        sel: &Selection,
        runtime: &Runtime,
    ) -> Self::View;

    // Provided methods
    fn select(&mut self, world: &World, runtime: &Runtime) -> Selection { ... }
    fn cache_key(&self, world: &World, runtime: &Runtime) -> Option<u64> { ... }
}

The typed interface between the Data layer and Lanes.

All three stages receive the engine’s [Runtime] so a Flow can look up services, backends, or resources its domain genuinely needs (text renderer, font cache, surface size, editor view overrides, …) without crossing the CLAD dependency graph in awkward ways.

Examples

A read-only Flow that projects the World into a typed View for its domain’s Lanes. select narrows the entities; project builds the view published into the LaneBus. (Marked ignore because a compiling impl needs a concrete View type and a SemanticDomain from the data layer’s domain set.)

use khora_data::ecs::{SemanticDomain, World};
use khora_data::flow::{Flow, Selection};
use khora_core::Runtime;

#[derive(Clone)]
struct MyView {
    entity_count: usize,
}

struct MyFlow;

impl Flow for MyFlow {
    type View = MyView;
    const DOMAIN: SemanticDomain = SemanticDomain::Render;
    const NAME: &'static str = "MyFlow";

    fn select(&mut self, world: &World, _runtime: &Runtime) -> Selection {
        // Pick the entities this domain cares about.
        Selection::new()
    }

    fn project(&self, world: &World, _sel: &Selection, _runtime: &Runtime) -> Self::View {
        MyView { entity_count: world.iter_entities().count() }
    }
}

Required Associated Constants

const DOMAIN: SemanticDomain

Domain identifier — matches the agent’s domain.

const NAME: &'static str

Stable identifier — used for telemetry and ordering.

Required Associated Types

type View: Any + Send + Sync + Clone + 'static

The typed view this Flow publishes into the LaneBus. Clone so the registration trampoline can republish a cached view without re-running select/project (views hold Arcs and plain data, so cloning is cheap relative to a full re-projection).

Required Methods

fn project( &self, world: &World, sel: &Selection, runtime: &Runtime, ) -> Self::View

Stage 2 — read-only projection of the world into a View.

Provided Methods

fn select(&mut self, world: &World, runtime: &Runtime) -> Selection

Stage 1 — read-only selection of relevant entities.

fn cache_key(&self, world: &World, runtime: &Runtime) -> Option<u64>

Cache key for view reuse. When Some(k) matches the key of the previously published view, the registration trampoline republishes the cached view without re-running select/project. None (default) disables caching — correct for flows whose projection depends on inputs without a change signal.

Implementations MUST fold every input the projection reads into the key: the relevant World::domain_epochs, World::instance_id (so a different World instance never aliases a cached key), and a bit-level hash of any runtime state consulted. A key that misses an input produces stale views; an over-broad key merely re-projects more often, which is always safe.

Dyn Compatibility

This trait is not dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety", so this trait is not object safe.

Implementors

impl Flow for AudioFlow

const DOMAIN: SemanticDomain = SemanticDomain::Audio

const NAME: &'static str = "audio"

type View = AudioView

impl Flow for PhysicsFlow

const DOMAIN: SemanticDomain = SemanticDomain::Physics

const NAME: &'static str = "physics"

type View = PhysicsView

impl Flow for RenderFlow

const DOMAIN: SemanticDomain = SemanticDomain::Render

const NAME: &'static str = "render"

type View = RenderWorld

impl Flow for ShadowFlow

const DOMAIN: SemanticDomain = SemanticDomain::Render

const NAME: &'static str = "shadow"

type View = ShadowView

impl Flow for UiFlow

const DOMAIN: SemanticDomain = SemanticDomain::Ui

const NAME: &'static str = "ui"

type View = UiScene