`compound` handler

Purpose

The compound handler is the binding-registry slot responsible for fanning a single control's value out to multiple leaf bindings — for example, a knob that simultaneously drives a plugin parameter, a MIDI CC, and a DMX channel. Unlike the leaf handlers, the compound handler always has a working default because compounding is a pure structural operation that doesn't depend on any external integration.

The default iterates binding.bindings in registration order and calls registry.dispatchLeaf(leaf, value) for each — every leaf is sent the same value, so the per-leaf range/scale logic stays in the leaf handlers. The schema rejects nested compounds at parse time, so the iteration is guaranteed to bottom out after one step.

Features

Default implementation needs no consumer wiring.
Stable iteration order (registration order) for deterministic test assertions.
Takes the owning BindingRegistry as a parameter so callers can customise the fan-out target (e.g. dispatch through a wrapping spy registry).

Usage: Basic

import { BindingRegistry } from "@suaveplan/react-control-surface/runtime/binding-registry";

// No compound override needed; the default fans out automatically.
const registry = new BindingRegistry({ pluginParam: handler });

Usage: Advanced

import { defaultCompoundHandler } from "@suaveplan/react-control-surface/runtime/binding-registry";

// Manually fan out, perhaps after a custom pre-flight check.
defaultCompoundHandler(compoundBinding, 0.42, registry);

API Reference

defaultCompoundHandler(binding: CompoundBinding, value: number, registry: BindingRegistry): void — iterates binding.bindings and dispatches each leaf through registry.dispatchLeaf.

Implementation Notes

The schema's nested-compound rejection is enforced at parse time, but the default handler defends in depth by routing through dispatchLeaf, which accepts only the LeafBinding union. A nested compound would fail the TypeScript narrowing at the boundary even if a malicious caller bypassed the schema validator.

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compound handler