ControlledGraph API

ControlledGraph declares your application the canonical owner of line topology. It renders nothing.

There is no lines prop. The handler’s return value is the channel, so a typical graph is one line:

<script lang="ts">
  import { applyLineChange } from "@snap-engine/snapline";
  let lines = $state.raw<LineRecord[]>([]);
</script>

<ControlledGraph
  onLineChangeRequest={(request) => (lines = applyLineChange(lines, request))}
/>

The assignment updates your state and evaluates to the array the bridge needs. Reject by returning the list unchanged (return lines) — the staged line is then discarded. The return type is required, so forgetting to return is a type error rather than an accidental rejection. The handler must be synchronous.

A LineChangeRequest carries an intent ("connect" | "disconnect" | "replace" | "reconnect") plus add (ProposedLine[] with SnapLine-minted ids), remove (LineId[]), and update (endpoint retargets). Adopting a proposed id settles the staged line in place, with no flicker and the same mirror.

For changes no request asked for — loading a saved graph, undo/redo, a collaborator’s edit — take a component reference and push:

<ControlledGraph bind:this={graph} onLineChangeRequest={...} />

graph.setLines(records) replaces the canonical document; graph.flush() runs any pending reconciliation synchronously.

ReconciliationError.code is one of "duplicate-id" (a record id appears twice in the snapshot), "capacity-exceeded" (a record violates a connector’s maxIncoming), or "connection-rejected" (an endpoint’s isValidConnection vetoed the record). Errored records stay in your document and are retried when relevant state changes; records whose endpoints are not mounted stay silently latent.