# SnapController

Import it from `@grafloria/renderer`.

```ts
class SnapController
```

**Methods**

- `constructor(config: Partial<SnapConfig> = {})`
- `getConfig(): SnapConfig`
- `updateConfig(patch: Partial<SnapConfig>): void`
- `syncWithEngineConfig(engine: DiagramEngine): void` — Read the snapping knobs off the engine's interaction config.
- `computeSnap(box: Rectangle, others: Rectangle[]): SnapResult` — Snap `box` against `others`.
- `snapPointToGrid(point: Point): Point` — Quantise a single point to the grid (used by the vertex drag).
- `keepInBounds(box: Rectangle, bounds: Rectangle): Rectangle` — Clamp a box so it stays fully inside `bounds` (no-op when it cannot fit).
- `siblingBoxes(engine: DiagramEngine, excludeIds: Iterable<string> = []): Rectangle[]` — World bounding boxes of every node EXCEPT `excludeIds` (the moving ones).
- `portPosition(node: NodeModel, port: PortModel): Point` — World position of a port — THE one the port is actually drawn at.
- `findPortMagnet( engine: DiagramEngine, worldX: number, worldY: number, options: { excludeNodeId?: string; radius?: number; filter?: (port: PortModel, node: NodeModel) => boolean; } = {} ): PortHit | null` — The nearest port to a world point within `snapToPortRadius` — the magnet the connection drag snaps to. `excludeNodeId` keeps a drag from snapping back to the node it started on.
- `findProximityConnection( engine: DiagramEngine, nodeId: string, radius?: number ): ProximityCandidate | null` — React-Flow-style proximity connect: after dragging `nodeId`, is one of ITS ports close enough to a compatible port on another node to auto-link them?
- `buildProximityLinkCommand(candidate: ProximityCandidate): Command` — Turn a candidate into the ONE undoable command that creates the link.
- `highlightProximityTarget(engine: DiagramEngine, candidate: ProximityCandidate | null): void` — Paint the nearest valid target: exactly the flags the SVG renderer already draws for a connection drag (`isValidTarget` = eligible, `isHighlighted` = the one that would win). Clears every other port so the highlight can never go stale — the failure mode of "highlight on, nothing turns it off".