Placement and camera interaction

PlacementController<T> is a framework-neutral state machine. It follows a payload and size, calculates an anchored world position, validates previews, and reports commit or cancellation. It deliberately does not create nodes.

const placement = new PlacementController<NodeTemplate>({
  screenToWorld(screen) {
    const camera = engine.camera!.getCameraFromScreen(screen.x, screen.y);
    const world = engine.camera!.getWorldFromCamera(camera[0], camera[1]);
    return { x: world[0], y: world[1] };
  },
  callbacks: {
    canPlace: ({ position }) => isInsideWorkspace(position),
    onCommit: ({ payload, position }) => addNode(payload, position),
  },
});

placement.begin(template, { width: 180, height: 96 });

Svelte and React Placement adapters feed pointer and Escape events into the controller and render an optional preview. Connector and node drags claim their pointer so the camera does not pan during the same gesture. Edge pan is enabled only when the engine exposes an edge-pan controller and the object permits it.