BrightScript SceneGraph Extension

This package publishes the Roku SceneGraph support as a standalone extension for the BrightScript Simulation Engine. It delivers the roSGScreen interpreter, component parser, node factory, tasks, and drawing pipeline as a plug-in so browser and Node.js hosts can enable RSG support on demand.

Overview

• Implements the shared BrsExtension contract and hooks into interpreter lifecycle events (onInit, onBeforeExecute, tick, execTask).
• Parses component XML files, builds inheritance trees, and spins up sub-interpreter environments for each component script.
• Registers RoSGScreen, RoSGNode, built-in SceneGraph nodes, events, and task helpers so Roku apps can execute unmodified.
• Ships both browser (lib/brs-sg.js) and Node.js (lib/brs-sg.node.js) builds plus TypeScript definitions.
• Bundles SceneGraph-specific assets (fonts, locale data, images) into assets/common.zip, merging the core src/core/common tree with the extension's overrides under src/extensions/scenegraph/common.

⚠️ Note:

SceneGraph support is in active development and currently released as alpha builds. See the current state of the SceneGraph implementation and other limitations of the engine in the Current Limitations document.

Project packages

This module belongs to the BrightScript Simulation Engine monorepo. Related npm packages:

| Package | Description | | --- | --- | | brs-engine | Browser/WebWorker build used by PWAs, Electron apps, and the web simulator | | brs-node | Node.js CLI and automation runtime | | brs-scenegraph (this package) | Optional SceneGraph extension consumed by the other packages |

Installation

npm install brs-scenegraph

The extension depends on brs-engine so the runtime contracts stay in sync. When designing your own extension consider adding brs-engine (or brs-node) as a peer dependency as well.

Usage

Browser builds (brs-engine)

1. Deploy lib/brs.worker.js, lib/brs.api.js, and lib/brs-sg.js together.

2. Replace assets/common.zip with the one from this package to provide SceneGraph fonts and resources.

3. Tell the engine that SceneGraph is available by adding it to DeviceInfo.extensions when you call brs.initialize. The map key is the SupportedExtension enum value and the value is the worker-relative path to the bundle:

   import { SupportedExtension, DeviceInfo } from "brs-engine";
   
   const deviceOverrides: Partial<DeviceInfo> = {
       extensions: new Map([[SupportedExtension.SceneGraph, "./brs-sg.js"]]),
   };
   
   brs.initialize(deviceOverrides, { debugToConsole: true });

4. When an app package contains a pkg:/components/ folder the packaging layer checks the map above and, if the extension is registered, injects { moduleId: "brs-scenegraph", modulePath: "./brs-sg.js" } into the worker payload.

5. The worker loads the script via importScripts, creates BrightScriptExtension, and registers it before running the app.

No extra glue is required if the file sits next to the worker bundle, but you can preload it manually by importing the module and calling registerExtension yourself if desired.

Node.js / CLI (brs-node)

• The brs-node CLI enables the extension by default (pass --no-sg to skip it for CLI runs).
• For custom Node.js scripts register it manually:

import { registerExtension } from "brs-engine";
import { BrightScriptExtension } from "brs-scenegraph";

registerExtension(() => new BrightScriptExtension());

Call registerExtension before constructing or executing interpreters so tasks and nodes are ready.

Development scripts

# build development artifacts
npm run build

# emit production bundles and declaration files
npm run release

# clean generated outputs
npm run clean

The build emits lib/brs-sg.js (browser) and lib/brs-sg.node.js (Node.js) plus types/ declarations referenced by the package exports.

During the build we also merge src/core/common with src/extensions/scenegraph/common, zip the results to assets/common.zip, and copy that archive into both packages/browser/assets and packages/node/assets so the main packages pick up the SceneGraph-ready common:/ volume automatically.

Documentation

• Main project README
• Extensions guide
• SceneGraph source code

License

Copyright © 2019-2025 Marcelo Lv Cabral. All rights reserved.

Licensed under the MIT license.