scratch-vm

Scratch VM is a library for representing, running, and maintaining the state of computer programs written using Scratch Blocks.

Information

This branch is a fork of the original scratch-vm repository. See the original repository for more information about the scratch-vm project.

Those modification are done for the Code Club Luxembourg project:

• "Scratch 3.0 for the robot" (https://codeclub.lu/projects/scratch-3-0-for-the-robot/) (Link not available yet)
• or "Sreatch 3.0 Coding-Is-Art" (https://codeclub.lu/projects/scratch-3-0-coding-is-art/) (Link not available yet)

The purpose of this project is to add the robot control feature to the scratch-vm.

• Or by editing existing extension like the Pen extension to add the robot control feature.
• Or by creating a new extension to add the robot control feature.

Pen Extension modification

a first attempt is to modify the Pen extension to add the robot control feature. The idea is to add a websocket connection to the robot and send the pen position to the robot. The robot will then move to the pen position. The robot itslef will need to be modified to add the websocket connection and the robot control feature.

New extension

a second attempt is to create a new extension to add the robot control feature. The idea is to add a websocket connection to the robot and send the robot control command to the robot. The robot will then move according to the command. The robot itslef will need to be modified to add the websocket connection and the robot control feature.

Original README.md

Installation

This requires you to have Git and Node.js installed.

To install as a dependency for your own application:

npm install scratch-vm

To set up a development environment to edit scratch-vm yourself:

git clone https://github.com/scratchfoundation/scratch-vm.git
cd scratch-vm
npm install

Development Server

This requires Node.js to be installed.

For convenience, we've included a development server with the VM. This is sometimes useful when running in an environment that's loading remote resources (e.g., SVGs from the Scratch server). If you would like to use your modified VM with the full Scratch 3.0 GUI, follow the instructions to link the VM to the GUI.

Running the Development Server

Open a Command Prompt or Terminal in the repository and run:

npm start

Playground

To view the Playground, make sure the dev server's running and go to http://localhost:8073/playground/ - you will be directed to the playground, which demonstrates various tools and internal state.

Standalone Build

npm run build

<script src="/path/to/dist/web/scratch-vm.js"></script>
<script>
    var vm = new window.VirtualMachine();
    // do things
</script>

How to include in a Node.js App

For an extended setup example, check out the /src/playground directory, which includes a fully running VM instance.

var VirtualMachine = require('scratch-vm');
var vm = new VirtualMachine();

// Block events
Scratch.workspace.addChangeListener(vm.blockListener);

// Run threads
vm.start();

Abstract Syntax Tree

Overview

The Virtual Machine constructs and maintains the state of an Abstract Syntax Tree (AST) by listening to events emitted by the scratch-blocks workspace via the blockListener. Each target (code-running object, for example, a sprite) keeps an AST for its blocks. At any time, the current state of an AST can be viewed by inspecting the vm.runtime.targets[...].blocks object.

Anatomy of a Block

The VM's block representation contains all the important information for execution and storage. Here's an example representing the "when key pressed" script on a workspace:

{
  "_blocks": {
    "Q]PK~yJ@BTV8Y~FfISeo": {
      "id": "Q]PK~yJ@BTV8Y~FfISeo",
      "opcode": "event_whenkeypressed",
      "inputs": {
      },
      "fields": {
        "KEY_OPTION": {
          "name": "KEY_OPTION",
          "value": "space"
        }
      },
      "next": null,
      "topLevel": true,
      "parent": null,
      "shadow": false,
      "x": -69.333333333333,
      "y": 174
    }
  },
  "_scripts": [
    "Q]PK~yJ@BTV8Y~FfISeo"
  ]
}

Testing

npm test

npm run coverage

Publishing to GitHub Pages

npm run deploy

This will push the currently built playground to the gh-pages branch of the currently tracked remote. If you would like to change where to push to, add a repo url argument:

npm run deploy -- -r <your repo url>

Donate

Scratch is provided free of charge. Please consider making a donation to support the continued engineering, design, community, and resource development efforts. Thank you!