mirror of
https://github.com/scratchfoundation/scratch-vm.git
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96 lines
2.9 KiB
Markdown
96 lines
2.9 KiB
Markdown
## scratch-vm
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#### Scratch VM is a library for representing, running, and maintaining the state of computer programs written using [Scratch Blocks](https://github.com/LLK/scratch-blocks).
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[](https://travis-ci.org/LLK/scratch-vm)
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[](https://david-dm.org/LLK/scratch-vm)
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[](https://david-dm.org/LLK/scratch-vm#info=devDependencies)
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## Installation
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```bash
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npm install scratch-vm
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```
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## Setup
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```js
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var VirtualMachine = require('scratch-vm');
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var vm = new VirtualMachine();
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// Block events
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workspace.addChangeListener(function(e) {
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// Handle "tapping" a block
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if (e instanceof Blockly.Events.Ui && e.element === 'click') {
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var stackBlock = workspace.getBlockById(e.blockId).getRootBlock().id;
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vm.runtime.toggleStack(stackBlock);
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// Otherwise, pass along to the block listener
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} else {
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vm.blockListener(e);
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}
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});
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// Run threads
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vm.runtime.start();
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```
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## Standalone Build
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```bash
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make build
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```
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```html
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<script src="/path/to/vm.js"></script>
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<script>
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var vm = new window.VirtualMachine();
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// do things
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</script>
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```
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## Abstract Syntax Tree
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#### Overview
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The Virtual Machine constructs and maintains the state of an [Abstract Syntax Tree](https://en.wikipedia.org/wiki/Abstract_syntax_tree) (AST) by listening to events emitted by the [scratch-blocks](https://github.com/LLK/scratch-blocks) workspace via the `blockListener`. At any time, the current state of the AST can be viewed by inspecting the `vm.runtime.blocks` object.
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#### Anatomy of a Block
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```json
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{
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"id": "^1r~63Gdl7;Dh?I*OP3_",
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"opcode": "wedo_motorclockwise",
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"next": null,
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"fields": {
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"DURATION": {
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"name": "DURATION",
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"value": null,
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"blocks": {
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"1?P=eV(OiDY3vMk!24Ip": {
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"id": "1?P=eV(OiDY3vMk!24Ip",
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"opcode": "math_number",
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"next": null,
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"fields": {
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"NUM": {
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"name": "NUM",
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"value": "10",
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"blocks": null
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}
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}
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}
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}
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},
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"SUBSTACK": {
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"name": "SUBSTACK",
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"value": "@1ln(HsUO4!]*2*%BrE|",
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"blocks": null
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}
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}
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}
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```
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## Testing
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```bash
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make test
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```
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```bash
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make coverage
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```
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## Donate
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We provide [Scratch](https://scratch.mit.edu) free of charge, and want to keep it that way! Please consider making a [donation](https://secure.donationpay.org/scratchfoundation/) to support our continued engineering, design, community, and resource development efforts. Donations of any size are appreciated. Thank you!
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