Virtual Machine for Scratch 3.0
npm install rotrics-scratch-vmbash
npm install scratch-vm
`
Setup
`js
var VirtualMachine = require('scratch-vm');
var vm = new VirtualMachine();
// Block events
workspace.addChangeListener(function(e) {
// Handle "tapping" a block
if (e instanceof Blockly.Events.Ui && e.element === 'click') {
var stackBlock = workspace.getBlockById(e.blockId).getRootBlock().id;
vm.runtime.toggleStack(stackBlock);
// Otherwise, pass along to the block listener
} else {
vm.blockListener(e);
}
});
// Run threads
vm.runtime.start();
`
Standalone Build
`bash
make build
`
`html
`
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. At any time, the current state of the AST can be viewed by inspecting the vm.runtime.blocks object.
#### Anatomy of a Block
`json
{
"id": "^1r~63Gdl7;Dh?I*OP3_",
"opcode": "wedo_motorclockwise",
"next": null,
"fields": {
"DURATION": {
"name": "DURATION",
"value": null,
"blocks": {
"1?P=eV(OiDY3vMk!24Ip": {
"id": "1?P=eV(OiDY3vMk!24Ip",
"opcode": "math_number",
"next": null,
"fields": {
"NUM": {
"name": "NUM",
"value": "10",
"blocks": null
}
}
}
}
},
"SUBSTACK": {
"name": "SUBSTACK",
"value": "@1ln(HsUO4!]2%BrE|",
"blocks": null
}
}
}
`
Testing
`bash
make test
`
`bash
make coverage
``