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<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta name="author" content="Katie Bell">
<meta name="description" content="Simple REPL for Python WASM">
<title>wasm-python terminal</title>
<link rel="stylesheet" href="https://unpkg.com/xterm@4.18.0/css/xterm.css" crossorigin/>
<style>
body {
font-family: arial;
max-width: 800px;
margin: 0 auto
}
#code {
width: 100%;
height: 180px;
}
#info {
padding-top: 20px;
}
.button-container {
display: flex;
justify-content: end;
height: 50px;
align-items: center;
gap: 10px;
}
button {
padding: 6px 18px;
}
</style>
<script src="https://unpkg.com/xterm@4.18.0/lib/xterm.js" crossorigin></script>
<script type="module">
class WorkerManager {
constructor(workerURL, standardIO, readyCallBack) {
this.workerURL = workerURL
this.worker = null
this.standardIO = standardIO
this.readyCallBack = readyCallBack
this.initialiseWorker()
}
async initialiseWorker() {
if (!this.worker) {
this.worker = new Worker(this.workerURL)
this.worker.addEventListener('message', this.handleMessageFromWorker)
}
}
async run(options) {
this.worker.postMessage({
type: 'run',
args: options.args || [],
files: options.files || {}
})
}
handleStdinData(inputValue) {
if (this.stdinbuffer && this.stdinbufferInt) {
let startingIndex = 1
if (this.stdinbufferInt[0] > 0) {
startingIndex = this.stdinbufferInt[0]
}
const data = new TextEncoder().encode(inputValue)
data.forEach((value, index) => {
this.stdinbufferInt[startingIndex + index] = value
})
this.stdinbufferInt[0] = startingIndex + data.length - 1
Atomics.notify(this.stdinbufferInt, 0, 1)
}
}
handleMessageFromWorker = (event) => {
const type = event.data.type
if (type === 'ready') {
this.readyCallBack()
} else if (type === 'stdout') {
this.standardIO.stdout(event.data.stdout)
} else if (type === 'stderr') {
this.standardIO.stderr(event.data.stderr)
} else if (type === 'stdin') {
// Leave it to the terminal to decide whether to chunk it into lines
// or send characters depending on the use case.
this.stdinbuffer = event.data.buffer
this.stdinbufferInt = new Int32Array(this.stdinbuffer)
this.standardIO.stdin().then((inputValue) => {
this.handleStdinData(inputValue)
})
} else if (type === 'finished') {
this.standardIO.stderr(`Exited with status: ${event.data.returnCode}\r\n`)
}
}
}
class WasmTerminal {
constructor() {
this.input = ''
this.resolveInput = null
this.activeInput = false
this.inputStartCursor = null
this.xterm = new Terminal(
{ scrollback: 10000, fontSize: 14, theme: { background: '#1a1c1f' }, cols: 100}
);
this.xterm.onKey((keyEvent) => {
// Fix for iOS Keyboard Jumping on space
if (keyEvent.key === " ") {
keyEvent.domEvent.preventDefault();
}
});
this.xterm.onData(this.handleTermData)
}
open(container) {
this.xterm.open(container);
}
handleReadComplete(lastChar) {
this.resolveInput(this.input + lastChar)
this.activeInput = false
}
handleTermData = (data) => {
if (!this.activeInput) {
return
}
const ord = data.charCodeAt(0);
let ofs;
// TODO: Handle ANSI escape sequences
if (ord === 0x1b) {
// Handle special characters
} else if (ord < 32 || ord === 0x7f) {
switch (data) {
case "\r": // ENTER
case "\x0a": // CTRL+J
case "\x0d": // CTRL+M
this.xterm.write('\r\n');
this.handleReadComplete('\n');
break;
case "\x7F": // BACKSPACE
case "\x08": // CTRL+H
case "\x04": // CTRL+D
this.handleCursorErase(true);
break;
}
} else {
this.handleCursorInsert(data);
}
}
handleCursorInsert(data) {
this.input += data;
this.xterm.write(data)
}
handleCursorErase() {
// Don't delete past the start of input
if (this.xterm.buffer.active.cursorX <= this.inputStartCursor) {
return
}
this.input = this.input.slice(0, -1)
this.xterm.write('\x1B[D')
this.xterm.write('\x1B[P')
}
prompt = async () => {
this.activeInput = true
// Hack to allow stdout/stderr to finish before we figure out where input starts
setTimeout(() => {this.inputStartCursor = this.xterm.buffer.active.cursorX}, 1)
return new Promise((resolve, reject) => {
this.resolveInput = (value) => {
this.input = ''
resolve(value)
}
})
}
clear() {
this.xterm.clear();
}
print(message) {
const normInput = message.replace(/[\r\n]+/g, "\n").replace(/\n/g, "\r\n");
this.xterm.write(normInput);
}
}
const replButton = document.getElementById('repl')
const clearButton = document.getElementById('clear')
window.onload = () => {
const terminal = new WasmTerminal()
terminal.open(document.getElementById('terminal'))
const stdio = {
stdout: (s) => { terminal.print(s) },
stderr: (s) => { terminal.print(s) },
stdin: async () => {
return await terminal.prompt()
}
}
replButton.addEventListener('click', (e) => {
// Need to use "-i -" to force interactive mode.
// Looks like isatty always returns false in emscripten
pythonWorkerManager.run({args: ['-i', '-'], files: {}})
})
clearButton.addEventListener('click', (e) => {
terminal.clear()
})
const readyCallback = () => {
replButton.removeAttribute('disabled')
clearButton.removeAttribute('disabled')
}
const pythonWorkerManager = new WorkerManager('./python.worker.js', stdio, readyCallback)
}
</script>
</head>
<body>
<h1>Simple REPL for Python WASM</h1>
<div id="terminal"></div>
<div class="button-container">
<button id="repl" disabled>Start REPL</button>
<button id="clear" disabled>Clear</button>
</div>
<div id="info">
The simple REPL provides a limited Python experience in the browser.
<a href="https://github.com/python/cpython/blob/main/Tools/wasm/README.md">
Tools/wasm/README.md</a> contains a list of known limitations and
issues. Networking, subprocesses, and threading are not available.
</div>
</body>
</html>
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