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theme: Grailbox footer: 50% slidenumbers: true

Why the Web Wants WebAssembly

Rob Warner

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[.slidenumbers: false]

Overview

  • What is WebAssembly?
  • WebAssembly Use Cases
  • Adder: Writing in wat
  • Using Rust and wasm-pack

What Is WebAssembly?

"WebAssembly ... is a binary instruction format for a stack-based virtual machine."

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WebAssembly Features

  • Binary instruction format
  • Stack-based
  • Hosted
  • Portable

How Is WebAssembly Different?

  • Still around
  • Standards-based (W3C)
  • Supports multiple languages
  • Integrates with JavaScript
  • Sandboxed
  • Efficient

Browser Support

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Use wasm2js for IE

Yeah, But Why?

"So for sure, WebAssembly is faster (50x)" "How We Used WebAssembly To Speed Up Our Web App By 20X (Case Study)" "WebAssembly cut Figma's load time by 3x"

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Why Wouldn't I Just Use JavaScript?

  • Performance
  • Competition
  • Choice
  • Reuse existing libraries

Use Cases

  • Full applications
  • Frame in WebAssembly, UI in HTML/JavaScript
  • Functions / Code called by JavaScript

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WASM Data Types

  • i32
  • i64
  • f32
  • f64

First Project: Adder

  • wasm function to add two integers
  • Page to input numbers and display sum
  • JavaScript to load module and call function
  • CSS to add mediocre styling

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Add Function

(module
  (func $add (param $lhs i32) (param $rhs i32) (result i32)
    get_local $lhs
    get_local $rhs
    i32.add)
  (export "add" (func $add))
)

HTML

<div class="content">
  <p>Adder</p>
  <input type="number" id="lhs" min="0" value="0">
  +
  <input type="number" id="rhs" min="0" value="0">
  =
  <span id="sum">0</span>
</div>
<script src="./adder.js"></script>

JavaScript

fetch('./add.wasm')
  .then(response => response.arrayBuffer())
  .then(bytes => WebAssembly.instantiate(bytes))
  .then(results => {
    setEventListener(results.instance);
  })
  .catch(console.error);

JavaScript (cont)

function setEventListener(wasm) {
  const lhs = document.getElementById('lhs');
  const rhs = document.getElementById('rhs');

  const adder = () => {
    document.getElementById('sum').textContent = 
      wasm.exports.add(parseInt(lhs.value), parseInt(rhs.value));
  };

  lhs.addEventListener('change', adder);
  rhs.addEventListener('change', adder);
}

Why Rust for WebAssembly?

  • Mozilla-backed
  • Small binaries / faster download, parsing, etc.
  • Fast
  • Great tooling
  • Memory safe
  • "Most loved"

Rust for JavaScript Developers

npm → cargo package.json → Cargo.toml node_modules → crates

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Colors

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Original

- (void)calculateHSLFromRGB {
  float red = _red / kRGBDivisor;
  float green = _green / kRGBDivisor;
  float blue = _blue / kRGBDivisor;

  float minValue = MIN(red, MIN(green, blue));
  float maxValue = MAX(red, MAX(green, blue));
  float range = maxValue - minValue;

  _lightness = (int)((maxValue + minValue) / 0.02f);

  if (range == 0.0f) {
    _hue = 0;
    _saturation = 0;
  } else {
    _saturation = (int)(100 * ((_lightness < 50) ?
      range / (maxValue + minValue) :
      range / (2 - maxValue - minValue)));

    if (fabs(red - maxValue) < kEpsilon) {
      _hue = (int)(60 * fmodf(((green - blue) / range), 6));
    } else if (fabs(green - maxValue) < kEpsilon) {
      _hue = (int)(60 * (((blue - red) / range) + 2));
    } else {
      _hue = (int)(60 * (((red - green) / range) + 4));
    }
  }
  if (_hue < 0) _hue += kDegreesInCircle;
}

https://github.com/hoop33/hc

Calculating Colors

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  • Hue (0 - 359º)
  • Saturation (0 - 100%)
  • Lightness (0 - 100%)

How to Spin

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Cargo.toml

[package]
name = "colors"
version = "0.1.0"
authors = ["Rob Warner <[email protected]>"]
edition = "2018"

[lib]
crate-type = ["cdylib", "rlib"]

[dependencies]
wasm-bindgen = "0.2"

Rust Source

src
├── lib.rs
└── utils.rs
tests
└── web.rs

Import / Export

#[wasm_bindgen]
extern {
    fn alert(s: &str);
}

#[wasm_bindgen]
pub fn greet() {
    alert("Hello, colors!");
}

Spin (Rust)

#[wasm_bindgen]
pub fn spin(color: &str, degrees: i32) -> String {
    let spin_degrees = normalize_degrees(degrees);
    let (r, g, b) = hex_to_rgb(color);
    let (h, s, l) = rgb_to_hsl(r, g, b);
    let hspin = normalize_spin(h, spin_degrees);
    let (sr, sg, sb) = hsl_to_rgb(hspin, s, l);
    rgb_to_hex(sr, sg, sb)
}

Colors.js

export function spin(color, degrees) {
    const ptr0 = passStringToWasm(color);
    const len0 = WASM_VECTOR_LEN;
    const retptr = globalArgumentPtr();
    try {
        wasm.spin(retptr, ptr0, len0, degrees);
        const mem = getUint32Memory();
        const rustptr = mem[retptr / 4];
        const rustlen = mem[retptr / 4 + 1];

        const realRet = getStringFromWasm(rustptr, rustlen).slice();
        wasm.__wbindgen_free(rustptr, rustlen * 1);
        return realRet;
    } finally {
        wasm.__wbindgen_free(ptr0, len0 * 1);
    }
}

Spin (JavaScript)

export function spin(color, degrees) {
  const spinDegrees = normalizeDegrees(degrees);
  const {r, g, b} = hexToRGB(color);
  const {h, s, l} = rgbToHSL(r, g, b);
  const hspin = normalizeSpin(h, spinDegrees);
  const {sr, sg, sb} = hslToRGB(hspin, s, l);
  return rgbToHex(sr, sg, sb);
}

Build Web App

$ npm init wasm-app www
npx: installed 1 in 2.104s
🦀 Rust + 🕸 Wasm = ❤

Add Module

"dependencies": {
  "colors": "file:../pkg",
  "jscolors": "file:../../jscolors"
}

HTML

<body>
  <div class="content">
    <p>Colors</p>
    <input type="color" id="base">

    <div class="palette">
      <p>WebAssembly Triadic</p>
      <span class="well" id="triad1"></span>
      <span class="well" id="triad2"></span>
      <span class="well" id="triad3"></span>
    </div>

  </div>
  <script src="./bootstrap.js"></script>
</body>

JavaScript

import * as colors from 'colors';

const base = document.getElementById('base');

const triad1 = document.getElementById('triad1');
const triad2 = document.getElementById('triad2');
const triad3 = document.getElementById('triad3');

base.addEventListener('change', event => {
  const bc = event.srcElement.value;

  triad1.style.backgroundColor = bc;
  triad2.style.backgroundColor = colors.spin(bc, 120);
  triad3.style.backgroundColor = colors.spin(bc, 240);
});

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Tools

Further Reading

Further Reading (cont)

Rob Warner