Houdini

programming in

CSS

CSS

.CSS { } 

.CSS { } 

CSS Houdini

.CSS-Houdini { } 

The objective of the CSS-TAG Houdini Task Force (CSS Houdini) is to jointly develop features that explain the “magic” of Styling and Layout on the web. - CSS Houdini

.CSS-Houdini { } 

.CSS-Houdini { } 

Extends CSS

Worklets

    .Extends-CSS { } 

Worklet connects to the browser engine

Is a Javascript Module

Without control over execution

It has no impact on performance

    .Extends-CSS { } 

    .Extends-CSS { } 

if ('paintWorklet' in CSS) {
    CSS.paintWorklet.addModule('PlaceholderBoxPainter.js');
}
class PlaceholderBoxPainter {
    paint(ctx, size) {
        // Magic 🎩
    }
}

registerPaint('placeholder-box', PlaceholderBoxPainter);

worklet

js

    .Extends-CSS { } 

Paint API

    .Extends-CSS { } 

if ('paintWorklet' in CSS) {
    CSS.paintWorklet.addModule('PlaceholderBoxPainter.js');
}
@supports (background: paint(slanted-bg)) {
  .el span {
    background: paint(slanted-bg);
  }
}

css

js

    .Extends-CSS { } 

class SlantedBg {
  constructor () {
    this.hue = 110;
  }
  paint (ctx, geom, props, args) {
    // draw random colors
    ctx.fillStyle = 'hsl(' + this.hue + ', 100%, 50%)';
    this.hue += 10;

    ...
  }
}

registerPaint('slanted-bg', SlantedBg)

worklet

    .Extends-CSS { } 

Demo or it didn't happen

    .Extends-CSS { } 

Canvas

Houdini

Properties & Values API

    .Extends-CSS { } 

    .Extends-CSS .Properties-Values-API { } 

CSS.registerProperty({
  name: '--color-stop',
  syntax: '<color>',
  inherits: false,
  initialValue: 'transparent'
})

js

@property --color-stop {
  syntax: '<color>';
  inherits: false;
  initial-value: transparent;
}

css

    .Extends-CSS .Properties-Values-API { } 

.element {
  --color-stop: deeppink;
  background: linear-gradient(white, var(--color-stop))
  transition: --color-stop 1s;
}

.element:hover {
  --color-stop: deepskyblue;
}

css

@property --theme {
  syntax: '<color>+';
  initial-value: #fff;
  inherits: true;
}
if ("registerProperty" in CSS) {
  CSS.registerProperty({
    name: "--theme",
    syntax: "<color>+",
    initialValue: "#fff",
    inherits: true
  });
}

input

output

    .Extends-CSS .Properties-Values-API { } 

Typed OM API

    .Extends-CSS { } 

el.style.opacity = 0.5;
window.getComputedStyle(el).opacity === "0.5" // Strings!

CSSOM

el.attributeStyleMap.set('opacity', 0.5);

el.computedStyleMap().get('opacity')// CSSUnitValue {value: 0.5, unit: "number"}
el.computedStyleMap().get('opacity').value // 0.5

Typed OM

    .Extends-CSS .Typed-OM-API { } 

calc(1px - 2 * 3em)


new CSSMathSum(
  CSS.px(1),
  new CSSMathNegate(
    new CSSMathProduct(2, CSS.em(3))
  )
);

Nested expressions

    .Extends-CSS .Typed-OM-API { } 

Animation Worklet

    .Extends-CSS { } 

    .Extends-CSS Animation-Worlet { } 

Layout API

    .Extends-CSS { } 

Image by @Una

    .Extends-CSS Layout API { } 

    .Extends-CSS Layout API { } 

Support

Conclusions

    .Conclusions { } 

Polyfills

This is not for me

Houdini is NOT like a Babel for CSS

Free will

Resources

    .Resources { } 

⭐️ are welcome 😊

¿?

Houdini: programming in CSS { Stay At Home Conf }

By Joan León

Houdini: programming in CSS { Stay At Home Conf }

Stay At Home Conf March '20: CSS has always been considered the least controllable, complicated, magical and sometimes somewhat random part. Houdini offers us a set of APIs and Javascript tools that give us the possibility to extend CSS to access the design process and style of the browser rendering engine.

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