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Extending CSS using
Houdini
Arnelle Balane
@arnellebalane
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Arnelle Balane
Tech Lead @ Newlogic
Google Developers Expert
for Web Technologies
@arnellebalane
UncaughtException
@uncaughtxcptn
Subscribe to our channel!
/UncaughtException
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bit.ly/cds-cebu-houdini
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what is
Houdini
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Houdini
● a collection of JavaScript APIs
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Houdini
● a collection of JavaScript APIs
● allows us to hook into the browser’s
rendering engine
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Houdini
● a collection of JavaScript APIs
● allows us to hook into the browser’s
rendering engine
● extends CSS, at CSS speed!
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ishoudinireadyyet.com
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How browsers render pages
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Houdini
Paint API
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Paint API
Draw an image as background
using JavaScript
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paint()
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paint(worklet)
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background-image:
paint(worklet);
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background-image:
paint(worklet, red);
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background-image:
paint(worklet, red);
<-custom-prop: 12px;
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CSS.paintWorklet
.addModule('worklet.js');
Load the paint worklet
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houdini.how
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paintlets.herokuapp.com
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npm: houdini paint worklet
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import worklet from
"url-loader!/worklet.js";
CSS.paintWorklet.addModule(worklet);
Usage with bundlers
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Demo time! ✨
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Creating our own
Paint Worklet
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class MyWorklet {
paint() {
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class MyWorklet {
paint() {
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class MyWorklet {
paint(ctx, geometry) {
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class MyWorklet {
paint(ctx, geom) {
ctx.beginPath();
ctx.moveTo(0, 0);
ctx.lineTo(geom.width, geom.height);
ctx.stroke();
}
}
worklet.js
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class MyWorklet {
paint(ctx, geom) {
ctx.beginPath();
ctx.moveTo(0, 0);
ctx.lineTo(geom.width, geom.height);
ctx.stroke();
}
}
worklet.js
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class MyWorklet {
static get inputProperties() {
return ['<-line-width', '<-line-color'];
}
paint(ctx, geom, props) {
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class MyWorklet {
static get inputProperties() {
return ['<-line-width', '<-line-color'];
}
paint(ctx, geom, props) {
const width = props.get('<-line-width');
const color = props.get('<-line-color');
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<-line-width: 3px;
<-line-color: red;
CSSUnparsedValue { ' 3px' }
CSSUnparsedValue { ' red' }
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<-line-width: 3rem;
<-line-color: red;
CSSUnparsedValue { ' 3rem' }
CSSUnparsedValue { ' red' }
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CSS.registerProperty({
name: '<-line-width',
syntax: '',
inherits: false,
initialValue: 3px
});
index.js
Houdini Properties & Values API
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CSS.registerProperty({
name: '<-line-width',
syntax: '',
inherits: false,
initialValue: 3px
});
index.js
![]()
<<.
https://www.w3.org/TR/css-propertie
s-values-api-1/#syntax-string
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@property <-line-width {
syntax: '';
inherits: false;
initial-value: 3px;
}
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<-line-width: 3px;
<-line-color: red;
CSSUnitValue { value: 3, unit: 'px' }
CSSStyleValue { 'rgb(255, 0, 0)' }
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<-line-width: 3rem;
<-line-color: #ff0000;
CSSUnitValue { value: 48, unit: 'px' }
CSSStyleValue { 'rgb(255, 0, 0)' }
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<-line-width: 3rem;
<-line-color: #ff0000;
CSSUnitValue { value: 48, unit: 'px' }
CSSStyleValue { 'rgb(255, 0, 0)' }
✨ Houdini TypedOM
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class MyWorklet {
static get inputProperties() {✨}
paint(ctx, geom, props) {
ctx.lineWidth =
props.get('<-line-width').value;
ctx.strokeStyle =
props.get('<-line-color').toString();
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class MyWorklet {
static get inputProperties() {✨}
paint(ctx, geom, props) {
ctx.lineWidth =
props.get('<-line-width').value;
ctx.strokeStyle =
props.get('<-line-color').toString();
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class MyWorklet {
static get inputArguments() {
return ['', ''];
}
paint(ctx, geom, props, args) {
const width = args[0].value;
const color = args[0].toString();
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Demo time! ✨
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css-paint-polyfill
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import 'css-paint-polyfill';
Using the polyfill
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What’s so exciting about
Houdini?
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Houdini
● Fancy backgrounds
● Reduce number of DOM nodes
● CSS polyfills
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css-houdini.rocks
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Thank you!
Extending CSS using Houdini
Arnelle Balane
@arnellebalane