isabella232 / css-paint-polyfill

CSS Custom Paint / Paint Worklet polyfill with special browser optimizations.

CSS Custom Paint / Paint Worklets polyfill

A polyfill that brings Houdini's CSS Custom Paint API and Paint Worklets to all modern browsers (Edge, Firefox, Safari and Chrome).

Performance is particularly good in Firefox and Safari, where this polyfill leverages -webkit-canvas() and -moz-element() for optimized rendering. For other browsers, framerate is governed by Canvas toDataURL() / toBlob() speed.

As of version 3, this polyfill also includes basic implementations of CSS.supports(), CSS.registerProperty() and CSS unit functions (CSS.px() etc), which are injected in browsers without native support.

What are Paint Worklets?

Paint Worklets are JavaScript modules in which you can program custom graphics code. Once registered, they can be applied to elements using CSS:

An example box.js worklet: registerPaint('box', class { paint(ctx, geom, properties) { ctx.fillRect(0, 0, geom.width, geom.height) } })

... registered and applied on a page: CSS.paintWorklet.addModule('./box.js') var el = document.querySelector('h1') el.style.background = 'paint(box)'

For a more complete example, see the demo.

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Installation & Usage

<script src="css-paint-polyfill.js"></script>
<!-- or: -->
<script src="https://unpkg.com/css-paint-polyfill"></script>

Or with a bundler:

import 'css-paint-polyfill';

... or with ES Modules on the web:

import 'https://unpkg.com/css-paint-polyfill';

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Contributing

See CONTRIBUTING.md.

To hack on the polyfill locally:

git clone [email protected]:GoogleChromeLabs/css-paint-polyfill.git
cd css-paint-polyfill
npm i
npm start
# open http://localhost:5000

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