Scroll-timeline Polyfill

A polyfill of ScrollTimeline and ViewTimeline as defined by the spec.

View a cool demo showing its usage!

Usage

To use this polyfill, import the module into your site and you can start creating animations that use a ScrollTimeline or ViewTimeline.

import 'https://flackr.github.io/scroll-timeline/dist/scroll-timeline.js';

document.getElementById('parallax').animate(
    { transform: ['translateY(0)', 'translateY(100px)']},
    { fill: 'both',
      timeline: new ScrollTimeline({
        source: document.documentElement,
      }),
      rangeStart: new CSSUnitValue(0, 'px'),
      rangeEnd: new CSSUnitValue(200, 'px'),
    });

Also works with CSS Animations that use a view-timeline or scroll-timeline

<script src="https://flackr.github.io/scroll-timeline/dist/scroll-timeline.js"></script>

@keyframes parallax-effect {
  to { transform: translateY(100px) }
}
#parallax {
  animation: parallax-effect linear both;
  animation-timeline: scroll(block root);
  animation-range: 0px 200px;
}

For more details on and use-cases of scroll-driven animations, please refer to https://developer.chrome.com/articles/scroll-driven-animations/ and https://scroll-driven-animations.style/

Contributing

1. Polyfill dev

Running a dev environment

`shell script npm i npm run dev

Then open the browser `http://localhost:3000`, choose one of the demos (test) to see how your changes. 

### 2. Configure & Run Tests

Test configurations are available in: `test/tests.config.json` that file includes:

1. polyfillFiles: an array of our JS shim / polyfill files, those will be injected in WPT tests files.
2. harnessTests: an array of WPT harness tests we want to test the polyfill against.
3. browsers.local: Browser our local selenium-webdriver will test against
4. browsers.sauce: Browser our local selenium-webdriver will test against in Saucelabs / CI environment.   

#### Run the tests locally

Simple test will serve the WPT tests folder and intercepts requests, if the request path matches a harness test we are interested in polyfilling, it will inject the polyfill.

*Required environment variables:*

```dotenv
WPT_DIR=test/wpt #defaults to test/wpt
WPT_SERVER_PORT=8081 # choose any port available on your machine

Command

`shell script npm run test:simple

Go to `localhost:8081/scroll-animations/current-time-nan.html` as an example.

#### Run the tests via Web Driver

##### Local web driver

*Required environment variables:*

```dotenv
WPT_DIR=test/wpt #defaults to test/wpt
WPT_SERVER_PORT=8081 # choose any port available on your machine
LOCAL_BROWSER=chrome # choose one of 'chrome', 'edge', 'firefox', 'safari'
LOCAL_WEBDRIVER_BIN=? #/path/to/webdriver-binaries

Command

`shell script npm run test:wpt

##### SauceLabs / CI

*Required environment variables:*

```dotenv
TEST_ENV=sauce
WPT_DIR=test/wpt #defaults to test/wpt
WPT_SERVER_PORT=8081 # choose any port available on your machine
SC_TUNNEL_ID=sc-wpt-tunnel # please specify 'sc-wpt-tunnel' as a SauceConnect Proxy Tunnel ID

SAUCE_NAME=<secret> # Your saucelabs account username
SAUCE_KEY=<secret> # Your API key

Command

shell script TEST_ENV=sauce npm run test:wpt