wpt VS yoga

To reply mostly with my WPT Core Team hat off, mostly summarising the history of how we've ended up here:

A build script used by significant swaths of the test suite is almost certainly out; it turns out people like being able to edit the tests they're actually running. (We _do_ have some build scripts — but they're mostly just mechanically generating lots of similar tests.

A lot of the goal of WPT (and the HTML Test Suite, which it effectively grew out of) has been to have a test suite that browsers are actually running in CI: historically, most standards test suites haven't been particularly amenable to automation (often a lot of, or exclusively, manual tests, little concern for flakiness, etc.), and with a lot of policy choices that effectively made browser vendors choose to write tests for themselves and not add new tests to the shared test suite: if you make it notably harder to write tests for the shared test suite, most engineers at a given vendor are simply going to not bother.

As such, there's a lot of hesitancy towards anything that regresses the developer experience for browser engineers (and realistically, browser engineers, by virtue of sheer number, are the ones who are writing the most tests for web technologies).

That said, there are probably ways we could make things better: a decent number of tests for things like Grid use check-layout-th.js (e.g., https://github.com/web-platform-tests/wpt/blob/f763dd7d7b7ed...).

One could definitely imagine a world in which these are a test type of their own, and the test logic (in check-layout-th.js) can be rewritten in a custom test harness to do the same comparisons in an implementation without any JS support.

The other challenge for things like Taffy only targeting flexbox and grid is we're unlikely to add any easy way to distinguish tests which are testing interactions with other layout features (`position: absolute` comes to mind!).

My suggestion would probably be to start with an issue at https://github.com/web-platform-tests/rfcs/issues, describing the rough constraints, and potentially with one or two possible solutions.

It also helps that there are tests

https://web-platform-tests.org/

You can see how Mozilla tests the compliance of their built-in elements in the Gecko repository (the ok and is assertions are defined in their SimpleTest testing framework). And here's the Web Platform Tests' reflection harness, with data for each built-in element in sibling files, that almost every browser pass.

We have our own test suite (orginally derived from the test suite of Meta's Yoga layout library [0]) which consists of text fixtures that are small HTML snippets [1] and a test harness [2] that turns those into runnable tests, utilising headless chrome both to parse the HTML and to generate the assertions based on the layout that Chrome renders (so we are effectively comparing our implementation against Chrome). We currently have 686 generated tests (covering both Flexbox and CSS Grid).

We would like to utilise the Web Platform Test suite [3], however these are not in a standard format and many of the tests require JavaScript so we are not currently able to do that.

[0]: https://github.com/facebook/yoga

[1]: https://github.com/DioxusLabs/taffy/tree/main/test_fixtures

[2]: https://github.com/DioxusLabs/taffy/tree/main/scripts/gentes...

[3]: https://github.com/web-platform-tests/wpt/tree/master/css/cs...

The metrics are based on the passing rate for the web-platform-tests (WPT) project, the automated test suite for web standards. The completion rate is categorised as either stable, or experimental. There is no definition of what experimental entails, presumably features that are behind experimental flags are included. Stable is better to go off in any case.

Depends on what you are trying to achieve. You can run WPT MSE https://github.com/web-platform-tests/wpt/tree/master/media-source and WebCodecs https://github.com/web-platform-tests/wpt/tree/master/webcodecs tests manually to learn by doing.

Manually running the tests in Web Platform Tests should keep you busy.

Not sure what you mean? I referred to Web API's, which generally means Web platform API's; that is Web platform API's tested by Web Platform Tests https://github.com/web-platform-tests/wpt.

If you want CSS to be the same across browsers then help implement CSS tests and file bugs

https://www.w3.org/Style/CSS/Test/Overview.en.html

https://web-platform-tests.org/

better specs are great, but tests will actually find the edge cases and lead to more convergence.

Run all these tests locally https://github.com/web-platform-tests/wpt/tree/master/dom.

We still wanted to leverage a layout engine that could be performant and easy-to-use. After doing some performance testing with native UIKit, Autolayout, and a few other third-party options, we ended up bringing FlexLayout into the mix, which is a Swift implementation of Facebook’s Yoga layout engine. All RPL components utilize FlexLayout in order to lay out content fast and efficiently. While we’ve enjoyed using it, we’ve found a few touch points to be mindful of. There are some rough edges we’ve found, such as utilizing stack views with subviews that use FlexLayout, that often come at odds with both UIKit and FlexLayout’s layout engines.

We have our own test suite (orginally derived from the test suite of Meta's Yoga layout library [0]) which consists of text fixtures that are small HTML snippets [1] and a test harness [2] that turns those into runnable tests, utilising headless chrome both to parse the HTML and to generate the assertions based on the layout that Chrome renders (so we are effectively comparing our implementation against Chrome). We currently have 686 generated tests (covering both Flexbox and CSS Grid).

We would like to utilise the Web Platform Test suite [3], however these are not in a standard format and many of the tests require JavaScript so we are not currently able to do that.

[0]: https://github.com/facebook/yoga

[1]: https://github.com/DioxusLabs/taffy/tree/main/test_fixtures

[2]: https://github.com/DioxusLabs/taffy/tree/main/scripts/gentes...

[3]: https://github.com/web-platform-tests/wpt/tree/master/css/cs...

The "engine" is built on top of amazing https://www.lwjgl.org/ and https://github.com/bkaradzic/bgfx/, and UI system is baked by https://github.com/memononen/nanovg and https://github.com/facebook/yoga

React Native uses the Yoga engine under the hood, which allows you to use CSS properties to layout your React Native UI in a way that translates really well. Layout in Yoga is limited to Flexbox and absolute/relative positioning, however; there is no CSS grid and no display attribute. This keeps things simpler and more performant, but if developers are accustomed to using other layout techniques on the web, they’ll need to adjust to this new limitation.

PR #246 is super interesting to check out: by fixing the caching strategy, we were able to eliminate an exponential time (with respect to tree depth) performance penalty, and get comparable speeds for flat and deeply nested layouts (something I'd never expected to be possible). Preliminary benchmarks shows us significantly faster than yoga, Meta's C++ library for the same thing, especially on deep trees. Not too shabby for a tiny team of volunteers!

You're going to build the CLI using Ink, a React component-based library for building interactive CLIs. It uses Yoga to build Flexbox layouts in the terminal, so most CSS-like props are available in Ink as well. Ink is simply a React renderer for the terminal, so all the React features are supported. No need to learn a new syntax specific to Ink.

Interesting.

I was thinking that this was going to be a crazy amount of layout engine work, but now I look a little closer it appears the layout work is farmed out to yoga [0] (not trying to take away anything from the effort here). So this project is almost a wrapper around running yoga as a renderer and using SVG as a form of backend target?

I say "appears" because the yoga landing page doesn't do a great job of explaining what it does.

[0] https://github.com/facebook/yoga