taffy VS wpt

I maintain a standalone web layout engine[0] (currently implementing Flexbox and CSS Grid) which has no scripting support. WPT layout tests using is a major blocker to us running WPT tests against our library. Yoga (used by React Native) is in a similar position.<p>Do you think the WPT would accept pull requests replacing such tests with equivalent tests that don't use <script> (perhaps using a build script to generate multiple tests instead - or simply writing out the tests longhand)?<p>I could run against only the ref-tests, but if I can't get full coverage then the WPT seems to provide little value over our own test suite.<p>[0]: <a href="https://github.com/DioxusLabs/taffy">https://github.com/DioxusLabs/taffy</a>

> Is there any easy to use/hack HTML layouting engine where I could experiment with custom CSS attributes and bridge that gap? Would anything from Servo be suitable?

Servo could be used for this. You'd want to add support for parsing the CSS properties themselves to the style crate in https://github.com/servo/stylo and then the layout implementation to the layout2020 crate in https://github.com/servo/servo. You do effectively get a whole browser though.

I'm currently working on building a lighter weight / hackable layout engine based on a combination of https://github.com/servo/stylo (for css parsing and selector resolution), https://github.com/DioxusLabs/taffy (for box-level layout) and https://github.com/pop-os/cosmic-text (for flow/inline layout). I expect to have something decent in around 6 months

Neither of these setups currently have any support for pagination though.

I maintain a web layout library that is designed to be integrated into other software:

https://github.com/DioxusLabs/taffy

It needs to be combined with a text layout engine (such as https://github.com/pop-os/cosmic-text), and it doesn't support everything yet (notable features that are currently missing: "float", "display: inline-block", "box-sizing: content-box", "position: static"). But we have Block, Flexbox and CSS Grid support with more on the way.

All of these projects have in common that they use Taffy (the project that I work on!) for box-level layout (which currently gives them block, flexbox, and grid layout) , and are either using or planning to use cosmic-text for text/inline layout. This gives you a decent first approximation of web layout, but it's not perfect and there are major features like float, display: inline-block, position: static, box-sizing: content-box missing. Not to mention that none of these implementations currently resolve CSS selectors, so you are effectively limited to inline styles (if you're interested in something in that direction then you may be interested in https://github.com/vizia/vizia).

While there are a lot of Rust UI frameworks, none of them are really recommended for production use yet. I suspect a few of the will die off and work will coalesce a few once things mature a bit.

Another nice feature of the Rust UI ecosystem is that lots of it is being built in a modular way. For example I maintain a layout engine [0] library which just does layout and can be easily integrated by anybody creating a UI library. And there a bunch of similar composable libraries covering rendering, text layout, accessibility, window creation, clipboard access, etc.

[0]: https://github.com/DioxusLabs/taffy

You might be interested in the combination of Taffy [0] which handles box-level browser layout (block, flexbox, grid, etc) and Cosmic Text [1] which handles text-level layout and basic text editing functionality.

Integrating them into browsers while retaining accessibility could be tricky. But in they're general they're relatively small standalone libraries implementing most of the layout algorithms that browsers implement (although there are currently a few key missing features like laying out "inline-block" items in line with text).

[0]: https://github.com/DioxusLabs/taffy

[1]: https://github.com/pop-os/cosmic-text

I maintain a library (https://github.com/DioxusLabs/taffy) that implements both Flexbox and CSS Grid, and is designed to be easily embedded (similar to Yoga, which Ink is using).

https://github.com/DioxusLabs/taffy (disclaimer: I work on this crate) which does CSS layout given CSS styles. This would probably be much more useful once we merge support for display: block (https://github.com/DioxusLabs/taffy/pull/474), and if in the future we support display: table. Taffy doesn't handle text layout but is designed to integrate nicely with external layout systems.

Ok, "1.4GB" made me look into this more. I hadn't realised that we were using a "superlinter" action that includes linters for over 10 languages. Switching to a different github action brought to time down to 3 seconds! https://github.com/DioxusLabs/taffy/pull/463

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.