bstr VS wpt

Libraries for a lot of this stuff exist (albeit in many cases not very mature yet):

- https://github.com/pop-os/cosmic-text does text layout (which Taffy explicitly considers out of scope)

- https://github.com/AccessKit/accesskit does accessibility

- https://github.com/servo/rust-cssparser does value-agnostic CSS parsing (it will parse the general syntax but leaves value parsing up to the user, meaning you can easily add support for whatever properties you what). Libraries like https://github.com/parcel-bundler/lightningcss implement parsing for the standard css properties.

- There are crates like https://github.com/BurntSushi/bstr and https://docs.rs/wtf8/latest/wtf8/ for working with non-unicode text

We are planning to add a C API to Taffy, but tbh I feel like C is not very good for this kind of modularised approach. You really want to be able to expose complex APIs with enforced type safety and this isn't possible with C.

As the author of bstr and also the regex implementation that bstr uses to implement word breaking, it is linear time.

NSFL: https://github.com/BurntSushi/bstr/blob/86947727666d7b21c97e...

OsStr uses WTF-8 on Windows, and just represents the raw underlying bytes on Unix.

Byte strings can be WTF-8. They can be anything. The problem is that there is no real way to (easily) get the underlying WTF-8 bytes of an OsStr on Windows. So there's no free conversion to and from byte strings.

I wrote more about this in the bstr docs (and don't miss the link to os_str_bytes): https://docs.rs/bstr/latest/bstr/#file-paths-and-os-strings

I'd be happy to answer more questions if you have them. :-) https://github.com/BurntSushi/bstr/discussions

Check out bstr, which does this exact thing for its BString and BStr types.

Currently slated for next Monday: https://github.com/BurntSushi/bstr/issues/40

This is just an FYI. I don't mean to say much to your overall point, although, as someone else who has spent a lot of time doing Unicode-y things, I do tend to agree with you. I had a very similar discussion a bit ago.[1]

Putting that aside, at least with respect to grapheme segmentation, it might be a little simpler than you think. But maybe only a little. The unicode-segmentation crate also does word segmentation, which is quite a bit more complicated than grapheme segmentation. For example, you can write a regex to parse graphemes without too much fuss[2]. (Compare that with the word segmentation regex, much to my chagrin.[3]) Once you build the regex, actually using it is basically as simple as running the regex.[4]

Sadly, not all regex engines will be able to parse that regex due to its use of somewhat obscure Unicode properties. But the Rust regex crate can. :-)

And of course, this somewhat shifts code size to heap size. So there's that too. But bottom line is, if you have a nice regex engine available to you, you can whip up a grapheme segmenter pretty quickly. And some regex engines even have grapheme segmentation built in via \X.

[1]: https://github.com/BurntSushi/aho-corasick/issues/72

[2]: https://github.com/BurntSushi/bstr/blob/e38e7a7ca986f9499b30...

[3]: https://github.com/BurntSushi/bstr/blob/e38e7a7ca986f9499b30...

[4]: https://github.com/BurntSushi/bstr/blob/e38e7a7ca986f9499b30...

This is a great idea. I realize the find implementation is not ideal and have considered bringing in an optional dependency to improve performance. I remembered bstr using two-way search, so I was wondering if depending on the full crate for searching would be worthwhile, but I see that changed. Thanks for the tip!

Fun little nit-pick that does not detract from your overall point: you can actually count graphemes with a regex and that's exactly what bstr does. :-)

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.