[menacingly]

it's actually because layout-via-code for arbitrary documents is a humblingly complex problem, so leveraging existing layout engines is preferred.

This impressive effort looks far better than what I'd achieve, but when this approach has been tried before, it is eventually discovered that few organizations have the resources to maintain a rendering engine long-term.

[chearon]

I do think complexity could be part of why we don't have many options here, but I don't agree that a layout engine is too difficult to maintain. More of the issue is that CSS layout (and maybe layout in general) is not widely well-understood. I've almost _never_ come across people interested in layout because generally it's a few properties to get something working and then you move on.

> few organizations have the resources to maintain a rendering engine long-term

I'm curious are there other instances of this happening than Edge switching to Blink? That event was one of my main motivators; it felt like further consolidation of obscure knowledge.

[Sesse__]

Opera switched from Presto to Blink, too.

Very fun project! Did you ever consider integrating with web-platform-tests? It's shared between all the common browser vendors, and we're always interested in more contributors :-)

[chearon]

> Opera switched from Presto to Blink, too

True. But I wonder if there are more special-purpose engines similar to Prince that have been abandoned.

> Did you ever consider integrating with web-platform-tests?

I've run some of the WPT tests manually, but I don't yet have <style> support, and some of them use <script> I think? That's a path I'm wary of (eval()?) but I could have a special mode just for tests.

I did discover lots of weird corners that would be great to make some WPT tests for. Definitely something I want to do!

[Sesse__]

Yes, a _lot_ of WPT tests depend on <script>. But there's also a bunch of ref-tests, where you just check that A and B match pixel for pixel (where B is typically written in the most obvious, dumb way possible). It lets you test advanced features in terms of simple ones. But yes, you'd need selector support in particular.

[nicoburns]

I maintain a standalone web layout engine[0] (currently implementing Flexbox and CSS Grid) which has no scripting support. WPT layout tests using <script> is a major blocker to us running WPT tests against our library. Yoga (used by React Native) is in a similar position.

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)?

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.

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

[Sesse__]

I don't decide WPT policies (and I honestly don't know who does), but I'm pretty sure using a build script would be right out, as WPT is deeply embedded in a lot of other projects. E.g., if you made a build script, you would need to add support for running that script in Blink and in Gecko and in WebKit, and their multiple different runners, and probably also various CI systems.

As for the second option, I don't actually know. If it becomes 10x as long, I would assume you get a no for maintainability and readability reasons. If it's 20% longer and becomes no less clear, I'd say give it a try with a couple tests first? It's possible that the WPT would be interested in expanding its scope to a wider web platform than just browsers. You would probably never get people to stop writing JS-dependent tests, though, so you would need to effectively maintain this yourself.

Of course, for a bunch of tests you really can't do without <script>, given that a lot of functionality is either _about_ scripting support (e.g. CSSOM), intimately tied to it (e.g. invalidation) or will be tested only rather indirectly by other forms of tests (e.g. computed values, as opposed to used values or specified values or actual values or …).