taffy VS accesskit

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

If you were to implement this yourself, i'd look into either swash or cosmic-text for the text rendering stack (this is one of the things you really don't want to write from the ground up). For accessibility, AccessKit has quickly become the standard for communicating with crossplatform accessibility APIs in rust GUI. lightningcss (or its lower level counterpart cssparser) are both decent options for CSS parsing. Taffy handles some of what browsers offer for a layout engine, but is still being worked on.

> Fleet relies on the Java AWT/Swing framework to get a window from an operating system, but it doesn’t use the Java platform for managing its GUI components besides one JFrame and JPanel on top of it.

This is a terrible decision that is going to bite them in the long run. Doing things this way makes it far, far more difficult to implement accessibility, and regulations on this are only going to get stricter.

Implementing accessibility for a framework like that would involve three separate implementations for three separate platforms and the need to interface with D-Bus, COM and Objective C, from Java. I imagine that the latter two would be particularly difficult, considering how bad Java's FFI support is. It's not just calling methods either, you'd actually need to implement your own classes that conform to the relevant COM interfaces / Objective C protocols. There are libraries that can help with this[1], but I don't think they would work particularly well for something as complex as a code editor.

[1] https://github.com/AccessKit/accesskit

fltk-accesskit is an accesskit integration crate for fltk-rs, the gui crate. It's implemented as an external crate to allow for more experimentation before stabilizing the api, especially since fltk is at version 1.4.

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.

There are a number of up-and-coming Rust-based frameworks in this niche:

- https://github.com/iced-rs/iced (probably the most usable today)

- https://github.com/vizia/vizia

- https://github.com/marc2332/freya

- https://github.com/linebender/xilem (currently very incomplete but exciting because it's from a team with a strong track record)

What is also exciting to me is that the Rust GUI ecosystem is in many cases building itself up with modular libraries. So while we have umpteen competing frameworks they are to a large degree all building and collaborating on the same foundations. For example, we have:

- https://github.com/rust-windowing/winit (cross-platform window creation)

- https://github.com/gfx-rs/wgpu (abstraction on top of vulkan/metal/dx12)

- https://github.com/linebender/vello (a canvas like imperative drawing API on top of wgpu)

- https://github.com/DioxusLabs/taffy (UI layout algorithms)

- https://github.com/pop-os/cosmic-text (text rendering and editing)

- https://github.com/AccessKit/accesskit (cross-platform accessibility APIs)

In many cases there a see https://blessed.rs/crates#section-graphics-subsection-gui for a more complete list of frameworks and foundational libraries)

Using HarfBuzz makes sense. But if you're looking for a pure-Rust alternative, I hear cosmic-text (made by Pop!_OS) is good. There's also AccessKit for accessibility.

There are efforts to support a cross platform accessibility library:

https://github.com/AccessKit/accesskit

egui is an easy-to-use immediate mode GUI for Rust, and I just released 0.20. It's a big release!

There is now support for AccessKit (https://github.com/AccessKit/accesskit) which brings accessibility to egui (a first for an immediate mode GUI?).

There is also better table support, nicer keyboard shortcut handling, better looking text in light mode (still not great, but better).

See more in the changelog: https://github.com/emilk/egui/blob/master/CHANGELOG.md

Try it out at www.egui.rs