xilem VS taffy

The web browser gives us an extremely frictionless development and deployment process. Our CI generates a fully deploy at a unique link for every commit which lets us open and test PRs with a single click. It deploys updates to users without needing to make them go through an updater. In these relatively early stages of our development process, the importance of the velocity that gives us cannot be understated. Plus, the ability for users to try it out in one second is quite helpful.

I've designed the whole architecture specifically to avoid the web UI "feeling like a web app" with the subtle latency of interacting with the site. I wrote all-custom UI components using the minimal amount of HTML and CSS to achieve the requirements instead of depending on an external component framework which always loves nesting dozens of `div`s inside each other to achieve what should be doable in one or two. And our highly-lightweight JS which calls into Rust (Wasm) lets it keep the slow logic out of slow JS. And we are using Svelte to move most of the frontend DOM management logic from runtime to compile time. This architecture really helps us keep performance levels as close as possible to feeling native despite using the web for its GUI rendering; and I believe it has succeeded at feeling responsive by comparison to most other web apps you use (even Slack, for example, which shouldn't be nearly as complex).

Web lets us build fast, deploy the latest version to users fast, leverage prevalent developer experience with HTML/CSS for creating GUIs, and avoid getting stuck in a box with Rust's currently-immature GUI ecosystem. That's the tradeoff we had to make early on, and it was a good decision. But we will eventually move towards a fully native version...

In the short term, we plan to use [Tauri](https://tauri.app/) which is sort of a hybrid between Electron and a native application. It uses the OS's webview to shrink the shipped binary to only a few megabytes and reuse shared memory resources with other webviews at runtime. It also runs all our Rust code natively instead of through WebAssembly so all the business logic in Graphite runs natively and only the thin UI layer becomes dependent on web tech for the GUI display.

In the long term, we plan to rewrite the entire GUI in [Xilem](https://github.com/linebender/xilem) which is the up-and-coming Rust GUI that I believe will finally get everything right, including performance (which is something many desktop GUI frameworks are actually bad it, and sometimes even worse than web). We'll still deploy a web version but at that point, it will become native-first.

Hopefully that roadmap and explanation of the architectural decisions clears up any worries about the short and long term state of our GUI.

That said, Xilem is very close to that idea, but it's in its very early stages and nowhere near Flutter's capabilities.

xilem#62 demonstrates how Xilem's reactive layer can target DOM nodes.

Inspired by Xilem, Leptos and rui, Floem aims to be a high performance declarative UI library with minimal effort from the user.

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)

Yeah, Druid is being replaced by Xilem, but unfortunately Xilem isn't ready yet. So that whole project's in a bit of an awkward in-between phase where there isn't really any toolkit that can be recommended.

Third, we are discontinuing Druid proper. Years of experience has shown that people can struggle with the Druid data architecture and we can do better. This layer will be replaced by a new project called Xilem. We have spent a lot of time thinking about it and this decision was not taken lightly. You can read a more detailed post about the Xilem architecture but the gist of it is that we've found at a way to code UI in Rust that feels a lot more effortless than previous attempts. Xilem will look very intuitive to those familiar with state of the art toolkits such as SwiftUI, Flutter, and React, while at the same time being idiomatic Rust. Also we plan to port as many widgets from Druid to Xilem as possible, which should give the project a reasonable timeline to v0.1. Hopefully later this year.

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