Show HN: Rust GUI Library via Flutter

[fzyzcjy]

Hi, I made a bridge (https://github.com/fzyzcjy/flutter_rust_bridge v2.0.0) between Flutter and Rust, which auto translates syntaxes like arbitrary types, &mut, async, traits, results, closure (callback), lifetimes, etc. The goal is to make a bridge between the two, seamlessly as if working in one single language.

Then, as an example, I showed how to write Rust applications with GUI by utilizing Flutter. That is discussed in the link in details.

To play with it, please visit the GitHub repo, or refer to the end of the article for detailed folders and commands.

When I first released 1.0.0 years ago, it only contained few features compared to today. It is the result of the hard work of contributors and me, and many thanks to all the contributors!

[tmpfs]

I have been using this to build an app[0] for the last couple of years and I want to say that it has been a pleasure to use, there are some wrinkles but overall I have been very happy with the experience.

Upgrading from v1 to v2 was not too difficult and v2 is a significant upgrade with lots of useful features, massively improved codegen experience and support for tokio async were the big gamechangers for me.

Writing all the app business logic in Rust and using Dart as the front-end works out really well. I know Flutter/Dart doesn't get much love here on HN but in my opinion I think it's much easier to reason about than a system like React which I think is the wrong level of abstraction compared to Flutter's render the entire widget tree approach.

Massive thanks to @fzyzcjy for all the work on FRB, great job!

[0]: https://saveoursecrets.com

[bmitc]

Flutter is not bad, but I hesitate diving into it based upon who controls it. Using a Google product feels like you're in constant threat of it just disappearing.

It also still has all the remnants of mobile and fingers and not desktop and mouse. Support for improving this is non-existent in my experience.

[MrJohz]

> I know Flutter/Dart doesn't get much love here on HN but in my opinion I think it's much easier to reason about than a system like React which I think is the wrong level of abstraction compared to Flutter's render the entire widget tree approach.

Could you expand on this a bit? My impression was that Flutter and React had relatively similar approaches to components, but I haven't had much experience with Flutter yet, so I'm interested to hear your experiences!

[satvikpendem]

But, Flutter and React work the same way where UI is a function of state. In fact, Flutter started off imperatively but after React was released, they changed it to be declarative, and now Android via Jetpack Compose is changing to be declarative, all on the same general principle. I also use packages like flutter_hooks or ReArch which make encapsulating state much easier, I couldn't stand using initState and not forgetting to dispose for each piece of functionality.

[fzyzcjy]

You are welcome, and happy to hear it works for you!

[nu11ptr]

> I know Flutter/Dart doesn't get much love here on HN but in my opinion I think it's much easier to reason about than a system like React which I think is the wrong level of abstraction compared to Flutter's render the entire widget tree approach.

Yeah I really like Flutter/Dart. I had less an issue with React itself than I did the whole HTML/CSS/Javascript ecosystem and tooling. Flutter is a breath of fresh air in that it is a purpose built ecosystem for UIs. You load the SDK and are ready to go with features like hot reload out of the box. No need for gamut of tools and to figure out how they all work together. Also, no need for HTML + CSS! I think the only reason it isn't more popular is because we have such a huge # of frontend devs already trained on HTML/CSS/JS, as Flutter is a lot simpler out of the gate, and much easier for traditional GUI paradigm people IMO.

[samstave]

Just want to say, your site is very aesthetically pleasing. I hate blue websites (FB Blue) -- but the deep tones that SOS uses and contrasts are really appealing.

So is the app, subscribed.

[nu11ptr]

Looks nice. What UI design system did you use here if I can ask?

[blopker]

While I don't see the advantage of writing UI in Rust vs Dart, I'm a huge fan of flutter_rust_bridge.

The work fzyzcjy and the community have put into calling Rust code from Dart seamlessly is such an asset to Flutter apps. I remade the popular image compression app ImageOptim in Flutter over a weekend because webp wasn't supported. After a little pain in the initial setup, I was able to call mature Rust image libraries using flutter_rust_bridge and a small wrapper[0]. It even handled all the parallelism for me.

The app ended up being more capable and faster than ImageOptim, largely just because of the Rust integration. Thank you fzyzcjy!

[0]: https://github.com/blopker/alic/blob/main/rust/src/api/compr...

[fzyzcjy]

You are welcome, and I am happy to see it helps! When I initially develop flutter_rust_bridge, my personal usage scenario is quite similar to yours: using Rust for some high performance algorithms.

[bubblebeard]

Commendable effort! I’m currently using Tauri for a project myself and was wondering if anyone has any pros/cons between the two?

[fzyzcjy]

Thank you! I heard some people saying that, for apps using JavaScript, Tauri is replacing Electron and is popular nowadays, since Electron is very widely used. It seems Tauri cannot let Rust communicate with JavaScript very seamlessly yet, e.g. https://tauri.app/v1/guides/features/command/ seems to have mainly basic features. oneshtein mentioned below that Tauri does not support mobile as first class citizen yet as well. Looking forward to seeing Tauri's bridge to improve and supporting mobile better in the future!

[bobajeff]

From what I can tell. I've not used Tauri and it's been years since I've tried flutter.

Tauri currently has poor support for mobile and Linux (because of the state of WebkitGtk).

Flutter uses Dart which is not widely used for anything else. Harder to learn as there is no MDN, w3schools or standard spec for it. Also Flutter Web has issues due to it's use of Canvas over the DOM.

IMO, electron is still the way to go for cross platform apps.

[burakemir]

Interesting! IIUC this is done using source-to-source translation? It is a bit hard to understand from the docs what technical approach is. The docs are clearly aimed at users and I find them impressive, well done. I'd be interested in knowing the approach and how it compares to wasm based Rust web frameworks before diving more deeply into it.

One advantage of combining Rust with Flutter seems to be that Flutter is a whole framework already and one would be able to share code and data structures between server and client side.

A comparison with other ways Rust

[fzyzcjy]

Thanks! Shortly speaking, the Rust code is parsed (e.g. "here is a function and there is a struct"), and then some Rust and Flutter code are generated. As for comparison, some pros and cons are discussed in the blog.

[sbt567]

Well done! I've heard only good things about rust_flutter_bridge. Some questions though (more like flutter question), how bloated flutter is (i.e. final app size) compared to mobile native (Java, Swift?) for simple app? And how's the UI performance looks like?

[fzyzcjy]

For app size, it depends on your specific scenario, because e.g. Flutter automatically removes library code that is not used. I remembered (but the memory is blur) simple app has something like ~5MB. Btw remember to split .so file per abi. For UI performance, I personally find it quite good, and Flutter(Dart) is compiled to assembly code via AOT (instead of e.g. JIT or interpreted), which theoretically speaking is also fast. For both, I would suggest to make a demo for your specific case to have more accurate results. Also I guess ask/discuss on the Flutter community may help.

[BodyCulture]

How is the a11y story with this? I did not find any info about it in the document, but I can not imagine anyone releasing a GUI kit in 2024 without extensive a11y support, so why not mention it?

[nsriv]

Do you mean in Flutter generally? I'd say it's very good, easy to build in on widget by widget basis, very easy to check and rest when running builds.

[nu11ptr]

I use Flutter for my desktop UI and Rust for my backend. However, I chose to separate the two using gRPC instead of the bridge. This allows me to be agnostic of language on both sides and I suspect gives me a cleaner interface for mocking the backend from my frontend. It also makes it easy to place the UI and backend on different machines giving a true client/server architecture. The con is likely that the interface is probably more verbose, however.

[nevi-me]

Do you run a gRPC service on the desktop where the UI runs, and connect the 2 via localhost?

[pjmlp]

Much better than reaching out to Chrome shells or Web widgets, kudos for the effort.

[fzyzcjy]

Thank you!

[danielvaughn]

Nice, I really enjoyed Flutter's approach to building UI, but I didn't really care for Dart all that much.

In theory shouldn't it be possible to create a programming language specifically for UI? Something that can be interfaced with from any major programming language. Kinda like protobuf with its IDL format, but instead of defining data, it's declaring user interfaces. Is that a crazy or stupid idea?

QT and XAML come to mind, but I believe QT is closed source (might be wrong about that), and XAML seems to have been dead in the water for a long time now (also might be wrong about that).

[Tmpod]

Qt has some commercial license only components, but the majority is open-source. In fact, the KDE Free Qt Foundation ensures that the framework is always available under GPL+LGPLv3.[0]

Anyway, there are some languages specifically desgined for making UIs. Qt has one of those, QML[1]. It's a "simple" language made precisely for UI development, that can be wired to C++, allowing you to write business logic in a general language, while keeping UI focused.

More interestingly, though, is Slint[2]. The language (and company behind it) was made by ex-QML devs which sought to improve the design, avoiding some pitfalls that QML ended up running into. It's core is written in Rust, but there are bindings for C++, JS and now Python too. They also have a focus on embedded devices, which ends up translating to always having good performance and memory footprint in mind, which is neat.

One of Slint's dev is ogoffart: https://news.ycombinator.com/user?id=ogoffart

[0]: https://www.qt.io/faq/tag/qt-open-source-licensing [1]: https://en.wikipedia.org/wiki/QML [2]: https://slint.dev

[neonsunset]

XAML is very much alive within Avalonia[0], Uno[1] and MAUI[2] (not to mention WPF) :)

There is support and growing popularity for declarative UI defined in C#[3] and F#[4] instead though.

[0]: https://docs.avaloniaui.net/docs/basics/user-interface/intro...

[1]: https://platform.uno/docs/articles/getting-started/counterap...

[2]: https://learn.microsoft.com/en-us/dotnet/maui/xaml/fundament...

[3]: https://github.com/AvaloniaUI/Avalonia.Markup.Declarative

[4]: https://github.com/fsprojects/Avalonia.FuncUI

[Zelphyr]

I’m curious what you don’t like about Dart? I thought I wouldn’t like it but I’ve found it surprisingly nice.

[_bent]

you mean CSS?

[sydbarrett74]

Does anyone know if Google plans to sunset the entire Flutter framework over time? Since they fired just about everybody internal who was working on it, I don't have a lot of confidence that Flutter will still have any Google support in 3-5 years. Has anyone talked about forking it and putting it under an independent foundation to ensure its long-term viability? Given Google's track record of long-term support for its various technologies, it would be a shame if Flutter got consigned to history's scrap-heap prematurely.

[satvikpendem]

What? No one in the Flutter team got fired. The only ones who potentially had something to do with it were people on the Google Cloud team that ran the pipelines for Flutter builds, but even then, they didn't directly work on Flutter, and their roles just got outsourced anyway to Europe, so it's not like Flutter itself was actually affected.

[mdhb]

What the fuck are you talking about? This literally never happened.

[polyaniline]

How does this compare to rinf?

[fzyzcjy]

The first image at the bottom of that post may be related to your question: https://www.reddit.com/r/rust/comments/191b2to/rinf_copies_a... Btw, why is your name green?

[abound]

And then there's also crux [1], which is the same "write your mobile app business logic once in Rust", but instead of Flutter, integrates directly with native iOS/Android/Web UIs

[1] https://redbadger.github.io/crux/

[satvikpendem]

Note that the linked thread by OP has now been resolved and the rinf author fixed and apologized [0]. This thread might be a better start on the differences [1].

[0] https://github.com/cunarist/rinf-status-report

[1] https://www.reddit.com/r/FlutterDev/comments/1dnwagk/flutter...

[j-krieger]

Flutter Rust Bridge is without a doubt the best FFI bridge I‘ve ever used. It works like magic. I have no idea how it‘s done.

[fzyzcjy]

Thank you!

[the__alchemist]

Does anyone know how this compares to EGUI in terms of performance, binary size, flexibility, and overall experience?

[api]

The sample with Google's IMHO ugly material design plus confetti is not the best look.

[webprofusion]

Cool, but the point of having stuff in Rust is to ideally have everything in Rust, or you're by definition not getting all the safety benefits of Rust.

[jenadine]

Dart is also safe.

[ramon156]

While dart is definitely not like rust, dart is a very safe language. I'd love a dart+rust project if the package ecosystem wasn't such a mess in dart

[mtizim]

Not at all, pretty much all popular languages (except C/C++) are as safe as (safe) rust. The only safety rust brings to the table is memory safety, which most languages achieve with a runtime and a garbage collector, which have a performance tradeoff.

[jurschreuder]

Isn't Flutter basically a way to use the C++ render engine from Chrome, with a "scripting" language most similar to Kotlin and Swift?

Why not just use the Chrome render engine directly from Rust?

Why all the extra steps?

[imadj]

> Why not just use the Chrome render engine directly from Rust?

This is what projects like Tauri (in Rust) and Wails (in Go) are doing[0][1]. Utilizing Webview to develop applications, but they still don't support mobile, Tauri mobile is in beta.

Basically Tauri and Wails are on one side (HTML/CSS) trying to approach cross platform by supporting mobile platforms, while Flutter and Kotlin Compose Multiplatform started from the other side.

So it depends on your needs, web-first or mobile-first, and what platforms matter to you. So far Flutter is in the lead offering the most polished experience when it comes to supporting all platforms (Web, desktop, iOS, Android).

[0] https://github.com/tauri-apps/tauri

[1] https://github.com/wailsapp/wails

[ThePhysicist]

They used to be based on Skia but now they have their own renderer (Impeller). That said rendering is only a small part of a UI toolkit, there's a ton of other stuff e.g. how to interact with system libraries, integrate with UI paradigms (e.g. tray icons, gestures, responsiveness, widgets).

[polyaniline]

There's too much infrastructure on top of the render engine to replicate. Flutter is backed by Google and has a fairly large ecosystem of community packages.

See Freya - which uses Skia - the render engine Flutter used until a while back.