egui

l you want? Maybe. That's a bit subjective. Does it handle all the little things correctly? When I'm using an app, I want it to scroll like how I'm used to scrolling working on my system. If you have differently styled buttons, I don't care, but if the scrolling feels wrong, it's going to annoy me. And there's so many little things. Frankly, one of the reasons why Electron often does well is that a lot of the little things "feel right" because the UI is essentially a Chromium-rendered web page which users are used to interacting with. But that has downsides too - shipping a web browser with your app and the memory usage. Heck, Qt apps in Gnome or GTK+ apps in KDE can look/feel "off". And it'll all depend on your ecosystem. Often cross-platform solutions are lacking in accessibility - sometimes completely missing, sometimes half-baked and it works in some parts and not in others or just is janky. Memory usage is often higher. Many little things that make an app feel right might not be there. Many have slower startup times since they're loading a bunch of stuff that native apps don't need to. And it really depends on what approach the cross-platform library is taking to determine what is going to cause pain. So you kinda have to pick your poison and what's acceptable to you will vary depending on your goals and tastes. Maybe React Native is the way to go for you with lots of native controls available and the feel that provides and the performance and size is acceptable. If you create a Flutter or Kotlin Compose Multiplatform or AvaloniaUI app and put it on the web, it's not going to feel right as something like HN does. Right-click, text selection, etc. are all going to be different or missing. If you're creating a solitaire game, maybe that doesn't matter - you get desktop and web in one go and it's not a big deal. But you have to know what you're building to know if the trade-offs being made are good ones. This isn't meant to sound anti-cross-platform, but as someone who has suffered some pain in this area, I guess I just wanted to impart that it isn't all sunshine and rainbows. Some times it can still be worth it, but just go in with your eyes open.

heritance does. OO languages like Java support a very similar approach, via interfaces. You can find similar code in any Rust GUI library, and indeed in almost any non-trivial Rust program. > Otherwise, there'd be no difference and everyone would call Rust an OO language. Rust is not a class-based OO language. But the fact that one of its core features, traits, have "methods", and those methods have a first argument traditionally named `self` should be a clue. Trait-based OO is very much OO. Whether "Rust is an OO language" depends on how strictly you want to define "OO" to match the rather obsolete 1970s conception of it. This is why the first question I asked you was "What OO features are you thinking of that Rust doesn't have?" Because "OO" is a broad label that covers a wide range of different features. Rust doesn't have "classes", but classes are a 1970s-era mish-mash of a whole bunch of different concerns munged together into a single poorly-factored construct. Now, half a century later, that's well understood, and better solutions exist in the form of traits and interfaces, and related capabilities. > Like why did ObjC feel the need to add ARC (not GC but similar goal)? Same reason Rust includes `Rc` and `Arc`. A general-purpose language has to provide some solution to memory management based on reachability. Reference counting and tracing GC are common solutions to that. Rust's static memory management plus RC is plenty good enough for GUI applications.

f that you can find a few egui examples in the rust-android-examples repo. Alright, so after I've got the basic examples running, I wanted to combine them with iced. Iced is a crossplatform gui library focusing on desktop and web. The mobile support is explicitly a non-goal, as far as I can tell at the moment of writing. Yet, there's an issue where some people posted their experiments. That's how I knew it was possible: https://github.com/iced-rs/iced/issues/302 There's a way to integrate iced in wgpu applications, so called integration example: https://github.com/iced-rs/iced/tree/0.14.0/examples/integra... Above I mentioned that using winit and wgpu in combination with android-activity is enough to build the app. Putting together 1 + 1 I got 2: let's use iced integration example with android-activity. It was quite easy to compile with almost no errors. First issue I encountered is that there was no text rendered. I solved this by loading fonts the way it was shown here: https://github.com/pop-os/cosmic-text/issues/243#issue-21899... Then I patched a few widgets to add touch support. And that's it. My role here was to take all the prior work and combine it together in a way that there's a working example. Some other ways of building Android apps using Rust: - xilem has an explicit goal to support mobile https://github.com/linebender/xilem - egui supports mobile https://github.com/emilk/egui - game engines such as Fyrox and Bevy support mobile: - https://github.com/FyroxEngine/Fyrox - https://github.com/bevyengine/bevy - pretty much anything built on top of winit and wgpu All of the above is related to building native apps using either NativeActivity or GameActivity. I'm leaving webview out of scope of current post. What about iOS? As far as I know it should be similar or maybe simpler compared to Android. I haven't built it yet, but the next time I have a sizeable amount of free time, I'll try to make it work. The plan is the same: pick winit, wgpu, iced integration example, mix it together until it works. It'll require the same trick to load fonts, and maybe something else, but no visible blockers as of now. Once again, thanks to all the people who made it possible and I wish you have a great time building mobile apps with Rust!

h is tiny. At some point, someone may need to fork Egui and create Egui-lite. [1] https://github.com/emilk/egui/issues/7059