Choosing the Right Rust GUI Library for Your Next Project

Rust has firmly established itself as a powerful and versatile language, celebrated for its performance, safety, and thriving open-source ecosystem. As Rust’s popularity continues to soar, so does the demand for robust and user-friendly graphical user interfaces (GUIs) built with it. Fortunately, the Rust community has responded with a diverse range of GUI libraries and frameworks, each catering to different needs and preferences.

This post aims to provide a comprehensive overview of some of the most popular Rust GUI options, highlighting their key features, strengths, weaknesses, and ideal use cases. By understanding the landscape of Rust GUI development, you’ll be better equipped to choose the perfect library for your next project.

A Tour of Popular Rust GUI Libraries

The Rust GUI ecosystem offers a rich tapestry of choices. Let’s delve into some of the prominent players:

• Tauri: A Lightweight and Flexible Option
• Druid: A Powerful and Flexible Layout System
• Xilem: An Experimental UI Library with a Focus on Performance
• Slint: A Comprehensive and Customizable UI Framework
• gtk-rs: The Power of GTK+ in Rust
• fltk-rs: A Rust Binding for the Lightweight FLTK
• Iced: A Delightful Elm-inspired GUI Framework
• Relm4: An Asynchronous GUI Library Inspired by Elm and GTK+
• Azul: A Native GUI Framework Written in Rust (Currently Under Heavy Development)
• Egui: An Immediate Mode GUI Library
• Yew: Building Web UIs with Rust and WebAssembly

Each of these libraries brings unique characteristics to the table. Let’s explore them in more detail.

In-Depth Look at Key Rust GUI Libraries

Tauri: Building Cross-Platform Desktop Apps with Web Technologies

As you mentioned, Tauri is an open-source framework that allows you to build lightweight, cross-platform desktop applications using web technologies like HTML, CSS, and JavaScript, powered by a Rust backend.

Key Features:

• Web-Based UI: Leverages familiar web technologies for UI development.
• Small Binaries: Produces significantly smaller application bundles compared to Electron.
• Cross-Platform: Supports Windows, macOS, and Linux.
• Rust Backend: Offers the performance and safety of Rust for core logic.
• Plugin System: Allows extending functionality with Rust plugins.
• Security Focus: Designed with security in mind.

Strengths:

• Lower barrier to entry for web developers.
• Rapid prototyping and development.
• Excellent for applications with web-centric UIs.

Weaknesses:

• Relies on a web runtime, which might not be ideal for all types of applications.
• Native look and feel might require more effort to achieve.

Use Cases: Desktop applications where leveraging web technologies is beneficial, such as utilities, dashboards, and communication tools.

use tauri::{Builder, Manager, Runtime};

fn main() -> Result<(), tauri::Error> {
    Builder::default()
        .setup(|app| {
            let main_window = app.get_window("main").unwrap();
            main_window.set_title("My Tauri App").unwrap();
            Ok(())
        })
        .run(tauri::generate_context!())
}

Druid: Crafting Native Desktop Experiences with a Focus on Layout

Druid is a powerful, native Rust GUI library designed for building rich desktop applications. Its constraint-based layout system is a standout feature, making complex UI arrangements more manageable.

Key Features:

• Native Look and Feel: Renders using the operating system’s native UI elements.
• Constraint-Based Layout: Provides a flexible and intuitive way to define UI layouts.
• Data-Driven Architecture: Encourages a clear separation of data and UI.
• Built-in Widgets: Offers a good set of common UI components.
• Theming and Customization: Allows for extensive UI styling.

Strengths:

• Excellent performance and responsiveness.
• Well-suited for complex desktop applications.
• Strong focus on layout management.

Weaknesses:

• Steeper learning curve compared to web-based options.
• Smaller community compared to some other libraries.

Use Cases: Desktop applications requiring a native look and feel, such as productivity tools, editors, and creative software.

use druid::{AppLauncher, Data, Lens, LocalizedString, PlatformError, Widget, WidgetExt, WindowDesc};
use druid::widget::{Button, Flex, Label};

#[derive(Clone, Data, Lens)]
struct AppState {
    name: String,
    count: u32,
}

fn build_ui() -> impl Widget<AppState> {
    let name_label = Label::new(|data: &AppState, _| format!("Hello, {}!", data.name));
    let count_label = Label::new(|data: &AppState, _| format!("Count: {}", data.count));
    let increment_button = Button::new("Increment")
        .on_click(|_ctx, data: &mut AppState, _env| {
            data.count += 1;
        });

    Flex::column()
        .with_child(name_label)
        .with_child(count_label)
        .with_child(increment_button)
        .padding(10.0)
}

fn main() -> Result<(), PlatformError> {
    let main_window = WindowDesc::new(build_ui())
        .title(LocalizedString::new("druid-demo-window"))
        .with_min_size((400.0, 300.0));

    let initial_state = AppState {
        name: "World".to_string(),
        count: 0,
    };

    AppLauncher::with_window(main_window)
        .launch(initial_state)?;

    Ok(())
}

Xilem: An Experimental Library Prioritizing Performance and Organization

As you mentioned, Xilem is an experimental UI library drawing inspiration from modern UI paradigms like SwiftUI, Flutter, and Elm. Its core focus lies in achieving high performance through minimal updates and a centralized state management system.

Key Features:

• Reactive Programming Model: Uses a declarative approach to UI development.
• Centralized State Management: Simplifies data handling and ensures predictable updates.
• Efficient Rendering: Aims for minimal UI re-renders for optimal performance.
• Inspired by Modern Frameworks: Incorporates concepts from popular UI libraries.

Strengths:

• Potentially excellent performance due to its design principles.
• Clean and organized approach to UI development.

Weaknesses:

• Still in an experimental phase, so the API might be unstable.
• Smaller community and less mature ecosystem compared to established libraries.

Use Cases: Applications where performance is critical and a modern, reactive programming model is desired.

Slint: Building Native UIs for Embedded, Desktop, and Web

Slint (formerly known as SixtyFPS) is a unique UI framework designed for creating fluent native user interfaces that can run on various platforms, including embedded devices, microcontrollers, desktops, and even the web via WebAssembly. It uses its own declarative language (.slint) for defining UI structure and styling.

Key Features:

• Declarative UI Language: Uses a dedicated language for UI definition.
• Cross-Platform Compatibility: Targets a wide range of platforms.
• Small Footprint: Optimized for resource-constrained environments.
• Multiple Language Bindings: Supports Rust, C++, and JavaScript.
• Prebuilt UI Components: Offers a library of customizable widgets.

Strengths:

• Excellent for embedded systems and resource-limited devices.
• Provides a consistent look and feel across different platforms.
• Strong focus on performance and efficiency.

Weaknesses:

• Requires learning a new declarative language.
• The ecosystem might be less extensive than some other options.

Use Cases: Embedded systems, IoT devices, desktop applications, and web applications where a performant and consistent UI is needed across platforms.

// Assuming you have a .slint file named "my_ui.slint"
// `export component MainWindow { ... }`

use slint::{ModelRc, VecModel};

slint::include_modules!();

fn main() -> Result<(), slint::Error> {
    let ui = MainWindow::new()?;

    let data = VecModel::from(vec![
        "Item 1".into(),
        "Item 2".into(),
        "Item 3".into(),
    ].into_iter());
    ui.set_items(ModelRc::new(data));

    let ui_handle = ui.as_weak();
    ui.on_button_clicked(move || {
        let ui = ui_handle.upgrade().unwrap();
        println!("Button clicked!");
        let new_data = VecModel::from(vec!["New Item".into()].into_iter());
        ui.set_items(ModelRc::new(new_data));
    });

    ui.run()
}

gtk-rs: Leveraging the Mature GTK+ Toolkit in Rust

gtk-rs provides Rust bindings for the widely used GTK+ toolkit. GTK+ is a mature and feature-rich cross-platform GUI toolkit originally developed for the GNOME desktop environment but also available on other platforms.

Key Features:

• Mature and Stable: GTK+ has a long history and a large, active community.
• Comprehensive Widget Set: Offers a vast array of prebuilt UI components.
• Cross-Platform: Runs on Linux, Windows, macOS, and other platforms.
• Native Look and Feel: Integrates well with desktop environments.
• Extensive Documentation: GTK+ has excellent documentation.

Strengths:

• Large and active community providing ample support and resources.
• Highly customizable and flexible.
• Well-established and reliable.

Weaknesses:

• Can have a steeper learning curve due to the complexity of GTK+.
• Bindings might sometimes lag behind the latest GTK+ features.

Use Cases: Desktop applications requiring a native look and feel, especially those intended for Linux environments.

use gtk::prelude::*;
use gtk::{Application, ApplicationWindow, Button};

const APP_ID: &str = "org.example.my_gtk_app";

fn main() {
    let application = Application::builder()
        .application_id(APP_ID)
        .build();

    application.connect_activate(|app| {
        let window = ApplicationWindow::builder()
            .application(app)
            .title("My GTK+ App")
            .build();

        let button = Button::builder()
            .label("Click me!")
            .build();

        button.connect_clicked(|_| {
            println!("Button clicked!");
        });

        window.set_child(Some(&button));
        window.present();
    });

    application.run();
}

fltk-rs: Rust Bindings for the Light and Fast FLTK

fltk-rs provides Rust bindings for the Fast Light Tool Kit (FLTK), a lightweight and cross-platform GUI toolkit known for its speed and simplicity.

Key Features:

• Lightweight and Fast: Produces small and efficient applications.
• Cross-Platform: Runs on Windows, macOS, Linux, and other platforms.
• Simple API: Relatively easy to learn and use.
• Native Look and Feel: Provides a native appearance on different platforms.

Strengths:

• Excellent performance and low resource consumption.
• Good choice for simple to moderately complex applications.
• Relatively small binary sizes.

Weaknesses:

• The widget set might be less extensive compared to GTK+ or Qt.
• Community support might be smaller.

Use Cases: Utilities, tools, and applications where performance and simplicity are paramount.

use fltk::{prelude::*, button::Button, window::Window};

fn main() {
    let app = fltk::app::App::default().with_scheme(fltk::app::Scheme::Gtk);
    let mut wind = Window::new(100, 100, 400, 300, "My FLTK App");
    let mut but = Button::new(160, 200, 80, 40, "Click Me");
    wind.end();
    wind.show();

    but.set_callback(move |_| {
        println!("Button clicked!");
    });

    app.run().unwrap();
}

Iced: A Delightful Elm-Inspired GUI Framework

Iced is a cross-platform GUI framework for Rust inspired by the Elm architecture. It focuses on simplicity, type safety, and a clear separation of concerns.

Key Features:

• Elm Architecture: Follows a functional, reactive programming model.
• Cross-Platform: Supports Windows, macOS, Linux, and the web (via WebAssembly).
• Type Safety: Leverages Rust’s strong typing for robust applications.
• Asynchronous Operations: Handles asynchronous tasks gracefully.
• Beginner-Friendly: Designed to be relatively easy to learn.

Strengths:

• Clear and predictable application structure.
• Excellent for building maintainable and scalable UIs.
• Strong focus on immutability and pure functions.

Weaknesses:

• The Elm architecture might require a shift in thinking for developers accustomed to other paradigms.
• The ecosystem is still growing compared to more established libraries.

Use Cases: Applications where maintainability, scalability, and a functional programming approach are desired.

use iced::{Application, Command, Element, Settings, Subscription, Theme};
use iced::widget::{button, column, row, text};
use iced::executor;
use iced::time;
use std::time::Duration;

#[derive(Debug, Clone, Copy)]
enum Message {
    IncrementPressed,
    DecrementPressed,
    Tick,
}

struct Counter {
    value: i32,
}

impl Application for Counter {
    type Executor = executor::Default;
    type Message = Message;
    type Theme = Theme;
    type Flags = ();

    fn new(_flags: ()) -> (Counter, Command<Message>) {
        (
            Counter { value: 0 },
            Command::none(),
        )
    }

    fn title(&self) -> String {
        String::from("Counter - Iced")
    }

    fn update(&mut self, message: Message) -> Command<Message> {
        match message {
            Message::IncrementPressed => {
                self.value += 1;
            }
            Message::DecrementPressed => {
                self.value -= 1;
            }
            Message::Tick => {
                // Do something on a timer tick if needed
            }
        }
        Command::none()
    }

    fn view(&self) -> Element<Message> {
        column![
            row![
                button("-").on_press(Message::DecrementPressed),
                text(self.value).size(50),
                button("+").on_press(Message::IncrementPressed),
            ]
            .spacing(20)
            .align_items(iced::Align::Center),
        ]
        .padding(20)
    }

    fn subscription(&self) -> Subscription<Message> {
        time::every(Duration::from_secs(1)).map(|_| Message::Tick)
    }
}

fn main() -> iced::Result {
    Counter::run(Settings::default())
}

Relm4: An Asynchronous GUI Library Inspired by Elm and GTK+

Relm4 is a modern, asynchronous GUI library for Rust heavily inspired by the Elm architecture and built on top of GTK+. It aims to provide a more Rusty and type-safe way to develop GTK+ applications following the principles of the Elm architecture.  

Key Features:

• Elm-like Architecture: Emphasizes a clear separation of state, messages, and updates.
• Asynchronous Operations: Provides built-in support for asynchronous tasks.
• Type Safety: Leverages Rust’s type system for safer code.  
• GTK+ Backend: Benefits from the maturity and features of GTK+.

Strengths:  

• Combines the benefits of the Elm architecture with the power of GTK+.
• Encourages a structured and maintainable codebase.
• Good choice for complex applications with asynchronous requirements.

Weaknesses:

• Requires understanding both the Elm architecture and GTK+.
• The community might be smaller compared to GTK+ itself.

Use Cases: Desktop applications built with GTK+ that benefit from the Elm architecture’s structure and asynchronous capabilities.

Azul: A Native GUI Framework Written Entirely in Rust (Work in Progress)

Azul is an ambitious native GUI framework written entirely in Rust, without relying on any external GUI toolkits. It aims to provide a performant and flexible platform for building native applications.

Key Features:

• Pure Rust: No external dependencies on other GUI toolkits.
• Native Rendering: Renders UI elements directly using the operating system’s graphics APIs.
• Modern Architecture: Designed with modern UI development principles in mind.

Strengths:

• Potential for high performance and fine-grained control.
• Complete control over the rendering pipeline.

Weaknesses:

• Still under heavy development and might not be production-ready.
• Smaller community and less mature ecosystem.

Use Cases: Applications requiring maximum performance and control over the UI rendering process, once it reaches a stable state.

Egui: An Immediate Mode GUI Library

Egui is an immediate mode GUI library written in Rust that can be integrated into various environments, including native applications, web browsers (via WebAssembly), and game engines.

Key Features:

• Immediate Mode: UI is defined and rendered every frame.
• Cross-Platform: Supports multiple platforms and rendering backends (e.g., WGPU, OpenGL).
• Easy to Use: Relatively simple API for creating UIs.
• Good for Tools and Debugging: Often used for editor interfaces, debugging tools, and internal application UIs.

Strengths:

• Quick iteration and prototyping.
• Simple and intuitive API.
• Excellent for creating utility interfaces and tools.

Weaknesses:

• Might not be ideal for highly complex or heavily styled UIs.
• Performance can be a concern for very large UIs if not managed carefully.

use egui::{CentralPanel, Context, Frame, Ui};
use egui_winit::State;
use winit::event::Event;
use winit::event_loop::{ControlFlow, EventLoop};
use winit::window::WindowBuilder;

fn main() {
    let event_loop = EventLoop::new().unwrap();
    let window = WindowBuilder::new()
        .with_title("My Egui App")
        .build(&event_loop)
        .unwrap();

    let mut egui_state = State::new(&event_loop, window.inner_size(), None, None);
    let mut counter = 0;

    event_loop.run(move |event, target| {
        egui_state.on_event(&event);

        match event {
            Event::WindowEvent { event, .. } => match event {
                winit::event::WindowEvent::CloseRequested => target.exit(),
                winit::event::WindowEvent::RedrawRequested => {
                    let output = egui_state.run(None, |ctx| {
                        CentralPanel::default().frame(Frame::dark_canvas(&ctx.style())).show(ctx, |ui| {
                            ui.heading("My Egui App");
                            ui.label(format!("Counter: {}", counter));
                            if ui.button("Increment").clicked() {
                                counter += 1;
                            }
                        });
                    });

                    let paint_jobs = output.platform_output.take_paint_jobs();
                    // Render the paint jobs using your chosen backend (e.g., WGPU, OpenGL)
                    // This part is backend-specific and omitted for brevity.

                    window.request_redraw();
                }
                _ => {}
            },
            Event::AboutToExit => println!("Exiting"),
            Event::NewEvents(_) => {}
            Event::UserEvent(_) => {}
            Event::DeviceEvent { .. } => {}
            Event::Suspended => {}
            Event::Resumed => {}
            Event::MainEventsCleared => {
                window.request_redraw();
            }
        }
    }).unwrap();
}

Yew: Building Modern Web UIs with Rust and WebAssembly

Yew is a popular Rust framework for building client-side web applications with WebAssembly. It draws inspiration from popular JavaScript frameworks like React and Vue.js, offering a component-based architecture.

Key Features:

• Component-Based Architecture: Organizes UI into reusable components.
• Virtual DOM: Efficiently updates the browser’s DOM.
• WebAssembly Integration: Runs Rust code directly in the browser.
• Strong Typing: Leverages Rust’s type system for safer web development.
• Interoperability with JavaScript: Allows interaction with existing JavaScript code.

Strengths:

• Excellent performance for web applications.
• Leverages Rust’s safety and performance in the browser.
• Familiar concepts for developers with experience in modern JavaScript frameworks.

Weaknesses:

• Requires understanding WebAssembly and browser APIs.
• Debugging WebAssembly can sometimes be more challenging.

Use Cases: Building complex and performant web applications that run entirely in the browser.

use yew::prelude::*;

#[function_component(App)]
fn app() -> Html {
    let counter = use_state(|| 0);
    let onclick = {
        let counter = counter.clone();
        Callback::from(move |_| {
            let value = *counter + 1;
            counter.set(value);
        })
    };

    html! {
        <div>
            <button {onclick}>{ "+1" }</button>
            <p>{ *counter }</p>
        </div>
    }
}

fn main() {
    yew::Renderer::<App>::new().render();
}

Factors to Consider When Choosing a Rust GUI Library

Selecting the right Rust GUI library depends on several crucial factors:

• Project Requirements: What kind of application are you building? Is it a desktop app, a web app, an embedded system UI, or something else? Different libraries excel in different domains.
• Performance Needs: How performance-critical is your application? Some libraries are designed for high-performance rendering, while others prioritize ease of use.
• Platform Support: Which platforms do you need to support (Windows, macOS, Linux, Web, Embedded)? Ensure the library you choose offers the necessary cross-platform capabilities.
• UI Complexity: How complex will your user interface be? Some libraries are better suited for simple UIs, while others can handle highly intricate designs.
• Team Experience: What is your team’s experience with different UI paradigms (e.g., web-based, native, reactive)? Choosing a library that aligns with your team’s skills can accelerate development.
• Learning Curve: How much time are you willing to invest in learning a new library? Some libraries have steeper learning curves than others.
• Community and Ecosystem: How active and supportive is the library’s community? A larger community often means better documentation, more resources, and faster bug fixes.  
• Maturity and Stability: Is the library mature and stable enough for your production needs? Experimental libraries might offer cutting-edge features but could also have more bugs and API changes.
• Licensing: Consider the licensing terms of the library and ensure they are compatible with your project.
• Desired Look and Feel: Do you need a native look and feel for each platform, or is a custom or web-like UI acceptable?