Building Cross-Platform GUI Apps in Rust Using Egui
Create desktop and web applications from a single Rust codebase
Introduction to Egui and Cross-Platform Development
Egui (pronounced "e-gui") is an immediate mode GUI library for Rust designed for simplicity and performance. Unlike retained mode GUI frameworks that maintain a persistent representation of the UI, egui rebuilds the entire interface every frame, making state management significantly easier for developers.
The library serves as the rendering layer for eframe, a cross-platform framework that compiles to native desktop applications and WebAssembly for browser deployment. This combination enables developers to write once and deploy across Windows, macOS, Linux, and web platforms without platform-specific code.
Egui's philosophy prioritizes developer experience and simplicity over advanced customization. The API is designed to be intuitive, with widgets that behave consistently across all platforms. This approach makes it particularly attractive for prototyping, tools, and applications where rapid development matters more than pixel-perfect custom designs. Our web development services team leverages modern frameworks like Rust and egui to build high-performance applications for clients across multiple platforms.
Key Prerequisites
1
Stable Rust toolchain
2
Cargo package manager
3
eframe crate dependency
4
Basic Rust knowledge
Setting Up Your First Egui Application
Get your development environment ready and create your first working egui application. The setup process follows standard Rust conventions, making it accessible to developers already familiar with the ecosystem.
1use eframe::egui;2 3struct MyApp {4 name: String,5 age: u32,6}7 8impl Default for MyApp {9 fn default() -> Self {10 Self { name: String::from("User"), age: 30 }11 }12}13 14impl eframe::App for MyApp {15 fn update(&mut self, ctx: &egui::Context, _: &mut eframe::Frame) {16 egui::CentralPanel::default().show(ctx, |ui| {17 ui.heading("Welcome to egui!");18 ui.label("Enter your name:");19 ui.text_edit_singleline(&mut self.name);20 ui.add(egui::Slider::new(&mut self.age, 0..=100).text("years"));21 if ui.button("Submit").clicked() {22 println!("Hello {}, you are {} years old!", self.name, self.age);23 }24 });25 }26}27 28fn main() -> Result<(), eframe::Error> {29 eframe::run_native(30 "egui Demo",31 eframe::NativeOptions::default(),32 Box::new(|_| Box::new(MyApp::default())),33 )34}Core Egui Concepts and Immediate Mode Rendering
Immediate mode GUI differs fundamentally from traditional retained mode interfaces. In retained mode, widgets exist as persistent objects that the framework manages and updates. In immediate mode, the interface rebuilds from scratch each frame, with widgets returning immediate results that describe their state.
This paradigm shift simplifies state management because your application state and UI representation exist in the same place. There is no synchronization needed between UI objects and application data. When state changes, the UI naturally reflects those changes on the next frame without explicit update calls.
The egui Context passed to your update function provides access to all UI operations. This context manages widget state, handles input events, and coordinates rendering. Every UI operation occurs within a closure that receives a UI object for building that portion of the interface.
Widgets in egui return Response objects that describe their current state and interactions. These responses provide methods like clicked(), hovered(), and changed() to query widget behavior. This design separates interaction detection from visual rendering. To learn more about the Rust programming language that powers egui, see our guide to Rust programming fundamentals.
1if ui.button("Submit").clicked() {2 // Handle click3}Essential Widgets and User Interface Elements
Master the fundamental widgets that form the building blocks of any egui interface. These widgets cover the most common interface needs while maintaining consistency across platforms.
Input Widgets
Labels, buttons, text fields, sliders, checkboxes, and radio buttons for collecting user data with automatic state binding.
Layout Containers
Horizontal and vertical layouts, CentralPanel, SidePanel, and Window widgets for organizing interface structure.
Visual Feedback
Progress bars, spinners, hyperlinks, and images to enhance user experience and interface richness.
1ui.text_edit_singleline(&mut self.name);2ui.add(egui::Slider::new(&mut self.age, 0..=100).text("years"));3ui.checkbox(&mut self.enabled, "Enable feature");1ui.horizontal(|ui| {2 ui.label("Name:");3 ui.text_edit_singleline(&mut self.name);4});5 6ui.vertical(|ui| {7 ui.heading("Section Title");8 ui.label("Content goes here");});Advanced Features and State Management
Building custom widgets combines existing egui primitives with application-specific behavior. The library's composition model encourages building reusable interface components that encapsulate both appearance and behavior. Custom widgets typically accept a UI reference and application state, returning a Response that describes interactions.
Egui applications compile to WebAssembly for browser deployment through eframe's web support. The compilation process generates JavaScript glue code that loads your WebAssembly module and connects it to the browser's rendering pipeline. Learn more about deploying Rust applications to the web in our WebAssembly development guide. Beyond eframe standalone usage, egui integrates with other Rust frameworks and engines. Tauri applications can embed egui interfaces for hybrid native applications. Bevy, a game engine, includes egui integration for editor interfaces and debugging tools.
State that persists across frames requires storage in your application struct. The egui Context provides memory slots for transient state that doesn't warrant application-level storage. This distinction helps organize different kinds of state appropriately.
Deployment and Distribution
Package and distribute your egui applications to desktop and web platforms. The same codebase targets multiple deployment environments without platform-specific code modifications.
Windows
Standard .exe executable - No installation required, portable execution, icon resources support.
macOS
.app bundle - Apple conventions, notarization available, bundle structure organization.
Linux
Executable + packages - AppImage portable, DEB/RPM packages, standard conventions.
Web
WebAssembly + JS - Browser sandbox, static file serving, progressive web support.
Best Practices and Development Workflow
Larger egui applications benefit from module organization beyond a single main.rs file. Widget implementations, state management, and business logic separation keeps code manageable. State serialization enables application persistence and undo functionality. The eframe framework supports serializing application state for later restoration.
The quick compile times of Rust and egui's simplicity enable rapid iteration. Egui includes built-in debugging features accessible through the top-right menu during development. These tools show layout information, performance metrics, and state inspection. Debug tools speed up interface development significantly. For comprehensive development practices, explore our web development best practices resource.
Egui's default styling provides reasonable accessibility through clear visual feedback. High contrast modes and font size adjustments suit different user needs. Internationalization requires external library support beyond egui's core functionality. Message catalogs and locale-specific formatting integrate with egui's text rendering.
Conclusion and Next Steps
Egui simplifies cross-platform GUI development through immediate mode rendering and a straightforward API. The eframe framework extends egui's capabilities to native and web deployment. This combination enables efficient application development with broad platform support.
Developers new to egui should start with basic widgets and the application structure demonstrated in this guide. Progressive complexity addition helps internalize the framework's patterns. The official examples provide reference implementations for various interface patterns. The same codebase produces native applications and web experiences without platform-specific code changes.
Learning Path
- Start with basic widgets and application structure
- Build complete applications to exercise state management
- Explore framework integration with Tauri or Bevy
- Optimize performance for complex interfaces
- Contribute to egui ecosystem or explore internals
For teams looking to build production applications, our AI automation services can help integrate intelligent features into your cross-platform applications. If you're building enterprise software solutions, our web development expertise can accelerate your project delivery.
Sources
- LogRocket Blog - Building Cross-Platform GUI Apps in Rust Using Egui
- GitHub emilk/egui - Official egui repository with documentation and examples
- whoisryosuke.com - Getting Started with Egui in Rust
- w3resource.com - Rust egui GUI Development Tutorial