Slint is a toolkit to efficiently develop fluid graphical user interfaces for any display: embedded devices and desktop applications. We support multiple programming languages, such as Rust, C++, and JavaScript. We invite you to use Slint and be part of its community.

Design Goals

We use the following design goals as a guide when developing Slint:

• Scalable: Run on any screen connected to a device, from desktop computers to low end embedded systems.
• Lightweight: Fit into a few hundred kilobytes of RAM and require little processing power.
• Intuitive: Both developers and designers should feel productive and enjoy the design and development process. The APIs should be consistent and easy to use, no matter the target language.
• Native: Slint apps should match the users' expectations of a native application. Various target platforms such as embedded devices, desktops, mobile and web should be supported so that both the user and the developer feel comfortable on their platform of choice.

The .slint Markup Language

Slint comes with a markup language that is specifically designed for user interfaces. This language is easy to learn, to read and write, and provides a powerful way to describe graphical elements, their placement, and the flow of data through the different states. It's a familiar syntax to describe the hierarchy of elements and property bindings.

Here's the obligatory "Hello World":

export component HelloWorld inherits Window {
    width: 400px;
    height: 400px;

    Text {
       y: parent.width / 2;
       x: parent.x + 200px;
       text: "Hello, world";
       color: blue;
    }
}

Current Status

Slint is in active development. The state of the toolkit for each platform is as follows:

• Embedded: Ready Slint is already being used in production projects by customers (running on an Arm processor with Linux).
• Microcontrollers (MCU): Ready. Slint apps can run on MCUs with less than 300K of RAM.
• Desktop: In Progress. While Slint is a good fit on Windows, Linux and Mac, we are working on improving the platform support in subsequent releases.
• Mobile (Android/iOS): Todo. We haven't started supporting mobile platforms yet, but it is our intention to do so in the near future.
• Web: In Progress. Slint apps can be compiled to WebAssembly and can run in a web browser. As there are many other web frameworks, the web platform is not one of our primary target platforms. The web support is currently limited to demo purposes.

Accessibility

Slint supports keyboard based navigation of many widgets, and user interfaces are scalable. The basic infrastructure for assistive technology like screen readers is in place, but currently requires the Qt backend. We're aware that more work is needed to get best-of-class support for users with special needs.

Stay up to date

Follow @slint-ui on Twitter or keep an eye out for our 🥠 Weekly Status Updates.

Documentation

For more details, check out the Slint Language Documentation.

The examples folder contains examples and demos, showing how to use the Slint markup language and how to interact with a Slint user interface from supported programming languages.

The docs folder contains a lot more information, including build instructions, and internal developer docs.

Refer to the README of each language directory in the api folder:

• C++ (Documentation | Tutorial | Getting Started Template)
• Rust (Documentation | Tutorial | Tutorial Video | Getting Started Template)
• JavaScript/NodeJS (Beta) (Documentation | Tutorial | Getting Started Template)

Demos

Embedded

Video of Slint on RaspberryPi

MCU

STM32	RP2040
Video of Slint on STM32	Video of Slint on RP2040

WebAssembly

Printer Demo	Slide Puzzle	Energy Monitor	Widget Gallery

Desktop Native Widgets

Windows	macOS	Linux

Architecture

An application is composed of the business logic written in Rust, C++, or JavaScript and the .slint user interface design markup, which is compiled to native code.

Compiler

The .slint files are compiled ahead of time. The expressions in the .slint are pure functions that the compiler can optimize. For example, the compiler could choose to "inline" properties and remove those that are constant or unchanged. In the future we hope to improve rendering time on low end devices by pre-processing images and text. The compiler could determine that a Text or an Image element is always on top of another Image in the same location. Consequently both elements could be rendered ahead of time into a single element, thus cutting down on rendering time.

The compiler uses the typical compiler phases of lexing, parsing, optimization, and finally code generation. It provides different back-ends for code generation in the target language. The C++ code generator produces a C++ header file, the Rust generator produces Rust code, and so on. An interpreter for dynamic languages is also included.

Runtime

The runtime library consists of an engine that supports properties declared in the .slint language. Components with their elements, items, and properties are laid out in a single memory region, to reduce memory allocations.

Rendering backends and styles are configurable at compile time:

• The femtovg renderer uses OpenGL ES 2.0 for rendering.
• The skia renderer uses Skia for rendering.
• The software renderer uses the CPU with no additional dependencies.
• When Qt is installed on the system, the native style uses Qt's QStyle to achieve native looking widgets.

Tooling

We have a few tools to help with the development of .slint files:

• A LSP Server that adds features like auto-complete and live preview of the .slint files to many editors.
• It is bundled in a Visual Studio Code Extension available from the market place.
• A slint-viewer tool which displays the .slint files. The --auto-reload argument makes it easy to preview your UI while you are working on it (when using the LSP preview is not possible).
• SlintPad, an online editor to try out .slint syntax without installing anything (sources).
• An updater to convert the .slint files from previous versions to newer versions.
• An experimental Figma importer.

Please check our Editors README for tips on how to configure your favorite editor to work well with Slint.

Made with Slint

List of some open source projects using Slint: (Contact us or open a pull request to add yours)

• Cargo UI: A graphical frontend for Cargo.
• ImageSieve : GUI based tool to sort and categorize images.
• Moiré : Musical live performance application with a DAW-like timeline interface.
• Chiptrack: A cross-platform sequencer that internally uses a Game Boy emulator to synthesize the sound. (online demo)
• Project Trains Launcher: Cross-platform game launcher made for Project Trains simulator.
• Mastermind: Mastermind game coded in Rust.
• Tetris: Tetris game coded in Rust. (online demo)
• coop_widgets: Custom widget library for Slint. (online demo)

License

Slint is available under either a proprietary license or GNU GPLv3

The proprietary license is provided free-of-charge in exchange for (1) consent that we can showcase the application, (2) attribution of Slint in the application and (3) feedback to improve Slint. Check out our ambassador program.

See also the Licensing FAQ

Contributions

We welcome your contributions: in the form of code, bug reports or feedback.

• If you see an RFC tag on an issue, feel free to chime in.
• For contribution guidelines see CONTRIBUTING.md. The dual-licensing of Slint requires the contributor to accept our CLA.

Frequently Asked Questions

Please see our separate FAQ.

About us (SixtyFPS GmbH)

We are passionate about software - API design, cross-platform software development and user interface components. Our aim is to make developing user interfaces fun for everyone: from JavaScript, C++, or Rust developers all the way to UI/UX designers. We believe that software grows organically and keeping it open source is the best way to sustain that growth. Our team members are located remotely in Germany.

Contact us

Feel free to join Github discussions for general chat or questions. Use Github issues to report public suggestions or bugs.

We chat in our Mattermost instance where you are welcome to listen in or ask your questions.

You can of course also tweet at @slint-ui or contact us privately via email to info@slint-ui.com.