Crate slint

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This crate is the main entry point for embedding user interfaces designed with Slint UI in Rust programs.

If you are new to Slint, start with the Walk-through tutorial. If you are already familiar with Slint, the following topics provide related information.

How to use this crate:

Designs of user interfaces are described in the .slint design markup language. There are three ways of including them in Rust:

With the first two methods, the markup code is translated to Rust code and each component is turned into a Rust struct with functions. Use these functions to instantiate and show the component, and to access declared properties. Check out our sample component for more information about the generation functions and how to use them.

The .slint code in a macro

This method combines your Rust code with the .slint design markup in one file, using a macro:

    HelloWorld := Window {
        Text {
            text: "hello world";
            color: green;
fn main() {

The .slint code in external files is compiled with build.rs

When your design becomes bigger in terms of markup code, you may want move it to a dedicated .slint file. It’s also possible to split a .slint file into multiple files using modules. Use a build script to compile your main .slint file:

In your Cargo.toml add a build assignment and use the slint-build crate in build-dependencies:

build = "build.rs"
edition = "2021"

slint = "0.2.1"

slint-build = "0.2.1"

Use the API of the slint-build crate in the build.rs file:

fn main() {

Finally, use the include_modules! macro in your main.rs:

fn main() {

The cargo-generate tool is a great tool to up and running quickly with a new Rust project. You can use it in combination with our Template Repository to create a skeleton file hierarchy that uses this method:

cargo install cargo-generate
cargo generate --git https://github.com/slint-ui/slint-rust-template

Generated components

Currently, only the last component in a .slint source file is mapped to a Rust structure that be instantiated. We are tracking the resolution of this limitation in https://github.com/slint-ui/slint/issues/784.

The component is generated and re-exported to the location of the include_modules! or slint! macro. It is represented as a struct with the same name as the component.

For example, if you have

export MyComponent := Window { /*...*/ }

in the .slint file, it will create a

struct MyComponent{ /*...*/ }

See also our sample component for more information about the API of the generated struct.

A component is instantiated using the fn new() -> Self function. The following convenience functions are available through the ComponentHandle implementation:

For each top-level property

For each top-level callback

Note: All dashes (-) are replaced by underscores (_) in names of types or functions.

After instantiating the component, call ComponentHandle::run() on show it on the screen and spin the event loop to react to input events. To show multiple components simultaneously, call ComponentHandle::show() on each instance. Call run_event_loop() when you’re ready to enter the event loop.

The generated component struct acts as a handle holding a strong reference (similar to an Rc). The Clone trait is not implemented. Instead you need to make explicit ComponentHandle::clone_strong and ComponentHandle::as_weak calls. A strong reference should not be captured by the closures given to a callback, as this would produce a reference loop and leak the component. Instead, the callback function should capture a weak component.

Threading and Event-loop

For platform-specific reasons, the event loop must run in the main thread, in most backends, and all the components must be created in the same thread as the thread the event loop is running or is going to run.

You should perform the minimum amount of work in the main thread and delegate the actual logic to another thread to avoid blocking animations. Use the invoke_from_event_loop function to communicate from your worker thread to the UI thread.

To run a function with a delay or with an interval use a Timer.

Type Mappings

The types used for properties in .slint design markup each translate to specific types in Rust. The follow table summarizes the entire mapping:

.slint TypeRust TypeNote
stringSharedStringA reference-counted string type that can be easily converted to a str reference.
physical_lengthf32The unit are physical pixels.
lengthf32At run-time, logical lengths are automatically translated to physical pixels using the device pixel ratio.
durationi64At run-time, durations are always represented as signed 64-bit integers with millisecond precision.
anglef32The value in degrees
structurestruct of the same name

For user defined structures in the .slint, an extra struct is generated. For example, if the .slint contains

export struct MyStruct := {
    foo: int,
    bar: string,

The following struct would be generated:

#[derive(Default, Clone, Debug, PartialEq)]
struct MyStruct {
    foo : i32,
    bar: slint::SharedString,

Exported Global singletons

When you export a global singleton from the main file, it is also generated with the exported name. Like the main component, the generated struct have inherent method to access the properties and callback:

For each property

  • A setter: fn set_<property_name>(&self, value: <PropertyType>)
  • A getter: fn get_<property_name>(&self) -> <PropertyType>

For each callback

  • fn invoke_<callback_name>(&self, <CallbackArgs>) -> <ReturnValue> to invoke the callback
  • fn on_<callback_name>(&self, callback: impl Fn(<CallbackArgs>) + 'static) to set the callback handler.

The global can be accessed with the ComponentHandle::global() function, or with Global::get()

See the documentation of the Global trait for an example.

Feature flags

  • compat-0-2-0 (enabled by default) — Mandatory feature: This feature is required to keep the compatibility with Slint 0.2.0 Newer patch version may put current functionality behind a new feature that would be enabled by default only if this feature was added

  • std (enabled by default) — Enable use of the Rust standard library.


  • backend-qt (enabled by default) — The Qt backend feature uses Qt for the windowing system integration and rendering. This backend is required to use the native style. It requires Qt 5.15 or later to be installed. If Qt is not installed, the backend will not be operational

  • backend-gl-all (enabled by default) — The GL backend uses the winit crate for the windowing system integration, and the femtovg crate for the rendering. With this feature, all windowing systems are supported. For a smaller build, omit this feature and select one of the other specific backend-gl-XX features.

  • backend-gl-x11 — Simliar to backend-gl-all this enables the GL backend but only with support for the X Window System on Unix.

  • backend-gl-wayland — Simliar to backend-gl-all this enables the GL backend but only with support for the Wayland window system on Unix.


This is a pseudo module which only exist for documentation purposes as a way to show the Slint documentation as part of rustdoc.

This module contains functions useful for unit tests


Include the code generated with the slint-build crate from the build script. After calling slint_build::compile in your build.rs build script, the use of this macro includes the generated Rust code and makes the exported types available for you to instantiate.

This macro allows you to use the .slint design markup language inline in Rust code. Within the braces of the macro you can use place .slint code and the named exported components will be available for instantiation.


Color represents a color in the Slint run-time, represented using 8-bit channels for red, green, blue and the alpha (opacity). It can be conveniently converted using the to_ and from_ (a)rgb helper functions:

An image type that can be displayed by the Image element. You can construct Image objects from a path to an image file on disk, using Self::load_from_path.

Error generated if an image cannot be loaded for any reasons.

Dispatch notifications from a Model to one or several ModelPeer. Typically, you would want to put this in the implementation of the Model

Represent a handle to a view that listens to changes to a model.

A Reference counted Model.

RgbaColor stores the red, green, blue and alpha components of a color with the precision of the generic parameter T. For example if T is f32, the values are normalized between 0 and 1. If T is u8, they values range is 0 to 255. This is merely a helper class for use with Color.

SharedPixelBuffer is a container for storing image data as pixels. It is internally reference counted and cheap to clone.

A string type used by the Slint run-time.

SharedVector holds a reference-counted read-only copy of [T].

Represent an item in a StandardListView

Timer is a handle to the timer system that allows triggering a callback to be called after a specified period of time.

A model backed by a Vec<T>

Struct that’s used to hold weak references of a Slint component

This type represents a window towards the windowing system, that’s used to render the scene of a component. It provides API to control windowing system specific aspects such as the position on the screen.


A brush is a data structure that is used to describe how a shape, such as a rectangle, path or even text, shall be filled. A brush can also be applied to the outline of a shape, that means the fill of the outline itself.

This enum describes a low-level access to specific graphics APIs used by the renderer.

This enum describes the different rendering states, that will be provided to the parameter of the callback for set_rendering_notifier on the slint::Window.

This enum describes the different error scenarios that may occur when the applicaton registers a rendering notifier on a crate::Window.

The TimerMode specifies what should happen after the timer fired.


This trait describes the common public API of a strongly referenced Slint component. It allows creating strongly-referenced clones, a conversion into/ a weak pointer as well as other convenience functions.

This trait is used to obtain references to global singletons exported in .slint markup. Alternatively, you can use ComponentHandle::global to obtain access.

A Model is providing Data for the Repeater or ListView elements of the .slint language

This trait defines the interface that users of a model can use to track changes to a model. It is supplied via Model::model_tracker and implementation usually return a reference to its field of ModelNotify.

Internal trait that’s used to map rendering state callbacks to either a Rust-API provided impl FnMut or a struct that invokes a C callback and implements Drop to release the closure on the C++ side.


Adds the specified function to an internal queue, notifies the event loop to wake up. Once woken up, any queued up functors will be invoked.

Schedules the main event loop for termination. This function is meant to be called from callbacks triggered by the UI. After calling the function, it will return immediately and once control is passed back to the event loop, the initial call to run_event_loop() will return.

Enters the main event loop. This is necessary in order to receive events from the windowing system in order to render to the screen and react to user input.

Type Definitions

Convenience alias for a pixel with three color channels (red, green and blue), each encoded as u8.

Convenience alias for a pixel with four color channels (red, green, blue and alpha), each encoded as u8.