relm4 0.6.2

An idiomatic GUI library inspired by Elm and based on gtk4-rs

CI Matrix Relm4 on Relm4 docs Relm4 book Minimum Rust version 1.65 dependency status

An idiomatic GUI library inspired by Elm and based on gtk4-rs. Relm4 is a new version of relm that's built from scratch and is compatible with GTK4 and libadwaita.

Why Relm4

We believe that GUI development should be easy, productive and delightful.
The gtk4-rs crate already provides everything you need to write modern, beautiful and cross-platform applications. Built on top of this foundation, Relm4 makes developing more idiomatic, simpler and faster and enables you to become productive in just a few hours.

Our goals

  • ⏱️ Productivity
  • Simplicity
  • 📎 Outstanding documentation
  • 🔧 Maintainability



Relm4 depends on GTK4: How to install GTK4 and Rust


Use this in to your Cargo.toml:

# Core library
relm4 = "0.6.2"
# Optional: reusable components
relm4-components = "0.6.2"
# Optional: icons
relm4-icons = { version = "0.6.0", features = ["plus"] }


The relm4 crate has four feature flags:

Flag Purpose Default
macros Enable macros by re-exporting relm4-macros
libadwaita Improved support for libadwaita -
libpanel Improved support for libpanel -
dox Linking to the underlying C libraries is skipped to allow building the docs without dependencies -
gnome_44 Enable all version feature flags of all dependencies to match the GNOME 44 SDK -
gnome_43 Enable all version feature flags of all dependencies to match the GNOME 43 SDK -
gnome_42 Enable all version feature flags of all dependencies to match the GNOME 42 SDK -

The macros feature is a default feature.


Several example applications are available at examples/.

📸 Screenshots from the example apps

A simple counter app

Simple app screenshot light Simple app screenshot dark

use gtk::prelude::*;
use relm4::prelude::*;

struct App {
    counter: u8,

enum Msg {

impl SimpleComponent for App {
    type Init = u8;
    type Input = Msg;
    type Output = ();

    view! {
        gtk::Window {
            set_title: Some("Simple app"),
            set_default_size: (300, 100),

            gtk::Box {
                set_orientation: gtk::Orientation::Vertical,
                set_spacing: 5,
                set_margin_all: 5,

                gtk::Button {
                    set_label: "Increment",
                    connect_clicked => Msg::Increment,

                gtk::Button {
                    set_label: "Decrement",
                    connect_clicked => Msg::Decrement,

                gtk::Label {
                    set_label: &format!("Counter: {}", model.counter),
                    set_margin_all: 5,

    // Initialize the component.
    fn init(
        counter: Self::Init,
        root: &Self::Root,
        sender: ComponentSender<Self>,
    ) -> ComponentParts<Self> {
        let model = App { counter };

        // Insert the code generation of the view! macro here
        let widgets = view_output!();

        ComponentParts { model, widgets }

    fn update(&mut self, msg: Self::Input, _sender: ComponentSender<Self>) {
        match msg {
            Msg::Increment => {
                self.counter = self.counter.wrapping_add(1);
            Msg::Decrement => {
                self.counter = self.counter.wrapping_sub(1);

fn main() {
    let app = RelmApp::new("relm4.example.simple");<App>(0);

Projects using Relm4


Licensed under either of

at your option.


Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.

Feedback and contributions are highly appreciated!