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

Documentation

• 📖 The Relm4 book
• 📜 Rust documentation

Dependencies

Relm4 depends on GTK4: How to install GTK4.

Ecosystem

• relm4-macros several macros for declarative UI definitions.
• relm4-components is a collections of reusable components you can easily integrate into your application.
• relm4-template is a starter template for creating Relm4 applications in the Flatpak package format.

To use all features, just add this to your Cargo.toml:

relm4 = "0.5.1"
relm4-components = "0.5.1"

Features

The relm4 crate has four feature flags:

Flag	Purpose
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 the dependencies
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.

Examples

Several example applications are available at examples/.

📸 Screenshots from the example apps

A simple counter app

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

struct App {
    counter: u8,
}

#[derive(Debug)]
enum Msg {
    Increment,
    Decrement,
}

#[relm4::component]
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 {
                    #[watch]
                    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.run::<App>(0);
}

Projects using Relm4

• fm — A small, general-purpose file manager.
• Done - A simple and versatile to do app.
• Reovim - GUI frontend for neovim.
• NixOS Configuration Editor - A graphical configuration editor for NixOS.
• Rhino Setup - Setup wizard for Rolling Rhino

License

Licensed under either of

• Apache License, Version 2.0, (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
• MIT license (LICENSE-MIT or http://opensource.org/licenses/MIT)

at your option.

Contribution

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!