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 and Rust

Ecosystem

• relm4-macros - several macros for declarative UI definitions.
• relm4-components - a collections of reusable components.
• relm4-icons - icons for your application.
• relm4-template - a starter template for creating Relm4 applications in the Flatpak package format.
• relm4-snippets - code snippets to speed up your development.

Use this in to your Cargo.toml:

```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"] } ```

Features

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.

Examples

Several example applications are available at examples/.

📸 Screenshots from the example apps

A simple counter app

```rust 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::(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
• Lemoa - Desktop client for Lemmy

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!