2023 ✔ 1.0 · Stable milestone Framework 2026: Stable API, commercially backed

Slint 1.0

A native toolkit that promised API stability.

Slint 1.0 arrived on 3 April 2023, about two and a half years after the first sixtyfps publish. Like Tauri's 1.0 it is a public-API promise: the .slint language and the language bindings will not break within 1.x. Here is the UI, as a separate file in the .slint language.

slint-file/ui/app.slint ✔ compiled · slint 1.18 · rustc 1.95.0

import { Button, VerticalBox } from "std-widgets.slint";

export component App inherits Window {
    in-out property <int> counter: 0;
    callback clicked();

    VerticalBox {
        Text { text: "Clicked \{root.counter} times"; }
        Button { text: "Click me"; clicked => { root.clicked(); } }
    }
}

A build script compiles that file into Rust at build time, and include_modules! makes the generated App type available. You then attach behaviour with generated setters, getters and callbacks. The SixtyFPS-to-Slint page shows the alternative, which embeds the same language in a macro.

slint-file/build.rs ✔ compiled · slint 1.18 · rustc 1.95.0

// Build scripts conventionally return a boxed error: Cargo prints it and fails the build.
fn main() -> Result<(), Box<dyn std::error::Error>> {
    // Compiles ui/app.slint to Rust at build time.
    slint_build::compile("ui/app.slint")?;
    Ok(())
}

slint-file/src/main.rs ✔ compiled · slint 1.18 · rustc 1.95.0

use book_error::Result;

slint::include_modules!();

fn main() -> Result<()> {
    let ui = App::new()?;
    let weak = ui.as_weak();
    ui.on_clicked(move || {
        if let Some(ui) = weak.upgrade() {
            ui.set_counter(ui.get_counter() + 1);
        }
    });
    ui.run()?;
    Ok(())
}

The promise is holding: Slint is at 1.18.1 today, eighteen minor releases after 1.0 and all of them 1.x. Both the file-based project and the macro version compile against 1.18. The cost of the stability is a language and compiler separate from Rust, and a licensing model (GPLv3, royalty-free, or commercial) that you need to read.