SuperLightTUI is an immediate-mode TUI library for Rust with a deliberately small public grammar. You write one closure, SLT calls it every frame, and the library handles layout, focus, diffing, and rendering.

It is designed for fast product iteration, approachable Rust syntax, and serious backend discipline. That makes it work equally well for humans prototyping a tool and for coding agents generating UI from docs.

Showcase

Widget Demo cargo run --example demo	Dashboard cargo run --example demo_dashboard	Website Layout cargo run --example demo_website
Spreadsheet cargo run --example demo_spreadsheet	Games cargo run --example demo_game	DOOM Fire Effect cargo run --release --example demo_fire

Quick Start

cargo add superlighttui

fn main() -> std::io::Result<()> {
    slt::run(|ui: &mut slt::Context| {
        ui.text("hello, world");
    })
}

5 lines. No App trait. No Model/Update/View. No manual event loop. Ctrl+C just works.

60-Second Grammar

There are four ideas most apps start with:

1. State lives in normal Rust variables or structs.
2. Layout is mostly row(), col(), and container().
3. Styling is method chaining.
4. Interactive widgets usually return Response.

ui.bordered(Border::Rounded).title("Status").p(1).gap(1).col(|ui| {
    ui.text("SLT").bold().fg(Color::Cyan);
    ui.row(|ui| {
        ui.text("mode:");
        ui.text("ready").fg(Color::Green);
        ui.spacer();
        if ui.button("Quit").clicked {
            ui.quit();
        }
    });
});

That is the core mental model. Everything else is depth, not a second framework.

A Real App

use slt::{Border, Color, Context, KeyCode};
fn main() -> std::io::Result<()> {
let mut count: i32 = 0;
slt::run(|ui: &amp;mut Context| {
    if ui.key(&#39;q&#39;) {
        ui.quit();
    }
    if ui.key(&#39;k&#39;) || ui.key_code(KeyCode::Up) {
        count += 1;
    }
    if ui.key(&#39;j&#39;) || ui.key_code(KeyCode::Down) {
        count -= 1;
    }

    ui.bordered(Border::Rounded).title(&quot;Counter&quot;).p(1).gap(1).col(|ui| {
        ui.text(&quot;Counter&quot;).bold().fg(Color::Cyan);
        ui.row(|ui| {
            ui.text(&quot;Count:&quot;);
            let color = if count &gt;= 0 { Color::Green } else { Color::Red };
            ui.text(format!(&quot;{count}&quot;)).bold().fg(color);
        });
        ui.text(&quot;k +1 / j -1 / q quit&quot;).dim();
    });
})

}

Why SLT

• Small public grammar. Most screens start with normal Rust state, row() / col() / container(), method chaining, and Response.
• Less framework ceremony. Many apps do not need an app trait, retained tree, or message enum just to get moving.
• Batteries included, backend still serious. Common widgets auto-wire focus, hover, click, and scroll behavior, while the runtime keeps a conservative low-level path through Backend, AppState, and frame().
• Conservative internals. SLT keeps the public surface small, but the internals stay deliberately boring: shared frame kernel, explicit backend contract coverage, zero unsafe, feature-gated runtime paths, and validation across all-features, no-default-features, WASM, clippy, examples, cargo-hack, semver, and deny checks.

For Rust users, that usually means less setup than retained-mode TUI frameworks. For AI-assisted workflows, it means the public grammar is easy to infer from docs and examples.

SLT fits best when you want to build terminal apps quickly without giving up Rust type safety or backend escape hatches. If you want a retained component tree or a GUI-first toolkit, another library may be a better fit.

Common API Surface

// Text and layout
ui.text("Hello").bold().fg(Color::Cyan);
ui.row(|ui| {
    ui.text("left");
    ui.spacer();
    ui.text("right");
});
// Inputs and actions
ui.text_input(&mut name);
if ui.button("Save").clicked {}
ui.checkbox("Dark mode", &mut dark);
// Data and navigation
ui.tabs(&mut tabs);
ui.list(&mut items);
ui.table(&mut data);
ui.command_palette(&mut palette);
// Overlays and rich output
ui.toast(&mut toasts);
ui.modal(|ui| {
ui.text("Confirm?").bold();
});
ui.markdown("# Hello world");
// Visualization
ui.chart(|c| {
c.line(&data);
c.grid(true);
}, 50, 16);
ui.sparkline(&values, 16);
ui.canvas(40, 10, |cv| {
cv.circle(20, 20, 15);
});

For the categorized widget list, see Widget Guide. For composition advice, see Patterns Guide.

Learn The Library

Document	What it covers
Quick Start	Install, first app, closure mental model, layout, widget state
Widget Guide	Complete API catalog of widgets, runtime methods, and state types
Patterns Guide	State placement, screen composition, helper extraction, large-app structure
Examples Guide	Runnable examples grouped by product shape and feature area
Backends Guide	Backend, AppState, frame(), inline mode, static output
Testing Guide	TestBackend, EventBuilder, multi-frame tests, backend contract tests
Debugging Guide	F12 overlay, clipping, focus surprises, previous-frame behavior
AI Guide	Fastest path for AI-assisted builders and coding agents
Architecture Guide	Module map, frame lifecycle, layout/render pipeline
Features Guide	Feature flags, optional dependencies, recommended combos
Animation Guide	Tween, spring, keyframes, sequence, stagger
Theming Guide	Theme struct, presets, ThemeBuilder, custom themes
Design Principles	API constraints and design philosophy

Representative Examples

Example	Command	Focus
hello	cargo run --example hello	Smallest possible app
counter	cargo run --example counter	State + keyboard input
demo	cargo run --example demo	Broad widget tour
demo_dashboard	cargo run --example demo_dashboard	Dashboard layout
demo_cli	cargo run --example demo_cli	CLI tool layout
demo_infoviz	cargo run --example demo_infoviz	Charts and data viz
demo_game	cargo run --example demo_game	Immediate-mode interaction
inline	cargo run --example inline	Inline rendering below a normal prompt
async_demo	cargo run --example async_demo --features async	Background messages

The full categorized index lives in Examples Guide.

Custom Widgets And Backends

• Implement Widget when you want reusable high-level building blocks.
• Implement Backend and drive frame() when you want a non-terminal target, external event loop, or embedded runtime.
• Use TestBackend for headless rendering checks and stable interaction tests.

The public grammar stays small even when you need the escape hatches.

Contributing

Read Contributing, then Design Principles and Architecture Guide. The release process expects format, check, clippy, tests, examples, and backend gates to stay green.

License

MIT