osteak

Elm Architecture for ratatui. We built this because our TUI kept accumulating state bugs as it grew — booleans disagreeing, async tasks outliving the UI state that spawned them, the usual. TEA fixed it for us. Maybe it helps you too.

You bring the event loop. osteak gives you update, view, and a Cmd type to describe side effects. There's an optional runner if you don't have a loop yet.

Quick Start

cargo add osteak

use osteak::{Tea, Cmd};
use ratatui::Frame;
use ratatui::widgets::Paragraph;

struct Counter { count: i32 }

enum Msg { Increment, Decrement, Quit }

impl Tea for Counter {
    type Msg = Msg;

    fn update(&mut self, msg: Msg) -> Cmd<Msg> {
        match msg {
            Msg::Increment => { self.count += 1; Cmd::dirty() }
            Msg::Decrement => { self.count -= 1; Cmd::dirty() }
            Msg::Quit => Cmd::quit(),
        }
    }

    fn view(&mut self, frame: &mut Frame) {
        let text = format!("Count: {}", self.count);
        frame.render_widget(Paragraph::new(text), frame.area());
    }
}

With the built-in runner

# use osteak::{Tea, Cmd};
# use ratatui::Frame;
# use ratatui::widgets::Paragraph;
# struct Counter { count: i32 }
# enum Msg { Increment, Decrement, Quit }
# impl Tea for Counter {
#     type Msg = Msg;
#     fn update(&mut self, msg: Msg) -> Cmd<Msg> { Cmd::none() }
#     fn view(&mut self, frame: &mut Frame) {}
# }
use crossterm::event::{Event, KeyCode, KeyEventKind};

#[tokio::main]
async fn main() -> std::io::Result<()> {
    osteak::runner::run(Counter { count: 0 }, |ev| {
        let Event::Key(k) = ev else { return None };
        if k.kind != KeyEventKind::Press { return None; }
        match k.code {
            KeyCode::Up => Some(Msg::Increment),
            KeyCode::Down => Some(Msg::Decrement),
            KeyCode::Char('q') => Some(Msg::Quit),
            _ => None,
        }
    }).await
}

Without the runner

Write your own loop — osteak doesn't take control. See examples/counter_manual.rs.

Architecture

    ┌──────────────────────┐
    │    Your Event Loop    │
    │  (or osteak::runner)  │
    └──────┬───────────────┘
           │ Msg
    ┌──────▼───────────────┐
    │   Tea::update(&mut)   │
    │   → Cmd { action,     │
    │         dirty }       │
    └──────┬───────────────┘
           │
  ┌────────┼────────┐
  │        │        │
Task     None     Quit
(you spawn)
  │
  │ Msg (on completion)
  └──────► back to update

Features

Feature	Default	Description
crossterm-backend	yes	Crossterm backend + EventStream
tokio-runtime	yes	Tokio integration for the runner

Just the traits, no runtime:

cargo add osteak --no-default-features

Examples

• counter — with the runner
• counter_manual — hand-written event loop
• async_tasks — Cmd::task + tokio::spawn
• multi_pane — composition with Cmd::map

cargo run --example counter

MSRV

1.86.0 (same as ratatui 0.30).

License

MIT