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Ratatui

main.rs

Putting it all together, we have the main.rs function:

/// Application.
pub mod app;


/// Terminal events handler.
pub mod event;


/// Widget renderer.
pub mod ui;


/// Terminal user interface.
pub mod tui;


/// Application updater.
pub mod update;
use app::App;
use color_eyre::Result;
use event::{Event, EventHandler};
use ratatui::{backend::CrosstermBackend, Terminal};
use tui::Tui;
use update::update;


fn main() -> Result<()> {
    // Create an application.
    let mut app = App::new();


    // Initialize the terminal user interface.
    let backend = CrosstermBackend::new(std::io::stderr());
    let terminal = Terminal::new(backend)?;
    let events = EventHandler::new(250);
    let mut tui = Tui::new(terminal, events);
    tui.enter()?;


    // Start the main loop.
    while !app.should_quit {
        // Render the user interface.
        tui.draw(&mut app)?;
        // Handle events.
        match tui.events.next()? {
            Event::Tick => {}
            Event::Key(key_event) => update(&mut app, key_event),
            Event::Mouse(_) => {}
            Event::Resize(_, _) => {}
        };
    }


    // Exit the user interface.
    tui.exit()?;
    Ok(())
}

Because we call tui.events.next() in a loop, it blocks until there’s an event generated. If there’s a key press, the state updates and the UI is refreshed. If there’s no key press, a Tick event is generated every 250 milliseconds, which causes the UI to be refreshed.

This is what it looks like in practice to:

  • Run the TUI
  • Wait 2.5 seconds
  • Press j 5 times
  • Wait 2.5 seconds
  • Press k 5 times
  • Wait 2.5 seconds
  • Press q

Counter app demo

You can find the full source code for this multiple files tutorial here: https://github.com/ratatui-org/website/tree/main/code/ratatui-counter-app.