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Hello World

Demonstrates a basic hello world app.

git clone --branch latest
cd ratatui
cargo run --example=hello_world --features=crossterm

//! # [Ratatui] Hello World example
//! The latest version of this example is available in the [examples] folder in the repository.
//! Please note that the examples are designed to be run against the `main` branch of the Github
//! repository. This means that you may not be able to compile with the latest release version on
//!, or the one that you have installed locally.
//! See the [examples readme] for more information on finding examples that match the version of the
//! library you are using.
//! [Ratatui]:
//! [examples]:
//! [examples readme]:
use std::{
io::{self, Stdout},
use anyhow::{Context, Result};
use crossterm::{
event::{self, Event, KeyCode},
terminal::{disable_raw_mode, enable_raw_mode, EnterAlternateScreen, LeaveAlternateScreen},
use ratatui::{prelude::*, widgets::Paragraph};
/// This is a bare minimum example. There are many approaches to running an application loop, so
/// this is not meant to be prescriptive. It is only meant to demonstrate the basic setup and
/// teardown of a terminal application.
/// A more robust application would probably want to handle errors and ensure that the terminal is
/// restored to a sane state before exiting. This example does not do that. It also does not handle
/// events or update the application state. It just draws a greeting and exits when the user
/// presses 'q'.
fn main() -> Result<()> {
let mut terminal = setup_terminal().context("setup failed")?;
run(&mut terminal).context("app loop failed")?;
restore_terminal(&mut terminal).context("restore terminal failed")?;
/// Setup the terminal. This is where you would enable raw mode, enter the alternate screen, and
/// hide the cursor. This example does not handle errors. A more robust application would probably
/// want to handle errors and ensure that the terminal is restored to a sane state before exiting.
fn setup_terminal() -> Result<Terminal<CrosstermBackend<Stdout>>> {
let mut stdout = io::stdout();
enable_raw_mode().context("failed to enable raw mode")?;
execute!(stdout, EnterAlternateScreen).context("unable to enter alternate screen")?;
Terminal::new(CrosstermBackend::new(stdout)).context("creating terminal failed")
/// Restore the terminal. This is where you disable raw mode, leave the alternate screen, and show
/// the cursor.
fn restore_terminal(terminal: &mut Terminal<CrosstermBackend<Stdout>>) -> Result<()> {
disable_raw_mode().context("failed to disable raw mode")?;
execute!(terminal.backend_mut(), LeaveAlternateScreen)
.context("unable to switch to main screen")?;
terminal.show_cursor().context("unable to show cursor")
/// Run the application loop. This is where you would handle events and update the application
/// state. This example exits when the user presses 'q'. Other styles of application loops are
/// possible, for example, you could have multiple application states and switch between them based
/// on events, or you could have a single application state and update it based on events.
fn run(terminal: &mut Terminal<CrosstermBackend<Stdout>>) -> Result<()> {
loop {
if should_quit()? {
/// Render the application. This is where you would draw the application UI. This example just
/// draws a greeting.
fn render_app(frame: &mut Frame) {
let greeting = Paragraph::new("Hello World! (press 'q' to quit)");
frame.render_widget(greeting, frame.size());
/// Check if the user has pressed 'q'. This is where you would handle events. This example just
/// checks if the user has pressed 'q' and returns true if they have. It does not handle any other
/// events. There is a 250ms timeout on the event poll so that the application can exit in a timely
/// manner, and to ensure that the terminal is rendered at least once every 250ms.
fn should_quit() -> Result<bool> {
if event::poll(Duration::from_millis(250)).context("event poll failed")? {
if let Event::Key(key) = event::read().context("event read failed")? {
return Ok(KeyCode::Char('q') == key.code);