ratatui/examples/paragraph.rs

//! # [Ratatui] Paragraph 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
//! crates.io, 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]: https://github.com/ratatui-org/ratatui
//! [examples]: https://github.com/ratatui-org/ratatui/blob/main/examples
//! [examples readme]: https://github.com/ratatui-org/ratatui/blob/main/examples/README.md

use std::{
    error::Error,
    io,
    time::{Duration, Instant},
};

use crossterm::{
    event::{self, DisableMouseCapture, EnableMouseCapture, Event, KeyCode},
    execute,
    terminal::{disable_raw_mode, enable_raw_mode, EnterAlternateScreen, LeaveAlternateScreen},
};
use ratatui::{
    prelude::*,
    widgets::{Block, Paragraph, Wrap},
};

struct App {
    scroll: u16,
}

impl App {
    const fn new() -> Self {
        Self { scroll: 0 }
    }

    fn on_tick(&mut self) {
        self.scroll += 1;
        self.scroll %= 10;
    }
}

fn main() -> Result<(), Box<dyn Error>> {
    // setup terminal
    enable_raw_mode()?;
    let mut stdout = io::stdout();
    execute!(stdout, EnterAlternateScreen, EnableMouseCapture)?;
    let backend = CrosstermBackend::new(stdout);
    let mut terminal = Terminal::new(backend)?;

    // create app and run it
    let tick_rate = Duration::from_millis(250);
    let app = App::new();
    let res = run_app(&mut terminal, app, tick_rate);

    // restore terminal
    disable_raw_mode()?;
    execute!(
        terminal.backend_mut(),
        LeaveAlternateScreen,
        DisableMouseCapture
    )?;
    terminal.show_cursor()?;

    if let Err(err) = res {
        println!("{err:?}");
    }

    Ok(())
}

fn run_app<B: Backend>(
    terminal: &mut Terminal<B>,
    mut app: App,
    tick_rate: Duration,
) -> io::Result<()> {
    let mut last_tick = Instant::now();
    loop {
        terminal.draw(|f| ui(f, &app))?;

        let timeout = tick_rate.saturating_sub(last_tick.elapsed());
        if crossterm::event::poll(timeout)? {
            if let Event::Key(key) = event::read()? {
                if key.code == KeyCode::Char('q') {
                    return Ok(());
                }
            }
        }
        if last_tick.elapsed() >= tick_rate {
            app.on_tick();
            last_tick = Instant::now();
        }
    }
}

fn ui(f: &mut Frame, app: &App) {
    let size = f.size();

    // Words made "loooong" to demonstrate line breaking.
    let s = "Veeeeeeeeeeeeeeeery    loooooooooooooooooong   striiiiiiiiiiiiiiiiiiiiiiiiiing.   ";
    let mut long_line = s.repeat(usize::from(size.width) / s.len() + 4);
    long_line.push('\n');

    let block = Block::new().black();
    f.render_widget(block, size);

    let layout = Layout::vertical([Constraint::Ratio(1, 4); 4]).split(size);

    let text = vec![
        Line::from("This is a line "),
        Line::from("This is a line   ".red()),
        Line::from("This is a line".on_blue()),
        Line::from("This is a longer line".crossed_out()),
        Line::from(long_line.on_green()),
        Line::from("This is a line".green().italic()),
        Line::from(vec![
            "Masked text: ".into(),
            Span::styled(
                Masked::new("password", '*'),
                Style::default().fg(Color::Red),
            ),
        ]),
    ];

    let create_block = |title| {
        Block::bordered()
            .style(Style::default().fg(Color::Gray))
            .title(Span::styled(
                title,
                Style::default().add_modifier(Modifier::BOLD),
            ))
    };

    let paragraph = Paragraph::new(text.clone())
        .style(Style::default().fg(Color::Gray))
        .block(create_block("Default alignment (Left), no wrap"));
    f.render_widget(paragraph, layout[0]);

    let paragraph = Paragraph::new(text.clone())
        .style(Style::default().fg(Color::Gray))
        .block(create_block("Default alignment (Left), with wrap"))
        .wrap(Wrap { trim: true });
    f.render_widget(paragraph, layout[1]);

    let paragraph = Paragraph::new(text.clone())
        .style(Style::default().fg(Color::Gray))
        .block(create_block("Right alignment, with wrap"))
        .right_aligned()
        .wrap(Wrap { trim: true });
    f.render_widget(paragraph, layout[2]);

    let paragraph = Paragraph::new(text)
        .style(Style::default().fg(Color::Gray))
        .block(create_block("Center alignment, with wrap, with scroll"))
        .centered()
        .wrap(Wrap { trim: true })
        .scroll((app.scroll, 0));
    f.render_widget(paragraph, layout[3]);
}