custom_widget.rs

use crossterm::{
    event::{self, DisableMouseCapture, EnableMouseCapture, Event, KeyCode},
    execute,
    terminal::{disable_raw_mode, enable_raw_mode, EnterAlternateScreen, LeaveAlternateScreen},
};
use std::{error::Error, io};
use tui::{
    backend::{Backend, CrosstermBackend},
    buffer::Buffer,
    layout::Rect,
    style::Style,
    widgets::Widget,
    Frame, Terminal,
};

#[derive(Default)]
struct Label<'a> {
    text: &'a str,
}

impl<'a> Widget for Label<'a> {
    fn render(self, area: Rect, buf: &mut Buffer) {
        buf.set_string(area.left(), area.top(), self.text, Style::default());
    }
}

impl<'a> Label<'a> {
    fn text(mut self, text: &'a str) -> Label<'a> {
        self.text = text;
        self
    }
}

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 res = run_app(&mut terminal);

    // 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>) -> io::Result<()> {
    loop {
        terminal.draw(ui)?;

        if let Event::Key(key) = event::read()? {
            if let KeyCode::Char('q') = key.code {
                return Ok(());
            }
        }
    }
}

fn ui<B: Backend>(f: &mut Frame<B>) {
    let size = f.size();
    let label = Label::default().text("Test");
    f.render_widget(label, size);
}