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//! # [Ratatui] Panic Hook 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
//! How to use a panic hook to reset the terminal before printing the panic to
//! the terminal.
//!
//! When exiting normally or when handling `Result::Err`, we can reset the
//! terminal manually at the end of `main` just before we print the error.
//!
//! Because a panic interrupts the normal control flow, manually resetting the
//! terminal at the end of `main` won't do us any good. Instead, we need to
//! make sure to set up a panic hook that first resets the terminal before
//! handling the panic. This both reuses the standard panic hook to ensure a
//! consistent panic handling UX and properly resets the terminal to not
//! distort the output.
//!
//! That's why this example is set up to show both situations, with and without
//! the chained panic hook, to see the difference.
use std::{error::Error, io};
use crossterm::{
event::{self, Event, KeyCode},
terminal::{disable_raw_mode, enable_raw_mode, EnterAlternateScreen, LeaveAlternateScreen},
};
use ratatui::{
prelude::*,
widgets::{Block, Borders, Paragraph},
};
type Result<T> = std::result::Result<T, Box<dyn Error>>;
#[derive(Default)]
struct App {
hook_enabled: bool,
}
impl App {
fn chain_hook(&mut self) {
let original_hook = std::panic::take_hook();
std::panic::set_hook(Box::new(move |panic| {
reset_terminal().unwrap();
original_hook(panic);
}));
self.hook_enabled = true;
}
}
fn main() -> Result<()> {
let mut terminal = init_terminal()?;
let mut app = App::default();
let res = run_tui(&mut terminal, &mut app);
reset_terminal()?;
if let Err(err) = res {
println!("{err:?}");
}
Ok(())
}
/// Initializes the terminal.
fn init_terminal() -> Result<Terminal<CrosstermBackend<io::Stdout>>> {
crossterm::execute!(io::stdout(), EnterAlternateScreen)?;
enable_raw_mode()?;
let backend = CrosstermBackend::new(io::stdout());
let mut terminal = Terminal::new(backend)?;
terminal.hide_cursor()?;
Ok(terminal)
}
/// Resets the terminal.
fn reset_terminal() -> Result<()> {
disable_raw_mode()?;
crossterm::execute!(io::stdout(), LeaveAlternateScreen)?;
Ok(())
}
/// Runs the TUI loop.
fn run_tui<B: Backend>(terminal: &mut Terminal<B>, app: &mut App) -> io::Result<()> {
loop {
terminal.draw(|f| ui(f, app))?;
if let Event::Key(key) = event::read()? {
match key.code {
KeyCode::Char('p') => {
panic!("intentional demo panic");
}
KeyCode::Char('e') => {
app.chain_hook();
}
_ => {
return Ok(());
}
}
}
}
}
/// Render the TUI.
fn ui(f: &mut Frame, app: &App) {
let text = vec![
if app.hook_enabled {
Line::from("HOOK IS CURRENTLY **ENABLED**")
} else {
Line::from("HOOK IS CURRENTLY **DISABLED**")
},
Line::from(""),
Line::from("press `p` to panic"),
Line::from("press `e` to enable the terminal-resetting panic hook"),
Line::from("press any other key to quit without panic"),
Line::from(""),
Line::from("when you panic without the chained hook,"),
Line::from("you will likely have to reset your terminal afterwards"),
Line::from("with the `reset` command"),
Line::from(""),
Line::from("with the chained panic hook enabled,"),
Line::from("you should see the panic report as you would without ratatui"),
Line::from(""),
Line::from("try first without the panic handler to see the difference"),
];
let b = Block::default()
.title("Panic Handler Demo")
.borders(Borders::ALL);
let p = Paragraph::new(text).block(b).centered();
f.render_widget(p, f.size());
}