rs-kilo/src/terminal_helpers.rs

//! # Helpers
//!
//! Various functions calling C wrappers to get/set terminal functionality
use nix::libc::ioctl;
use nix::libc::{c_ushort, STDIN_FILENO, STDOUT_FILENO, TIOCGWINSZ};
use nix::sys::termios;
use nix::sys::termios::{
    ControlFlags, InputFlags, LocalFlags, OutputFlags, SpecialCharacterIndices, Termios,
};
use std::io;
use std::io::prelude::*;
use std::io::BufReader;
use std::os::unix::io::RawFd;
use std::sync::Arc;

#[derive(Debug)]
pub struct TermSize {
    /// number of rows
    pub rows: u16,
    /// number of columns
    pub cols: u16,
}

/// Get a `Termios` struct, for getting/setting terminal flags
pub fn get_termios(fd: RawFd) -> Termios {
    termios::tcgetattr(fd).unwrap()
}

/// Put terminal into raw mode so there is full control of terminal output
pub fn enable_raw_mode() {
    let mut raw = get_termios(STDOUT_FILENO);

    raw.input_flags.remove(
        InputFlags::BRKINT
            | InputFlags::ICRNL
            | InputFlags::INPCK
            | InputFlags::ISTRIP
            | InputFlags::IXON,
    );

    raw.output_flags.remove(OutputFlags::OPOST);

    // 8 bit characters
    raw.control_flags |= ControlFlags::CS8;

    raw.local_flags
        .remove(LocalFlags::ECHO | LocalFlags::ICANON | LocalFlags::IEXTEN | LocalFlags::ISIG);

    raw.control_chars[SpecialCharacterIndices::VMIN as usize] = 0;
    raw.control_chars[SpecialCharacterIndices::VTIME as usize] = 1;

    // Raw mode or bust!
    termios::tcsetattr(STDIN_FILENO, termios::SetArg::TCSAFLUSH, &raw).unwrap();
}

/// Restore terminal to "cooked"/canonical mode
pub fn disable_raw_mode() {
    let mutex = Arc::clone(&super::ORIGINAL_TERMIOS);
    let termios = mutex.lock().unwrap();

    // First attempt to reset terminal settings via a terminal code
    print!("\x1bc");

    // Restore previous terminal settings
    termios::tcsetattr(STDIN_FILENO, termios::SetArg::TCSAFLUSH, &termios).unwrap();
}

/// Attempt to get the size of the terminal (in rows and columns) from an `ioctl` call
#[inline]
pub fn get_term_size() -> Option<TermSize> {
    #[repr(C)]
    #[derive(Debug)]
    struct UnixTermSize {
        /// number of rows
        pub rows: c_ushort,
        /// number of columns
        pub cols: c_ushort,
        x: c_ushort,
        y: c_ushort,
    }

    let raw = UnixTermSize {
        rows: 0,
        cols: 0,
        x: 0,
        y: 0,
    };

    let r = unsafe { ioctl(STDOUT_FILENO, TIOCGWINSZ.into(), &raw) };

    if r == 0 {
        Some(TermSize {
            rows: raw.rows,
            cols: raw.cols,
        })
    } else {
        None
    }
}

/// Get the terminal size, the hard way.
pub fn get_cursor_position() -> TermSize {
    // Ask the shell where the cursor is
    write!(io::stdout(), "\x1b[999C\x1b[999B").unwrap();
    write!(io::stdout(), "\x1b[6n").unwrap();

    // Explicitly flush, so that next input should be the terminal response
    io::stdout().flush().unwrap();

    let mut buffer = vec![];

    let stdin = io::stdin();
    let mut br = BufReader::new(stdin.lock());
    br.read_until('R' as u8, &mut buffer).unwrap();

    let input = String::from_utf8(buffer).unwrap();

    // Parse the escape sequence into a location
    // The escape sequence looks like so: Esc[y;xR
    let mut row_str = String::new();
    let mut col_str = String::new();
    let mut index = 0;
    for ch in input.chars() {
        if ch == '\x1b' || ch == '[' {
            continue;
        }

        match ch {
            ';' => {
                index += 1;
            }
            'R' => break,
            _ => {
                if index == 0 {
                    row_str.push(ch)
                } else {
                    col_str.push(ch)
                }
            }
        }
    }

    let rows = clean_unwrap(row_str.parse());
    let cols = clean_unwrap(col_str.parse());

    return TermSize { cols, rows };
}

/// Do the equivalent of a Result::unwrap, but cleanup terminal output
/// first, so it doesn't destroy console output afterwards.
pub fn clean_unwrap<O, E>(res: Result<O, E>) -> O
where
    E: std::fmt::Debug,
{
    match res {
        Ok(value) => value,
        Err(e) => {
            print!("\x1bc");
            disable_raw_mode();
            panic!("{:?}", e);
        }
    }
}