crossterm.rs

//! This module provides the `CrosstermBackend` implementation for the `Backend` trait.
//! It uses the `crossterm` crate to interact with the terminal.
//!
//!
//! [`Backend`]: trait.Backend.html
//! [`CrosstermBackend`]: struct.CrosstermBackend.html

use std::io::{self, Write};

use crossterm::{
    cursor::{Hide, MoveTo, Show},
    execute, queue,
    style::{
        Attribute as CAttribute, Color as CColor, Print, SetAttribute, SetBackgroundColor,
        SetForegroundColor, SetUnderlineColor,
    },
    terminal::{self, Clear},
};

use crate::{
    backend::{Backend, ClearType, WindowSize},
    buffer::Cell,
    layout::Size,
    prelude::Rect,
    style::{Color, Modifier},
};

/// A backend implementation using the `crossterm` crate.
///
/// The `CrosstermBackend` struct is a wrapper around a type implementing `Write`, which
/// is used to send commands to the terminal. It provides methods for drawing content,
/// manipulating the cursor, and clearing the terminal screen.
///
/// # Example
///
/// ```rust
/// use ratatui::backend::{Backend, CrosstermBackend};
///
/// # fn main() -> Result<(), Box<dyn std::error::Error>> {
/// let buffer = std::io::stdout();
/// let mut backend = CrosstermBackend::new(buffer);
/// backend.clear()?;
/// # Ok(())
/// # }
/// ```
#[derive(Debug, Default, Clone, Eq, PartialEq, Hash)]
pub struct CrosstermBackend<W: Write> {
    buffer: W,
}

impl<W> CrosstermBackend<W>
where
    W: Write,
{
    /// Creates a new `CrosstermBackend` with the given buffer.
    pub fn new(buffer: W) -> CrosstermBackend<W> {
        CrosstermBackend { buffer }
    }
}

impl<W> Write for CrosstermBackend<W>
where
    W: Write,
{
    /// Writes a buffer of bytes to the underlying buffer.
    fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
        self.buffer.write(buf)
    }

    /// Flushes the underlying buffer.
    fn flush(&mut self) -> io::Result<()> {
        self.buffer.flush()
    }
}

impl<W> Backend for CrosstermBackend<W>
where
    W: Write,
{
    fn draw<'a, I>(&mut self, content: I) -> io::Result<()>
    where
        I: Iterator<Item = (u16, u16, &'a Cell)>,
    {
        let mut fg = Color::Reset;
        let mut bg = Color::Reset;
        let mut underline_color = Color::Reset;
        let mut modifier = Modifier::empty();
        let mut last_pos: Option<(u16, u16)> = None;
        for (x, y, cell) in content {
            // Move the cursor if the previous location was not (x - 1, y)
            if !matches!(last_pos, Some(p) if x == p.0 + 1 && y == p.1) {
                queue!(self.buffer, MoveTo(x, y))?;
            }
            last_pos = Some((x, y));
            if cell.modifier != modifier {
                let diff = ModifierDiff {
                    from: modifier,
                    to: cell.modifier,
                };
                diff.queue(&mut self.buffer)?;
                modifier = cell.modifier;
            }
            if cell.fg != fg {
                let color = CColor::from(cell.fg);
                queue!(self.buffer, SetForegroundColor(color))?;
                fg = cell.fg;
            }
            if cell.bg != bg {
                let color = CColor::from(cell.bg);
                queue!(self.buffer, SetBackgroundColor(color))?;
                bg = cell.bg;
            }
            if cell.underline_color != underline_color {
                let color = CColor::from(cell.underline_color);
                queue!(self.buffer, SetUnderlineColor(color))?;
                underline_color = cell.underline_color;
            }

            queue!(self.buffer, Print(&cell.symbol))?;
        }

        queue!(
            self.buffer,
            SetForegroundColor(CColor::Reset),
            SetBackgroundColor(CColor::Reset),
            SetUnderlineColor(CColor::Reset),
            SetAttribute(CAttribute::Reset)
        )
    }

    fn hide_cursor(&mut self) -> io::Result<()> {
        execute!(self.buffer, Hide)
    }

    fn show_cursor(&mut self) -> io::Result<()> {
        execute!(self.buffer, Show)
    }

    fn get_cursor(&mut self) -> io::Result<(u16, u16)> {
        crossterm::cursor::position()
            .map_err(|e| io::Error::new(io::ErrorKind::Other, e.to_string()))
    }

    fn set_cursor(&mut self, x: u16, y: u16) -> io::Result<()> {
        execute!(self.buffer, MoveTo(x, y))
    }

    fn clear(&mut self) -> io::Result<()> {
        self.clear_region(ClearType::All)
    }

    fn clear_region(&mut self, clear_type: ClearType) -> io::Result<()> {
        execute!(
            self.buffer,
            Clear(match clear_type {
                ClearType::All => crossterm::terminal::ClearType::All,
                ClearType::AfterCursor => crossterm::terminal::ClearType::FromCursorDown,
                ClearType::BeforeCursor => crossterm::terminal::ClearType::FromCursorUp,
                ClearType::CurrentLine => crossterm::terminal::ClearType::CurrentLine,
                ClearType::UntilNewLine => crossterm::terminal::ClearType::UntilNewLine,
            })
        )
    }

    fn append_lines(&mut self, n: u16) -> io::Result<()> {
        for _ in 0..n {
            queue!(self.buffer, Print("\n"))?;
        }
        self.buffer.flush()
    }

    fn size(&self) -> io::Result<Rect> {
        let (width, height) = terminal::size()?;
        Ok(Rect::new(0, 0, width, height))
    }

    fn window_size(&mut self) -> Result<WindowSize, io::Error> {
        let crossterm::terminal::WindowSize {
            columns,
            rows,
            width,
            height,
        } = terminal::window_size()?;
        Ok(WindowSize {
            columns_rows: Size {
                width: columns,
                height: rows,
            },
            pixels: Size { width, height },
        })
    }

    fn flush(&mut self) -> io::Result<()> {
        self.buffer.flush()
    }
}

impl From<Color> for CColor {
    fn from(color: Color) -> Self {
        match color {
            Color::Reset => CColor::Reset,
            Color::Black => CColor::Black,
            Color::Red => CColor::DarkRed,
            Color::Green => CColor::DarkGreen,
            Color::Yellow => CColor::DarkYellow,
            Color::Blue => CColor::DarkBlue,
            Color::Magenta => CColor::DarkMagenta,
            Color::Cyan => CColor::DarkCyan,
            Color::Gray => CColor::Grey,
            Color::DarkGray => CColor::DarkGrey,
            Color::LightRed => CColor::Red,
            Color::LightGreen => CColor::Green,
            Color::LightBlue => CColor::Blue,
            Color::LightYellow => CColor::Yellow,
            Color::LightMagenta => CColor::Magenta,
            Color::LightCyan => CColor::Cyan,
            Color::White => CColor::White,
            Color::Indexed(i) => CColor::AnsiValue(i),
            Color::Rgb(r, g, b) => CColor::Rgb { r, g, b },
        }
    }
}

/// The `ModifierDiff` struct is used to calculate the difference between two `Modifier`
/// values. This is useful when updating the terminal display, as it allows for more
/// efficient updates by only sending the necessary changes.
#[derive(Debug, Default, Clone, Copy, Eq, PartialEq, Hash)]
struct ModifierDiff {
    pub from: Modifier,
    pub to: Modifier,
}

impl ModifierDiff {
    fn queue<W>(&self, mut w: W) -> io::Result<()>
    where
        W: io::Write,
    {
        //use crossterm::Attribute;
        let removed = self.from - self.to;
        if removed.contains(Modifier::REVERSED) {
            queue!(w, SetAttribute(CAttribute::NoReverse))?;
        }
        if removed.contains(Modifier::BOLD) {
            queue!(w, SetAttribute(CAttribute::NormalIntensity))?;
            if self.to.contains(Modifier::DIM) {
                queue!(w, SetAttribute(CAttribute::Dim))?;
            }
        }
        if removed.contains(Modifier::ITALIC) {
            queue!(w, SetAttribute(CAttribute::NoItalic))?;
        }
        if removed.contains(Modifier::UNDERLINED) {
            queue!(w, SetAttribute(CAttribute::NoUnderline))?;
        }
        if removed.contains(Modifier::DIM) {
            queue!(w, SetAttribute(CAttribute::NormalIntensity))?;
        }
        if removed.contains(Modifier::CROSSED_OUT) {
            queue!(w, SetAttribute(CAttribute::NotCrossedOut))?;
        }
        if removed.contains(Modifier::SLOW_BLINK) || removed.contains(Modifier::RAPID_BLINK) {
            queue!(w, SetAttribute(CAttribute::NoBlink))?;
        }

        let added = self.to - self.from;
        if added.contains(Modifier::REVERSED) {
            queue!(w, SetAttribute(CAttribute::Reverse))?;
        }
        if added.contains(Modifier::BOLD) {
            queue!(w, SetAttribute(CAttribute::Bold))?;
        }
        if added.contains(Modifier::ITALIC) {
            queue!(w, SetAttribute(CAttribute::Italic))?;
        }
        if added.contains(Modifier::UNDERLINED) {
            queue!(w, SetAttribute(CAttribute::Underlined))?;
        }
        if added.contains(Modifier::DIM) {
            queue!(w, SetAttribute(CAttribute::Dim))?;
        }
        if added.contains(Modifier::CROSSED_OUT) {
            queue!(w, SetAttribute(CAttribute::CrossedOut))?;
        }
        if added.contains(Modifier::SLOW_BLINK) {
            queue!(w, SetAttribute(CAttribute::SlowBlink))?;
        }
        if added.contains(Modifier::RAPID_BLINK) {
            queue!(w, SetAttribute(CAttribute::RapidBlink))?;
        }

        Ok(())
    }
}