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//! The terminal itself: raw mode, the alternate screen, and the diff that
//! turns a grid of cells into the fewest escape sequences that will do.
//!
//! Everything above this file paints into a [`Screen`] and never writes a byte,
//! which is what makes the widget layer testable. This is the one place that
//! knows a TTY exists, and it is behind the `terminal` feature so a build for a
//! machine with no terminal crate at all still has the tree and the layout.
use std::io::{self, Stdout, Write};
use crossterm::event::{
DisableMouseCapture, EnableMouseCapture, Event, KeyEventKind, MouseButton, MouseEventKind,
};
use crossterm::terminal::{
disable_raw_mode, enable_raw_mode, EnterAlternateScreen, LeaveAlternateScreen,
};
use crossterm::{cursor, execute, queue, style};
use crate::keys;
use crate::screen::{attr, Color, Screen, Style};
/// One thing that happened, in the vocabulary [`crate::ui::Ui`] takes.
#[derive(Clone, Debug, PartialEq, Eq)]
pub enum Input {
Key(String),
Click(u16, u16),
Wheel(u16, u16, i32),
Resize(u16, u16),
}
pub struct Term {
out: Stdout,
/// What is on the screen now, so a frame only sends what changed.
last: Screen,
mouse: bool,
}
impl Term {
/// Take the terminal: raw mode, the alternate screen, mouse reporting, and
/// no cursor until a focused entry asks for one.
pub fn open(mouse: bool) -> io::Result<Self> {
let (w, h) = crossterm::terminal::size().unwrap_or((80, 24));
let mut out = io::stdout();
enable_raw_mode()?;
execute!(out, EnterAlternateScreen, cursor::Hide)?;
if mouse {
execute!(out, EnableMouseCapture)?;
}
Ok(Self {
out,
last: Screen::new(w, h),
mouse,
})
}
pub fn size(&self) -> (u16, u16) {
crossterm::terminal::size().unwrap_or((80, 24))
}
/// Give the terminal back. Called from `tui_close`, and again from a panic
/// hook — leaving a shell in raw mode with no cursor is the one failure a
/// TUI must not have.
pub fn close(&mut self) {
if self.mouse {
let _ = execute!(self.out, DisableMouseCapture);
}
let _ = execute!(self.out, cursor::Show, LeaveAlternateScreen);
let _ = disable_raw_mode();
}
/// Wait up to `timeout_ms` for input and answer everything that had
/// arrived. A zero timeout is a poll.
pub fn poll(&mut self, timeout_ms: u64) -> Vec<Input> {
let mut out = Vec::new();
let deadline = std::time::Duration::from_millis(timeout_ms);
if !crossterm::event::poll(deadline).unwrap_or(false) {
return out;
}
// Drain what is queued rather than one event a call: a held arrow key
// or a paste arrives as a burst, and handling one per frame would make
// the UI lag behind the keyboard.
loop {
match crossterm::event::read() {
Ok(Event::Key(key)) => {
// Windows reports both press and release; a release would
// type every character twice.
if key.kind != KeyEventKind::Release {
if let Some(name) = keys::name(key) {
out.push(Input::Key(name));
}
}
}
Ok(Event::Resize(w, h)) => out.push(Input::Resize(w, h)),
Ok(Event::Mouse(mouse)) => match mouse.kind {
MouseEventKind::Down(MouseButton::Left) => {
out.push(Input::Click(mouse.column, mouse.row))
}
MouseEventKind::ScrollDown => {
out.push(Input::Wheel(mouse.column, mouse.row, 1))
}
MouseEventKind::ScrollUp => out.push(Input::Wheel(mouse.column, mouse.row, -1)),
_ => {}
},
Ok(_) => {}
Err(_) => break,
}
if !crossterm::event::poll(std::time::Duration::ZERO).unwrap_or(false) {
break;
}
}
out
}
/// Send whatever differs between `screen` and what is already up there.
pub fn flush(&mut self, screen: &Screen, cursor: Option<(u16, u16)>) -> io::Result<()> {
if (self.last.width(), self.last.height()) != (screen.width(), screen.height()) {
self.last = Screen::new(screen.width(), screen.height());
queue!(
self.out,
crossterm::terminal::Clear(crossterm::terminal::ClearType::All)
)?;
}
let mut style = None;
let mut at: Option<(u16, u16)> = None;
let width = screen.width();
for (i, cell) in screen.cells().iter().enumerate() {
let (x, y) = ((i as u16) % width, (i as u16) / width);
if self.last.cell(x, y) == Some(cell) {
continue;
}
// Only move when the run breaks: a full-width change is one seek
// and a line of text, not a seek a cell.
if at != Some((x, y)) {
queue!(self.out, cursor::MoveTo(x, y))?;
}
if style != Some(cell.style) {
write_style(&mut self.out, cell.style)?;
style = Some(cell.style);
}
queue!(self.out, style::Print(cell.ch))?;
at = Some((x + 1, y));
}
queue!(self.out, style::ResetColor)?;
match cursor {
Some((x, y)) => queue!(self.out, cursor::MoveTo(x, y), cursor::Show)?,
None => queue!(self.out, cursor::Hide)?,
}
self.out.flush()?;
self.last = screen.clone();
Ok(())
}
}
impl Drop for Term {
fn drop(&mut self) {
self.close();
}
}
fn convert(color: Color) -> style::Color {
match color {
Color::Default => style::Color::Reset,
// The terminal downgrades the 256-colour palette itself, which is the
// only place that knows how many colours it really has.
Color::Indexed(i) => style::Color::AnsiValue(i),
Color::Rgb(r, g, b) => style::Color::Rgb { r, g, b },
}
}
fn write_style(out: &mut Stdout, style: Style) -> io::Result<()> {
use style::Attribute;
queue!(out, style::SetAttribute(Attribute::Reset))?;
for (bit, on) in [
(attr::BOLD, Attribute::Bold),
(attr::DIM, Attribute::Dim),
(attr::UNDERLINE, Attribute::Underlined),
(attr::REVERSE, Attribute::Reverse),
(attr::BLINK, Attribute::SlowBlink),
(attr::ITALIC, Attribute::Italic),
] {
if style.has(bit) {
queue!(out, style::SetAttribute(on))?;
}
}
queue!(
out,
style::SetForegroundColor(convert(style.fg)),
style::SetBackgroundColor(convert(style.bg))
)
}
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