Vendor ratatui temporarily (#835)

* Vendor ratatui temporarily

Once https://github.com/tui-rs-revival/ratatui/pull/114 has been merged,
we can undo this! But otherwise we can't publish to crates.io with a git
dependency.

* make tests pass

* Shush.

* these literally just fail in nix, nowhere else

idk how to work with nix properly, and they're also not our tests

1 files changed, 487 insertions, 0 deletions

diff --git a/src/ratatui/terminal.rs b/src/ratatui/terminal.rs
new file mode 100644
index 00000000..32accffa
--- /dev/null
+++ b/src/ratatui/terminal.rs
@@ -0,0 +1,487 @@
+use crate::ratatui::{
+    backend::{Backend, ClearType},
+    buffer::Buffer,
+    layout::Rect,
+    widgets::{StatefulWidget, Widget},
+};
+use std::io;
+
+#[derive(Debug, Clone, PartialEq)]
+pub enum Viewport {
+    Fullscreen,
+    Inline(u16),
+    Fixed(Rect),
+}
+
+impl Viewport {
+    pub fn fixed(area: Rect) -> Viewport {
+        Self::Fixed(area)
+    }
+}
+
+#[derive(Debug, Clone, PartialEq)]
+/// Options to pass to [`Terminal::with_options`]
+pub struct TerminalOptions {
+    /// Viewport used to draw to the terminal
+    pub viewport: Viewport,
+}
+
+/// Interface to the terminal backed by Termion
+#[derive(Debug)]
+pub struct Terminal<B>
+where
+    B: Backend,
+{
+    backend: B,
+    /// Holds the results of the current and previous draw calls. The two are compared at the end
+    /// of each draw pass to output the necessary updates to the terminal
+    buffers: [Buffer; 2],
+    /// Index of the current buffer in the previous array
+    current: usize,
+    /// Whether the cursor is currently hidden
+    hidden_cursor: bool,
+    /// Viewport
+    viewport: Viewport,
+    viewport_area: Rect,
+    /// Last known size of the terminal. Used to detect if the internal buffers have to be resized.
+    last_known_size: Rect,
+    /// Last known position of the cursor. Used to find the new area when the viewport is inlined
+    /// and the terminal resized.
+    last_known_cursor_pos: (u16, u16),
+}
+
+/// Represents a consistent terminal interface for rendering.
+pub struct Frame<'a, B: 'a>
+where
+    B: Backend,
+{
+    terminal: &'a mut Terminal<B>,
+
+    /// Where should the cursor be after drawing this frame?
+    ///
+    /// If `None`, the cursor is hidden and its position is controlled by the backend. If `Some((x,
+    /// y))`, the cursor is shown and placed at `(x, y)` after the call to `Terminal::draw()`.
+    cursor_position: Option<(u16, u16)>,
+}
+
+impl<'a, B> Frame<'a, B>
+where
+    B: Backend,
+{
+    /// Frame size, guaranteed not to change when rendering.
+    pub fn size(&self) -> Rect {
+        self.terminal.viewport_area
+    }
+
+    /// Render a [`Widget`] to the current buffer using [`Widget::render`].
+    ///
+    /// # Examples
+    ///
+    /// ```rust
+    /// # use ratatui::Terminal;
+    /// # use ratatui::backend::TestBackend;
+    /// # use ratatui::layout::Rect;
+    /// # use ratatui::widgets::Block;
+    /// # let backend = TestBackend::new(5, 5);
+    /// # let mut terminal = Terminal::new(backend).unwrap();
+    /// let block = Block::default();
+    /// let area = Rect::new(0, 0, 5, 5);
+    /// let mut frame = terminal.get_frame();
+    /// frame.render_widget(block, area);
+    /// ```
+    pub fn render_widget<W>(&mut self, widget: W, area: Rect)
+    where
+        W: Widget,
+    {
+        widget.render(area, self.terminal.current_buffer_mut());
+    }
+
+    /// Render a [`StatefulWidget`] to the current buffer using [`StatefulWidget::render`].
+    ///
+    /// The last argument should be an instance of the [`StatefulWidget::State`] associated to the
+    /// given [`StatefulWidget`].
+    ///
+    /// # Examples
+    ///
+    /// ```rust
+    /// # use ratatui::Terminal;
+    /// # use ratatui::backend::TestBackend;
+    /// # use ratatui::layout::Rect;
+    /// # use ratatui::widgets::{List, ListItem, ListState};
+    /// # let backend = TestBackend::new(5, 5);
+    /// # let mut terminal = Terminal::new(backend).unwrap();
+    /// let mut state = ListState::default();
+    /// state.select(Some(1));
+    /// let items = vec![
+    ///     ListItem::new("Item 1"),
+    ///     ListItem::new("Item 2"),
+    /// ];
+    /// let list = List::new(items);
+    /// let area = Rect::new(0, 0, 5, 5);
+    /// let mut frame = terminal.get_frame();
+    /// frame.render_stateful_widget(list, area, &mut state);
+    /// ```
+    pub fn render_stateful_widget<W>(&mut self, widget: W, area: Rect, state: &mut W::State)
+    where
+        W: StatefulWidget,
+    {
+        widget.render(area, self.terminal.current_buffer_mut(), state);
+    }
+
+    /// After drawing this frame, make the cursor visible and put it at the specified (x, y)
+    /// coordinates. If this method is not called, the cursor will be hidden.
+    ///
+    /// Note that this will interfere with calls to `Terminal::hide_cursor()`,
+    /// `Terminal::show_cursor()`, and `Terminal::set_cursor()`. Pick one of the APIs and stick
+    /// with it.
+    pub fn set_cursor(&mut self, x: u16, y: u16) {
+        self.cursor_position = Some((x, y));
+    }
+}
+
+/// CompletedFrame represents the state of the terminal after all changes performed in the last
+/// [`Terminal::draw`] call have been applied. Therefore, it is only valid until the next call to
+/// [`Terminal::draw`].
+pub struct CompletedFrame<'a> {
+    pub buffer: &'a Buffer,
+    pub area: Rect,
+}
+
+impl<B> Drop for Terminal<B>
+where
+    B: Backend,
+{
+    fn drop(&mut self) {
+        // Attempt to restore the cursor state
+        if self.hidden_cursor {
+            if let Err(err) = self.show_cursor() {
+                eprintln!("Failed to show the cursor: {}", err);
+            }
+        }
+    }
+}
+
+impl<B> Terminal<B>
+where
+    B: Backend,
+{
+    /// Wrapper around Terminal initialization. Each buffer is initialized with a blank string and
+    /// default colors for the foreground and the background
+    pub fn new(backend: B) -> io::Result<Terminal<B>> {
+        Terminal::with_options(
+            backend,
+            TerminalOptions {
+                viewport: Viewport::Fullscreen,
+            },
+        )
+    }
+
+    pub fn with_options(mut backend: B, options: TerminalOptions) -> io::Result<Terminal<B>> {
+        let size = match options.viewport {
+            Viewport::Fullscreen | Viewport::Inline(_) => backend.size()?,
+            Viewport::Fixed(area) => area,
+        };
+        let (viewport_area, cursor_pos) = match options.viewport {
+            Viewport::Fullscreen => (size, (0, 0)),
+            Viewport::Inline(height) => compute_inline_size(&mut backend, height, size, 0)?,
+            Viewport::Fixed(area) => (area, (area.left(), area.top())),
+        };
+        Ok(Terminal {
+            backend,
+            buffers: [Buffer::empty(viewport_area), Buffer::empty(viewport_area)],
+            current: 0,
+            hidden_cursor: false,
+            viewport: options.viewport,
+            viewport_area,
+            last_known_size: size,
+            last_known_cursor_pos: cursor_pos,
+        })
+    }
+
+    /// Get a Frame object which provides a consistent view into the terminal state for rendering.
+    pub fn get_frame(&mut self) -> Frame<B> {
+        Frame {
+            terminal: self,
+            cursor_position: None,
+        }
+    }
+
+    pub fn current_buffer_mut(&mut self) -> &mut Buffer {
+        &mut self.buffers[self.current]
+    }
+
+    pub fn backend(&self) -> &B {
+        &self.backend
+    }
+
+    pub fn backend_mut(&mut self) -> &mut B {
+        &mut self.backend
+    }
+
+    /// Obtains a difference between the previous and the current buffer and passes it to the
+    /// current backend for drawing.
+    pub fn flush(&mut self) -> io::Result<()> {
+        let previous_buffer = &self.buffers[1 - self.current];
+        let current_buffer = &self.buffers[self.current];
+        let updates = previous_buffer.diff(current_buffer);
+        if let Some((col, row, _)) = updates.last() {
+            self.last_known_cursor_pos = (*col, *row);
+        }
+        self.backend.draw(updates.into_iter())
+    }
+
+    /// Updates the Terminal so that internal buffers match the requested size. Requested size will
+    /// be saved so the size can remain consistent when rendering.
+    /// This leads to a full clear of the screen.
+    pub fn resize(&mut self, size: Rect) -> io::Result<()> {
+        let next_area = match self.viewport {
+            Viewport::Fullscreen => size,
+            Viewport::Inline(height) => {
+                let offset_in_previous_viewport = self
+                    .last_known_cursor_pos
+                    .1
+                    .saturating_sub(self.viewport_area.top());
+                compute_inline_size(&mut self.backend, height, size, offset_in_previous_viewport)?.0
+            }
+            Viewport::Fixed(area) => area,
+        };
+        self.set_viewport_area(next_area);
+        self.clear()?;
+
+        self.last_known_size = size;
+        Ok(())
+    }
+
+    fn set_viewport_area(&mut self, area: Rect) {
+        self.buffers[self.current].resize(area);
+        self.buffers[1 - self.current].resize(area);
+        self.viewport_area = area;
+    }
+
+    /// Queries the backend for size and resizes if it doesn't match the previous size.
+    pub fn autoresize(&mut self) -> io::Result<()> {
+        // fixed viewports do not get autoresized
+        if matches!(self.viewport, Viewport::Fullscreen | Viewport::Inline(_)) {
+            let size = self.size()?;
+            if size != self.last_known_size {
+                self.resize(size)?;
+            }
+        };
+        Ok(())
+    }
+
+    /// Synchronizes terminal size, calls the rendering closure, flushes the current internal state
+    /// and prepares for the next draw call.
+    pub fn draw<F>(&mut self, f: F) -> io::Result<CompletedFrame>
+    where
+        F: FnOnce(&mut Frame<B>),
+    {
+        // Autoresize - otherwise we get glitches if shrinking or potential desync between widgets
+        // and the terminal (if growing), which may OOB.
+        self.autoresize()?;
+
+        let mut frame = self.get_frame();
+        f(&mut frame);
+        // We can't change the cursor position right away because we have to flush the frame to
+        // stdout first. But we also can't keep the frame around, since it holds a &mut to
+        // Terminal. Thus, we're taking the important data out of the Frame and dropping it.
+        let cursor_position = frame.cursor_position;
+
+        // Draw to stdout
+        self.flush()?;
+
+        match cursor_position {
+            None => self.hide_cursor()?,
+            Some((x, y)) => {
+                self.show_cursor()?;
+                self.set_cursor(x, y)?;
+            }
+        }
+
+        // Swap buffers
+        self.buffers[1 - self.current].reset();
+        self.current = 1 - self.current;
+
+        // Flush
+        self.backend.flush()?;
+
+        Ok(CompletedFrame {
+            buffer: &self.buffers[1 - self.current],
+            area: self.last_known_size,
+        })
+    }
+
+    pub fn hide_cursor(&mut self) -> io::Result<()> {
+        self.backend.hide_cursor()?;
+        self.hidden_cursor = true;
+        Ok(())
+    }
+
+    pub fn show_cursor(&mut self) -> io::Result<()> {
+        self.backend.show_cursor()?;
+        self.hidden_cursor = false;
+        Ok(())
+    }
+
+    pub fn get_cursor(&mut self) -> io::Result<(u16, u16)> {
+        self.backend.get_cursor()
+    }
+
+    pub fn set_cursor(&mut self, x: u16, y: u16) -> io::Result<()> {
+        self.backend.set_cursor(x, y)?;
+        self.last_known_cursor_pos = (x, y);
+        Ok(())
+    }
+
+    /// Clear the terminal and force a full redraw on the next draw call.
+    pub fn clear(&mut self) -> io::Result<()> {
+        match self.viewport {
+            Viewport::Fullscreen => self.backend.clear_region(ClearType::All)?,
+            Viewport::Inline(_) => {
+                self.backend
+                    .set_cursor(self.viewport_area.left(), self.viewport_area.top())?;
+                self.backend.clear_region(ClearType::AfterCursor)?;
+            }
+            Viewport::Fixed(area) => {
+                for row in area.top()..area.bottom() {
+                    self.backend.set_cursor(0, row)?;
+                    self.backend.clear_region(ClearType::AfterCursor)?;
+                }
+            }
+        }
+        // Reset the back buffer to make sure the next update will redraw everything.
+        self.buffers[1 - self.current].reset();
+        Ok(())
+    }
+
+    /// Queries the real size of the backend.
+    pub fn size(&self) -> io::Result<Rect> {
+        self.backend.size()
+    }
+
+    /// Insert some content before the current inline viewport. This has no effect when the
+    /// viewport is fullscreen.
+    ///
+    /// This function scrolls down the current viewport by the given height. The newly freed space is
+    /// then made available to the `draw_fn` closure through a writable `Buffer`.
+    ///
+    /// Before:
+    /// ```ignore
+    /// +-------------------+
+    /// |                   |
+    /// |      viewport     |
+    /// |                   |
+    /// +-------------------+
+    /// ```
+    ///
+    /// After:
+    /// ```ignore
+    /// +-------------------+
+    /// |      buffer       |
+    /// +-------------------+
+    /// +-------------------+
+    /// |                   |
+    /// |      viewport     |
+    /// |                   |
+    /// +-------------------+
+    /// ```
+    ///
+    /// # Examples
+    ///
+    /// ## Insert a single line before the current viewport
+    ///
+    /// ```rust
+    /// # use ratatui::widgets::{Paragraph, Widget};
+    /// # use ratatui::text::{Spans, Span};
+    /// # use ratatui::style::{Color, Style};
+    /// # use ratatui::{Terminal};
+    /// # use ratatui::backend::TestBackend;
+    /// # let backend = TestBackend::new(10, 10);
+    /// # let mut terminal = Terminal::new(backend).unwrap();
+    /// terminal.insert_before(1, |buf| {
+    ///     Paragraph::new(Spans::from(vec![
+    ///         Span::raw("This line will be added "),
+    ///         Span::styled("before", Style::default().fg(Color::Blue)),
+    ///         Span::raw(" the current viewport")
+    ///     ])).render(buf.area, buf);
+    /// });
+    /// ```
+    pub fn insert_before<F>(&mut self, height: u16, draw_fn: F) -> io::Result<()>
+    where
+        F: FnOnce(&mut Buffer),
+    {
+        if !matches!(self.viewport, Viewport::Inline(_)) {
+            return Ok(());
+        }
+
+        self.clear()?;
+        let height = height.min(self.last_known_size.height);
+        self.backend.append_lines(height)?;
+        let missing_lines =
+            height.saturating_sub(self.last_known_size.bottom() - self.viewport_area.top());
+        let area = Rect {
+            x: self.viewport_area.left(),
+            y: self.viewport_area.top().saturating_sub(missing_lines),
+            width: self.viewport_area.width,
+            height,
+        };
+        let mut buffer = Buffer::empty(area);
+
+        draw_fn(&mut buffer);
+
+        let iter = buffer.content.iter().enumerate().map(|(i, c)| {
+            let (x, y) = buffer.pos_of(i);
+            (x, y, c)
+        });
+        self.backend.draw(iter)?;
+        self.backend.flush()?;
+
+        let remaining_lines = self.last_known_size.height - area.bottom();
+        let missing_lines = self.viewport_area.height.saturating_sub(remaining_lines);
+        self.backend.append_lines(self.viewport_area.height)?;
+
+        self.set_viewport_area(Rect {
+            x: area.left(),
+            y: area.bottom().saturating_sub(missing_lines),
+            width: area.width,
+            height: self.viewport_area.height,
+        });
+
+        Ok(())
+    }
+}
+
+fn compute_inline_size<B: Backend>(
+    backend: &mut B,
+    height: u16,
+    size: Rect,
+    offset_in_previous_viewport: u16,
+) -> io::Result<(Rect, (u16, u16))> {
+    let pos = backend.get_cursor()?;
+    let mut row = pos.1;
+
+    let max_height = size.height.min(height);
+
+    let lines_after_cursor = height
+        .saturating_sub(offset_in_previous_viewport)
+        .saturating_sub(1);
+
+    backend.append_lines(lines_after_cursor)?;
+
+    let available_lines = size.height.saturating_sub(row).saturating_sub(1);
+    let missing_lines = lines_after_cursor.saturating_sub(available_lines);
+    if missing_lines > 0 {
+        row = row.saturating_sub(missing_lines);
+    }
+    row = row.saturating_sub(offset_in_previous_viewport);
+
+    Ok((
+        Rect {
+            x: 0,
+            y: row,
+            width: size.width,
+            height: max_height,
+        },
+        pos,
+    ))
+}