justerm_core/
cursor.rs

1//! The cursor and its drawing pen.
2
3use crate::cell::{Cell, CellFlags};
4use crate::color::Color;
5
6/// The current SGR state — the appearance copied into each printed cell.
7///
8/// Modelling it as a "template cell" mirrors Alacritty: a later slice can make
9/// erase (ED/EL) fill cleared cells with `bg` instead of `Default` and that
10/// *is* Background Color Erase (BCE), no structural change. See `term.rs`.
11#[derive(Clone, Copy, Debug, Default)]
12pub struct Pen {
13    pub fg: Color,
14    pub bg: Color,
15    pub flags: CellFlags,
16    /// The underline colour (SGR 58, #520): what an underline / strikethrough draws
17    /// in, independent of `fg`. `Default` means "follow the fg". It is *not* packed
18    /// into the printed `Cell` (the 12-byte cell is full); the print path stamps a
19    /// non-default value into the row's ucolor map. See `term.rs::write_glyph`.
20    pub underline_color: Color,
21}
22
23impl Pen {
24    /// Reset to default appearance (SGR 0).
25    pub fn reset(&mut self) {
26        *self = Pen::default();
27    }
28
29    /// Build a cell carrying this pen's appearance and the given glyph.
30    pub fn cell(&self, c: char) -> Cell {
31        Cell::from_parts(c, self.fg, self.bg, self.flags)
32    }
33}
34
35/// The cursor's drawn shape (DECSCUSR / the renderer's caret glyph). The engine
36/// reports it on the frame; the renderer draws it. Default `Block` (#81).
37#[derive(Clone, Copy, Debug, PartialEq, Eq, Default)]
38pub enum CursorShape {
39    #[default]
40    Block,
41    Underline,
42    Bar,
43}
44
45/// The input position, its pending-wrap state, and the current pen.
46#[derive(Clone, Copy, Debug)]
47pub struct Cursor {
48    pub row: usize,
49    pub col: usize,
50    /// Deferred last-column wrap (xterm's "wrapnext"). Set when a print fills the
51    /// last column: the cursor stays put and the actual line wrap happens on the
52    /// *next* print. Eager wrapping here is the classic off-by-one that shifts
53    /// lines (see `docs/architecture.md` "Hidden VT state").
54    pub pending_wrap: bool,
55    pub pen: Pen,
56    /// Whether the cursor is shown (DEC ?25). The engine only reports it.
57    pub visible: bool,
58    /// The caret shape (DECSCUSR, #89) — reported on the frame, drawn by the
59    /// renderer.
60    pub shape: CursorShape,
61    /// Whether the caret blinks (att610 ?12, #81). The engine reports the *mode*;
62    /// the actual animation is the renderer's.
63    pub blink: bool,
64}
65
66impl Cursor {
67    /// The cursor's `(row, col)` position.
68    pub(crate) fn point(&self) -> (usize, usize) {
69        (self.row, self.col)
70    }
71
72    /// Set the position, clamped to a `rows` x `cols` screen.
73    pub(crate) fn set_point(&mut self, point: (usize, usize), rows: usize, cols: usize) {
74        self.row = point.0.min(rows - 1);
75        self.col = point.1.min(cols - 1);
76    }
77}
78
79impl Default for Cursor {
80    fn default() -> Self {
81        // The cursor starts visible; a manual impl is needed because `bool`'s
82        // derived default is `false`.
83        Cursor {
84            row: 0,
85            col: 0,
86            pending_wrap: false,
87            pen: Pen::default(),
88            visible: true,
89            shape: CursorShape::Block,
90            blink: false,
91        }
92    }
93}
justerm_core/cursor.rs

justerm_core/
cursor.rs
