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use crate::{GlyphRegistry, Style};
use unicode_segmentation::UnicodeSegmentation;
#[derive(Debug, Clone, PartialEq, Eq)]
pub enum Cell {
Empty,
Glyph {
grapheme: String,
style: Style,
},
/// Placeholder cell occupied by the trailing half of a width=2 glyph.
Continuation,
}
impl Cell {
pub fn is_continuation(&self) -> bool {
matches!(self, Cell::Continuation)
}
}
#[derive(Debug, Clone, PartialEq, Eq)]
pub struct Grid {
pub width: u16,
pub height: u16,
cells: Vec<Cell>,
}
impl Grid {
pub fn new(width: u16, height: u16) -> Self {
let len = width as usize * height as usize;
Self {
width,
height,
cells: vec![Cell::Empty; len],
}
}
pub fn clear(&mut self) {
for c in &mut self.cells {
*c = Cell::Empty;
}
}
pub fn get(&self, x: u16, y: u16) -> Option<&Cell> {
let idx = self.idx(x, y)?;
self.cells.get(idx)
}
pub fn set(&mut self, x: u16, y: u16, cell: Cell) {
if let Some(idx) = self.idx(x, y) {
self.cells[idx] = cell;
}
}
pub fn idx(&self, x: u16, y: u16) -> Option<usize> {
if x >= self.width || y >= self.height {
return None;
}
Some(y as usize * self.width as usize + x as usize)
}
fn clear_overlaps_at(&mut self, x: u16, y: u16, reg: &GlyphRegistry) {
let here = self.get(x, y).cloned();
// If we're overwriting the trailing half of a wide glyph, clear the leading half too.
if matches!(here, Some(Cell::Continuation)) {
self.set(x, y, Cell::Empty);
if x > 0 {
if let Some(Cell::Glyph { grapheme, .. }) = self.get(x - 1, y).cloned() {
if reg.width(&grapheme) == 2 {
self.set(x - 1, y, Cell::Empty);
}
}
}
return;
}
// If we're overwriting the leading half of a wide glyph, clear its continuation.
if let Some(Cell::Glyph { grapheme, .. }) = here {
if reg.width(&grapheme) == 2
&& x + 1 < self.width
&& matches!(self.get(x + 1, y), Some(Cell::Continuation))
{
self.set(x + 1, y, Cell::Empty);
}
}
// If the cell to our left is a wide glyph but we are not its continuation, clear it.
if x > 0 {
if let Some(Cell::Glyph { grapheme, .. }) = self.get(x - 1, y).cloned() {
if reg.width(&grapheme) == 2 && !matches!(self.get(x, y), Some(Cell::Continuation))
{
self.set(x - 1, y, Cell::Empty);
}
}
}
}
/// Places `text` starting at (`x`, `y`) using the registry for width policy.
///
/// This function is newline-agnostic: `\n` will stop placement.
/// Returns the next x position after the last placed glyph.
pub fn put_text(
&mut self,
mut x: u16,
y: u16,
text: &str,
style: Style,
reg: &GlyphRegistry,
) -> u16 {
if y >= self.height {
return x;
}
for g in UnicodeSegmentation::graphemes(text, true) {
if g == "\n" || g == "\r" {
break;
}
let w = reg.width(g);
if x >= self.width {
break;
}
// Avoid placing half of a wide glyph at the right edge.
if w == 2 && x + 1 >= self.width {
break;
}
// Maintain wide-glyph invariants when overwriting.
self.clear_overlaps_at(x, y, reg);
if w == 2 {
self.clear_overlaps_at(x + 1, y, reg);
}
self.set(
x,
y,
Cell::Glyph {
grapheme: g.to_string(),
style,
},
);
if w == 2 {
self.set(x + 1, y, Cell::Continuation);
x = x.saturating_add(2);
} else {
x = x.saturating_add(1);
}
}
x
}
pub fn rows(&self) -> impl Iterator<Item = &[Cell]> {
self.cells.chunks(self.width as usize)
}
}
#[derive(Debug, Clone, PartialEq, Eq)]
pub enum InvariantError {
ContinuationAtColumn0 { y: u16 },
OrphanContinuation { x: u16, y: u16 },
MissingContinuationHalf { x: u16, y: u16 },
}
impl Grid {
/// Validate internal grid invariants.
///
/// This is intended for tests and debug builds. Production callers can
/// enable it via the `debug-validate` feature.
pub fn validate_invariants(&self, reg: &GlyphRegistry) -> Result<(), InvariantError> {
for y in 0..self.height {
for x in 0..self.width {
let c = self.get(x, y).expect("in-bounds");
match c {
Cell::Continuation => {
if x == 0 {
return Err(InvariantError::ContinuationAtColumn0 { y });
}
let prev = self.get(x - 1, y).expect("in-bounds");
match prev {
Cell::Glyph { grapheme, .. } => {
if reg.width(grapheme) != 2 {
return Err(InvariantError::OrphanContinuation { x, y });
}
}
_ => return Err(InvariantError::OrphanContinuation { x, y }),
}
}
Cell::Glyph { grapheme, .. } => {
if reg.width(grapheme) == 2 {
if x + 1 >= self.width {
// A width=2 glyph must never be placed half-visible.
return Err(InvariantError::MissingContinuationHalf { x, y });
}
let next = self.get(x + 1, y).expect("in-bounds");
if !matches!(next, Cell::Continuation) {
return Err(InvariantError::MissingContinuationHalf { x, y });
}
}
}
Cell::Empty => {}
}
}
}
Ok(())
}
}