tui-rs/src/widgets/canvas/line.rs

use crate::{
    style::Color,
    widgets::canvas::{Painter, Shape},
};

/// Shape to draw a line from (x1, y1) to (x2, y2) with the given color
#[derive(Debug, Clone)]
pub struct Line {
    pub x1: f64,
    pub y1: f64,
    pub x2: f64,
    pub y2: f64,
    pub color: Color,
}

impl Shape for Line {
    fn draw(&self, painter: &mut Painter) {
        let (x1, y1) = match painter.get_point(self.x1, self.y1) {
            Some(c) => c,
            None => return,
        };
        let (x2, y2) = match painter.get_point(self.x2, self.y2) {
            Some(c) => c,
            None => return,
        };
        let (dx, x_range) = if x2 >= x1 {
            (x2 - x1, x1..=x2)
        } else {
            (x1 - x2, x2..=x1)
        };
        let (dy, y_range) = if y2 >= y1 {
            (y2 - y1, y1..=y2)
        } else {
            (y1 - y2, y2..=y1)
        };

        if dx == 0 {
            for y in y_range {
                painter.paint(x1, y, self.color);
            }
        } else if dy == 0 {
            for x in x_range {
                painter.paint(x, y1, self.color);
            }
        } else if dy < dx {
            if x1 > x2 {
                draw_line_low(painter, x2, y2, x1, y1, self.color);
            } else {
                draw_line_low(painter, x1, y1, x2, y2, self.color);
            }
        } else if y1 > y2 {
            draw_line_high(painter, x2, y2, x1, y1, self.color);
        } else {
            draw_line_high(painter, x1, y1, x2, y2, self.color);
        }
    }
}

fn draw_line_low(painter: &mut Painter, x1: usize, y1: usize, x2: usize, y2: usize, color: Color) {
    let dx = (x2 - x1) as isize;
    let dy = (y2 as isize - y1 as isize).abs();
    let mut d = 2 * dy - dx;
    let mut y = y1;
    for x in x1..=x2 {
        painter.paint(x, y, color);
        if d > 0 {
            y = if y1 > y2 {
                y.saturating_sub(1)
            } else {
                y.saturating_add(1)
            };
            d -= 2 * dx;
        }
        d += 2 * dy;
    }
}

fn draw_line_high(painter: &mut Painter, x1: usize, y1: usize, x2: usize, y2: usize, color: Color) {
    let dx = (x2 as isize - x1 as isize).abs();
    let dy = (y2 - y1) as isize;
    let mut d = 2 * dx - dy;
    let mut x = x1;
    for y in y1..=y2 {
        painter.paint(x, y, color);
        if d > 0 {
            x = if x1 > x2 {
                x.saturating_sub(1)
            } else {
                x.saturating_add(1)
            };
            d -= 2 * dy;
        }
        d += 2 * dx;
    }
}