current line.rs

    pub fn draw_line(&mut self, p0: &Point, p1: &Point) {
        if p0.y == p1.y {
            return;
        }
        let (dir, p0, p1) = if p0.y < p1.y {
            (1.0, p0, p1)
        } else {
            (-1.0, p1, p0)
        };
        let dxdy = (p1.x - p0.x) / (p1.y - p0.y);
        let mut x = p0.x;
        let y0 = p0.y as usize;
        if p0.y < 0.0 {
            x -= p0.y * dxdy;
        }
        for y in y0..min(self.h, p1.y.ceil() as usize) {
            let linestart = (y * self.w) as i32;
            let dy = ((y + 1) as f32).min(p1.y) - (y as f32).max(p0.y);
            let xnext = x + dxdy * dy;
            let d = dy * dir;
            let (x0, x1) = if x < xnext {
                (x, xnext)
            } else {
                (xnext, x)
            };
            let x0floor = x0.floor();
            let x0i = x0floor as i32;
            let x1ceil = x1.ceil();
            let x1i = x1ceil as i32;
            if x1i <= x0i + 1 {
                let xmf = 0.5 * (x + xnext) - x0floor;
                self.add(linestart + x0i, d - d * xmf);
                self.add(linestart + x0i + 1, d * xmf);
            } else {
                let s = (x1 - x0).recip();
                let x0f = x0 - x0floor;
                let a0 = 0.5 * s * (1.0 - x0f) * (1.0 - x0f);
                let x1f = x1 - x1ceil + 1.0;
                let am = 0.5 * s * x1f * x1f;
                self.add(linestart + x0i, d * a0);
                if x1i == x0i + 2 {
                    self.add(linestart + x0i + 1, d * (1.0 - a0 - am));
                } else {
                    let a1 = s * (1.5 - x0f);
                    self.add(linestart + x0i + 1, d * (a1 - a0));
                    for xi in x0i + 2..x1i - 1 {
                        self.add(linestart + xi, d * s);
                    }
                    let a2 = a1 + (x1i - x0i - 3) as f32 * s;
                    self.add(linestart + x1i - 1, d * (1.0 - a2 - am));
                }
                self.add(linestart + x1i, d * am);
            }
            x = xnext;
        }
    }

new line.rs

fn line(x0: f32, y0: f32, x1: f32, y1: f32) {
    if y0 == y1 {
        // Doesn't matter rn.
        return;
    }
    // x0 == x1 does matter but w/e right now
    let dx = x1 - x0;
    let dy = y1 - y0;
    let (mut px, sx) = if dx < 0.0 {
        (x0.floor(), -1.0)
    } else {
        (x0.floor() + 1.0, 1.0)
    };
    let (mut py, sy) = if dy < 0.0 {
        (y0.floor(), -1.0)
    } else {
        (y0.floor() + 1.0, 1.0)
    };
    let mut dist = (x1 as i32 - x0 as i32).abs() + (y1 as i32 - y0 as i32).abs();
    println!("dx {} dy {} dist {}", dx, dy, dist);
    let xb = 1.0 / (x1 - x0);
    let yb = 1.0 / (y1 - y0);
    let xc = -x0 * xb;
    let yc = -y0 * yb;
    let mut x = x0;
    let mut y = y0;
    println!("S ({}, {})", x0, y0);
    while dist > 0 {
        dist -= 1;
        let tx = px * xb + xc;
        let ty = py * yb + yc;
        if tx < ty {
            x = px;
            y = tx * dy + y0;
            px += sx;
            println!("X ({}, {})", x, y);
        } else {
            x = ty * dx + x0;
            y = py;
            py += sy;
            println!("Y ({}, {})", x, y);
        }
    }
    println!("E ({}, {})", x1, y1);
}