From 635585dd0990f1d4308f7c412542d4199359a279 Mon Sep 17 00:00:00 2001
From: Joe Ardent <code@ardent.nebcorp.com>
Date: Fri, 5 Sep 2025 15:43:03 -0700
Subject: [PATCH] line drawing works well, room for optimization

---
 src/main.rs  | 25 ++++++++++++++++++-------
 src/point.rs |  4 ++--
 2 files changed, 20 insertions(+), 9 deletions(-)

diff --git a/src/main.rs b/src/main.rs
index 9bfb53a..ee06e20 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -57,13 +57,24 @@ fn main() {
         .unwrap();
 }
 
-fn line(a: Point, b: Point, fb: &mut TGAImage, color: TGAColor) {
-    let mut t = 0.0;
-    let step = 0.02;
-    while t < 1.0 {
-        let x = (a.x as f32 + (b.x - a.x) as f32 * t).round_ties_even() as u32;
+fn line(mut a: Point, mut b: Point, fb: &mut TGAImage, color: TGAColor) {
+    let is_steep = (a.x - b.x).abs() < (a.y - b.y).abs();
+    if is_steep {
+        std::mem::swap(&mut a.x, &mut a.y);
+        std::mem::swap(&mut b.x, &mut b.y);
+    }
+    if a.x > b.x {
+        std::mem::swap(&mut a.x, &mut b.x);
+        std::mem::swap(&mut a.y, &mut b.y);
+    }
+
+    for x in (a.x)..b.x {
+        let t = (x - a.x) as f32 / (b.x - a.x) as f32;
         let y = (a.y as f32 + (b.y - a.y) as f32 * t).round_ties_even() as u32;
-        fb.set(x, y, color);
-        t += step;
+        if is_steep {
+            fb.set(y, x as u32, color);
+        } else {
+            fb.set(x as u32, y, color);
+        }
     }
 }
diff --git a/src/point.rs b/src/point.rs
index 7c51252..fbcc517 100644
--- a/src/point.rs
+++ b/src/point.rs
@@ -31,8 +31,8 @@ impl Sub for Point {
 
     fn sub(self, rhs: Self) -> Self::Output {
         Self {
-            x: self.x.saturating_sub(rhs.x),
-            y: self.y.saturating_sub(rhs.y),
+            x: self.x - rhs.x,
+            y: self.y - rhs.y,
         }
     }
 }