Start updating line drawing to the approach by Tom Forsynth

For more information check:
https://cohost.org/tomforsyth/post/648716-how-to-draw-ugly-lin

1 files changed, 17 insertions, 5 deletions

diff --git a/src/renderer_m0.c b/src/renderer_m0.c
index 45923e8..94a3d9d 100644
--- a/src/renderer_m0.c
+++ b/src/renderer_m0.c
@@ -184,15 +184,27 @@ draw_line(size_t x0, size_t y0, size_t x1, size_t y1, u8 clr) {
         int x_step = x0 > x1 ? -1 : 1;
         int y_step = y0 > y1 ? -1 : 1;
         if (dx >= dy) {
-            int diff = 2 * dy - dx;
+            // int diff = 2 * dy - dx;
+            // int distance = dx * dy - (y1 - y0) * dx;
+            int distance = (dy - dx) / 2;
             for (int i = 0; i < dx + 1; i++) {
-                draw_pixel(x0, y0, clr);
-                if (diff >= 0) {
-                    diff -= 2 * dx;
+                // Previous implementation (Tom Forsyth).
+                if (distance > dx / 2) {
+                    distance -= dx;
                     y0 += y_step;
                 }
-                diff += 2 * dy;
+                draw_pixel(x0, y0, clr);
+                distance += dy;
                 x0 += x_step;
+
+                // Previous implementation, slightly faster.
+                // draw_pixel(x0, y0, clr);
+                // if (diff >= 0) {
+                //     diff -= 2 * dx;
+                //     y0 += y_step;
+                // }
+                // diff += 2 * dy;
+                // x0 += x_step;
             }
         } else {
             int diff = 2 * dx - dy;