From a87f1450e750f4b0cf08510e68be970212fb237a Mon Sep 17 00:00:00 2001
From: Sergey Semushin <predelnik@gmail.com>
Date: Mon, 6 May 2019 02:32:19 +0300
Subject: [PATCH] Add algorithm description comment for DrawLine.

---
 Source/engine.cpp | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/Source/engine.cpp b/Source/engine.cpp
index 3ee5341b8..065c9ea4b 100644
--- a/Source/engine.cpp
+++ b/Source/engine.cpp
@@ -2094,6 +2094,12 @@ void engine_draw_pixel(int sx, int sy)
 // * global variable instead of reverse flag
 // * condition for pixels_left < 0 removed
 
+/*
+Symmetric Double Step Line Algorithm
+by Brian Wyvill
+from "Graphics Gems", Academic Press, 1990
+*/
+
 #define GG_SWAP(A, B) \
 	{                 \
 		(A) ^= (B);   \