From fbab60d89369faa29ee9ac36a39883595a4ea676 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Miloslav=20=C4=8C=C3=AD=C5=BE?= <tastyfish@seznam.cz>
Date: Sat, 1 Jun 2019 17:58:32 +0200
Subject: [PATCH] Fix bug

---
 small3dlib.h | 12 ++++++++----
 testSDL.c    | 20 ++++++++++++++++++++
 2 files changed, 28 insertions(+), 4 deletions(-)

diff --git a/small3dlib.h b/small3dlib.h
index dee5d42..7f18457 100644
--- a/small3dlib.h
+++ b/small3dlib.h
@@ -1485,14 +1485,20 @@ void S3L_drawTriangle(
       }
 
 #if S3L_PERSPECTIVE_CORRECTION == 1
-      S3L_ScreenCoord i = lXClipped - lX;  /* helper var to save one
-                                              substraction in the inner loop */
+      S3L_ScreenCoord i = lXClipped - lX - 1;  /* helper var to save one
+                                                  substraction in the inner
+                                                  loop */
 #endif
 
       // draw the row -- inner loop:
 
       for (S3L_ScreenCoord x = lXClipped; x < rXClipped; ++x)
       {
+#if S3L_PERSPECTIVE_CORRECTION == 1
+        ++i; /* Has to be done here, because the following tests can skip the
+                the rest of the loop. */
+#endif
+
 #if S3L_STENCIL_BUFFER
         if (!S3L_stencilTest(x,p.y))
           continue;
@@ -1531,8 +1537,6 @@ void S3L_drawTriangle(
            (lOverZ - S3L_interpolateFrom0(lOverZ,i,rowLength))
            * p.depth
          ) / S3L_FRACTIONS_PER_UNIT;
-
-        i++;
 #else
         *barycentric0 = S3L_getFastLerpValue(b0FLS);
         *barycentric1 = S3L_getFastLerpValue(b1FLS);
diff --git a/testSDL.c b/testSDL.c
index 0be8351..9ca7109 100644
--- a/testSDL.c
+++ b/testSDL.c
@@ -11,6 +11,7 @@
 
 #define S3L_PERSPECTIVE_CORRECTION 1
 #define S3L_Z_BUFFER 1
+#define S3L_SORT 0
 
 #define S3L_PIXEL_FUNCTION drawPixel
 
@@ -32,6 +33,7 @@ S3L_Scene scene;
 int8_t keys[256];
 
 const uint8_t testTexture[] =
+/*
 {
   2,2,2,0,0,0,2,2,2,2,0,0,0,2,2,2,
   2,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2,
@@ -50,6 +52,24 @@ const uint8_t testTexture[] =
   2,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2,
   2,2,2,0,0,0,2,2,2,2,0,0,0,2,2,2
 };
+*/
+{
+  0,1,2,0,1,2,0,1,2,0,1,2,0,1,2,0,
+  1,2,0,1,2,0,1,2,0,1,2,0,1,2,0,1,
+  2,0,1,2,0,1,2,0,1,2,0,1,2,0,1,2,
+  0,1,2,0,1,2,0,1,2,0,1,2,0,1,2,0,
+  1,2,0,1,2,0,1,2,0,1,2,0,1,2,0,1,
+  2,0,1,2,0,1,2,0,1,2,0,1,2,0,1,2,
+  0,1,2,0,1,2,0,1,2,0,1,2,0,1,2,0,
+  1,2,0,1,2,0,1,2,0,1,2,0,1,2,0,1,
+  2,0,1,2,0,1,2,0,1,2,0,1,2,0,1,2,
+  0,1,2,0,1,2,0,1,2,0,1,2,0,1,2,0,
+  1,2,0,1,2,0,1,2,0,1,2,0,1,2,0,1,
+  2,0,1,2,0,1,2,0,1,2,0,1,2,0,1,2,
+  0,1,2,0,1,2,0,1,2,0,1,2,0,1,2,0,
+  1,2,0,1,2,0,1,2,0,1,2,0,1,2,0,1,
+  2,0,1,2,0,1,2,0,1,2,0,1,2,0,1,2
+};
 
 uint32_t pixels[S3L_RESOLUTION_X * S3L_RESOLUTION_Y];