From 932fcaabc84870b5a24dc6b3dd54392977e832ca Mon Sep 17 00:00:00 2001
From: Fabian Greffrath <fabian@greffrath.com>
Date: Tue, 12 Dec 2023 13:35:17 +0100
Subject: [PATCH] fix non-power-of-two wide sky textures (#1323)

---
 src/r_data.c  | 17 +++++++++++++++++
 src/r_data.h  |  1 +
 src/r_plane.c |  2 +-
 3 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/src/r_data.c b/src/r_data.c
index 48183116..bc20306c 100644
--- a/src/r_data.c
+++ b/src/r_data.c
@@ -504,6 +504,23 @@ byte *R_GetColumnMod(int tex, int col)
   return texturecomposite[tex] + ofs;
 }
 
+// [FG] wrapping column getter function for non-power-of-two wide sky textures
+byte *R_GetColumnMod2(int tex, int col)
+{
+  int ofs;
+
+  while (col < 0)
+    col += texturewidth[tex];
+
+  col %= texturewidth[tex];
+  ofs  = texturecolumnofs2[tex][col];
+
+  if (!texturecomposite2[tex])
+    R_GenerateComposite(tex);
+
+  return texturecomposite2[tex] + ofs;
+}
+
 //
 // R_InitTextures
 // Initializes the texture list
diff --git a/src/r_data.h b/src/r_data.h
index 98c89b04..556c872b 100644
--- a/src/r_data.h
+++ b/src/r_data.h
@@ -31,6 +31,7 @@
 // Retrieve column data for span blitting.
 byte *R_GetColumn(int tex, int col);
 byte *R_GetColumnMod(int tex, int col);
+byte *R_GetColumnMod2(int tex, int col);
 
 // I/O, setting up the stuff.
 void R_InitData (void);
diff --git a/src/r_plane.c b/src/r_plane.c
index f8cdc25a..8d1728f4 100644
--- a/src/r_plane.c
+++ b/src/r_plane.c
@@ -423,7 +423,7 @@ static void do_draw_plane(visplane_t *pl)
         for (x = pl->minx; (dc_x = x) <= pl->maxx; x++)
           if ((dc_yl = pl->top[x]) != USHRT_MAX && dc_yl <= (dc_yh = pl->bottom[x]))
             {
-              dc_source = R_GetColumnMod(texture, ((an + xtoskyangle[x])^flip) >>
+              dc_source = R_GetColumnMod2(texture, ((an + xtoskyangle[x])^flip) >>
 				         ANGLETOSKYSHIFT);
               colfunc();
             }