From 3698c2583d36a0d302e2b005cea221d838ad80af Mon Sep 17 00:00:00 2001
From: Monster Iestyn <iestynjealous@ntlworld.com>
Date: Fri, 25 Mar 2016 20:04:49 +0000
Subject: [PATCH] wrap prevention code now takes flipped patches into account

---
 src/v_video.c | 31 ++++++++++++++++++++++---------
 1 file changed, 22 insertions(+), 9 deletions(-)

diff --git a/src/v_video.c b/src/v_video.c
index 3eb71bb0..b9bdb271 100644
--- a/src/v_video.c
+++ b/src/v_video.c
@@ -336,6 +336,8 @@ void V_DrawFixedPatch(fixed_t x, fixed_t y, fixed_t pscale, INT32 scrn, patch_t
 	const column_t *column;
 	UINT8 *desttop, *dest, *deststart, *destend;
 	const UINT8 *source, *deststop;
+	fixed_t pwidth; // patch width
+	fixed_t offx = 0; // x offset
 
 	if (rendermode == render_none)
 		return;
@@ -476,25 +478,36 @@ void V_DrawFixedPatch(fixed_t x, fixed_t y, fixed_t pscale, INT32 scrn, patch_t
 		}
 	}
 
-	deststart = desttop;
 	if (pscale != FRACUNIT) // scale width properly
 	{
-		fixed_t pwidth = SHORT(patch->width)<<FRACBITS;
+		pwidth = SHORT(patch->width)<<FRACBITS;
 		pwidth = FixedMul(pwidth, pscale);
 		pwidth = FixedMul(pwidth, dupx<<FRACBITS);
 		pwidth >>= FRACBITS;
-		destend = desttop + pwidth;
 	}
 	else
-		destend = desttop + SHORT(patch->width) * dupx;
+		pwidth = SHORT(patch->width) * dupx;
 
-	for (col = 0; (col>>FRACBITS) < SHORT(patch->width); col += colfrac, ++x, desttop++)
+	deststart = desttop;
+	destend = desttop + pwidth;
+
+	for (col = 0; (col>>FRACBITS) < SHORT(patch->width); col += colfrac, ++offx, desttop++)
 	{
 		INT32 topdelta, prevdelta = -1;
-		if (x < 0) // don't draw off the left of the screen (WRAP PREVENTION)
-			continue;
-		if (x >= vid.width) // don't draw off the right of the screen (WRAP PREVENTION)
-			break;
+		if (flip) // offx is measured from right edge instead of left
+		{
+			if (x+pwidth-offx < 0) // don't draw off the left of the screen (WRAP PREVENTION)
+				break;
+			if (x+pwidth-offx >= vid.width) // don't draw off the right of the screen (WRAP PREVENTION)
+				continue;
+		}
+		else
+		{
+			if (x+offx < 0) // don't draw off the left of the screen (WRAP PREVENTION)
+				continue;
+			if (x+offx >= vid.width) // don't draw off the right of the screen (WRAP PREVENTION)
+				break;
+		}
 		column = (const column_t *)((const UINT8 *)(patch) + LONG(patch->columnofs[col>>FRACBITS]));
 
 		while (column->topdelta != 0xff)