From 7adca2ef1990e07a130b4d438ba386a784289cc8 Mon Sep 17 00:00:00 2001
From: toaster <rollerorbital@gmail.com>
Date: Wed, 7 Sep 2022 13:05:40 +0100
Subject: [PATCH] Fix papersprites being rotated incorrectly in Software when
 viewing them on the flipped side

Rewritten version of STJr/SRB2!1770
---
 src/r_things.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/src/r_things.c b/src/r_things.c
index cc5694dff..97e164a5b 100644
--- a/src/r_things.c
+++ b/src/r_things.c
@@ -1690,8 +1690,14 @@ static void R_ProjectSprite(mobj_t *thing)
 	if (spriterotangle
 	&& !(splat && !(thing->renderflags & RF_NOSPLATROLLANGLE)))
 	{
-		rollangle = R_GetRollAngle(vflip
-				? InvAngle(spriterotangle) : spriterotangle);
+		if ((papersprite && ang >= ANGLE_180) != vflip)
+		{
+			rollangle = R_GetRollAngle(InvAngle(spriterotangle));
+		}
+		else
+		{
+			rollangle = R_GetRollAngle(spriterotangle);
+		}
 		rotsprite = Patch_GetRotatedSprite(sprframe, (thing->frame & FF_FRAMEMASK), rot, flip, false, sprinfo, rollangle);
 
 		if (rotsprite != NULL)