From 166fafd71708553539c753783b924496387ba4d0 Mon Sep 17 00:00:00 2001
From: Monster Iestyn <iestynjealous@ntlworld.com>
Date: Sat, 6 Feb 2016 18:57:26 +0000
Subject: [PATCH] Fixed div-by-zero crash relating to portals, drawsegs and
 midtextures

Had to remove Red's scale hack in order to do so, because it utterly fails when the drawseg doesn't actually belong to the portal in the first place.
---
 src/r_bsp.c    |  4 +++-
 src/r_bsp.h    |  1 +
 src/r_defs.h   |  2 ++
 src/r_main.c   | 11 +----------
 src/r_segs.c   |  5 +++++
 src/r_things.c |  3 +++
 6 files changed, 15 insertions(+), 11 deletions(-)

diff --git a/src/r_bsp.c b/src/r_bsp.c
index c87d8baa7..52be9a0e3 100644
--- a/src/r_bsp.c
+++ b/src/r_bsp.c
@@ -26,6 +26,7 @@ side_t *sidedef;
 line_t *linedef;
 sector_t *frontsector;
 sector_t *backsector;
+boolean portalline; // is curline a portal seg?
 
 // very ugly realloc() of drawsegs at run-time, I upped it to 512
 // instead of 256.. and someone managed to send me a level with
@@ -378,6 +379,7 @@ static void R_AddLine(seg_t *line)
 		return;
 
 	curline = line;
+	portalline = false;
 
 	// OPTIMIZE: quickly reject orthogonal back sides.
 	angle1 = R_PointToAngle(line->v1->x, line->v1->y);
@@ -431,7 +433,7 @@ static void R_AddLine(seg_t *line)
 	backsector = line->backsector;
 
 	// Portal line
-	if (line->linedef->special == 40 && P_PointOnLineSide(viewx, viewy, line->linedef) == 0)
+	if (line->linedef->special == 40 && line->side == 0)
 	{
 		if (portalrender < cv_maxportals.value)
 		{
diff --git a/src/r_bsp.h b/src/r_bsp.h
index 14b11ea77..3d0429fec 100644
--- a/src/r_bsp.h
+++ b/src/r_bsp.h
@@ -23,6 +23,7 @@ extern side_t *sidedef;
 extern line_t *linedef;
 extern sector_t *frontsector;
 extern sector_t *backsector;
+extern boolean portalline; // is curline a portal seg?
 
 // drawsegs are allocated on the fly... see r_segs.c
 
diff --git a/src/r_defs.h b/src/r_defs.h
index f18410fe8..a982a598b 100644
--- a/src/r_defs.h
+++ b/src/r_defs.h
@@ -675,6 +675,8 @@ typedef struct drawseg_s
 	INT32 numthicksides;
 	fixed_t frontscale[MAXVIDWIDTH];
 
+	UINT8 portalpass; // if > 0 and == portalrender, do not clip sprites
+
 #ifdef ESLOPE
 	fixed_t maskedtextureheight[MAXVIDWIDTH]; // For handling sloped midtextures
 
diff --git a/src/r_main.c b/src/r_main.c
index ccaa14b8e..a6b13302e 100644
--- a/src/r_main.c
+++ b/src/r_main.c
@@ -91,7 +91,6 @@ typedef struct portal_pair
 	INT16 *ceilingclip;
 	INT16 *floorclip;
 	fixed_t *frontscale;
-	size_t seg;
 } portal_pair;
 portal_pair *portal_base, *portal_cap;
 line_t *portalclipline;
@@ -1230,7 +1229,7 @@ void R_AddPortal(INT32 line1, INT32 line2, INT32 x1, INT32 x2)
 	portal->start = x1;
 	portal->end = x2;
 
-	portal->seg = ds_p-drawsegs;
+	portalline = true; // this tells R_StoreWallRange that curline is a portal seg
 
 	portal->viewx = viewx;
 	portal->viewy = viewy;
@@ -1344,14 +1343,6 @@ void R_RenderPlayerView(player_t *player)
 
 		validcount++;
 
-		if (portal->seg)
-		{
-			// Push the portal's old drawseg out of the way so it isn't interfering with sprite clipping. -Red
-			drawseg_t *seg = drawsegs+portal->seg;
-			seg->scale1 = 0;
-			seg->scale2 = 0;
-		}
-
 		R_RenderBSPNode((INT32)numnodes - 1);
 		R_ClipSprites();
 		//R_DrawPlanes();
diff --git a/src/r_segs.c b/src/r_segs.c
index 04873b29c..0106a1bac 100644
--- a/src/r_segs.c
+++ b/src/r_segs.c
@@ -2887,6 +2887,11 @@ void R_StoreWallRange(INT32 start, INT32 stop)
 		R_RenderSegLoop();
 	colfunc = wallcolfunc;
 
+	if (portalline) // if curline is a portal, set portalrender for drawseg
+		ds_p->portalpass = portalrender+1;
+	else
+		ds_p->portalpass = 0;
+
 	// save sprite clipping info
 	if (((ds_p->silhouette & SIL_TOP) || maskedtexture) && !ds_p->sprtopclip)
 	{
diff --git a/src/r_things.c b/src/r_things.c
index 2a3f8e771..667a26e0f 100644
--- a/src/r_things.c
+++ b/src/r_things.c
@@ -2058,6 +2058,9 @@ void R_ClipSprites(void)
 				continue;
 			}
 
+			if (ds->portalpass > 0 && ds->portalpass == portalrender)
+				continue; // is a portal
+
 			r1 = ds->x1 < spr->x1 ? spr->x1 : ds->x1;
 			r2 = ds->x2 > spr->x2 ? spr->x2 : ds->x2;