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Fix glass hack windows where a linedef is flagged as two sided but has
only one side. Fixes WADs such as OTTAWAU.WAD (thanks Never_Again).

Subversion-branch: /trunk/chocolate-doom
Subversion-revision: 1826

--- a/NEWS

+++ b/NEWS

@@ -50,6 +50,8 @@

        instead of the red colormaps normally used when taking damage

        or using the berserk pack.  This matches Vanilla chex.exe

        behavior (thanks Fuzztooth).

+     * Impassible glass now displays and works the same as in Vanilla,

+       fixing wads such as OTTAWAU.WAD (thanks Never_Again).

     Bugs fixed:

      * Memory-mapped WAD I/O is disabled by default, as it caused

--- a/src/p_map.c

+++ b/src/p_map.c

@@ -885,7 +885,17 @@

 	dist = FixedMul (attackrange, in->frac);

-	if (li->frontsector->floorheight != li->backsector->floorheight)

+        // Return false if there is no back sector.  This should never

+        // be the case if the line is two-sided; however, some WADs

+        // (eg. ottawau.wad) use this as an "impassible glass" trick

+        // and rely on Vanilla Doom's (unintentional) support for this.

+

+        if (li->backsector == NULL)

+        {

+            return false;

+        }

+

+        if (li->frontsector->floorheight != li->backsector->floorheight)

 	{

 	    slope = FixedDiv (openbottom - shootz , dist);

 	    if (slope > bottomslope)

@@ -973,7 +983,14 @@

 	dist = FixedMul (attackrange, in->frac);

-	if (li->frontsector->floorheight != li->backsector->floorheight)

+        // Check if backsector is NULL.  See comment in PTR_AimTraverse.

+

+	if (li->backsector == NULL)

+        {

+            goto hitline;

+        }

+

+        if (li->frontsector->floorheight != li->backsector->floorheight)

 	{

 	    slope = FixedDiv (openbottom - shootz , dist);

 	    if (slope > aimslope)

--- a/src/p_setup.c

+++ b/src/p_setup.c

@@ -167,6 +167,7 @@

     line_t*		ldef;

     int			linedef;

     int			side;

+    int                 sidenum;

     numsegs = W_LumpLength (lump) / sizeof(mapseg_t);

     segs = Z_Malloc (numsegs*sizeof(seg_t),PU_LEVEL,0);	

@@ -179,7 +180,7 @@

     {

 	li->v1 = &vertexes[SHORT(ml->v1)];

 	li->v2 = &vertexes[SHORT(ml->v2)];

-					

+

 	li->angle = (SHORT(ml->angle))<<16;

 	li->offset = (SHORT(ml->offset))<<16;

 	linedef = SHORT(ml->linedef);

@@ -188,10 +189,28 @@

 	side = SHORT(ml->side);

 	li->sidedef = &sides[ldef->sidenum[side]];

 	li->frontsector = sides[ldef->sidenum[side]].sector;

-	if (ldef-> flags & ML_TWOSIDED)

-	    li->backsector = sides[ldef->sidenum[side^1]].sector;

-	else

+

+        if (ldef-> flags & ML_TWOSIDED)

+        {

+            sidenum = ldef->sidenum[side ^ 1];

+

+            // If the sidenum is out of range, this may be a "glass hack"

+            // impassible window.  Point at side #0 (this may not be

+            // the correct Vanilla behavior; however, it seems to work for

+            // OTTAWAU.WAD, which is the one place I've seen this trick

+            // used).

+

+            if (sidenum < 0 || sidenum >= numsides)

+            {

+                sidenum = 0;

+            }

+

+            li->backsector = sides[sidenum].sector;

+        }

+        else

+        {

 	    li->backsector = 0;

+        }

     }

     W_ReleaseLumpNum(lump);

--- a/src/p_sight.c

+++ b/src/p_sight.c

@@ -173,7 +173,7 @@

 	    continue;

 	line->validcount = validcount;

-		

+

 	v1 = line->v1;

 	v2 = line->v2;

 	s1 = P_DivlineSide (v1->x,v1->y, &strace);

@@ -193,6 +193,14 @@

 	// line isn't crossed?

 	if (s1 == s2)

 	    continue;	

+

+        // Backsector may be NULL if this is an "impassible

+        // glass" hack line.

+

+        if (line->backsector == NULL)

+        {

+            return false;

+        }

 	// stop because it is not two sided anyway

 	// might do this after updating validcount?