Fixed the uses of P_LineOpening now

Author: ioan-chera

source/p_trace.cpp

@@ -139,14 +139,19 @@ static bool PTR_AimTraverse(intercept_t *in, void *context, const divline_t &tra
 
         dist = FixedMul(trace.attackrange, in->frac);
 
-        if(li->frontsector->srf.floor.getZAt(edgepos) != li->backsector->srf.floor.getZAt(edgepos))
+        const sector_t *const frontsector =
+            li->intflags & MLI_DYNASEGLINE ? R_PointInSubsector(edgepos)->sector : li->frontsector;
+        const sector_t *const backsector = li->intflags & MLI_DYNASEGLINE ? frontsector : li->backsector;
+        // IMPORTANT: no portals here, no 1sportalline or edgepos2
+
+        if(frontsector->srf.floor.getZAt(edgepos) != backsector->srf.floor.getZAt(edgepos))
         {
             slope = FixedDiv(clip.open.height.floor - trace.z, dist);
             if(slope > trace.bottomslope)
                 trace.bottomslope = slope;
         }
 
-        if(li->frontsector->srf.ceiling.getZAt(edgepos) != li->backsector->srf.ceiling.getZAt(edgepos))
+        if(frontsector->srf.ceiling.getZAt(edgepos) != backsector->srf.ceiling.getZAt(edgepos))
         {
             slope = FixedDiv(clip.open.height.ceiling - trace.z, dist);
             if(slope < trace.topslope)
@@ -368,6 +373,7 @@ static bool PTR_ShootTraverseVanilla(intercept_t *in, void *context, const divli
 
         if(li->flags & ML_TWOSIDED)
         {
+            // NOTE: no polyobjects in vanilla, no worry there. No Hexen demo support either.
             clip.open    = P_LineOpening(li, nullptr);
             fixed_t dist = FixedMul(trace.attackrange, in->frac);
             fixed_t slope;
@@ -460,10 +466,8 @@ static bool P_Shoot2SLine(line_t *li, int side, fixed_t dist)
             ceilingsame = becomp && P_SlopesEqual(fs, bs, surf_ceil);
     }
 
-    if((floorsame || (clip.open.height.floor == D_MININT && demo_version >= 406) ||
-        FixedDiv(clip.open.height.floor - trace.z, dist) <= trace.aimslope) &&
-       (ceilingsame || (clip.open.height.ceiling == D_MAXINT && demo_version >= 406) ||
-        FixedDiv(clip.open.height.ceiling - trace.z, dist) >= trace.aimslope))
+    if((floorsame || FixedDiv(clip.open.height.floor - trace.z, dist) <= trace.aimslope) &&
+       (ceilingsame || FixedDiv(clip.open.height.ceiling - trace.z, dist) >= trace.aimslope))
     {
         if(li->special)
             P_ShootSpecialLine(trace.thing, li, side);