add "Walk Under Solid Hanging Bodies" from PrBoom+ (#786)

src/m_menu.c

@@ -3864,6 +3864,7 @@ enum {
   general_end5,
 
   general_title6,
+  general_hangsolid,
   general_blockmapfix,
   general_pistolstart,
   general_end6,
@@ -4044,6 +4045,9 @@ setup_menu_t gen_settings3[] = { // General Settings screen3
   {"Compatibility-breaking Features"  ,S_SKIP|S_TITLE, m_null, M_X,
    M_Y + general_title6*M_SPC},
 
+  {"Walk Under Solid Hanging Bodies", S_YESNO, m_null, M_X,
+   M_Y + general_hangsolid*M_SPC, {"hangsolid"}},
+
   {"Improved Hit Detection", S_YESNO, m_null, M_X,
    M_Y + general_blockmapfix*M_SPC, {"blockmapfix"}},
 
@@ -6950,6 +6954,8 @@ void M_ResetSetupMenu(void)
 
 void M_UpdateCriticalItems(void)
 {
+  DISABLE_CRITICAL(gen_settings3[general_hangsolid]);
+
   if (demo_compatibility && overflow[emu_intercepts].enabled)
     gen_settings3[general_blockmapfix].m_flags |= S_DISABLE;
   else

src/m_misc.c

@@ -105,6 +105,7 @@ extern boolean r_swirl;
 extern int death_use_action;
 extern boolean palette_changes;
 extern boolean screen_melt;
+extern boolean hangsolid;
 extern boolean blockmapfix;
 extern int extra_level_brightness;
 extern int menu_background;
@@ -463,6 +464,13 @@ default_t defaults[] = {
     "1 to enable \"ghost monsters\" (resurrected pools of gore are translucent)"
   },
 
+  {
+    "hangsolid",
+    (config_t *) &hangsolid, NULL,
+    {0}, {0,1}, number, ss_enem, wad_no,
+    "1 to walk under solid hanging bodies"
+  },
+
   {
     "blockmapfix",
     (config_t *) &blockmapfix, NULL,

src/p_map.c

@@ -477,6 +477,8 @@ static boolean PIT_CheckLine(line_t *ld) // killough 3/26/98: make static
 // PIT_CheckThing
 //
 
+boolean hangsolid;
+
 // mbf21: dehacked projectile groups
 static boolean P_ProjectileImmune(mobj_t *target, mobj_t *source)
 {
@@ -645,6 +647,19 @@ static boolean PIT_CheckThing(mobj_t *thing) // killough 3/26/98: make static
       return !solid;
     }
 
+  // RjY
+  // comperr_hangsolid, an attempt to handle blocking hanging bodies
+  // A solid hanging body will allow sufficiently small things underneath it.
+  if (CRITICAL(hangsolid) &&
+      !((~thing->flags) & (MF_SOLID | MF_SPAWNCEILING)) // solid and hanging
+      // invert everything, then both bits should be clear
+      && tmthing->z + tmthing->height <= thing->z) // head height <= base
+      // top of thing trying to move under the body <= bottom of body
+  {
+    tmceilingz = thing->z; // pretend ceiling height is at body's base
+    return true;
+  }
+
   // killough 3/16/98: Allow non-solid moving objects to move through solid
   // ones, by allowing the moving thing (tmthing) to move if it's non-solid,
   // despite another solid thing being in the way.