shithub: choc

Download patch

ref: 3ac445e219bbfd2caa252a3896d65c8555bcf9d8
parent: be0bd464d19758f3e87b79766e9820b1efbda04b
author: Simon Howard <fraggle@gmail.com>
date: Sat Mar 22 22:08:23 EDT 2014 

doom: Emulate 'no fog on spawn west' Vanilla bug.

A deathmatch player spawning facing directly west does not see the
normal teleport fog (or hear it). This is because of an angle that
should be unsigned but is actually signed. Import PrBoom's code to
emulate this bug. This fixes #186.


--- a/src/doom/g_game.c
+++ b/src/doom/g_game.c
@@ -1093,7 +1093,6 @@
     fixed_t		x;
     fixed_t		y; 
     subsector_t*	ss; 
-    unsigned		an; 
     mobj_t*		mo; 
     int			i;
 	
@@ -1118,15 +1117,71 @@
 	P_RemoveMobj (bodyque[bodyqueslot%BODYQUESIZE]); 
     bodyque[bodyqueslot%BODYQUESIZE] = players[playernum].mo; 
     bodyqueslot++; 
-	
-    // spawn a teleport fog 
-    ss = R_PointInSubsector (x,y); 
-    an = ( ANG45 * (((unsigned int) mthing->angle)/45) ) >> ANGLETOFINESHIFT; 
- 
-    mo = P_SpawnMobj (x+20*finecosine[an], y+20*finesine[an] 
-		      , ss->sector->floorheight 
-		      , MT_TFOG); 
-	 
+
+    // spawn a teleport fog
+    ss = R_PointInSubsector (x,y);
+
+
+    // The code in the released source looks like this:
+    //
+    //    an = ( ANG45 * (((unsigned int) mthing->angle)/45) )
+    //         >> ANGLETOFINESHIFT;
+    //    mo = P_SpawnMobj (x+20*finecosine[an], y+20*finesine[an]
+    //                     , ss->sector->floorheight
+    //                     , MT_TFOG);
+    //
+    // But 'an' can be a signed value in the DOS version. This means that
+    // we get a negative index and the lookups into finecosine/finesine
+    // end up dereferencing values in finetangent[].
+    // A player spawning on a deathmatch start facing directly west spawns
+    // "silently" with no spawn fog. Emulate this.
+    //
+    // This code is imported from PrBoom+.
+
+    {
+        fixed_t xa, ya;
+        signed int an;
+
+        an = (ANG45 * ((signed int) mthing->angle / 45));
+        // Right-shifting a negative signed integer is implementation-defined,
+        // so divide instead.
+        an /= 1 << ANGLETOFINESHIFT;
+
+        switch (an)
+        {
+            case -4096:
+                xa = finetangent[2048];    // finecosine[-4096]
+                ya = finetangent[0];       // finesine[-4096]
+                break;
+            case -3072:
+                xa = finetangent[3072];    // finecosine[-3072]
+                ya = finetangent[1024];    // finesine[-3072]
+                break;
+            case -2048:
+                xa = finesine[0];          // finecosine[-2048]
+                ya = finetangent[2048];    // finesine[-2048]
+                break;
+            case -1024:
+                xa = finesine[1024];       // finecosine[-1024]
+                ya = finetangent[3072];    // finesine[-1024]
+                break;
+            case 0:
+            case 1024:
+            case 2048:
+            case 3072:
+            case 4096:
+                xa = finecosine[an];
+                ya = finesine[an];
+                break;
+            default:
+                I_Error("G_CheckSpot: unexpected angle %d\n", an);
+                xa = ya = 0;
+                break;
+        }
+        mo = P_SpawnMobj(x + 20 * xa, y + 20 * ya,
+                         ss->sector->floorheight, MT_TFOG);
+    }
+
     if (players[consoleplayer].viewz != 1) 
 	S_StartSound (mo, sfx_telept);	// don't start sound on first frame