CON: add sprite pseudo-member 'isvalid', getting 1 if the sprite is valid.

And 0 otherwise. Before accessing a sprite that is not not known to be
definitely valid (e.g. a loop over all sprites from 0 to MAXSPRITES-1),
one should check for validity before accessing it in any other fashion.

git-svn-id: https://svn.eduke32.com/eduke32@4146 1a8010ca-5511-0410-912e-c29ae57300e0

polymer/eduke32/source/gamedef.c

@@ -824,6 +824,8 @@ const memberlabel_t ActorLabels[]=
     { "ulotag", ACTOR_ULOTAG, 0, 0 },
     { "uhitag", ACTOR_UHITAG, 0, 0 },
 
+    { "isvalid", ACTOR_ISVALID, 0, 0 },
+
     { "", -1, 0, 0  }     // END OF LIST
 };
 

polymer/eduke32/source/gamedef.h

@@ -518,6 +518,7 @@ enum ActorLabel_t
     ACTOR_ALPHA,
     ACTOR_ULOTAG,
     ACTOR_UHITAG,
+    ACTOR_ISVALID,
     ACTOR_END
 };
 

polymer/eduke32/source/gamestructures.c

@@ -2930,6 +2930,10 @@ static void __fastcall VM_GetSprite(int32_t lVar1, int32_t lLabelID, int32_t lVa
         Gv_SetVarX(lVar2, (uint8_t)(spriteext[iActor].alpha * 255.0f));
         return;
 
+    case ACTOR_ISVALID:
+        Gv_SetVarX(lVar2, sprite[iActor].statnum != MAXSTATUS);
+        return;
+
     default:
         return;
     }
@@ -3553,6 +3557,7 @@ static int32_t __fastcall VM_AccessSpriteX(int32_t iActor, int32_t lLabelID, int
     case ACTOR_YPANNING: return spriteext[iActor].ypanning;
     case ACTOR_HTFLAGS: return actor[iActor].flags;
     case ACTOR_ALPHA: return (uint8_t)(spriteext[iActor].alpha*255.0f);
+    case ACTOR_ISVALID: return (sprite[iActor].statnum != MAXSTATUS);
     default: return -1;
     }
 

polymer/eduke32/source/lunatic/con_lang.lua

@@ -414,6 +414,8 @@ local ActorLabels = {
 
     -- Read access differs from write, write not available:
     alpha = { "_math.floor(spriteext[%s].alpha*255)", "spriteext[%s].alpha=(%%s)/255" },
+
+    isvalid = { "_con._isvalid(%s)" },
 }
 
 local function spr2tspr(code)

polymer/eduke32/source/lunatic/control.lua

@@ -1424,11 +1424,20 @@ function _cansee(aci, ps)
     return can
 end
 
+function _isvalid(i)
+    check_sprite_idx(i)
+    return ffiC.sprite[i].statnum ~= ffiC.MAXSTATUS and 1 or 0
+end
+
 function _canseespr(s1, s2)
-    local spr1, spr2 = sprite[s1], sprite[s2]
+    check_sprite_idx(s1)
+    check_sprite_idx(s2)
+
+    local spr1, spr2 = ffiC.sprite[s1], ffiC.sprite[s2]
     -- Redundant, but points the error messages to the CON code:
     check_sector_idx(spr1.sectnum)
     check_sector_idx(spr2.sectnum)
+
     return cansee(spr1, spr1.sectnum, spr2, spr2.sectnum) and 1 or 0
 end