Fix crash with drawing swipe

config/fxdata/creature.cfg

@@ -70,10 +70,8 @@ RangeMax = 0
 ; 3,4 will only target other players, 5,6 only own player.
 ; 7 will target traps.
 PrimaryTarget = 0
-; Instance used by creature "going postal" while working in a room
-; Creature will only use available instances with the highest priority,
-; If multiple instances have the same PostalPriority, one is chosen randomly
-; 0 disables the instance for beeing used while "going postal".
+; Instance used when the creature is 'going postal' in a room. It will use the instance with the highest priority.
+; If multiple have the same priority, one is chosen randomly. 0 disables the instance.
 PostalPriority = 0
 ; Instance properties flags:
 ; REPEAT_TRIGGER allows player to hold down the mouse button to cast.

src/thing_creature.c

@@ -375,51 +375,62 @@ void draw_swipe_graphic(void)
     if (thing_is_creature(thing))
     {
         struct CreatureControl* cctrl = creature_control_get_from_thing(thing);
-        if (instance_draws_possession_swipe(cctrl->instance_id))
+        if ((instance_draws_possession_swipe(cctrl->instance_id)) && (cctrl->inst_total_turns > 0))
         {
             lbDisplay.DrawFlags = Lb_SPRITE_TRANSPAR4;
             long n = (int)cctrl->inst_turn * (5 << 8) / cctrl->inst_total_turns;
             long allwidth = 0;
             long i = (abs(n) >> 8) -1;
             if (i >= SWIPE_SPRITE_FRAMES)
+            {
                 i = SWIPE_SPRITE_FRAMES-1;
-            // FIXME: sprites may not be adjacent in the future, causing code below incorrect sprites and possibly crash
+            }
+            // FIXME: sprites may not be adjacent in the future, causing code below incorrect sprites and possibly crash.
             const struct TbSprite* sprlist = get_sprite(swipe_sprites, SWIPE_SPRITES_X * SWIPE_SPRITES_Y * i);
             const struct TbSprite* startspr = &sprlist[1];
             const struct TbSprite* endspr = &sprlist[1];
-            for (n=0; n < SWIPE_SPRITES_X; n++)
+            for (n = 0; n < SWIPE_SPRITES_X; n++)
             {
                 allwidth += endspr->SWidth;
                 endspr++;
             }
+            if (allwidth == 0)
+            {
+                return; // No point trying to draw a zero-width sprite.
+            }
             int units_per_px = (LbScreenWidth() * 59 / 64) * 16 / allwidth;
+            if (units_per_px == 0)
+            {
+                return;
+            }
             int scrpos_y = (MyScreenHeight * 16 / units_per_px - (startspr->SHeight + endspr->SHeight)) / 2;
             const struct TbSprite *spr;
             int scrpos_x;
             if (myplyr->swipe_sprite_drawLR)
             {
                 int delta_y = sprlist[1].SHeight;
-                for (i=0; i < SWIPE_SPRITES_X*SWIPE_SPRITES_Y; i+=SWIPE_SPRITES_X)
+                for (i = 0; i < SWIPE_SPRITES_X*SWIPE_SPRITES_Y; i += SWIPE_SPRITES_X)
                 {
                     spr = &startspr[i];
                     scrpos_x = (MyScreenWidth * 16 / units_per_px - allwidth) / 2;
-                    for (n=0; n < SWIPE_SPRITES_X; n++)
+                    for (n = 0; n < SWIPE_SPRITES_X; n++)
                     {
                         LbSpriteDrawResized(scrpos_x * units_per_px / 16, scrpos_y * units_per_px / 16, units_per_px, spr);
                         scrpos_x += spr->SWidth;
                         spr++;
                     }
                     scrpos_y += delta_y;
                 }
-            } else
+            }
+            else
             {
                 lbDisplay.DrawFlags = Lb_SPRITE_TRANSPAR4 | Lb_SPRITE_FLIP_HORIZ;
-                for (i=0; i < SWIPE_SPRITES_X*SWIPE_SPRITES_Y; i+=SWIPE_SPRITES_X)
+                for (i = 0; i < SWIPE_SPRITES_X*SWIPE_SPRITES_Y; i += SWIPE_SPRITES_X)
                 {
                     spr = &sprlist[SWIPE_SPRITES_X+i];
                     int delta_y = spr->SHeight;
                     scrpos_x = (MyScreenWidth * 16 / units_per_px - allwidth) / 2;
-                    for (n=0; n < SWIPE_SPRITES_X; n++)
+                    for (n = 0; n < SWIPE_SPRITES_X; n++)
                     {
                         LbSpriteDrawResized(scrpos_x * units_per_px / 16, scrpos_y * units_per_px / 16, units_per_px, spr);
                         scrpos_x += spr->SWidth;
@@ -432,7 +443,7 @@ void draw_swipe_graphic(void)
             return;
         }
     }
-    // we get here many times a second when in possession mode and not attacking: to randomise the swipe direction
+    // We get here many times a second when in possession mode and not attacking: to randomise the swipe direction.
     randomise_swipe_graphic_direction();
 }