From b9b8e01e323a089b6288fdb21bbe5b2d44b7fd6e Mon Sep 17 00:00:00 2001
From: helixhorned <helixhorned@1a8010ca-5511-0410-912e-c29ae57300e0>
Date: Mon, 22 Apr 2013 10:35:48 +0000
Subject: [PATCH] Revert an awful stupidity I committed in r3700.

git-svn-id: https://svn.eduke32.com/eduke32@3703 1a8010ca-5511-0410-912e-c29ae57300e0
---
 polymer/eduke32/build/src/engine.c | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/polymer/eduke32/build/src/engine.c b/polymer/eduke32/build/src/engine.c
index 30c0ba1f3..50c2885c0 100644
--- a/polymer/eduke32/build/src/engine.c
+++ b/polymer/eduke32/build/src/engine.c
@@ -9200,17 +9200,21 @@ killsprite:
         pos.x = (float)globalposx;
         pos.y = (float)globalposy;
 
-        while (maskwallcnt--)
+        // CAUTION: maskwallcnt and spritesortcnt may be zero!
+        // Writing e.g. "while (maskwallcnt--)" is wrong!
+        while (maskwallcnt)
         {
             _point2d dot, dot2, middle;
             // PLAG: sorting stuff
             _equation maskeq, p1eq, p2eq;
 
             const int32_t w = (getrendermode()==REND_POLYMER) ?
-                maskwall[maskwallcnt] : thewall[maskwall[maskwallcnt]];
+                maskwall[maskwallcnt-1] : thewall[maskwall[maskwallcnt-1]];
 
             const int32_t otherside_spr_first = (getrendermode() == REND_CLASSIC);
 
+            maskwallcnt--;
+
             dot.x = (float)wall[w].x;
             dot.y = (float)wall[w].y;
             dot2.x = (float)wall[wall[w].point2].x;
@@ -9228,8 +9232,9 @@ killsprite:
             }
 
             i = spritesortcnt;
-            while (i--)
+            while (i)
             {
+                i--;
                 if (tspriteptr[i] != NULL)
                 {
                     _point2d spr;
@@ -9251,8 +9256,9 @@ killsprite:
             drawmaskwall(maskwallcnt);
         }
 
-        while (spritesortcnt--)
+        while (spritesortcnt)
         {
+            spritesortcnt--;
             if (tspriteptr[spritesortcnt] != NULL)
                 drawsprite(spritesortcnt);
         }