From f8fe5eeea0376e5f1cba12fdef87fa687db34885 Mon Sep 17 00:00:00 2001
From: John Popplewell <johnnypops@users.sourceforge.net>
Date: Tue, 25 Dec 2007 00:22:02 +0000
Subject: [PATCH] Fix bug in special_notify(). Reproducable crash on win32
 after exactly 40 flips or mirrors. Was (probably) corrupting an element in
 SDL_Surface *undo_bufs[].

---
 src/tuxpaint.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/src/tuxpaint.c b/src/tuxpaint.c
index 7ff70a44c..3cb5c6187 100644
--- a/src/tuxpaint.c
+++ b/src/tuxpaint.c
@@ -17019,7 +17019,8 @@ void special_notify(int flags)
 {
   int tmp_int;
 
-  tmp_int = (cur_undo - 1) % NUM_UNDO_BUFS;
+  tmp_int = cur_undo - 1;
+  if (tmp_int < 0) tmp_int = NUM_UNDO_BUFS - 1;
 
   if (flags & SPECIAL_MIRROR)
   {