From 4e37ce697b2c9c15b5df86a6ea21c756b5cfaa9b Mon Sep 17 00:00:00 2001
From: James Tabor <james.tabor@reactos.org>
Date: Sun, 16 Nov 2008 02:19:43 +0000
Subject: [PATCH] - Fix AlphaBlend checks that pass wine bitmap gdi32
 crosstests. Tested in 16 and 24 bit mode Qemu and 32 bit mode hardware, with
 our AlphaBlend rendering demo program.

svn path=/trunk/; revision=37385
---
 reactos/subsystems/win32/win32k/objects/bitblt.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/reactos/subsystems/win32/win32k/objects/bitblt.c b/reactos/subsystems/win32/win32k/objects/bitblt.c
index db8e188e202..14d888ba2d1 100644
--- a/reactos/subsystems/win32/win32k/objects/bitblt.c
+++ b/reactos/subsystems/win32/win32k/objects/bitblt.c
@@ -96,11 +96,24 @@ NtGdiAlphaBlend(
 	DestRect.top    = YOriginDest;
 	DestRect.right  = XOriginDest + WidthDest;
 	DestRect.bottom = YOriginDest + HeightDest;
+	IntLPtoDP(DCDest, (LPPOINT)&DestRect, 2);
 
 	SourceRect.left   = XOriginSrc;
 	SourceRect.top    = YOriginSrc;
 	SourceRect.right  = XOriginSrc + WidthSrc;
 	SourceRect.bottom = YOriginSrc + HeightSrc;
+	IntLPtoDP(DCSrc, (LPPOINT)&SourceRect, 2);
+
+        if (!DestRect.right ||
+            !DestRect.bottom ||
+            !SourceRect.right ||
+            !SourceRect.bottom)
+            {
+               if (hDCSrc != hDCDest)
+                   DC_UnlockDc(DCSrc);
+               DC_UnlockDc(DCDest);
+               return TRUE;
+            }
 
 	/* Determine surfaces to be used in the bitblt */
 	BitmapDest = BITMAPOBJ_LockBitmap(DCDest->w.hBitmap);