From 9bbb8836098433f6110e129dd354f00443930225 Mon Sep 17 00:00:00 2001
From: Friedemann Kleint <Friedemann.Kleint@digia.com>
Date: Wed, 9 Dec 2015 09:54:20 +0100
Subject: [PATCH] Windows backing store: Clamp region to 0,0.

Workaround to prevent UpdateLayeredWindowIndirect from failing
when invalid regions are passed by graphical effects.

Task-number:  QTBUG-49785
Change-Id: Icfd964d6b55fa945bc2afefc164ab047c3b2d0f8
---
 src/plugins/platforms/windows/qwindowsbackingstore.cpp | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/src/plugins/platforms/windows/qwindowsbackingstore.cpp b/src/plugins/platforms/windows/qwindowsbackingstore.cpp
index bd5c350..20fc638 100644
--- a/src/plugins/platforms/windows/qwindowsbackingstore.cpp
+++ b/src/plugins/platforms/windows/qwindowsbackingstore.cpp
@@ -87,7 +87,10 @@ void QWindowsBackingStore::flush(QWindow *window, const QRegion &region,
         QPoint frameOffset(QHighDpi::toNativePixels(QPoint(window->frameMargins().left(), window->frameMargins().top()),
                                                     static_cast<const QWindow *>(Q_NULLPTR)));
         QRect dirtyRect = br.translated(offset + frameOffset);
-
+        if (dirtyRect.x() < 0)
+            dirtyRect.setX(0);
+        if (dirtyRect.y() < 0)
+            dirtyRect.setY(0);
         SIZE size = {r.width(), r.height()};
         POINT ptDst = {r.x(), r.y()};
         POINT ptSrc = {0, 0};
-- 
1.9.4.msysgit.0