From 7a7b745917d538e61cb5c9d4da1a53804c4ceade Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Tor=20Arne=20Vestb=C3=B8?= <tor.arne.vestbo@qt.io>
Date: Mon, 26 Sep 2016 16:36:38 +0200
Subject: [PATCH] Ensure that QBackingStore::flush() is not used across window
 hierarchies

Change-Id: I0713d7499f32819db4263e36dff58812a9ac763c
Reviewed-by: Laszlo Agocs <laszlo.agocs@qt.io>
---
 src/gui/painting/qbackingstore.cpp | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/src/gui/painting/qbackingstore.cpp b/src/gui/painting/qbackingstore.cpp
index ceaad61e13..53349dcef4 100644
--- a/src/gui/painting/qbackingstore.cpp
+++ b/src/gui/painting/qbackingstore.cpp
@@ -112,6 +112,8 @@ void QBackingStore::flush(const QRegion &region, QWindow *win, const QPoint &off
     }
 #endif
 
+    Q_ASSERT(win == this->window() || this->window()->isAncestorOf(win, QWindow::ExcludeTransients));
+
     d_ptr->platformBackingStore->flush(win, QHighDpi::toNativeLocalRegion(region, win),
                                             QHighDpi::toNativeLocalPosition(offset, win));
 }