Destroy backingstore before window

The window is created before the backingstore, so the destruction should
happen in the reverse order. Also, the backingstore is created based on
a pointer to a QWindow, so the dependency is from backingstore to window.
Thirdly, this fixes a crash when using QQuickWidget/QOpenGLWidget.

Task-number: QTBUG-37045
Change-Id: I6e782c553fddfeef877be30ca2610aff75a425a0
Reviewed-by: Laszlo Agocs <laszlo.agocs@digia.com>
Reviewed-by: Jørgen Lind <jorgen.lind@digia.com>

1 files changed, 6 insertions, 4 deletions

diff --git a/src/widgets/kernel/qwidget_qpa.cpp b/src/widgets/kernel/qwidget_qpa.cpp
index 174b7eb5d5..5885673591 100644
--- a/src/widgets/kernel/qwidget_qpa.cpp
+++ b/src/widgets/kernel/qwidget_qpa.cpp
@@ -939,6 +939,12 @@ void QWidgetPrivate::createTLSysExtra()
 void QWidgetPrivate::deleteTLSysExtra()
 {
     if (extra && extra->topextra) {
+        //the qplatformbackingstore may hold a reference to the window, so the backingstore
+        //needs to be deleted first
+        extra->topextra->backingStoreTracker.destroy();
+        delete extra->topextra->backingStore;
+        extra->topextra->backingStore = 0;
+
         //the toplevel might have a context with a "qglcontext associated with it. We need to
         //delete the qglcontext before we delete the qplatformopenglcontext.
         //One unfortunate thing about this is that we potentially create a glContext just to
@@ -950,10 +956,6 @@ void QWidgetPrivate::deleteTLSysExtra()
         delete extra->topextra->window;
         extra->topextra->window = 0;
 
-        extra->topextra->backingStoreTracker.destroy();
-        delete extra->topextra->backingStore;
-        extra->topextra->backingStore = 0;
-
 #ifndef QT_NO_OPENGL
         delete extra->topextra->shareContext;
         extra->topextra->shareContext = 0;