Fixes crash when widget with WA_StaticContents child become toplevel.

Happens for example if a DockWidget is undocked and has a child
whith the WA_StaticContents attribute.

The parent does not change (so newParent is false) but still, the
top level widget change. So staticWidget need to be moved to the
new backingstore.

Reviewed-by: Benjamin Poulain
Task-number: QTBUG-6883
(cherry picked from commit 03baad51d584778a99f4b393232ccc1312db3391)

2 files changed, 34 insertions, 7 deletions

diff --git a/src/gui/kernel/qwidget.cpp b/src/gui/kernel/qwidget.cpp
index f6ae581..95d8413 100644
--- a/src/gui/kernel/qwidget.cpp
+++ b/src/gui/kernel/qwidget.cpp
@@ -9774,13 +9774,12 @@ void QWidget::setParent(QWidget *parent, Qt::WindowFlags f)
     }
 #endif
 
-    if (newParent) {
-        if (QWidgetBackingStore *oldBs = oldtlw->d_func()->maybeBackingStore()) {
+    if (QWidgetBackingStore *oldBs = oldtlw->d_func()->maybeBackingStore()) {
+        if (newParent)
             oldBs->removeDirtyWidget(this);
-            // Move the widget and all its static children from
-            // the old backing store to the new one.
-            oldBs->moveStaticWidgets(this);
-        }
+        // Move the widget and all its static children from
+        // the old backing store to the new one.
+        oldBs->moveStaticWidgets(this);
     }
 
     if ((QApplicationPrivate::app_compile_version < 0x040200
diff --git a/tests/auto/qwidget/tst_qwidget.cpp b/tests/auto/qwidget/tst_qwidget.cpp
index 7039f06..7405704 100644
--- a/tests/auto/qwidget/tst_qwidget.cpp
+++ b/tests/auto/qwidget/tst_qwidget.cpp
@@ -66,6 +66,8 @@
 #include <private/qapplication_p.h>
 #include <qcalendarwidget.h>
 #include <qmainwindow.h>
+#include <qdockwidget.h>
+#include <qtoolbar.h>
 #include <QtGui/qpaintengine.h>
 #include <private/qbackingstore_p.h>
 
@@ -356,6 +358,7 @@ private slots:
     void paintOnScreenPossible();
 #endif
     void reparentStaticWidget();
+    void QTBUG6883_reparentStaticWidget2();
 #ifdef Q_WS_QWS
     void updateOutsideSurfaceClip();
 #endif
@@ -8728,6 +8731,31 @@ void tst_QWidget::reparentStaticWidget()
     // Please don't crash.
     paintOnScreen.resize(paintOnScreen.size() + QSize(2, 2));
     QTest::qWait(20);
+
+}
+
+void tst_QWidget::QTBUG6883_reparentStaticWidget2()
+{
+    QMainWindow mw;
+    QDockWidget *one = new QDockWidget("one", &mw);
+    mw.addDockWidget(Qt::LeftDockWidgetArea, one , Qt::Vertical);
+
+    QWidget *child = new QWidget();
+    child->setPalette(Qt::red);
+    child->setAutoFillBackground(true);
+    child->setAttribute(Qt::WA_StaticContents);
+    child->resize(100, 100);
+    one->setWidget(child);
+
+    QToolBar *mainTools = mw.addToolBar("Main Tools");
+    mainTools->addWidget(new QLineEdit);
+
+    mw.show();
+    QTest::qWaitForWindowShown(&mw);
+
+    one->setFloating(true);
+    QTest::qWait(20);
+    //do not crash
 }
 
 #ifdef Q_WS_QWS
@@ -9726,7 +9754,7 @@ public:
     void deleteBackingStore()
     {
         if (static_cast<QWidgetPrivate*>(d_ptr.data())->maybeBackingStore()) {
-            delete static_cast<QWidgetPrivate*>(d_ptr.data())->topData()->backingStore;    
+            delete static_cast<QWidgetPrivate*>(d_ptr.data())->topData()->backingStore;
             static_cast<QWidgetPrivate*>(d_ptr.data())->topData()->backingStore = 0;
         }
     }