Fix crash when windowcontainer is used in a dockwidget

The dockwidget's toplevel window would be a parent of the container's
window when floating. When plugged back into the mainwindow the
dockwidget's window is destroyed and the container's window along
with it. Added a function toplevelAboutToBeDestroyed to unparent
the containers window before this happens so parentWasChanged will
work correctly.

Change-Id: I06679cfb3a8fa3834c0db0be5973c012b8277275
Reviewed-by: Ulf Hermann <ulf.hermann@digia.com>
Reviewed-by: Jørgen Lind <jorgen.lind@digia.com>

src/widgets/kernel/qwidget_qpa.cpp

@@ -53,6 +53,7 @@
 #include <qpa/qplatformintegration.h>
 #include "QtGui/private/qwindow_p.h"
 #include "QtGui/private/qguiapplication_p.h"
+#include <private/qwindowcontainer_p.h>
 
 #include <qpa/qplatformcursor.h>
 #include <QtGui/QGuiApplication>
@@ -267,8 +268,11 @@ void QWidgetPrivate::setParent_sys(QWidget *newparent, Qt::WindowFlags f)
     bool explicitlyHidden = q->testAttribute(Qt::WA_WState_Hidden) && q->testAttribute(Qt::WA_WState_ExplicitShowHide);
 
     // Reparenting toplevel to child
-    if (wasCreated && !(f & Qt::Window) && (oldFlags & Qt::Window) && !q->testAttribute(Qt::WA_NativeWindow))
+    if (wasCreated && !(f & Qt::Window) && (oldFlags & Qt::Window) && !q->testAttribute(Qt::WA_NativeWindow)) {
+        if (extra && extra->hasWindowContainer)
+            QWindowContainer::toplevelAboutToBeDestroyed(q);
         q->destroy();
+    }
 
     adjustFlags(f, q);
     data.window_flags = f;

src/widgets/kernel/qwindowcontainer.cpp

@@ -300,15 +300,28 @@ static void qwindowcontainer_traverse(QWidget *parent, qwindowcontainer_traverse
     }
 }
 
+void QWindowContainer::toplevelAboutToBeDestroyed(QWidget *parent)
+{
+    if (QWindowContainerPrivate *d = QWindowContainerPrivate::get(parent)) {
+        d->window->setParent(&d->fakeParent);
+    }
+    qwindowcontainer_traverse(parent, toplevelAboutToBeDestroyed);
+}
+
 void QWindowContainer::parentWasChanged(QWidget *parent)
 {
     if (QWindowContainerPrivate *d = QWindowContainerPrivate::get(parent)) {
         if (d->window->parent()) {
             d->updateUsesNativeWidgets();
             d->markParentChain();
-            d->window->setParent(d->usesNativeWidgets
-                                 ? parent->windowHandle()
-                                 : parent->window()->windowHandle());
+            QWidget *toplevel = d->usesNativeWidgets ? parent : parent->window();
+            if (!toplevel->windowHandle()) {
+                QWidgetPrivate *tld = static_cast<QWidgetPrivate *>(QWidgetPrivate::get(toplevel));
+                tld->createTLExtra();
+                tld->createTLSysExtra();
+                Q_ASSERT(toplevel->windowHandle());
+            }
+            d->window->setParent(toplevel->windowHandle());
             d->updateGeometry();
         }
     }

src/widgets/kernel/qwindowcontainer_p.h

@@ -57,6 +57,7 @@ public:
     explicit QWindowContainer(QWindow *embeddedWindow, QWidget *parent = 0, Qt::WindowFlags f = 0);
     ~QWindowContainer();
 
+    static void toplevelAboutToBeDestroyed(QWidget *parent);
     static void parentWasChanged(QWidget *parent);
     static void parentWasMoved(QWidget *parent);
     static void parentWasRaised(QWidget *parent);

tests/auto/widgets/kernel/qwindowcontainer/tst_qwindowcontainer.cpp

@@ -46,6 +46,8 @@
 #include <qwindow.h>
 #include <qwidget.h>
 
+#include <qdockwidget.h>
+#include <qmainwindow.h>
 
 
 class Window : public QWindow
@@ -80,6 +82,7 @@ private slots:
     void testUnparenting();
     void testActivation();
     void testAncestorChange();
+    void testDockWidget();
 };
 
 
@@ -278,6 +281,7 @@ void tst_QWindowContainer::testAncestorChange()
     newRoot->setGeometry(100, 100, 200, 200);
     newRoot->show();
     QVERIFY(QTest::qWaitForWindowExposed(newRoot));
+    QCOMPARE(newRoot->windowHandle(), window->parent());
     //      newRoot
     //      + right
     //        + container
@@ -285,6 +289,31 @@ void tst_QWindowContainer::testAncestorChange()
     QCOMPARE(window->geometry(), QRect(100, 0, 100, 100));
 }
 
+
+void tst_QWindowContainer::testDockWidget()
+{
+    QMainWindow mainWindow;
+    mainWindow.resize(200, 200);
+
+    QDockWidget *dock = new QDockWidget();
+    QWindow *window = new QWindow();
+    QWidget *container = QWidget::createWindowContainer(window);
+    dock->setWidget(container);
+    mainWindow.addDockWidget(Qt::RightDockWidgetArea, dock);
+
+    mainWindow.show();
+    QVERIFY(QTest::qWaitForWindowExposed(&mainWindow));
+    QVERIFY(window->parent() == mainWindow.window()->windowHandle());
+
+    QTest::qWait(1000);
+    dock->setFloating(true);
+    QTRY_VERIFY(window->parent() != mainWindow.window()->windowHandle());
+
+    QTest::qWait(1000);
+    dock->setFloating(false);
+    QTRY_VERIFY(window->parent() == mainWindow.window()->windowHandle());
+}
+
 QTEST_MAIN(tst_QWindowContainer)
 
 #include "tst_qwindowcontainer.moc"