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>

3 files changed, 22 insertions, 4 deletions

diff --git a/src/widgets/kernel/qwidget_qpa.cpp b/src/widgets/kernel/qwidget_qpa.cpp
index 18045e3b09..3c4985591e 100644
--- a/src/widgets/kernel/qwidget_qpa.cpp
+++ b/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;
diff --git a/src/widgets/kernel/qwindowcontainer.cpp b/src/widgets/kernel/qwindowcontainer.cpp
index 6914f64f8e..7c319c5095 100644
--- a/src/widgets/kernel/qwindowcontainer.cpp
+++ b/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();
         }
     }
diff --git a/src/widgets/kernel/qwindowcontainer_p.h b/src/widgets/kernel/qwindowcontainer_p.h
index e2446bef42..a21f9bd35a 100644
--- a/src/widgets/kernel/qwindowcontainer_p.h
+++ b/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);