1 files changed, 18 insertions, 10 deletions

diff --git a/src/widgets/widgets/qdockwidget.cpp b/src/widgets/widgets/qdockwidget.cpp
index ba8bd90da6..4041c730b8 100644
--- a/src/widgets/widgets/qdockwidget.cpp
+++ b/src/widgets/widgets/qdockwidget.cpp
@@ -67,18 +67,21 @@ extern QString qt_setWindowTitle_helperHelper(const QString&, const QWidget*); /
 // qmainwindow.cpp
 extern QMainWindowLayout *qt_mainwindow_layout(const QMainWindow *window);
 
-static inline QMainWindowLayout *qt_mainwindow_layout_from_dock(const QDockWidget *dock)
+static const QMainWindow *mainwindow_from_dock(const QDockWidget *dock)
 {
-    const QWidget *p = dock->parentWidget();
-    while (p) {
-        const QMainWindow *window = qobject_cast<const QMainWindow*>(p);
-        if (window)
-            return qt_mainwindow_layout(window);
-        p = p->parentWidget();
+    for (const QWidget *p = dock->parentWidget(); p; p = p->parentWidget()) {
+        if (const QMainWindow *window = qobject_cast<const QMainWindow*>(p))
+            return window;
     }
     return nullptr;
 }
 
+static inline QMainWindowLayout *qt_mainwindow_layout_from_dock(const QDockWidget *dock)
+{
+    auto mainWindow = mainwindow_from_dock(dock);
+    return mainWindow ? qt_mainwindow_layout(mainWindow) : nullptr;
+}
+
 static inline bool hasFeature(const QDockWidgetPrivate *priv, QDockWidget::DockWidgetFeature feature)
 { return (priv->features & feature) == feature; }
 
@@ -839,8 +842,9 @@ void QDockWidgetPrivate::endDrag(bool abort)
     q->releaseMouse();
 
     if (state->dragging) {
-        QMainWindowLayout *mwLayout = qt_mainwindow_layout_from_dock(q);
-        Q_ASSERT(mwLayout != 0);
+        const QMainWindow *mainWindow = mainwindow_from_dock(q);
+        Q_ASSERT(mainWindow != nullptr);
+        QMainWindowLayout *mwLayout = qt_mainwindow_layout(mainWindow);
 
         if (abort || !mwLayout->plug(state->widgetItem)) {
             if (hasFeature(this, QDockWidget::DockWidgetFloatable)) {
@@ -861,8 +865,12 @@ void QDockWidgetPrivate::endDrag(bool abort)
                 } else {
                     setResizerActive(false);
                 }
-                if (q->isFloating()) // Might not be floating when dragging a QDockWidgetGroupWindow
+                if (q->isFloating()) { // Might not be floating when dragging a QDockWidgetGroupWindow
                     undockedGeometry = q->geometry();
+#if QT_CONFIG(tabwidget)
+                    tabPosition = mwLayout->tabPosition(mainWindow->dockWidgetArea(q));
+#endif
+                }
                 q->activateWindow();
             } else {
                 // The tab was not plugged back in the QMainWindow but the QDockWidget cannot