QDockWidget: Store tab position when undocking

Add a field remembering the tab position of the dock widget area to
QDockWidgetPrivate and use that when grouping floating docks.

Fixes: QTBUG-74242
Change-Id: I2a453080cb39dd4a5491976f1aeca70ae681682a
Reviewed-by: Richard Moe Gustavsen <richard.gustavsen@qt.io>

3 files changed, 53 insertions, 11 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
diff --git a/src/widgets/widgets/qdockwidget_p.h b/src/widgets/widgets/qdockwidget_p.h
index 03d7efce98..e224ba7143 100644
--- a/src/widgets/widgets/qdockwidget_p.h
+++ b/src/widgets/widgets/qdockwidget_p.h
@@ -57,6 +57,10 @@
 #include "QtWidgets/qboxlayout.h"
 #include "QtWidgets/qdockwidget.h"
 
+#if QT_CONFIG(tabwidget)
+#  include "QtWidgets/qtabwidget.h"
+#endif
+
 QT_REQUIRE_CONFIG(dockwidget);
 
 QT_BEGIN_NAMESPACE
@@ -86,6 +90,11 @@ public:
     void _q_toggleTopLevel(); // private slot
 
     void updateButtons();
+
+#if QT_CONFIG(tabwidget)
+    QTabWidget::TabPosition tabPosition = QTabWidget::North;
+#endif
+
     DragState *state = nullptr;
 
     QDockWidget::DockWidgetFeatures features = QDockWidget::DockWidgetClosable
diff --git a/src/widgets/widgets/qmainwindowlayout.cpp b/src/widgets/widgets/qmainwindowlayout.cpp
index ed054c7e9a..f54835f23b 100644
--- a/src/widgets/widgets/qmainwindowlayout.cpp
+++ b/src/widgets/widgets/qmainwindowlayout.cpp
@@ -2525,6 +2525,30 @@ void QMainWindowLayout::updateGapIndicator()
 #endif // QT_CONFIG(rubberband)
 }
 
+static QTabBar::Shape tabwidgetPositionToTabBarShape(QWidget *w)
+{
+    QTabBar::Shape result = QTabBar::RoundedSouth;
+#if QT_CONFIG(tabwidget)
+    if (qobject_cast<QDockWidget *>(w)) {
+        switch (static_cast<QDockWidgetPrivate *>(qt_widget_private(w))->tabPosition) {
+        case QTabWidget::North:
+            result = QTabBar::RoundedNorth;
+            break;
+        case QTabWidget::South:
+            result = QTabBar::RoundedSouth;
+            break;
+        case QTabWidget::West:
+            result = QTabBar::RoundedWest;
+            break;
+        case QTabWidget::East:
+            result = QTabBar::RoundedEast;
+            break;
+        }
+    }
+#endif // tabwidget
+    return result;
+}
+
 void QMainWindowLayout::hover(QLayoutItem *widgetItem, const QPoint &mousePos)
 {
     if (!parentWidget()->isVisible() || parentWidget()->isMinimized()
@@ -2573,8 +2597,9 @@ void QMainWindowLayout::hover(QLayoutItem *widgetItem, const QPoint &mousePos)
                 QDockWidgetGroupWindow *floatingTabs = createTabbedDockWindow(); // FIXME
                 floatingTabs->setGeometry(dropTo->geometry());
                 QDockAreaLayoutInfo *info = floatingTabs->layoutInfo();
+                const QTabBar::Shape shape = tabwidgetPositionToTabBarShape(dropTo);
                 *info = QDockAreaLayoutInfo(&layoutState.dockAreaLayout.sep, QInternal::LeftDock,
-                                            Qt::Horizontal, QTabBar::RoundedSouth,
+                                            Qt::Horizontal, shape,
                                             static_cast<QMainWindow *>(parentWidget()));
                 info->tabbed = true;
                 QLayout *parentLayout = dropTo->parentWidget()->layout();