Fix QMainWindow::restoreDockWidget() with GroupedDragging

We need to account for the fact that the placeholder might be in a
floating tab.

Task-number: QTBUG-50491
Change-Id: I03d8e49cc40f58691154f5c3984f3b0670a974d5
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@qt.io>
Reviewed-by: Sérgio Martins <sergio.martins@kdab.com>

4 files changed, 80 insertions, 46 deletions

diff --git a/src/widgets/widgets/qdockarealayout.cpp b/src/widgets/widgets/qdockarealayout.cpp
index d22e89c6e1..1d10de904d 100644
--- a/src/widgets/widgets/qdockarealayout.cpp
+++ b/src/widgets/widgets/qdockarealayout.cpp
@@ -2604,6 +2604,21 @@ void QDockAreaLayout::remove(const QList<int> &path)
     docks[index].remove(path.mid(1));
 }
 
+void QDockAreaLayout::removePlaceHolder(const QString &name)
+{
+    QList<int> index = indexOfPlaceHolder(name);
+    if (!index.isEmpty())
+        remove(index);
+    foreach (QDockWidgetGroupWindow *dwgw, mainWindow->findChildren<QDockWidgetGroupWindow *>(
+                                               QString(), Qt::FindDirectChildrenOnly)) {
+        index = dwgw->layoutInfo()->indexOfPlaceHolder(name);
+        if (!index.isEmpty()) {
+            dwgw->layoutInfo()->remove(index);
+            dwgw->destroyOrHideIfEmpty();
+        }
+    }
+}
+
 static inline int qMax(int i1, int i2, int i3) { return qMax(i1, qMax(i2, i3)); }
 
 void QDockAreaLayout::getGrid(QVector<QLayoutStruct> *_ver_struct_list,
@@ -3030,15 +3045,27 @@ QRect QDockAreaLayout::constrainedRect(QRect rect, QWidget* widget)
 
 bool QDockAreaLayout::restoreDockWidget(QDockWidget *dockWidget)
 {
-    QList<int> index = indexOfPlaceHolder(dockWidget->objectName());
-    if (index.isEmpty())
-        return false;
+    QDockAreaLayoutItem *item = 0;
+    foreach (QDockWidgetGroupWindow *dwgw, mainWindow->findChildren<QDockWidgetGroupWindow *>(
+                                               QString(), Qt::FindDirectChildrenOnly)) {
+        QList<int> index = dwgw->layoutInfo()->indexOfPlaceHolder(dockWidget->objectName());
+        if (!index.isEmpty()) {
+            dockWidget->setParent(dwgw);
+            item = const_cast<QDockAreaLayoutItem *>(&dwgw->layoutInfo()->item(index));
+            break;
+        }
+    }
+    if (!item) {
+        QList<int> index = indexOfPlaceHolder(dockWidget->objectName());
+        if (index.isEmpty())
+            return false;
+        item = const_cast<QDockAreaLayoutItem *>(&this->item(index));
+    }
 
-    QDockAreaLayoutItem &item = this->item(index);
-    QPlaceHolderItem *placeHolder = item.placeHolderItem;
+    QPlaceHolderItem *placeHolder = item->placeHolderItem;
     Q_ASSERT(placeHolder != 0);
 
-    item.widgetItem = new QDockWidgetItem(dockWidget);
+    item->widgetItem = new QDockWidgetItem(dockWidget);
 
     if (placeHolder->window) {
         const QRect r = constrainedRect(placeHolder->topLevelRect, dockWidget);
@@ -3050,7 +3077,7 @@ bool QDockAreaLayout::restoreDockWidget(QDockWidget *dockWidget)
         dockWidget->d_func()->setWindowState(true);
 #endif
 
-    item.placeHolderItem = 0;
+    item->placeHolderItem = 0;
     delete placeHolder;
 
     return true;
@@ -3086,9 +3113,7 @@ void QDockAreaLayout::addDockWidget(QInternal::DockPosition pos, QDockWidget *do
         info = new_info;
     }
 
-    QList<int> index = indexOfPlaceHolder(dockWidget->objectName());
-    if (!index.isEmpty())
-        remove(index);
+    removePlaceHolder(dockWidget->objectName());
 }
 
 void QDockAreaLayout::tabifyDockWidget(QDockWidget *first, QDockWidget *second)
@@ -3101,9 +3126,7 @@ void QDockAreaLayout::tabifyDockWidget(QDockWidget *first, QDockWidget *second)
     Q_ASSERT(info != 0);
     info->tab(path.last(), new QDockWidgetItem(second));
 
-    QList<int> index = indexOfPlaceHolder(second->objectName());
-    if (!index.isEmpty())
-        remove(index);
+    removePlaceHolder(second->objectName());
 }
 
 void QDockAreaLayout::resizeDocks(const QList<QDockWidget *> &docks,
@@ -3165,9 +3188,7 @@ void QDockAreaLayout::splitDockWidget(QDockWidget *after,
     Q_ASSERT(info != 0);
     info->split(path.last(), orientation, new QDockWidgetItem(dockWidget));
 
-    QList<int> index = indexOfPlaceHolder(dockWidget->objectName());
-    if (!index.isEmpty())
-        remove(index);
+    removePlaceHolder(dockWidget->objectName());
 }
 
 void QDockAreaLayout::apply(bool animate)
diff --git a/src/widgets/widgets/qdockarealayout_p.h b/src/widgets/widgets/qdockarealayout_p.h
index 5d352f0124..8a35d8b035 100644
--- a/src/widgets/widgets/qdockarealayout_p.h
+++ b/src/widgets/widgets/qdockarealayout_p.h
@@ -255,6 +255,7 @@ public:
     QLayoutItem *plug(const QList<int> &path);
     QLayoutItem *unplug(const QList<int> &path);
     void remove(const QList<int> &path);
+    void removePlaceHolder(const QString &name);
 
     void fitLayout();
 
diff --git a/src/widgets/widgets/qmainwindowlayout.cpp b/src/widgets/widgets/qmainwindowlayout.cpp
index 6b247d8d11..f581fe4d88 100644
--- a/src/widgets/widgets/qmainwindowlayout.cpp
+++ b/src/widgets/widgets/qmainwindowlayout.cpp
@@ -215,11 +215,10 @@ public:
     }
     void setGeometry(const QRect&r) Q_DECL_OVERRIDE
     {
+        static_cast<QDockWidgetGroupWindow *>(parent())->destroyOrHideIfEmpty();
         QDockAreaLayoutInfo *li = layoutInfo();
-        if (li->isEmpty()) {
-            static_cast<QDockWidgetGroupWindow *>(parent())->destroyIfEmpty();
+        if (li->isEmpty())
             return;
-        }
         int fw = frameWidth();
         li->reparentWidgets(parentWidget());
         li->rect = r.adjusted(fw, fw, -fw, -fw);
@@ -272,6 +271,10 @@ bool QDockWidgetGroupWindow::event(QEvent *e)
         if (qobject_cast<QDockWidget *>(static_cast<QChildEvent*>(e)->child()))
             adjustFlags();
         break;
+    case QEvent::LayoutRequest:
+        // We might need to show the widget again
+        destroyOrHideIfEmpty();
+        break;
     default:
         break;
     }
@@ -325,34 +328,43 @@ QDockWidget *QDockWidgetGroupWindow::topDockWidget() const
 }
 
 /*! \internal
-    Destroy this window if there is no more QDockWidget in it.
+    Destroy or hide this window if there is no more QDockWidget in it.
+    Otherwise make sure it is shown.
  */
-void QDockWidgetGroupWindow::destroyIfEmpty()
-{
-    if (layoutInfo()->isEmpty()) {
-        // Make sure to reparent the possibly floating or hidden QDockWidgets to the parent
-        foreach (QDockWidget *dw,
-                 findChildren<QDockWidget *>(QString(), Qt::FindDirectChildrenOnly)) {
-            bool wasFloating = dw->isFloating();
-            bool wasHidden = dw->isHidden();
-            dw->setParent(parentWidget());
-            if (wasFloating) {
-                dw->setFloating(true);
-            } else {
-                // maybe it was hidden, we still have to put it back in the main layout.
-                QMainWindowLayout *ml = qt_mainwindow_layout(static_cast<QMainWindow*>(parentWidget()));
-                Qt::DockWidgetArea area = ml->dockWidgetArea(this);
-                if (area == Qt::NoDockWidgetArea)
-                    area = Qt::LeftDockWidgetArea;
-                static_cast<QMainWindow*>(parentWidget())->addDockWidget(area, dw);
-            }
-            if (!wasHidden)
-                dw->show();
+void QDockWidgetGroupWindow::destroyOrHideIfEmpty()
+{
+    if (!layoutInfo()->isEmpty()) {
+        show(); // It might have been hidden,
+        return;
+    }
+    // There might still be placeholders
+    if (!layoutInfo()->item_list.isEmpty()) {
+        hide();
+        return;
+    }
+
+    // Make sure to reparent the possibly floating or hidden QDockWidgets to the parent
+    foreach (QDockWidget *dw, findChildren<QDockWidget *>(QString(), Qt::FindDirectChildrenOnly)) {
+        bool wasFloating = dw->isFloating();
+        bool wasHidden = dw->isHidden();
+        dw->setParent(parentWidget());
+        if (wasFloating) {
+            dw->setFloating(true);
+        } else {
+            // maybe it was hidden, we still have to put it back in the main layout.
+            QMainWindowLayout *ml =
+                qt_mainwindow_layout(static_cast<QMainWindow *>(parentWidget()));
+            Qt::DockWidgetArea area = ml->dockWidgetArea(this);
+            if (area == Qt::NoDockWidgetArea)
+                area = Qt::LeftDockWidgetArea;
+            static_cast<QMainWindow *>(parentWidget())->addDockWidget(area, dw);
         }
-        foreach (QTabBar *tb, findChildren<QTabBar *>(QString(), Qt::FindDirectChildrenOnly))
-            tb->setParent(parentWidget());
-        deleteLater();
+        if (!wasHidden)
+            dw->show();
     }
+    foreach (QTabBar *tb, findChildren<QTabBar *>(QString(), Qt::FindDirectChildrenOnly))
+        tb->setParent(parentWidget());
+    deleteLater();
 }
 
 /*! \internal
@@ -2075,7 +2087,7 @@ void QMainWindowLayout::animationFinished(QWidget *widget)
                 item.subinfo->reparentWidgets(parentWidget());
                 item.subinfo->setTabBarShape(parentInfo->tabBarShape);
             }
-            dwgw->destroyIfEmpty();
+            dwgw->destroyOrHideIfEmpty();
         }
 
         if (QDockWidget *dw = qobject_cast<QDockWidget*>(widget)) {
diff --git a/src/widgets/widgets/qmainwindowlayout_p.h b/src/widgets/widgets/qmainwindowlayout_p.h
index 9a13e5f5ce..7475da8bdc 100644
--- a/src/widgets/widgets/qmainwindowlayout_p.h
+++ b/src/widgets/widgets/qmainwindowlayout_p.h
@@ -86,7 +86,7 @@ public:
         : QWidget(parent, f) {}
     QDockAreaLayoutInfo *layoutInfo() const;
     QDockWidget *topDockWidget() const;
-    void destroyIfEmpty();
+    void destroyOrHideIfEmpty();
     void adjustFlags();
 protected:
     bool event(QEvent *) Q_DECL_OVERRIDE;