Merge pull request qt#91 from autodesk-forks/kandass1/MAYA-131102/res…

…olve_docking_issues_post_qt6_new

- Dragging an individual DockWidget (Tab) doesn't require a QDockWidgetGroupWindow immediately, Hence, returning the unplugged DockWidget directly.
- Hovering a DockWidget on top of another DockWidget, creates a QDockWidgetGroupWindow if one doesn't already exist. However, dropTarget's widgetItem might not be already available in the parent layout which causes a crash. Hence, setting a DockWidgetItem.
- Closing all the child DockWidgets would eventually cause the QDockWidgetGroupWindow to be hidden. However, when we re-toggle DockWidget visibility from the menu items, the DockWidget won't become visible since its parent QDockWidgetGroupWindow is hidden. Hence adding a listener for the DockWidget's toggle action ensures the parent is shown before the widget.

src/widgets/widgets/qmainwindowlayout.cpp

@@ -35,6 +35,8 @@
 #include <qmap.h>
 #include <qtimer.h>
 #include <qpointer.h>
+#include <qobject.h>
+#include <qaction.h>
 
 #ifndef QT_NO_DEBUG_STREAM
 #  include <qdebug.h>
@@ -264,6 +266,20 @@ bool QDockWidgetGroupWindow::event(QEvent *e)
         if (QDockWidget *dw = activeTabbedDockWidget()) {
             dw->close();
             adjustFlags();
+            // when all child QDockWidgets' are closed, this QDockWidgetGroupWindow will be hidden
+            // after receiving the `LayoutRequest` event. This causes subsequent call to show
+            // on the current QDockWidget to fail. Hence, adding a connection to the 
+            // QDockWidget's toggle action to re-show this QDockWidgetGroupWindow along with the 
+            // current QDockWidget.
+            m_widgetConnections[dw] = connect(dw->toggleViewAction(), &QAction::toggled, [this, dw]() {
+                // show this QDockWidgetGroupWindow before showing the child QDockWidget.
+                show();
+                dw->show();
+                // once at least one child becomes visible, clear all listeners since we no longer need them..
+                for (const auto& pair : m_widgetConnections)
+                    disconnect(pair.second);
+                m_widgetConnections.clear();
+            });
         }
 #endif
         return true;
@@ -288,6 +304,10 @@ bool QDockWidgetGroupWindow::event(QEvent *e)
         if (qobject_cast<QDockWidget *>(static_cast<QChildEvent*>(e)->child()))
             adjustFlags();
         break;
+    case QEvent::ChildRemoved:
+        if (auto widget = qobject_cast<QDockWidget *>(static_cast<QChildEvent*>(e)->child()))
+            m_widgetConnections.erase(widget);
+        break;
     case QEvent::LayoutRequest:
         // We might need to show the widget again
         destroyOrHideIfEmpty();
@@ -2577,70 +2597,7 @@ QLayoutItem *QMainWindowLayout::unplug(QWidget *widget, bool group)
 
             // unplug the widget first
             dockWidget->d_func()->unplug(widget->geometry());
-
-            // Create a floating tab, copy properties and generate layout info
-            QDockWidgetGroupWindow *floatingTabs = createTabbedDockWindow();
-            const QInternal::DockPosition dockPos = groupWindow->layoutInfo()->dockPos;
-            QDockAreaLayoutInfo *info = floatingTabs->layoutInfo();
-
-            const QTabBar::Shape shape = tabwidgetPositionToTabBarShape(dockWidget);
-
-            // Populate newly created DockAreaLayoutInfo of floating tabs
-            *info = QDockAreaLayoutInfo(&layoutState.dockAreaLayout.sep, dockPos,
-                                        Qt::Horizontal, shape,
-                                        layoutState.mainWindow);
-
-            // Create tab and hide it as group window contains only one widget
-            info->tabbed = true;
-            info->tabBar = getTabBar();
-            info->tabBar->hide();
-            updateGapIndicator();
-
-            // Reparent it to a QDockWidgetGroupLayout
-            floatingTabs->setGeometry(dockWidget->geometry());
-
-            // Append reference to floatingTabs to the dock's item_list
-            parentItem.widgetItem = new QDockWidgetGroupWindowItem(floatingTabs);
-            layoutState.dockAreaLayout.docks[dockPos].item_list.append(parentItem);
-
-            // use populated parentItem to set reference to dockWidget as the first item in own list
-            parentItem.widgetItem = new QDockWidgetItem(dockWidget);
-            info->item_list = {parentItem};
-
-            // Add non-gap items of the dock to the tab bar
-            for (const auto &listItem : layoutState.dockAreaLayout.docks[dockPos].item_list) {
-                if (listItem.GapItem || !listItem.widgetItem)
-                    continue;
-                info->tabBar->addTab(listItem.widgetItem->widget()->objectName());
-            }
-
-            // Re-parent and fit
-            floatingTabs->setParent(layoutState.mainWindow);
-            floatingTabs->layoutInfo()->fitItems();
-            floatingTabs->layoutInfo()->apply(dockOptions & QMainWindow::AnimatedDocks);
-            groupWindow->layoutInfo()->fitItems();
-            groupWindow->layoutInfo()->apply(dockOptions & QMainWindow::AnimatedDocks);
-            dockWidget->d_func()->tabPosition = layoutState.mainWindow->tabPosition(toDockWidgetArea(dockPos));
-            info->reparentWidgets(floatingTabs);
-            dockWidget->setParent(floatingTabs);
-            info->updateTabBar();
-
-            // Show the new item
-            const QList<int> path = layoutState.indexOf(floatingTabs);
-            QRect r = layoutState.itemRect(path);
-            savedState = layoutState;
-            savedState.fitLayout();
-
-            // Update gap, fix orientation, raise and show
-            currentGapPos = path;
-            currentGapRect = r;
-            updateGapIndicator();
-            fixToolBarOrientation(parentItem.widgetItem, currentGapPos.at(1));
-            floatingTabs->show();
-            floatingTabs->raise();
-
-            qCDebug(lcQpaDockWidgets) << "Unplugged from floating dock:" << widget << "from" << parentItem.widgetItem;
-            return parentItem.widgetItem;
+            return item;
         }
     }
 #endif
@@ -2837,10 +2794,18 @@ void QMainWindowLayout::hover(QLayoutItem *hoverTarget,
                     info->tabBar = getTabBar();
                     info->tabbed = true;
                     QLayout *parentLayout = dropTo->parentWidget()->layout();
-                    info->item_list.append(
-                        QDockAreaLayoutItem(parentLayout->takeAt(parentLayout->indexOf(dropTo))));
-
+                    auto parentItem = QDockAreaLayoutItem(parentLayout->takeAt(parentLayout->indexOf(dropTo)));
+                    if (!parentItem.widgetItem)
+                        parentItem.widgetItem = new QDockWidgetItem(dropTo);
+                    info->item_list.append(parentItem);
+
+                    auto oldGroupWindow = qobject_cast<QDockWidgetGroupWindow *>(dropTo->parent());
                     dropTo->setParent(floatingTabs);
+                    // just an early cleanup to if there are no other children.
+                    if (oldGroupWindow) {
+                        oldGroupWindow->destroyOrHideIfEmpty();
+                    }
+
                     qCDebug(lcQpaDockWidgets) << "Wrapping" << widget << "into floating tabs" << floatingTabs;
                     w = floatingTabs;
                 }

src/widgets/widgets/qmainwindowlayout_p.h

@@ -38,6 +38,7 @@
 #include "qtoolbararealayout_p.h"
 #endif
 #include <QtCore/qloggingcategory.h>
+#include <unordered_map>
 
 QT_REQUIRE_CONFIG(mainwindow);
 
@@ -335,6 +336,7 @@ class Q_AUTOTEST_EXPORT QDockWidgetGroupWindow : public QWidget
 
 private:
     QSize m_removedFrameSize;
+    std::unordered_map<QDockWidget*, QMetaObject::Connection> m_widgetConnections;
 };
 
 // This item will be used in the layout for the gap item. We cannot use QWidgetItem directly