From 36fadb4c130c12847ac53bc588f944494d69603d Mon Sep 17 00:00:00 2001
From: Axel Spoerl <axel.spoerl@qt.io>
Date: Fri, 17 Nov 2023 11:12:26 +0100
Subject: [PATCH] QMainWindowTabBar: Add destructor

QMainWindowLayout re-uses tab bars. A QSet and a QList member are kept,
to track used and unused tab bars.

Corner cases upon application close down leave dangling pointers in
those containers.

=> Add a destructor to QMainWindowTabBar
=> remove the tab bar from used and unused tab bar containers, if
not directly parented to the main window.

=> No longer reparent unused tab bars of a QDockWidgetGroupWindow
to the main window. Let them be destroyed as a group window child,
and its destructor remove it from the used/unused tab bar container.

Pick-to: 6.5
Change-Id: If2388cf878553dc89583dbc8585748fad65bbab2
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>
(cherry picked from commit b6b489db6968fbc3b4aab3755d0166ee09712ff0)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>
---
 src/widgets/widgets/qmainwindowlayout.cpp | 21 ++++++++++++++++-----
 1 file changed, 16 insertions(+), 5 deletions(-)

diff --git a/src/widgets/widgets/qmainwindowlayout.cpp b/src/widgets/widgets/qmainwindowlayout.cpp
index 8f8e60888f3..f07180e8ea5 100644
--- a/src/widgets/widgets/qmainwindowlayout.cpp
+++ b/src/widgets/widgets/qmainwindowlayout.cpp
@@ -448,11 +448,6 @@ void QDockWidgetGroupWindow::destroyOrHideIfEmpty()
         if (!wasHidden)
             dw->show();
     }
-#if QT_CONFIG(tabbar)
-    const auto tabBars = findChildren<QTabBar *>(Qt::FindDirectChildrenOnly);
-    for (QTabBar *tb : tabBars)
-        tb->setParent(parentWidget());
-#endif
     deleteLater();
 }
 
@@ -1776,6 +1771,7 @@ class QMainWindowTabBar : public QTabBar
 {
     QMainWindow *mainWindow;
     QPointer<QDockWidget> draggingDock; // Currently dragging (detached) dock widget
+    ~QMainWindowTabBar();
 public:
     QMainWindowTabBar(QMainWindow *parent);
 protected:
@@ -1841,6 +1837,21 @@ void QMainWindowTabBar::mouseMoveEvent(QMouseEvent *e)
     QTabBar::mouseMoveEvent(e);
 }
 
+QMainWindowTabBar::~QMainWindowTabBar()
+{
+    if (!mainWindow || mainWindow == parentWidget())
+        return;
+
+    // tab bar is not parented to the main window
+    // => can only be a dock widget group window
+    // => remove itself from used and unused tab bar containers
+    auto *mwLayout = qt_mainwindow_layout(mainWindow);
+    if (!mwLayout)
+        return;
+    mwLayout->unusedTabBars.removeOne(this);
+    mwLayout->usedTabBars.remove(this);
+}
+
 void QMainWindowTabBar::mouseReleaseEvent(QMouseEvent *e)
 {
     if (draggingDock && e->button() == Qt::LeftButton) {