Designer crashes when previewing QMainWindow with native Toolbar on Mac

The crash happens when a QMainWindow with a native toolbar is reparented.
While re-parenting, the QToolBar triggers a new setParent() with the
MacWindowToolBarButtonHint. This messes up the internal state, hence the
crash. To avoid re-entering setParent() for the QMainWindow, this hint
is set depending on the unifiedTitleAndToolBarOnMac property.

This patch also fixes a related issue in Cocoa, we need to remove the
reused NSToolbar from the old window while recreating the QMainWindow.

Task-number: QTBUG-7162
Reviewed-by: Richard Moe Gustavsen

1 files changed, 13 insertions, 0 deletions

diff --git a/src/gui/kernel/qwidget_mac.mm b/src/gui/kernel/qwidget_mac.mm
index 354a666..b18830f 100644
--- a/src/gui/kernel/qwidget_mac.mm
+++ b/src/gui/kernel/qwidget_mac.mm
@@ -110,6 +110,7 @@
 #include "qevent_p.h"
 #include "qdnd_p.h"
 #include <QtGui/qgraphicsproxywidget.h>
+#include "qmainwindow.h"
 
 QT_BEGIN_NAMESPACE
 
@@ -1721,6 +1722,15 @@ bool QWidgetPrivate::qt_widget_rgn(QWidget *widget, short wcode, RgnHandle rgn,
 void QWidgetPrivate::determineWindowClass()
 {
     Q_Q(QWidget);
+#if !defined(QT_NO_MAINWINDOW) && !defined(QT_NO_TOOLBAR)
+    // Make sure that QMainWindow has the MacWindowToolBarButtonHint when the
+    // unifiedTitleAndToolBarOnMac property is ON. This is to avoid reentry of
+    // setParent() triggered by the QToolBar::event(QEvent::ParentChange).
+    QMainWindow *mainWindow = qobject_cast<QMainWindow *>(q);
+    if (mainWindow && mainWindow->unifiedTitleAndToolBarOnMac()) {
+        data.window_flags |= Qt::MacWindowToolBarButtonHint;
+    }
+#endif
 #ifndef QT_MAC_USE_COCOA
 // ### COCOA:Interleave these better!
 
@@ -2743,7 +2753,9 @@ void QWidgetPrivate::setParent_sys(QWidget *parent, Qt::WindowFlags f)
         }
         if (wasWindow) {
             oldToolbar = [oldWindow toolbar];
+            [oldToolbar retain];
             oldToolbarVisible = [oldToolbar isVisible];
+            [oldWindow setToolbar:nil];
         }
 #endif
     }
@@ -2787,6 +2799,7 @@ void QWidgetPrivate::setParent_sys(QWidget *parent, Qt::WindowFlags f)
             if (oldToolbar && !(f & Qt::FramelessWindowHint)) {
                 OSWindowRef newWindow = qt_mac_window_for(q);
                 [newWindow setToolbar:oldToolbar];
+                [oldToolbar release];
                 [oldToolbar setVisible:oldToolbarVisible];
             }
 #endif