Mac: fix bug when reparenting non-native menu bars

If we reparent a naive menu bar inside a widget that
has a menu bar from before, the old menu bar is lost.
This patch makes sure that we don't set the new
menu bar in this case, but let it remain as-is in
case the widget is reparanted out again later.

Rev-By: MortenS

3 files changed, 26 insertions, 4 deletions

diff --git a/src/gui/widgets/qmenu_mac.mm b/src/gui/widgets/qmenu_mac.mm
index cee38ee..b238faf 100644
--- a/src/gui/widgets/qmenu_mac.mm
+++ b/src/gui/widgets/qmenu_mac.mm
@@ -1771,6 +1771,16 @@ QMenuBarPrivate::QMacMenuBarPrivate::removeAction(QMacMenuAction *action)
     actionItems.removeAll(action);
 }
 
+bool QMenuBarPrivate::macWidgetHasNativeMenubar(QWidget *widget)
+{
+    // This function is different from q->isNativeMenuBar(), as
+    // it returns true only if a native menu bar is actually
+    // _created_.
+    if (!widget)
+        return false;
+    return menubars()->contains(widget->window());
+}
+
 void
 QMenuBarPrivate::macCreateMenuBar(QWidget *parent)
 {
@@ -1778,16 +1788,22 @@ QMenuBarPrivate::macCreateMenuBar(QWidget *parent)
     static int dontUseNativeMenuBar = -1;
     // We call the isNativeMenuBar function here
     // because that will make sure that local overrides
-    // are dealt with correctly.
+    // are dealt with correctly. q->isNativeMenuBar() will, if not
+    // overridden, depend on the attribute Qt::AA_DontUseNativeMenuBar:
     bool qt_mac_no_native_menubar = !q->isNativeMenuBar();
     if (qt_mac_no_native_menubar == false && dontUseNativeMenuBar < 0) {
+        // The menubar is set to be native. Let's check (one time only
+        // for all menubars) if this is OK with the rest of the environment.
+        // As a result, Qt::AA_DontUseNativeMenuBar is set. NB: the application
+        // might still choose to not respect, or change, this flag.
         bool isPlugin = QApplication::testAttribute(Qt::AA_MacPluginApplication);
         bool environmentSaysNo = !qgetenv("QT_MAC_NO_NATIVE_MENUBAR").isEmpty();
         dontUseNativeMenuBar = isPlugin || environmentSaysNo;
         QApplication::instance()->setAttribute(Qt::AA_DontUseNativeMenuBar, dontUseNativeMenuBar);
         qt_mac_no_native_menubar = !q->isNativeMenuBar();
     }
-    if (!qt_mac_no_native_menubar) {
+    if (qt_mac_no_native_menubar == false) {
+        // INVARIANT: Use native menubar.
         extern void qt_event_request_menubarupdate(); //qapplication_mac.cpp
         qt_event_request_menubarupdate();
         if (!parent && !fallback) {
diff --git a/src/gui/widgets/qmenubar.cpp b/src/gui/widgets/qmenubar.cpp
index 13e7de4..f2f0722 100644
--- a/src/gui/widgets/qmenubar.cpp
+++ b/src/gui/widgets/qmenubar.cpp
@@ -1370,8 +1370,13 @@ void QMenuBarPrivate::handleReparent()
     oldWindow = newWindow;
 
 #ifdef Q_WS_MAC
-    macDestroyMenuBar();
-    macCreateMenuBar(newParent);
+    if (q->isNativeMenuBar() && !macWidgetHasNativeMenubar(newParent)) {
+        // If the new parent got a native menubar from before, keep that
+        // menubar rather than replace it with this one (because a parents
+        // menubar has precedence over children menubars).
+        macDestroyMenuBar();
+        macCreateMenuBar(newParent);
+    }
 #endif
 
 #ifdef Q_WS_WINCE
diff --git a/src/gui/widgets/qmenubar_p.h b/src/gui/widgets/qmenubar_p.h
index 0b27b97..7815969 100644
--- a/src/gui/widgets/qmenubar_p.h
+++ b/src/gui/widgets/qmenubar_p.h
@@ -196,6 +196,7 @@ public:
             return 0;
         }
     } *mac_menubar;
+    bool macWidgetHasNativeMenubar(QWidget *widget);
     void macCreateMenuBar(QWidget *);
     void macDestroyMenuBar();
     OSMenuRef macMenu();