QMenuBar, QMenu and QAction

[SPlatten]

@SGaist , I just used Qt Creator to add a menu to the splash window I've created and when the splash window gets the focus, the menu does appear in the top left of the desktop, but this isn't true of my programmatically created window when it gets the focus.

[SPlatten]

I've been looking at a UI which I modified in Qt Creator to add a menu, this works:

/********************************************************************************
** Form generated from reading UI file 'splash.ui'
**
** Created by: Qt User Interface Compiler version 5.15.2
**
** WARNING! All changes made in this file will be lost when recompiling UI file!
********************************************************************************/

#ifndef UI_SPLASH_H
#define UI_SPLASH_H

#include <QtCore/QVariant>
#include <QtWidgets/QAction>
#include <QtWidgets/QApplication>
#include <QtWidgets/QLabel>
#include <QtWidgets/QMainWindow>
#include <QtWidgets/QMenu>
#include <QtWidgets/QMenuBar>
#include <QtWidgets/QWidget>

QT_BEGIN_NAMESPACE

class Ui_splash
{
public:
    QAction *actionAnother_Menu;
    QWidget *centralwidget;
    QLabel *lblHdr;
    QLabel *lblAppTitle;
    QLabel *lblWidth;
    QLabel *lblHeight;
    QLabel *lblWidthVal;
    QLabel *lblHeightVal;
    QMenuBar *menuBar;
    QMenu *menuTest;

    void setupUi(QMainWindow *splash)
    {
        if (splash->objectName().isEmpty())
            splash->setObjectName(QString::fromUtf8("splash"));
        splash->setWindowModality(Qt::NonModal);
        splash->resize(172, 102);
        splash->setFocusPolicy(Qt::NoFocus);
        splash->setWindowTitle(QString::fromUtf8(""));
#if QT_CONFIG(tooltip)
        splash->setToolTip(QString::fromUtf8(""));
#endif // QT_CONFIG(tooltip)
#if QT_CONFIG(statustip)
        splash->setStatusTip(QString::fromUtf8(""));
#endif // QT_CONFIG(statustip)
        actionAnother_Menu = new QAction(splash);
        actionAnother_Menu->setObjectName(QString::fromUtf8("actionAnother_Menu"));
        centralwidget = new QWidget(splash);
        centralwidget->setObjectName(QString::fromUtf8("centralwidget"));
        centralwidget->setStyleSheet(QString::fromUtf8("background-color:#ff333333"));
        lblHdr = new QLabel(centralwidget);
        lblHdr->setObjectName(QString::fromUtf8("lblHdr"));
        lblHdr->setGeometry(QRect(7, 0, 161, 38));
        lblHdr->setText(QString::fromUtf8(""));
        lblHdr->setPixmap(QPixmap(QString::fromUtf8(":/CMPY_LOGO")));
        lblHdr->setScaledContents(false);
        lblHdr->setAlignment(Qt::AlignCenter);
        lblAppTitle = new QLabel(centralwidget);
        lblAppTitle->setObjectName(QString::fromUtf8("lblAppTitle"));
        lblAppTitle->setGeometry(QRect(8, 40, 161, 20));
        lblAppTitle->setStyleSheet(QString::fromUtf8("color:#ffffffff;"));
        lblAppTitle->setAlignment(Qt::AlignCenter);
        lblAppTitle->setOpenExternalLinks(true);
        lblWidth = new QLabel(centralwidget);
        lblWidth->setObjectName(QString::fromUtf8("lblWidth"));
        lblWidth->setGeometry(QRect(8, 80, 91, 20));
        lblWidth->setStyleSheet(QString::fromUtf8("color:#ffffffff;"));
        lblWidth->setAlignment(Qt::AlignLeading|Qt::AlignLeft|Qt::AlignVCenter);
        lblHeight = new QLabel(centralwidget);
        lblHeight->setObjectName(QString::fromUtf8("lblHeight"));
        lblHeight->setGeometry(QRect(8, 60, 91, 20));
        lblHeight->setStyleSheet(QString::fromUtf8("color:#ffffffff;"));
        lblHeight->setAlignment(Qt::AlignLeading|Qt::AlignLeft|Qt::AlignVCenter);
        lblWidthVal = new QLabel(centralwidget);
        lblWidthVal->setObjectName(QString::fromUtf8("lblWidthVal"));
        lblWidthVal->setGeometry(QRect(110, 80, 60, 20));
        lblWidthVal->setStyleSheet(QString::fromUtf8("color:#ffffffff;"));
        lblWidthVal->setAlignment(Qt::AlignRight|Qt::AlignTrailing|Qt::AlignVCenter);
        lblHeightVal = new QLabel(centralwidget);
        lblHeightVal->setObjectName(QString::fromUtf8("lblHeightVal"));
        lblHeightVal->setGeometry(QRect(110, 60, 60, 20));
        lblHeightVal->setStyleSheet(QString::fromUtf8("color:#ffffffff;"));
        lblHeightVal->setAlignment(Qt::AlignRight|Qt::AlignTrailing|Qt::AlignVCenter);
        splash->setCentralWidget(centralwidget);
        menuBar = new QMenuBar(splash);
        menuBar->setObjectName(QString::fromUtf8("menuBar"));
        menuBar->setGeometry(QRect(0, 0, 172, 24));
        menuTest = new QMenu(menuBar);
        menuTest->setObjectName(QString::fromUtf8("menuTest"));
        splash->setMenuBar(menuBar);

        menuBar->addAction(menuTest->menuAction());
        menuTest->addAction(actionAnother_Menu);

        retranslateUi(splash);

        QMetaObject::connectSlotsByName(splash);
    } // setupUi

    void retranslateUi(QMainWindow *splash)
    {
        actionAnother_Menu->setText(QCoreApplication::translate("splash", "Another Menu", nullptr));
#if QT_CONFIG(tooltip)
        lblAppTitle->setToolTip(QCoreApplication::translate("splash", "XML Multi-Platform Application Manager", nullptr));
#endif // QT_CONFIG(tooltip)
        lblAppTitle->setText(QCoreApplication::translate("splash", "XMLMPAM", nullptr));
        lblWidth->setText(QCoreApplication::translate("splash", "Display width: ", nullptr));
        lblHeight->setText(QCoreApplication::translate("splash", "Display height:", nullptr));
        lblWidthVal->setText(QCoreApplication::translate("splash", "0", nullptr));
        lblHeightVal->setText(QCoreApplication::translate("splash", "0", nullptr));
        menuTest->setTitle(QCoreApplication::translate("splash", "Test", nullptr));
        (void)splash;
    } // retranslateUi

};

namespace Ui {
    class splash: public Ui_splash {};
} // namespace Ui

QT_END_NAMESPACE

#endif // UI_SPLASH_H

I then tried to replicate this in my own, the code is now:

        } else if ( mstrName.compare(clsXMLnode::mscszNodeMenu) == 0 ) {
            Q_ASSERT_X(blnIsParentAMenuBar()==true, cpszClassConstr
                       , "Menu's can only be added to a menu bar!");
            const QString cstrShortcut(strGetAttribute(clsXMLnode::mscszAttrShortcut))
                         ,cstrText(strGetAttribute(clsXMLnode::mscszAttrText))
                         ,cstrTooltip(strGetAttribute(clsXMLnode::mscszAttrTooltip));
            clsXMLnode* pobjMainWindowNode(nullptr);
            if ( pobjParent != nullptr && pobjParent->mpobjParent != nullptr ) {
                pobjMainWindowNode = pobjParent->mpobjParent;
            }
            Q_ASSERT_X(pobjMainWindowNode!=nullptr
                    && pobjMainWindowNode->mpobjMainWindow!=nullptr, cpszClassConstr
                     ,"Cannot get parent window!");
            QMainWindow* pobjMainWindow(pobjMainWindowNode->mpobjMainWindow);
            QMenuBar* pobjMenuBar(pobjMainWindow->menuBar());
            Q_ASSERT_X(pobjMenuBar!=nullptr, cpszClassConstr, "Menu bar isn't present!");
            QMenu* pobjMenu(new QMenu(pobjMenuBar));
            Q_ASSERT_X(pobjMenu!=nullptr, cpszClassConstr, "Menu cannot be created!");
            QAction* pobjAction(pobjMenu->menuAction());
            if ( pobjAction != nullptr ) {
                pobjAction->setShortcut(cstrShortcut);
                pobjAction->setText(cstrText);
                pobjAction->setToolTip(cstrTooltip);
                pobjMenuBar->addAction(pobjAction);
                pobjMainWindow->setMenuBar(pobjMenuBar);
                pobjWidget = pobjMenu;
            }
        } else if ( mstrName.compare(clsXMLnode::mscszNodeMenuBar) == 0 ) {
    //The parent node must be a window
            if ( pobjParent != nullptr && pobjParent->blnIsMainWindow() == true ) {
                QMainWindow* pobjMainWindow(pobjParent->pobjGetMainWindow());
                if ( pobjMainWindow != nullptr ) {
                    QMenuBar* pobjMenuBar(new QMenuBar(pobjMainWindow));
                    if ( pobjMenuBar != nullptr ) {
                        int intHeight(pobjMenuBar->fontMetrics().height());
                        QRect rctWindow(pobjParent->rctGetGeometry())
                             ,rctMenuBar(0, 0, 172,24); //rctWindow.width(), intHeight);
                        pobjMenuBar->setGeometry(rctMenuBar);
                        pobjWidget = pobjMenuBar;
                    }
                }
            }
        }

I've singled stepped in the debugger and all the pointers are correct and valid, but I do not see the menus at the top of the desktop when the window has the focus. Can anyone help or suggest how it could be different and what could be wrong?

[SGaist]

Did you try to dump the object tree to see how is your QMainWindow structured ?

[Pl45m4]

@SPlatten

I used

    MainWindow w; // standard mainwindow defined using UI


    QMainWindow* myMW(&w);  // myMW points to w

    QMenuBar* myMenuBar(myMW->menuBar());
    QMenu* myMenu(new QMenu(myMenuBar));

    QAction* myAction(myMenu->menuAction());

    myMenuBar->addAction(myAction);
    myAction->setText("myAction");
    myMW->setMenuBar(myMenuBar);

    myMW->show(); // basically showing w

to reproduce your code.
And it works. I see my MainWindow while the new QMenu and the corresponding action were added to the existing QMenuBar.

I feel a bit silly to ask this, but are you aware that you are working on the "toplevel" QMainWindow the whole time?! Or is it just the "splash" QMainWindow here? Somewhere (maybe even in a separate post) you've mentioned two QMainWindow (are you looking at the right one?!)

As @SGaist mentioned, check your QMainWindow object tree, esp. what widget is parent of what subwidgets, menu, etc.

[SPlatten]

@SGaist , how do I do that?

[SPlatten]

@Pl45m4 , what do you mean, "are you aware that you are working on the "toplevel" QMainWindow the whole time" ?

[JonB]

@SPlatten said in QMenuBar, QMenu and QAction:

@SGaist , how do I do that?

Do what? "dump the object tree to see how is your QMainWindow structured"?

Every QObject (including widgets) has const QObjectList &QObject::children() const. @SGaist suggests you write a debugging routine which calls that recursively starting from your QMainWindow so as to examine the actual object tree (widgets) hierarchy.

[SPlatten]

@Pl45m4 , also, is the call to setMenuBar actually required because the menuBar came from QMainWindow in the first place ?

[SGaist]

@JonB said in QMenuBar, QMenu and QAction:

@SPlatten said in QMenuBar, QMenu and QAction:

@SGaist , how do I do that?

Do what? "dump the object tree to see how is your QMainWindow structured"?

Every QObject (including widgets) has const QObjectList &QObject::children() const. @SGaist suggests you write a debugging routine which calls that recursively starting from your QMainWindow so as to examine the actual object tree (widgets) hierarchy.

I was rather thinking of dumpObjectTree but that's the idea.

[JonB]

@SPlatten
I haven't followed your code, but if you mean that it is taking the menubar which has been set on a QMainWindow and calling setMenuBar() on it to set it elsewhere I don't think you can do that. But maybe that's not what your code is trying to do, I don't know.

[JonB]

@SGaist said in QMenuBar, QMenu and QAction:

I was rather thinking of dumpObjectTree but that's the idea.

LOL, I didn't notice that QObject already provides a method to do this for debugging. Laziness ;-)

[SPlatten]

@SGaist , I added:

qdbg() << "dumpObectTree";
pobjMainWindow->dumpObjectTree();

The result in my log:

dumpObectTree
S000000000004E000000000214T09:04:55.954D:QMainWindow::
S000000000005E000000000214T09:04:55.954D:    QMainWindowLayout::_layout
S000000000006E000000000214T09:04:55.954D:    QWidget::
S000000000007E000000000214T09:04:55.954D:        QPropertyAnimation::
S000000000008E000000000214T09:04:55.954D:        QPropertyAnimation::
S000000000009E000000000214T09:04:55.954D:    QMenuBar::
S000000000010E000000000214T09:04:55.954D:        QToolButton::qt_menubar_ext_button
S000000000011E000000000214T09:04:55.954D:        QMenu::
S000000000012E000000000214T09:04:55.954D:            QAction::

[SPlatten]

@SGaist, @JonB, @Pl45m4 , found something...

In Qt Creator I edited the splash window and added a menubar to it, I then added a single menu to that, compiled, nothing was displayed, then I added a submenu and compiled again, this time the menu was displayed. I have experimented removing the submenu, compiled and run and each time there is no submenu then the top line menu is not shown either.

[JonB]

@SPlatten
Let's get Creator out of this. You can see the code it generates in the ui_....h file. Using that you can produce a minimal example showing the behaviour you state, for good and for bad.

Depending on what that is, I have no knowledge whether MacOS is relevant, I know that does something about top-level menus. Nor do I know whether "splash screen" is relevant. I know no more than this.

[SPlatten]

@JonB , this is the splash ui_splash.h that works, however only when it has a submenu with actions.

/********************************************************************************
** Form generated from reading UI file 'splash.ui'
**
** Created by: Qt User Interface Compiler version 5.15.2
**
** WARNING! All changes made in this file will be lost when recompiling UI file!
********************************************************************************/

#ifndef UI_SPLASH_H
#define UI_SPLASH_H

#include <QtCore/QVariant>
#include <QtWidgets/QAction>
#include <QtWidgets/QApplication>
#include <QtWidgets/QLabel>
#include <QtWidgets/QMainWindow>
#include <QtWidgets/QMenu>
#include <QtWidgets/QMenuBar>
#include <QtWidgets/QWidget>

QT_BEGIN_NAMESPACE

class Ui_splash
{
public:
    QAction *action_New;
    QAction *action_Open;
    QAction *action_Save;
    QWidget *centralwidget;
    QLabel *lblHdr;
    QLabel *lblAppTitle;
    QLabel *lblWidth;
    QLabel *lblHeight;
    QLabel *lblWidthVal;
    QLabel *lblHeightVal;
    QMenuBar *menuBar;
    QMenu *menu_File;

    void setupUi(QMainWindow *splash)
    {
        if (splash->objectName().isEmpty())
            splash->setObjectName(QString::fromUtf8("splash"));
        splash->setWindowModality(Qt::NonModal);
        splash->resize(172, 102);
        splash->setFocusPolicy(Qt::NoFocus);
        splash->setWindowTitle(QString::fromUtf8(""));
#if QT_CONFIG(tooltip)
        splash->setToolTip(QString::fromUtf8(""));
#endif // QT_CONFIG(tooltip)
#if QT_CONFIG(statustip)
        splash->setStatusTip(QString::fromUtf8(""));
#endif // QT_CONFIG(statustip)
        action_New = new QAction(splash);
        action_New->setObjectName(QString::fromUtf8("action_New"));
        action_Open = new QAction(splash);
        action_Open->setObjectName(QString::fromUtf8("action_Open"));
        action_Save = new QAction(splash);
        action_Save->setObjectName(QString::fromUtf8("action_Save"));
        centralwidget = new QWidget(splash);
        centralwidget->setObjectName(QString::fromUtf8("centralwidget"));
        centralwidget->setStyleSheet(QString::fromUtf8("background-color:#ff333333"));
        lblHdr = new QLabel(centralwidget);
        lblHdr->setObjectName(QString::fromUtf8("lblHdr"));
        lblHdr->setGeometry(QRect(7, 0, 161, 38));
        lblHdr->setText(QString::fromUtf8(""));
        lblHdr->setPixmap(QPixmap(QString::fromUtf8(":/CMPY_LOGO")));
        lblHdr->setScaledContents(false);
        lblHdr->setAlignment(Qt::AlignCenter);
        lblAppTitle = new QLabel(centralwidget);
        lblAppTitle->setObjectName(QString::fromUtf8("lblAppTitle"));
        lblAppTitle->setGeometry(QRect(8, 40, 161, 20));
        lblAppTitle->setStyleSheet(QString::fromUtf8("color:#ffffffff;"));
        lblAppTitle->setAlignment(Qt::AlignCenter);
        lblAppTitle->setOpenExternalLinks(true);
        lblWidth = new QLabel(centralwidget);
        lblWidth->setObjectName(QString::fromUtf8("lblWidth"));
        lblWidth->setGeometry(QRect(8, 80, 91, 20));
        lblWidth->setStyleSheet(QString::fromUtf8("color:#ffffffff;"));
        lblWidth->setAlignment(Qt::AlignLeading|Qt::AlignLeft|Qt::AlignVCenter);
        lblHeight = new QLabel(centralwidget);
        lblHeight->setObjectName(QString::fromUtf8("lblHeight"));
        lblHeight->setGeometry(QRect(8, 60, 91, 20));
        lblHeight->setStyleSheet(QString::fromUtf8("color:#ffffffff;"));
        lblHeight->setAlignment(Qt::AlignLeading|Qt::AlignLeft|Qt::AlignVCenter);
        lblWidthVal = new QLabel(centralwidget);
        lblWidthVal->setObjectName(QString::fromUtf8("lblWidthVal"));
        lblWidthVal->setGeometry(QRect(110, 80, 60, 20));
        lblWidthVal->setStyleSheet(QString::fromUtf8("color:#ffffffff;"));
        lblWidthVal->setAlignment(Qt::AlignRight|Qt::AlignTrailing|Qt::AlignVCenter);
        lblHeightVal = new QLabel(centralwidget);
        lblHeightVal->setObjectName(QString::fromUtf8("lblHeightVal"));
        lblHeightVal->setGeometry(QRect(110, 60, 60, 20));
        lblHeightVal->setStyleSheet(QString::fromUtf8("color:#ffffffff;"));
        lblHeightVal->setAlignment(Qt::AlignRight|Qt::AlignTrailing|Qt::AlignVCenter);
        splash->setCentralWidget(centralwidget);
        menuBar = new QMenuBar(splash);
        menuBar->setObjectName(QString::fromUtf8("menuBar"));
        menuBar->setGeometry(QRect(0, 0, 172, 24));
        menu_File = new QMenu(menuBar);
        menu_File->setObjectName(QString::fromUtf8("menu_File"));
        splash->setMenuBar(menuBar);

        menuBar->addAction(menu_File->menuAction());
        menu_File->addAction(action_New);
        menu_File->addAction(action_Open);
        menu_File->addAction(action_Save);

        retranslateUi(splash);

        QMetaObject::connectSlotsByName(splash);
    } // setupUi

    void retranslateUi(QMainWindow *splash)
    {
        action_New->setText(QCoreApplication::translate("splash", "&New", nullptr));
        action_Open->setText(QCoreApplication::translate("splash", "&Open", nullptr));
        action_Save->setText(QCoreApplication::translate("splash", "&Save", nullptr));
#if QT_CONFIG(tooltip)
        lblAppTitle->setToolTip(QCoreApplication::translate("splash", "XML Multi-Platform Application Manager", nullptr));
#endif // QT_CONFIG(tooltip)
        lblAppTitle->setText(QCoreApplication::translate("splash", "XMLMPAM", nullptr));
        lblWidth->setText(QCoreApplication::translate("splash", "Display width: ", nullptr));
        lblHeight->setText(QCoreApplication::translate("splash", "Display height:", nullptr));
        lblWidthVal->setText(QCoreApplication::translate("splash", "0", nullptr));
        lblHeightVal->setText(QCoreApplication::translate("splash", "0", nullptr));
        menu_File->setTitle(QCoreApplication::translate("splash", "&File", nullptr));
        (void)splash;
    } // retranslateUi

};

namespace Ui {
    class splash: public Ui_splash {};
} // namespace Ui

QT_END_NAMESPACE

#endif // UI_SPLASH_H

[SPlatten]

Finally fixed:

        if ( mstrName.compare(clsXMLnode::mscszNodeAction) == 0 ) {
            Q_ASSERT_X(blnIsParentAMenu()==true, cpszClassConstr
                       , "Actions only be used in a menu!");
            Q_ASSERT_X(pobjParWidget!=nullptr, cpszClassConstr, "No menubar!");
            const QString cstrShortcut(strGetAttribute(clsXMLnode::mscszAttrShortcut))
                         ,cstrText(strGetAttribute(clsXMLnode::mscszAttrText))
                         ,cstrTooltip(strGetAttribute(clsXMLnode::mscszAttrTooltip));
            QMenu* pobjParentMenu(qobject_cast<QMenu*>(pobjParWidget));
            Q_ASSERT_X(pobjParentMenu!=nullptr, cpszClassConstr, "Widget is not a menu!");
            QWidget* pobjWindow(pobjParentMenu->window());
            Q_ASSERT_X(pobjWindow!=nullptr, cpszClassConstr, "Cannot get window!");
            QAction* pobjAction(new QAction(pobjWindow));
            Q_ASSERT_X(pobjAction!=nullptr, cpszClassConstr, "Cannot create an action!");
            pobjAction->setShortcut(QCoreApplication::translate("clsMainWnd"
                                                               ,cstrShortcut.toLatin1()
                                   ,nullptr));
            pobjAction->setText(cstrText);
            pobjAction->setToolTip(cstrTooltip);
            pobjParentMenu->addAction(pobjAction);
        } else if ( mstrName.compare(clsXMLnode::mscszNodeMenu) == 0 ) {
            Q_ASSERT_X(blnIsParentAMenuBar()==true, cpszClassConstr
                       , "Menu's can only be added to a menu bar!");
            const QString cstrShortcut(strGetAttribute(clsXMLnode::mscszAttrShortcut))
                         ,cstrText(strGetAttribute(clsXMLnode::mscszAttrText))
                         ,cstrTooltip(strGetAttribute(clsXMLnode::mscszAttrTooltip));
            clsXMLnode* pobjMainWindowNode(nullptr);
            if ( pobjParent != nullptr && pobjParent->mpobjParent != nullptr ) {
                pobjMainWindowNode = pobjParent->mpobjParent;
            }
            Q_ASSERT_X(pobjMainWindowNode!=nullptr
                    && pobjMainWindowNode->mpobjMainWindow!=nullptr, cpszClassConstr
                     ,"Cannot get parent window!");
            QMainWindow* pobjMainWindow(pobjMainWindowNode->mpobjMainWindow);
            QMenuBar* pobjMenuBar(pobjMainWindow->menuBar());
            Q_ASSERT_X(pobjMenuBar!=nullptr, cpszClassConstr, "Cannot get menu bar!");
            QMenu* pobjMenu(new QMenu(pobjMenuBar));
            Q_ASSERT_X(pobjMenu!=nullptr, cpszClassConstr, "Cannot create menu!");
            QAction* pobjAction(pobjMenu->menuAction());
            Q_ASSERT_X(pobjAction!=nullptr, cpszClassConstr, "Cannot get action!");
            pobjAction->setShortcut(cstrShortcut);
            pobjAction->setText(cstrText);
            pobjAction->setToolTip(cstrTooltip);
            pobjMenuBar->addAction(pobjAction);
            pobjMenu->show();
            pobjMenuBar->show();
            pobjWidget = pobjMenu;
        } else if ( mstrName.compare(clsXMLnode::mscszNodeMenuBar) == 0 ) {
    //Nothing required menubar should already be present in an instance of QMainWindow!
      }

[Pl45m4]

@SPlatten said in QMenuBar, QMenu and QAction:

@Pl45m4 , what do you mean, "are you aware that you are working on the "toplevel" QMainWindow the whole time" ?

Are there two MainWindows involved in your app or is it just one?! Does this MainWindow have a QMenuBar already? Because your arent creating a new one

[Pl45m4]

@SPlatten said in QMenuBar, QMenu and QAction:

pobjMenu->show();
pobjMenuBar->show();

Still weird that this seems to fix it because usually you dont have to show a QMenuBar explicitly.
Or what fixed it in the end?

QMainWindow::menuBar() says:

Returns the menu bar for the main window. This function creates and returns an empty menu bar if the menu bar does not exist.

And this, either existing QMenuBar or the newly created one, is already a child of QMainWindow.
So I wouldn't expect that you have to show it or apply it to your mainWindow manually again.

Dont know if this is somewhat relevant for you but reading the documentation further, it says:

If you want all windows in a Mac application to share one menu bar, don't use this function to create it, because the menu bar created here will have this QMainWindow as its parent. Instead, you must create a menu bar that does not have a parent, which you can then share among all the Mac windows. Create a parent-less menu bar this way:

QMenuBar *menuBar = new QMenuBar(0);