add the same menu to multiple windows with Qt

Question

I am writing a program with Qt. I have a QMainWindow and a function called createMenus() that returns a QMenuBar*.

Within the class MainWindow : QMainWindow, I call: this->setMenuBar(createMenus());

So I have a beautiful MainWindow with a menu in the top.

Now, in "File", I want to put a button that creates a new window (presumably a QWidget?). And I would like to show the same MenuBar in the top part of my new window.

void MainWindow::createWindow()
{
    QWidget* window = new QWidget;

    QVBoxLayout* center_box = new QVBoxLayout;
    center_box->setContentsMargins(0, 0, 0, 0);
    center_box->setSpacing(0);

#ifndef Q_OS_MAC
    QMenuBar* newMenu = createMenus();
    center_box->setMenuBar(newMenu);
#endif

    window->setLayout(center_box);
}

This works (in Linux), as a QMenuBar is shown in the new window. The aftereffect is that the QMenuBar in the MainWindow has disappeared.

Can someone direct me to the best implementation to create multiple windows with the same QMenuBar?

Answer 1

I've looked up your issue and noticed the same behaviour, however you cannot simply copy the existing QMenuBar of your QMainWindow .

You could however use a factory method like you did, but you have to assure that you don't return an empty QMenuBar , otherwise the menu won't show up.

Possible implementation:

QMenuBar* MainWindow::createMenu()
{
    QMenuBar *menu = new QMenuBar();


    menu->addMenu("Test0");
    menu->addMenu("Test1");
    menu->addMenu("Test2");
    menu->addMenu("Test3");

    return menu;
}

And then in your method you can do:

void MainWindow::createWindow()
{
    QWidget* window = new QWidget;

    QVBoxLayout* center_box = new QVBoxLayout;

#ifndef Q_OS_MAC
    center_box->setMenuBar(createMenu());
#endif

    window->setLayout(center_box);
    window->show();
}

---

Another way would be to subclass QMenuBar , which is however more suitable if you want to create a specific kind of implementation or add to the functionality of the already existing class.

custommenubar.h

#ifndef CUSTOMMENUBAR_H
#define CUSTOMMENUBAR_H

#include <QObject>
#include <QMenuBar>

class CustomMenuBar : public QMenuBar
{
    Q_OBJECT

    public:
        explicit CustomMenuBar();
};

#endif // CUSTOMMENUBAR_H

---

custommenubar.cpp

#include "custommenubar.h"

CustomMenuBar::CustomMenuBar()
{
    addMenu("Test");
    addMenu("1");
    addMenu("2");
    addMenu("3");
}

---

And then in your method:

void MainWindow::createWindow()
{
    QWidget* window = new QWidget;

    QVBoxLayout* center_box = new QVBoxLayout;

#ifndef Q_OS_MAC
    QMenuBar* newMenu = new CustomMenuBar();
    center_box->setMenuBar(newMenu);
#endif

    window->setLayout(center_box);
    window->show();
}

---

Make sure you take care of cleaning everything up :)