Create custom widget as toolbar for QMainWindow

Question

I want to create a custom toolbar widget (something like a ribbon). Then I want to create a QMainWindow that uses this custom widget as its toolbar.

I can do something like

class RibbonToolbar : public QToolBar {
...
};

...


QMainWindow *window = new QMainWindow();
RibbonToolbar *toolbar = new RibbonToolbar(window);
window->addToolBar(toolbar);

The problem is that in this way RibbonToolbar inherits all methods from QToolbar and I don't want it because my widget does not use them. It's a completely new widget.

I'd like to do this:

class RibbonToolbar : public QWidget {
...
};

So if I declare my class in this way, what's the best way to add it to the top of the QMainWindow?

PS: My widget can be adapted if QMainWindow is resized but, like the ribbon in Microsoft Office, it's a fixed position so it can't move around into the main window.

Answer 1

In C++ , it is not possible to remove functionality from a class. However, it is possible to hide existing functionality. (1)

That being said, how about you hide QToolBar member functions that you don't want to use by declaring them private ?

Let's use a QWidget as an example:

widget.h:

#ifndef WIDGET_H
#define WIDGET_H

#include <QWidget>

class Widget : public QWidget
{
    Q_OBJECT

public:
    explicit Widget(QWidget *parent = 0);
    ~Widget();

private:
    void setGeometry(const QRect &);
    void setGeometry(int x, int y, int w, int h);
};

#endif // WIDGET_H

widget.cpp:

#include "widget.h"

Widget::Widget(QWidget *parent) :
    QWidget(parent)
{
}

Widget::~Widget()
{
}

void Widget::setGeometry(const QRect &)
{
}

void Widget::setGeometry(int x, int y, int w, int h)
{
}

In this case, even though setGeometry is a member function of QWidget , you can't use it in anymore from Widget . Similarly you could hide QToolBar::isMovable by declaring it private and provide an empty implementation for it.

Also more conveniently would be to declare them protected so that they will be accessible from derived classes if you want.

AFAIK you can't use

class RibbonToolbar : public QWidget {
...
};

because QMainWindow API is made in such way that it will accept only pointers to QToolBar for its toolbar areas. You could trick it by creating a RibbonToolbar which is binary compatible with QToolBar and reinterpret_cast the object to QToolBar* but then you would need to deeply know the inner guts of Qt and it would still be bad practice.