QSpinBox inside a QScrollArea: How to prevent Spin Box from stealing focus when scrolling?

Question

I have a control with several QSpinBox objects inside a QScrollArea. All works fine when scrolling in the scroll area unless the mouse happens to be over one of the QSpinBoxes. Then the QSpinBox steals focus and the wheel events manipulate the spin box value rather than scrolling the scroll area.

I don't want to completely disable using the mouse wheel to manipulate the QSpinBox, but I only want it to happen if the user explicitly clicks or tabs into the QSpinBox. Is there a way to prevent the QSpinBox from stealing the focus from the QScrollArea?

As said in a comment to an answer below, setting Qt::StrongFocus does prevent the focus rect from appearing on the control, however it still steals the mouse wheel and adjusts the value in the spin box and stops the QScrollArea from scrolling. Same with Qt::ClickFocus.

Answer 1

In order to solve this, we need to care about the two following things:

1. The spin box mustn't gain focus by using the mouse wheel. This can be done by setting the focus policy to Qt::StrongFocus.
2. The spin box must only accept wheel events if it already has focus. This can be done by reimplementing QWidget::wheelEvent within a QSpinBox subclass.

Complete code for a MySpinBox class which implements this:

class MySpinBox : public QSpinBox {

    Q_OBJECT

public:

    MySpinBox(QWidget *parent = 0) : QSpinBox(parent) {
        setFocusPolicy(Qt::StrongFocus);
    }

protected:

    virtual void wheelEvent(QWheelEvent *event) {
        if (!hasFocus()) {
            event->ignore();
        } else {
            QSpinBox::wheelEvent(event);
        }
    }
};

That's it. Note that if you don't want to create a new QSpinBox subclass, then you can also use event filters instead to solve this.