How can I move the icon above text in QComboBox

I have been looking at the QComboBox source file for a while now and I can't figure out what I need to change so that the icon is positioned above text in a QComboBox.

|-----------------------|
|         -----         |
|         |icn|         |
|         -----         |
|    Text label here    |
-------------------------

The paint method in QCombobox is very simple and references something called QStyleOptionComboBox, but I don't think I want to be making changes here though as this will impact portability.

Would I be better inventing something new to act and behave like a QComboBox?

I should have added that it I am looking at changing both the ListView and selected item i.e the button portion.

Solution

In order to handle the icon's (decoration) position in the combo box's pull down view, you need to override its view options QAbstractItemView::viewOptions(). Let's create a custom view and replace the native combo box view with ours:

class ComboView : public QListView
{
protected:
    QStyleOptionViewItem viewOptions() const
    {
        // Set icon on the top and center of combo box item.
        QStyleOptionViewItem option = QListView::viewOptions();
        option.decorationAlignment = Qt::AlignHCenter | Qt::AlignCenter;
        option.decorationPosition = QStyleOptionViewItem::Top;
        option.displayAlignment = Qt::AlignCenter;   
        return option;
    }
};

and for the combo box:

QComboBox cb;
cb.setView(new ComboView); // Sets the custom view.
cb.addItem(QIcon("icon.png"), "Item1");
cb.addItem(QIcon("icon.png"), "Item2");
cb.show();