QComboBox with only a toolbar icon, how?

Question

I would like to make combobox with QT and want to install it on the toolbar.

The user should see only the icons on the toolbar, so this comboBox should only show the icon of the item on the toolbar.

But after clicking on it, a pop-up menu appears in which not only the icons are displayed, but also its text in the second column.

How can I show only the icon in the comboBox on the toolbar with QT 4.6.1?

Appendix: or with any version of QT? (on Windows)