QToolBox / QToolBoxButton sizeHint does not honor button size

The sizeHint of QToolBox is not calculated correctly. The QToolBoxButton uses only the iconSize and the textSize for ist sizeHint.
QSize total(iconSize.width() + textSize.width(), qMax(iconSize.height(), textSize.height()));

It has to respect the style "PM_ButtonMargin" and "PM_DefaultFrameWidth" like QPushButton does.
style()->sizeFromContents(QStyle::CT_PushButton, &opt, QSize(w, h), this)