I've written code a bit like this, where I wanted to put a tree view inside a combo box and I needed to take an action when the check box on the tree was clicked. What I ended up doing was installing an event filter on the combo box to intercept mouse clicks, figure out where the mouse click was happening, and then take an action. Probably you can do the same kind of thing with your icon. Here is the code:
bool TreeComboBox::eventFilter(QObject* object, QEvent* event)
{
if (event->type() == QEvent::MouseButtonPress || event->type() == QEvent::MouseButtonRelease)
{
QMouseEvent* m = static_cast<QMouseEvent*>(event);
QModelIndex index = view()->indexAt(m->pos());
QRect vrect = view()->visualRect(index);
if(event->type() == QEvent::MouseButtonPress &&
(model()->flags(index) & Qt::ItemIsUserCheckable) &&
vrect.contains(m->pos()))
{
// Your action here
ToggleItem(index);
UpdateSelectionString();
}
if (view()->rect().contains(m->pos()))
skipNextHide = true;
}
return QComboBox::eventFilter(object, event);
}