QComboBox with checkboxes

I'm creating QComboBox with checkboxes. How I can prevent collapsing of view on mouse clicking? I want to be able to set up checkboxes, but each time I click on item - drop-down of QComboBox is collapsed.

Note: currently I'm debugging Qt sources and looking for workaround...

First of all you need to install an event filter to the combo box view, i.e.:

combobox->view()->viewport()->installEventFilter(someobj);

than you need to filter all mouse release events that happen on the combo box view to prevent its closing when you click on it:

bool SomeObject::eventFilter(QObject *obj, QEvent *event)
{
     if (event->type() == QEvent::MouseButtonRelease) {
         int index = view()->currentIndex().row();

         if (itemData(index, Qt::CheckStateRole) == Qt::Checked) {
            setItemData(index, Qt::Unchecked, Qt::CheckStateRole);
         } else {
            setItemData(index, Qt::Checked, Qt::CheckStateRole);
         }

         [..]

         return true;
     } else {
         // Propagate to the parent class.
         return QObject::eventFilter(obj, event);
     }
}