[KevinH]

The actual Qt code includes that modifier (from qevent.cpp)

Qt::KeyboardModifiers QKeyEvent::modifiers() const
{
    if (key() == Qt::Key_Shift)
        return Qt::KeyboardModifiers(QInputEvent::modifiers()^Qt::ShiftModifier);
    if (key() == Qt::Key_Control)
        return Qt::KeyboardModifiers(QInputEvent::modifiers()^Qt::ControlModifier);
    if (key() == Qt::Key_Alt)
        return Qt::KeyboardModifiers(QInputEvent::modifiers()^Qt::AltModifier);
    if (key() == Qt::Key_Meta)
        return Qt::KeyboardModifiers(QInputEvent::modifiers()^Qt::MetaModifier);
    if (key() == Qt::Key_AltGr)
        return Qt::KeyboardModifiers(QInputEvent::modifiers()^Qt::GroupSwitchModifier);
    return QInputEvent::modifiers();
}

But I think the Windows platform code may not enable it?