Decide what to do with QDropEvent's ### Qt5 remark

QDropEvent::QDropEvent(const QPointF& pos, Qt::DropActions actions, const QMimeData *data,
                       Qt::MouseButtons buttons, Qt::KeyboardModifiers modifiers, Type type)
    : QEvent(type), p(pos), mouseState(buttons),
      modState(modifiers), act(actions),
      mdata(data)
{
    default_action = Qt::CopyAction; // ### Qt5: QDragManager::self()->defaultAction(act, modifiers);
    drop_action = default_action;
    ignore();
}