How can I make the children widget visible when the parent mainwindow transparent?

[charlse]

Hi all:
I created a mainwindow(QMainWindow) and attached a listwidget(QListWidget) to it , I use QWidget::setMask() to make the mainwindow transparent , but the listwidget is transparent too . That isn't what I want .
So how can I make the listwidget visible when the mainwindow is transparent ?
I don't use QWidget::setWindowOpacity()because I develop this application on WIN_CE with a Qt-4.4.0 , this OS doesn't support this method !

here is my code:

ui.setupUi(this);
 
QSize Size = size();
QPixmap maskPix(Size);
maskPix.fill(Qt::transparent);
setMask(maskPix.mask());

ui.setupUi(this);

QSize Size = size();
QPixmap maskPix(Size);
maskPix.fill(Qt::transparent);
setMask(maskPix.mask());

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Thanks for you suggestion.