On Mac OS X Carbon, setMask() is not applied correctly

 
//////////////////// 
// sample code 
//////////////////// 

#include <QtGui> 
#include <QtDebug> 
 
int main(int argc, char *argv[]) 
{ 
    QApplication app(argc, argv); 
 
    /////////////// 
    // BUG widget 
    /////////////// 
    QWidget* qwBug = new QWidget (0 , Qt::Window |Qt::FramelessWindowHint); //bug 
    QPushButton* bt1 = new QPushButton(qwBug); 
    bt1->setText("Button 1"); 
    bt1->move(10,10); 
    bt1->show(); 
    QPushButton* bt2 = new QPushButton(qwBug); 
    bt2->setText("Button 2"); 
    bt2->move(110,10); 
    bt2->show(); 
 
    qwBug->setGeometry(100, 100, 210, 50); 
    qwBug->showNormal(); 
 
    // next line should chop the left 100 pixels 
    qDebug() << qwBug->geometry().width()-100; 
    qDebug() << qwBug->geometry().height(); 
    qwBug->setMask (QRect(100, 0, qwBug->geometry().width()-100, qwBug->geometry().height())); 
    qwBug->show(); 
 
    ////////////////// 
    // Normal Widget 
    ////////////////// 
    QWidget* qw = new QWidget (0 , Qt::Window ); //fine 
    QPushButton* bt3 = new QPushButton(qw); 
    bt3->setText("Button 3"); 
    bt3->move(10,10); 
    bt3->show(); 
    QPushButton* bt4 = new QPushButton(qw); 
    bt4->setText("Button 4"); 
    bt4->move(110,10); 
    bt4->show(); 
 
    qw->setGeometry(100, 200, 210, 50); 
    qw->showNormal(); 
 
    // next line should chop the left 100 pixels 
    qDebug() << qw->geometry().width()-100; 
    qDebug() << qw->geometry().height(); 
    qw->setMask (QRect(100, 0, qw->geometry().width()-100, qw->geometry().height())); 
    qw->show(); 
 
    return app.exec(); 
}