i try to show the vertical scrollbar of a QTableView, have tried all methods :

setHorizontalScrollBarPolicy( Qt::ScrollBarAlwaysOff );
setVerticalScrollBarPolicy( Qt::ScrollBarAlwaysOn );

QScrollBar * poScrollBar = verticalScrollBar();
poScrollBar->setAutoFillBackground( true );
poScrollBar->setHidden( false );
poScrollBar->show();
poScrollBar->setHidden( false );
poScrollBar->setShown( true );
poScrollBar->show();
poScrollBar->showNormal();

but still i can't see any scrollbar...
what's the trick to display it ?