QScrollBar's background and or its margin render problem!

[srazi]

Please see the attached photo! (OS: Ubuntu-11.04 with Radiance Theme)
How can I update that part of QScrollBar when scrolling? I mean some codes like followng code that I use for QTableWidget::viewport().

//updating table's viewport
connect(table->verticalScrollBar(), SIGNAL(valueChanged(int)), table->viewport(), SLOT(update()));
connect(table->horizontalScrollBar(), SIGNAL(valueChanged(int)), table->viewport(), SLOT(update()));

//updating table's viewport
connect(table->verticalScrollBar(), SIGNAL(valueChanged(int)), table->viewport(), SLOT(update()));
connect(table->horizontalScrollBar(), SIGNAL(valueChanged(int)), table->viewport(), SLOT(update()));

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and it works good.
There is a way for set that margin to zero pixel?(The QtCreator's scrollbars have zero margins!)