drawing errors

[Dp0H]

Hello.
Qt 4.8.0
QGraphicsView scale factor 3.779527559..
The following code

painter->setPen(Qt::red);
painter->drawRect(0, 0, 10, 10);
 
painter->setPen(Qt::darkGreen);
painter->drawLine(0, 3, 10, 3);
 
painter->setPen(Qt::blue);
painter->drawLine(3, 2, 3, 7);
painter->drawLine(3, 5, 8, 5);

painter->setPen(Qt::red);
painter->drawRect(0, 0, 10, 10);

painter->setPen(Qt::darkGreen);
painter->drawLine(0, 3, 10, 3);

painter->setPen(Qt::blue);
painter->drawLine(3, 2, 3, 7);
painter->drawLine(3, 5, 8, 5);

To copy to clipboard, switch view to plain text mode 

gives (contrast lines in front of other drawings - just for test)
qt1.jpg

It is possible to adjust the view's scale factor to avoid off-lying resections, but it's unacceptable.
May I avoid these strange sticks?