[Interest] double-buffering, quality drop

[Michael Sué]

1) Does your QPixmap look correct if you save it to a file?

2) We do something similar in a QGraphicsView derived class with the following differences:

- we use a QImage object (as we have to fill it pixel by pixel)
- we draw the QImage in drawBackground 

This way SmoothPixeltransform works definitely (never checked for scaling < 1 of the image geometry, though).

But we always draw the graphics items live in the paint events i.e. relay to the default QGraphicsView::paintEvent().QGraphicsView is initialized with setRenderHint(QPainter::Antialiasing);

- Michael.