I have placed several QwtPlots on a QGraphicsView used to resemble a textual document.
I want to use the zooming capabilities of the QGraphicsScene, of course.
This is what I get at default zooming factors, that is, a neat and perfect plot:

nozoom.png

But, when I operate some zooming on the scene, this is what I get:

yeszoom.png

As you can see, the labels and the axes of the plot are still perfect and vectorial, whereas the canvas looks grainy, such as if it were a bitmap that has been scaled up.
What I do not understand is why the characters in the labels of the axes look good, but the canvas looks so horrible.
Any help or clue is appreciated, thanks.