[Interest] double-buffering, quality drop

[Michael Sué]

> Yes, I think so too. Now I just need to understand the difference between
> the
> QPainter passed to QGraphicsImem::paint() and the painter I localy create in
> Curve::updatePixmap(). On the other hand, what I'm doing in
> updatePixmap() is
> pretty much the standard way to draw on a QPixmap according to Qt's
> documentation. I don't believe this standard way without setting any
> "advanced" flags for QPainter leads to such a bad quality...
You can set a breakpoint in Curve::Paint, go up in the stack trace and look for yourself. It is way more than just QPixmap pixmap(width,height). 

But seeing your attachment I have another idea: There can be a problem with the missing background: Antialiasing usually happens with a real background, as it produces a mixture (smearing of the colors) between your curve and the background. So it seems your real problem is that antialiasing with a transparent background does not work correctly, or at least not with a simple QPixmap pixmap(width,height). On the other hand, in Curve::paint you already draw on the real background which gives AA something to work with.

- Michael.