painting suggestions

[Riccardo Iaconelli]

hello,
so, I have the following code:

        QPixmap temp = *d->p;
        QPainter p(&temp);
        p.setCompositionMode(QPainter::CompositionMode_Source);
        p.drawPixmap(0, 0, *d->p);
        p.setCompositionMode(QPainter::CompositionMode_DestinationIn);
        p.fillRect(temp.rect(), QColor(0, 0, 0, qreal(d->frame)*5.0/100.0));
        p.end();
        painter->drawPixmap(d->optV4.rect, temp);

where d->p is a cached pixmap of an expensive operation obtained through 
manipuladig a QImage, and shouldn't be changed for this reason.
I was wondering if that's the best approach (which requires a pixmap copy) or 
it's faster to call painter->setOpacity and then drawPixmap.

As my knowledge of the inner Qt painting system is not so wide, I'm asking 
here. =)

if you have questions, or need more code, please ask.

Bye,
-Riccardo
p.s. aye, that's raptor code, if someone wants more context (not sure if it's 
needed)
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