I run in release, yes.
What is strange to me is this:
One of my main and large widget draws thousands of lines (no
antialisaing), a gradient background, a bit of to text, to display data
changing in real time (hence the importance of speed).
I need to maintain a cache hence I draw into a QImage. I choose a QImage
because it is faster than drawing into a QPixmap, at least for the
graphics I do, as I could test it.
Now, if I do:
QApplication::setGraphicsSystem("raster");
then my widget display is much slower than if I do nothing (eg. "native").
I don't understand this, as drawing into a QImage is "raster" (as far as
I understand). So I don't know why there is any difference of speed at
all.
And as far as I remember, there was not this difference with 4.5.0.
However, I don't have 4.5.x installed anymore to confirm today.
BTW, one thing I don't understand, is that drawing so in a QImage is
much faster under Windows than Mac (same machine). I know the difference
of quality between VC++ and GCC, but the speed difference is large
enough not to rely on this sole explanation, IMHO.
Maybe the time needed to render a QImage onto screen is different
between the two platforms?...
Philippe
On Mon, 19 Oct 2009 07:10:49 +0200
Gunnar Sletta <[email protected]> wrote:
> Philippe wrote:
> > Usually I got better performances using the raster engine under OSX.
> >
> > With 4.6, it's quite the opposite, the raster engine is dead slow.
> > Using the raster engine is also an easy way to demonstrate the drawText
> > issue I have mentionned recently. Do this at your application startup:
> >
> > QApplication::setGraphicsSystem(QLatin1String("raster"));
> >
> > And you'll see the whole OSX application UI (texts) look bad.
> >
> > I guess the performance problem is directly related to the text drawing bug.
>
> Hi Philippe,
>
> I doubt the broken text drawing will be that costly overall. What else
> is your app doing? You are running in release right? Raster is several x
> worse in debug mode.
>
> -
> Gunnar
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