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List:       kde-devel
Subject:    Re: Graphics system with Qt 4.5
From:       Thiago Macieira <thiago () kde ! org>
Date:       2009-02-12 10:46:49
Message-ID: 200902121146.49847.thiago () kde ! org
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Em Quinta-feira 12 Fevereiro 2009, Ã s 10:31:49, Lubos Lunak escreveu:
> On Wednesday 11 of February 2009, Thiago Macieira wrote:
> > You didn't answer Luboš's question. He asked why QPixmap::handle()
> > couldn't cause the QImage to be transformed into an XPixmap on the fly,
> > like we did for alien in 4.4.
> >
> > The answer is that this is a much, much deeper change than alien. The
> > entire graphics system is involved, which includes the backing store. It
> > would increase the complexity many times over, because in the raster
> > engine, not all QPixmaps would be QImage -- some would be on the X11
> > server, some could be MacOS equivalent. It would require lots of
> > round-trips to keep the local and remote copies updated.
> >
> > What's more, if we did it, what would be the gain when using the OpenGL
> > backend? You wouldn't get textures (or whatever the OpenGL equivalent is)
> > by calling handle() and wouldn't be able to do OpenGL transformations /
> > effects on the pixmaps.
>
>  I think that's not the point. If I call handle() on a QPixmap, I'm
> interested in using the QPixmap as the X pixmap, not in using the OpenGL
> capabilities. The same way the decreased performance because of the
> roundtrips shouldn't matter much - there usually shouldn't be any in the
> first place, except for the first conversion to X pixmap. I just have to
> wonder how many breakages will show over time because of this.

That's why raster and OpenGL are not the default graphics system.

It's a incompatible change, so we default to compatibility.

Besides, you're generalising. Given the ability to do GL transforms on a 
QPixmap, people may want to get access to the underlying infrastructure. It's 
just that, up until now, this was not possible because QPixmap was not OpenGL-
based.

Now it can be.

-- 
Thiago Macieira - thiago (AT) macieira.info - thiago (AT) kde.org
  Senior Product Manager - Nokia, Qt Software
        PGP/GPG: 0x6EF45358; fingerprint:
        E067 918B B660 DBD1 105C   966C 33F5 F005 6EF4 5358

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