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List:       kde-core-devel
Subject:    Re: Alpha blending with XRender prototype
From:       Lars Knoll <lars () trolltech ! com>
Date:       2001-04-14 13:27:59
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On Saturday 14 April 2001 00:54, Antonio Larrosa Jiménez wrote:
> El Vie 13 Abr 2001 01:42, Richard Moore escribió:
> > Hi all,
> >
> > I've got a first hack of alpha blending with the render extension
> > working. Using Render means that the blending can be hardware
> > accelerated, so ultimately I think this should replace the current client
> > side blending we use for icons etc. for now though, this is just a
> > prototype. It will not be ready for the 2.2 alpha. You can grab the
> > example sources from
> > http://www.ipso-facto.demon.co.uk/development/render/ I've also put a
> > couple of screenshots there. To comppile the example extract it below
> > into a standard KDE app template (because I didn't include the configure
> > scripts etc just the Makefile.am).
>
> I thought about implementing that by myself some time ago (after doing the
> client side blending), but then I saw that Qt 3.0 will do that by itself
> (and it already does in the snapshots) so I think there's no need to
> implement XRender based blending in kdelibs (in fact, the current classes
> for alpha blending should go away when we change to Qt 3.0 as I suppose
> that Qt already implements a client-based blending when X11 doesn't have a
> Render extension) I suppose Bradley could correct me if I'm wrong.

You are wrong. Client side alpha blending is a mess, and _way_ to slow (it 
requires 2 round trips to the Xserver). We can't really add that to Qt. Qt 
will support alpha bending on platforms that support it (meaning XFree-4.x at 
the moment), but it will fall back to simple masking based on aplha values on 
older platforms. I think this is the more reasonable behaviour as everything 
else would just give the impression of Qt/KDE getting very slow. This merely 
due to the fact that once a feature is available, people will start using it 
without thinking about the consequences it may have on older hard/software.

Regards,
Lars

>
> Sorry,
>
> Greetings,
>
> --
> Antonio Larrosa Jimenez
> KDE Core developer  - larrosa@kde.org
> SuSE Labs developer - larrosa@suse.de
> http://perso.wanadoo.es/antlarr
> KDE - The development framework of the future, today.

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