Re: Proposal to deprecate Xlib backend

[Yen-Ju Chen]

On 12/25/06, Fred Kiefer <address@hidden> wrote:
> Gregory John Casamento schrieb:
> > Richard,
> >
> > The reasons behind the move to Cairo are as follows:
> >
> > 1) Cairo is being used by a number of other projects.  It is very stable and 
> well maintained.
> > 2) Cairo has been ported to a number of other operating systems, including 
> windows and has a large number of output targets.  This way, Cairo would do much 
> of the heavy lifting for us with regards to getting things to render acceptably on 
> other platforms.
> >
> > I agree with what Richard is saying here as well.
> >
>
> Looks like everybody agrees with Richard:-)
>
> So let's focus on the cairo backend for now and when it is finished
> deprecate xlib and art, but let them stick around for some time afterwards.
>
> Things to be done for the cairo backend:
> - Test with the latest cairo release.
> - Sort out copying from one cairo GState onto itself.
> - Get transparent images working.

 I guess this is the reason why transparency does not work in Cairo backend:
 cairo backend draw everything directly on xwindow.
 In -gui, an image is often draw on a hidden window, then composite
on the destination.
 Because cairo backend draw directly on xwindow first,
 it loses the alpha value.
 Then when it is composited to the destination,
 the transparent part becomes the background of the hidden window.

 I have a copy of cairo backend in Etoile project:
 http://svn.gna.org/viewcvs/etoile/branches/yjchen/etoile_back/
 It basically draw on the x11/XWindowBuffer first as what art backend does.
 Therefore, it keeps the alpha value for composition.
 The modification is very little.
 You can check out README.etoile_back.
 A simple diff is sufficient to see the difference of source code.
 There are some minor issues here and there, though.

 Happy holidays.

 Yen-Ju

> There is more, but these I remember from the top of my head.
>
> Cheers,
> Fred
>
>
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