Re: Proposal to deprecate Xlib backend

[Yen-Ju Chen]

On 12/26/06, Fred Kiefer <address@hidden> wrote:
> Yen-Ju Chen schrieb:
> >  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.
> >
>
> Great, this resolves the transparency issue! I added your changes for
> this to the official GNUstep cairo backend. I did not take over your
> changes to x11, on which I need to take another look.

 Don't bother with the x11 part.
 It is just for some experimental stuffs.

> You also have a change to add the freetype2 libraries and settings to
> the configuration. This should not be needed if cairo is configured
> correctly. Could you please type in "pkg-config --libs cairo" at a
> command prompt to see if this includes freetype or not?

 I have problem with linking to freetype2 before.
 I will try it again.

> I also added you endianess change, hope I did get it correct.

 I am not sure I did this one right because
 sometimes I see weird colors here and there.
 Again, it is just some experiments I were working on.

> As you have the unbuffered code commented out yourself, I did not take
> it over. And the NSClipView change is clearly a hack. We need to resolve
> the actual issue behind it.

 The unbuffered stuff is from art backend.
 But frankly, I don't really understand the difference between
 the non-retained, retained and buffered window.
 So, just ignore it for now.

 You can treat the NSClipView category as a not-so-elegant implementation.
 GNUstep-gui try to save time by copy old area to new position.
 For a not-so-good implementation, it probably just ask backend to
draw everything again.
 And it is what this category does. :)

 Yen-Ju

> With images now drawn transparent you will see that many images get
> flipped. I will have to take another look into the horrible
> compositeGState:... method to sort this out. If we are lucky the clip
> view issue will get resolved by that as well.
>
> The next thing to investigate will than be the text drawing, as the
> metrics seem to be wrong here.
>
> Cheers,
> Fred