Re: Proposal to deprecate Xlib backend

[Fred Kiefer]

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.

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

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.

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