Re: Opal/CoreGraphics (was Re: UIKit?)

[Gregory Casamento]

Eric,

On Sat, Jan 2, 2010 at 6:04 PM, Eric Wasylishen <ewasylishen@gmail.com> wrote:
> Hey,
>
> As David mentioned, I implemented a bit more of Opal over the holidays 
> (transparency layers,
> and CGLayer). I think Balaton's approach of implementing CoreGraphics as a 
> thin wrapper
> over  Cairo is the right choice in terms of performance (should be excellent, 
> especially
> with Cairo's
> new OpenGL compositor backend under development), completeness/output quality 
> (should
> closely match Apple's), and feasibility/minimal development effort. It 
> currently implements a
> fairly large subset of CG and is under 4k lines of code. I'll move it to the 
> /dev-libs directory in
> GNUstep SVN soon.
>
> There are a few ways we could use Opal in GNUstep. The possibility I am 
> currently exploring
> (planning to put in a branch in svn) is modifying -gui to use CoreGraphics 
> directly. This would
> entail making Opal a dependency of -gui, eliminating the Display PostScript 
> api between -gui
> and -back. -back would be reduced to the xlib and Win32 window server code.

I think this is a good idea, but I should mention that even Apple
still has the Display Postscript operators/API available in spite of
the fact that they are undocumented on Mac OS X.   They are, in fact,
there.  :)   Even though they are not officially supported, it would
be nice to keep support for them.

> At the cost
> of not having a choice of graphics backend, this could make the code in -gui 
> clearer, improve
> performance, and make possible a CoreAnimation implementation and porting a 
> larger set of
> OS X applications.

GNUstep's backend was conceived of at a time when there weren't any
cross platform graphics libraries such as Cairo.   Basically, this
change would offload the work to support additional drawing backends
onto the Cairo team, which has done an excellent job of making it work
on a large number of platforms.

> Regards,
>
> Eric

Thanks, GC

-- 
Gregory Casamento
Open Logic Corporation, Principal Consultant
## GNUstep Chief Maintainer
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