Re: ABI compatibility with Cocoa

[Luboš Doležel]

On Mon, 6 Aug 2012 15:41:20 +0100, David Chisnall wrote:
> You might be interested in a NetBSD project that did the same thing
> about 8 years ago.  They eventually gave up because all of the
> interesting OS X software (e.g. the window server) has hooks so 
> deeply
> into the Mach layer, and everything on top of it has close
> dependencies on it, that you effectively need 99% of OS X to have
> anything interesting.

Oh yes, I've read all about that NetBSD project. But their approach was 
quite different from mine. They actually tried to make *the system* be 
like Darwin/OS X, while I'm doing everything in the user space. Just 
like Wine doesn't emulate any sort of very low level windowing 
functionality, they simply reimplemented the Windows APIs that are used 
to create GUIs.

That means I will certainly not be dealing with the window server the 
level the NetBSD guys did, I'll only be providing a 
semi-reimplementation of the upper-level libraries the applications use.

I'm also not making any modifications to the Linux kernel at all.

> Replacing Cocoa's AppKit with GNUstep is difficult.  In theory, you
> should be able to just add Apple runtime parts for the
> runtime-specific things in, for example, NSObject.  This isn't
> trivial, because OS X does layering in different places to us.  
> You'll
> also find problems from any applications that rely on implementation
> details of the OS X frameworks.
>
> David

Right, I know there will be a lot of missing libs that will have to be 
rewritten. But as long as the function calls remain the same API/ABI 
wise (e.g. same arguments...) between GNUstep and AppKit, it could get 
many apps running.

Well, I'll let you know of my progress! If things work out, I think it 
could get more people interested in improving GNUstep.

--
Luboš Doležel