How do you port a Cocoa/Mac application to Windows? I mean how would you go about it? Assume the app was written with Objective-C and Cocoa, there’s nothing fancy going on, no “engine” that could be factored out, etc.
Rewrite from scratch? I don’t think there will be huge overlaps between the Mac and Windows codebases, right?
The problem with Objective C is its very poor support on any platform that is not OS X. You can attempt to use the Cocotron, but I wouldn’t consider it production ready yet.
For portability, a re-write is in order. With judicious use of standard C or C++ for the “core” of the application, you could still implement platform specific GUI code. If you don’t like maintaining two GUIs, you can also try a toolkit such as Qt