Turning Cocoa app into cross-platform app?

Does anyone has experience in "turning" Cocoa app into cross-platform one for Mac/Win/Linux?

I开发者_高级运维 was thinking of using GCC as a compiler for Obj-C and making new GUI based on wxC.

However, I never had any experience with Obj-C and Cocoa development, so I'm not sure what is possible and what is not.

If you have such experience - what widget toolkit, compiler, etc you choose and did it work?

I have tried Cocotron for that and it's quite mature. After installing Cocotron you create a new target for your project and you can create the Windows, Linux, ... (tried with Windows) from out of Xcode.

Using a remote debugger I was also able to debug the app running in a VirtualBox virtual machine from out of Xcode.

But some parts of Cocoa and AppKit are still missing so I needed to extend Cocotron quite a bit. But that's makeable because it's open source.