Question: is it possible to write GUI applications?

[hronro]

I don't have much experience on Cocoa nor Objective-C, just wonder if it's possible to write native macOS GUI apps in Zig?

[hippietrail]

I have this exact question. I want to be able to program both native Win32 and native MacOS apps in any/all of the new batch of languages. Whichever can do it best/first out of Rust, Kotlin Native, Swift, and Zig. But Zig is the one I really want and expect to be able to do it especially since it can cross-compile across all the major platforms.

My understanding is that MacOS is harder than Win32 because of the Objective C runtime which must be used for interacting with Cocoa/Foundation even in the age of Swift, and that the Objective C runtime does things that can't be done in C for its "message passing". When you program MacOS in C there are key functions for calling Objective C APIs such as objc_getClass() and objc_msgSend(). But though they look like wrapper functions for FFI they are in fact some kind of trampoline IIRC that jump to the API code rather than calling it like in a normal language because of how the stack is used. They involve something called IMP and SEL. Apparently implementing variadic functions is especially tricky.

I believe Apple uses assembly for these stubs but maybe they get Clang/LLVM to just emit the correct opcodes to do that stuff directly. This is a very difficult subject to read up on due to not many low-level technical people in the MacOS world seemingly, and what is there is old and so quite possibly out of date.

Apple does provide the source code to the Objective C runtime though.