For the latter I looked at skiko, but the only nat...

# kotlin-native

[martmists]

For the latter I looked at skiko, but the only native bindings available seem to be for macOS and not common native code.

[Gavin Ray]

So the Skiko thing is kind of weird, I also looked. Reached same conclusion. The only bit of Kotlin Native functionality available right now is hard-coded stuff for Mac OS.

Also, the way it works, it calls the Jetbrains skija library which is Java, bound to some JNI code in C++.
I didn't know Kotlin Native could even do this (import Java code that used JNI -- thought you could only use direct C bindings)

EG, class Canvas, Canvas.drawPicture()
• https://github.com/JetBrains/skija/blob/64b715ceb0764e366eb98ff852d3c42fe30328ab/platform/cc/Canvas.cc#L147-L154
• https://github.com/JetBrains/skija/blob/64b715ceb0764e366eb98ff852d3c42fe30328ab/shared/java/Canvas.java#L448-L461
Then the skiko Kotlin Native code for drawing on canvas:
• https://github.com/JetBrains/skiko/blob/023a169556129b0f68d236eac1c38d08d9741039/s[…]nativeMain/kotlin/org/jetbrains/skiko/context/ContextHandler.kt

[Gavin Ray]

Generally if you wanted to use something like Skia, you would:
• Check if it has a C ABI (Skia does, but it's "experimental" and not meant for production use)
◦ https://github.com/google/skia/blob/main/experimental/c-api-example/c.md
• If it doesn't, let's say it's C++ or Rust or whatnot, then you need to expose a C ABI for it
◦ (I mean, technically you don't -- you could use some naughty linker tricks and directly call mangled symbol names but let's pretend you can't do that, because you shouldn't)
◦ You can use something like CPPBind to generate a C ABI for C++, or rust-bindgen for generating a C ABI for Rust, etc
▪︎ https://github.com/Time0o/CPPBind
▪︎ https://github.com/rust-lang/rust-bindgen
• Then you follow the c-interop guide for consuming the C ABI from Kotlin Native
◦ https://kotlinlang.org/docs/native-c-interop.html
◦ This amounts to basically linking in the static/shared library that exposes the C ABI, and running a tool to auto-generate the Kotlin type signatures for the C ABI headers

[Gavin Ray]

If you want to get Skia working with KN today, you can use the guide they have there on building the C ABI and use that, rather than the C++ API. But it would be stripped down.

[Gavin Ray]

The final step is to wait for the day when Kotlin gets direct C++ interop, the way that Swift does, as it has on it's native roadmap
And then you can just consume symbols from C++ objects natively, courtesy of LLVM and a bunch of magic. None of this ABI nonsense \o/