I really hope they do and the rendering engine is decently decoupled, I'll give a try building a framework on top of it.
I wish all platforms gave access to their rendering engine similar to DOM on the web, imo SwiftUI/WinUI (or WPF, but they are very similar) are not that good.
Haven't built anything native on Linux, though, no idea how good those are.
What do you mean by access? APIs to program against or fully open sourcing the rendering engine? Because you can mix SwiftUI with a few different rendering frameworks at varying abstraction levels that it itself renders to (AppKit, UIKit, Core Graphics, Metal etc.)
Basically I want an API available to build my own SwiftUI. Definitely not on the Core Graphics level :)
But good point, I actually think AppKit might be a good abstraction level. I'll play with it a bit and see if I can abstract it behind a good component model.
What's wrong with Skia? Chrome, Firefox, and OpenOffice all use it, and it works on Windows, Linux, MacOS, and Android.
It is a ton of C++ for what is essentially something that an OS like Windows/MacOS/Android/iOS or the browser would provide anyway. Apps that use it ship with a substantial minimum amount of bloat, e.g. Flutter for web.
Nothing wrong with it, just want something a bit higher level and ideally with at least some native components/styles.