Adding GPU shader target

[jwosty]

I had a crazy idea today. Imagine if Fable could target the GPU so that we could write shaders in F#... There used to be an F#-to-shader transpiler like a decade ago (Alea GPU I think?) but it's long dead.

It would probably target either Slang, or HLSL, or maybe SPIR-V. All of these can target Vulkan and modern DirectX. Slang can even target OpenGL (not that anybody is writing any new OpenGL projects anymore...). I think you can also get all of those to target WebGL? Imagine the possibilities...

Obviously the allowed subset of F# would be pretty restricted, but hopefully anyone trying it would know what they're getting themselves into.

Imagine marrying this to MonoGame. Or imagine if you made a 3d browser game in JS Fable and wrote shaders for it in F#.

[MangelMaxime]

Hello,

I think we are open to adding new targets to Fable, however the work needs to come from the community. We can provide guidance / explanation regarding how Fable works in general.

It is important to note that creating a target is a long term project because it is a complex task and will need maintenance over time.

At first need to live in a long living PR until it reaches a "usable" state.

[jwosty]

Yep, completely agree. I wouldn't expect y'all to just magically produce that one day -- it's just an idea for if someone super adventurous feels like giving it a try someday. Perhaps I will one day but I am rather short on time these days.

Do custom target languages currently have to be built into fable itself or is there a way to do it as a sort of 3rd party library/plugin/whatever? Could allow for more experiments like this. OTOH maybe it is better to avoid that kind of splintering so as to not lose the cohesive "official" experience

[MangelMaxime]

Do custom target languages currently have to be built into fable itself or is there a way to do it as a sort of 3rd party library/plugin/whatever?

Custom targets need to be build into Fable itself.

In theory, we could create a plugin system or something like that but doing so means that we can't easily changes the internal APIs. For example, this is how Fable plugins currently works but we need to be extremely careful when modifying anything inside Fable.AST project as it can breaks the plugins.

For example, even rename field on a DUs can break it.

type Type =
	| Number of v : float

// Changes:
type Type =
	| Number of value : float

The change above make it not fully compatible anymore.

[jwosty]

I figured that would be the case. You'd probably have to introduce some sort of Fable IR layer in order to make a stable API more feasible, but that sounds like a huge undertaking and very tricky to get right. Probably not worth it.