Making a Vulkan layer?

[YellowOnion]

I was gonna ask this on matrix but the link doesn't work anymore, the cert on the website seems dead.

My Vulkan understanding is rather basic, I'm using this guide https://renderdoc.org/vulkan-layer-guide.html

I've been trying to understand the API and to create the export shims to call a more high level polymorphic implementation that I want to write.

For clarity sake, I'm using qualified imports.

I want to implement createInstance, for this I'm trying to write a shim to convert to the high level API.

foreign export ccall "Kairos_createInstance" c_createInstance
  :: Ptr (Vk.SomeStruct Vk.InstanceCreateInfo)
  -> Ptr (Vk.AllocationCallbacks)
  -> Ptr (Ptr Vk.Instance_T)
  -> IO Vk.Result

This seems to work, but I'm unsure how to correctly convert Ptr (Vk.SomeStruct a) to the type (Vk.Extendss b es) => (a b es), I think I want to use peekSomeCStruct , but the return type is still just SomeStruct?

I'm struggling to piece all the parts together, I don't feel very confident with my understanding of the higher level polymorphic types, and grepping the source code I can't find many examples of my use case.

Any help would be much appreciated.

Also as an aside, I have a hunch due to the nature of vulkan layers, I need to recompile this library with safe calls?

[dpwiz]

Is there any specific thing that you want to do with the struct or its extensions?
If you only need the first layer and let the rest pass through, then you're set. SomeStruct will hide the chain so you wouldn't be bothered by the rest.
If you want to find some particular extension in the pNext chain that would involve some more dancing.
Try to create an extended structure, poke it to a buffer, then experiment in REPL with whatever the Extends module provides.

[YellowOnion]

There's a few things that need to be done with VkLayerInstanceCreateInfo, from my understanding this is core to making any sort of layer.

I eventually got something "working", ended up with this error:

 peekChainHead: invalid argument (Unrecognized struct type: STRUCTURE_TYPE_LOADER_INSTANCE_CREATE_INFO)

Here's the code:

foreign export ccall "Kairos_GetInstanceProcAddr" c_getInstanceProcAddr
  :: Ptr Vk.Instance_T
  -> CString
  -> IO Vk.PFN_vkVoidFunction

c_getInstanceProcAddr :: Ptr Vk.Instance_T -> CString -> IO (Vk.PFN_vkVoidFunction)
c_getInstanceProcAddr inst name' = do
  name <- peekCString name'
  putStrLn $ "getInstance for " ++ name

  return $ castFunPtr $ case name of
    "vkCreateInstance" -> pCreateInstance
    _                  -> nullFunPtr

foreign import ccall "&Kairos_CreateInstance"
        pCreateInstance :: FunPtr c_createInstance
foreign export ccall "Kairos_CreateInstance" c_createInstance
  :: Ptr (Vk.SomeStruct Vk.InstanceCreateInfo)
  -> Ptr (Vk.AllocationCallbacks)
  -> Ptr (Vk.Instance_T)
  -> IO Vk.Result

c_createInstance
  :: Ptr (Vk.SomeStruct Vk.InstanceCreateInfo)
  -> Ptr (Vk.AllocationCallbacks)
  -> Ptr (Vk.Instance_T)
  -> IO Vk.Result
c_createInstance info cbs inst = do
  info' <- Vk.peekSomeCStruct info
  cbs' <- Vk.peekCStruct cbs
  inst' <- Vk.Instance inst <$> initInstanceCmds inst
  Vk.withSomeStruct info' $ \info -> do
    createInstance info cbs' inst'

createInstance :: (Vk.Extendss Vk.InstanceCreateInfo a, Vk.PokeChain a)
               => Vk.InstanceCreateInfo a
               -> Vk.AllocationCallbacks
               -> Vk.Instance
               -> IO Vk.Result
createInstance a b c = do
  putStrLn "Instance Created"
  return Vk.SUCCESS

I guess VkLayerInstanceCreateInfo is missing from vulkan, this seems to be provided by vk_layer.h, not vulkan.h, this would need a fix right?

I can probably create an type class instance for it, but with the way peekChainHead uses pattern matching, it would need a fix in that to fully work.

Edit: corrected to VkLayerInstanceCreateInfo

[dpwiz]

You may want to cast your ptr to BaseInStructure and manually iterate on its sType/next until you find the STRUCTURE_TYPE_LOADER_INSTANCE_CREATE_INFO (or other thing) you need, then use its ptr from next to peek a known type.

[dpwiz]

If you manage to get it working, I'm happy to accept a new vulkan-layer package (=

[YellowOnion]

BTW I found another URI for accessing the matrix channel, so if you want to talk there it might be easier for me.