Making a Vulkan layer? #619

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1. dpwiz commented on Mar 21, 2026

   

   dpwiz

   on Mar 21, 2026

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   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.
2. YellowOnion commented on Mar 21, 2026

   

   YellowOnion

   on Mar 21, 2026

   Last edited by YellowOnion

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   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
3. dpwiz commented on Mar 21, 2026

   

   dpwiz

   on Mar 21, 2026

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   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.
4. dpwiz commented on Mar 21, 2026

   

   dpwiz

   on Mar 21, 2026

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   If you manage to get it working, I'm happy to accept a new vulkan-layer package (=
5. YellowOnion commented on Mar 22, 2026

   

   YellowOnion

   on Mar 22, 2026

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