Broken binding of central picture in one pass

src/Shader/Poke.hs

@@ -1,8 +1,10 @@
 module Shader.Poke
     ( pokeArrayOff
     , pokeShader
+    , pokeShaderLayer
     ) where
 import Shader.Data
+import Shader.Parameters
 import Picture.Data
 
 import Foreign
@@ -17,6 +19,15 @@ pokeShader fs = F.FoldM (pokeVertices fls ptr stride)  (return 0) return
     stride = sum $ _vboAttribSizes theVBO
     fls = _shaderPokeStrategy fs
 
+pokeShaderLayer :: (Int,FullShader) -> F.FoldM IO (Int,RenderType) Int
+pokeShaderLayer (l,fs) = F.FoldM (pokeVerticesOff fls ptr stride l)  (return 0) return
+  where 
+    theVBO = _vaoVBO $ _shaderVAO fs
+    ptr = _vboPointer theVBO
+    stride = sum $ _vboAttribSizes theVBO
+    fls = _shaderPokeStrategy fs
+
+
 pokeVertices 
     :: (RenderType -> [[Float]])
     -> Ptr Float
@@ -26,6 +37,24 @@ pokeVertices
     -> IO Int
 pokeVertices toFs ptr stride n rt = foldM (pokeVertex ptr stride) n (toFs rt)
 
+pokeVerticesOff
+    :: (RenderType -> [[Float]])
+    -> Ptr Float
+    -> Int  -- ^ stride
+    -> Int  -- ^ offset
+    -> Int  -- ^ number of vertices already poked
+    -> (Int,RenderType)
+    -> IO Int
+pokeVerticesOff toFs ptr stride offset n (i,rt) 
+    | offset == i = foldM (pokeVertexOff ptr stride offset) n (toFs rt)
+    | otherwise = return n
+
+pokeVertexOff :: Ptr Float -> Int -> Int -> Int -> [Float] -> IO Int
+pokeVertexOff ptr stride offset n fs = do
+    pokeArrayOff ptr (stride * (n + offset * numSubElements)) fs
+    return $ n + 1
+
+
 pokeVertex :: Ptr Float -> Int -> Int -> [Float] -> IO Int
 pokeVertex ptr stride n fs = do
     pokeArrayOff ptr (stride * n) fs