change byte offset to offset in number of buffer elements

src/Classes/Graphics/Buffer.hs

@@ -37,7 +37,7 @@ class (Bindable a, Storable (StoreType a)) =>
     write
       :: a
       -> Word
-        -- ^ write offset from beginning of buffer in bytes
+        -- ^ write offset from beginning of buffer in number of data elements
       -> StoreContainer a (StoreType a)
         -- ^ Data to write
       -> IO ()

src/Types/Graphics/IndexBuffer.hs

@@ -52,7 +52,8 @@ instance Buffer IndexBuffer where
   write buf offset dat = do
     currentBufSize <- readTVarIO (iBufSize buf)
     whileM_
-      (pure $ offset + VS.length dat * sizeOf (undefined :: StoreType IndexBuffer)
+      (pure $ (offset + VS.length dat) *
+        sizeOf (undefined :: StoreType IndexBuffer)
         > currentBufSize) $ do
           allocaArray
             (currentBufSize `div` sizeOf (undefined :: StoreType IndexBuffer))
@@ -77,9 +78,10 @@ instance Buffer IndexBuffer where
       GL.bufferSubData
         (target buf)
         GL.WriteToBuffer
-        (CPtrdiff $ fromIntegral offset)
+        (CPtrdiff $ fromIntegral offset *
+          sizeOf (undefined :: StoreType IndexBuffer))
         (CPtrdiff $ fromIntegral $
-          VS.length dat * sizeOf (undefined ::StoreType IndexBuffer))
+          VS.length dat * sizeOf (undefined :: StoreType IndexBuffer))
         ptr
 
   expand buf = do

src/Types/Graphics/VertexBuffer.hs

@@ -90,8 +90,8 @@ instance Buffer VertexBuffer where
   write buf offset dat = do
     currentBufSize <- readTVarIO (vBufSize buf)
     whileM_
-      (pure $ fromIntegral offset +
-        VS.length dat * sizeOf (undefined :: StoreType VertexBuffer)
+      (pure $ (fromIntegral offset + VS.length dat) *
+        sizeOf (undefined :: StoreType VertexBuffer)
         > fromIntegral currentBufSize) $ do
           allocaArray
             (fromIntegral currentBufSize `div`
@@ -119,7 +119,8 @@ instance Buffer VertexBuffer where
           -- target buffer type
         GL.WriteToBuffer
           -- data access direction
-        (CPtrdiff $ fromIntegral offset)
+        (CPtrdiff $ fromIntegral offset *
+          fromIntegral (sizeOf (undefined :: StoreType VertexBuffer)))
           -- offset from buffer start
         (CPtrdiff $ fromIntegral $
           VS.length dat * sizeOf (undefined :: StoreType VertexBuffer))