    --------------------------------------------------------------------------------
    -- |
    -- Module      :  Graphics.Rendering.OpenGL.GL.PixelRectangles.PixelStorage
    -- Copyright   :  (c) Sven Panne 2002-2006
    -- License     :  BSD-style (see the file libraries/OpenGL/LICENSE)
    --
    -- Maintainer  :  sven.panne@aedion.de
    -- Stability   :  stable
    -- Portability :  portable
    --
    -- This module corresponds to section 3.6.1 (Pixel Storage Modes) of the
    -- OpenGL 2.1 specs.
    --
    --------------------------------------------------------------------------------

    module Graphics.Rendering.OpenGL.GL.PixelRectangles.PixelStorage (
       PixelStoreDirection(..), swapBytes, lsbFirst, rowLength, skipRows,
       skipPixels, rowAlignment, imageHeight, skipImages
    ) where

    import Graphics.Rendering.OpenGL.GL.BasicTypes ( GLenum, GLint )
    import Graphics.Rendering.OpenGL.GL.GLboolean (
       marshalGLboolean, unmarshalGLboolean )
    import Graphics.Rendering.OpenGL.GL.QueryUtils (
       GetPName(GetUnpackSwapBytes,GetUnpackLSBFirst,GetUnpackRowLength,
                GetUnpackSkipRows,GetUnpackSkipPixels,GetUnpackAlignment,
                GetUnpackImageHeight,GetUnpackSkipImages,GetPackSwapBytes,
                GetPackLSBFirst,GetPackRowLength,GetPackSkipRows,GetPackSkipPixels,
                GetPackAlignment,GetPackImageHeight,GetPackSkipImages),
       getBoolean1, getInteger1 )
    import Graphics.Rendering.OpenGL.GL.StateVar ( StateVar, makeStateVar )

    --------------------------------------------------------------------------------

    data PixelStoreDirection =
         Pack
       | Unpack
       deriving ( Eq, Ord, Show )

    --------------------------------------------------------------------------------

    data PixelStore =
         UnpackSwapBytes
       | UnpackLSBFirst
       | UnpackRowLength
       | UnpackSkipRows
       | UnpackSkipPixels
       | UnpackAlignment
       | PackSwapBytes
       | PackLSBFirst
       | PackRowLength
       | PackSkipRows
       | PackSkipPixels
       | PackAlignment
       | PackSkipImages
       | PackImageHeight
       | UnpackSkipImages
       | UnpackImageHeight

    marshalPixelStore :: PixelStore -> GLenum
    marshalPixelStore x = case x of
       UnpackSwapBytes -> 0xcf0
       UnpackLSBFirst -> 0xcf1
       UnpackRowLength -> 0xcf2
       UnpackSkipRows -> 0xcf3
       UnpackSkipPixels -> 0xcf4
       UnpackAlignment -> 0xcf5
       PackSwapBytes -> 0xd00
       PackLSBFirst -> 0xd01
       PackRowLength -> 0xd02
       PackSkipRows -> 0xd03
       PackSkipPixels -> 0xd04
       PackAlignment -> 0xd05
       PackSkipImages -> 0x806b
       PackImageHeight -> 0x806c
       UnpackSkipImages -> 0x806d
       UnpackImageHeight -> 0x806e

    --------------------------------------------------------------------------------

    swapBytes :: PixelStoreDirection -> StateVar Bool
    swapBytes Pack   = pixelStoreb GetPackSwapBytes PackSwapBytes
    swapBytes Unpack = pixelStoreb GetUnpackSwapBytes UnpackSwapBytes

    lsbFirst :: PixelStoreDirection -> StateVar Bool
    lsbFirst Pack   = pixelStoreb GetPackLSBFirst PackLSBFirst
    lsbFirst Unpack = pixelStoreb GetUnpackLSBFirst UnpackLSBFirst

    rowLength :: PixelStoreDirection -> StateVar GLint
    rowLength Pack   = pixelStorei GetPackRowLength PackRowLength
    rowLength Unpack = pixelStorei GetUnpackRowLength UnpackRowLength

    skipRows :: PixelStoreDirection -> StateVar GLint
    skipRows Pack   = pixelStorei GetPackSkipRows PackSkipRows
    skipRows Unpack = pixelStorei GetUnpackSkipRows UnpackSkipRows

    skipPixels :: PixelStoreDirection -> StateVar GLint
    skipPixels Pack   = pixelStorei GetPackSkipPixels PackSkipPixels
    skipPixels Unpack = pixelStorei GetUnpackSkipPixels UnpackSkipPixels

    rowAlignment :: PixelStoreDirection -> StateVar GLint
    rowAlignment Pack   = pixelStorei GetPackAlignment PackAlignment
    rowAlignment Unpack = pixelStorei GetUnpackAlignment UnpackAlignment

    imageHeight :: PixelStoreDirection -> StateVar GLint
    imageHeight Pack   = pixelStorei GetPackImageHeight PackImageHeight
    imageHeight Unpack = pixelStorei GetUnpackImageHeight UnpackImageHeight

    skipImages :: PixelStoreDirection -> StateVar GLint
    skipImages Pack   = pixelStorei GetPackSkipImages PackSkipImages
    skipImages Unpack = pixelStorei GetUnpackSkipImages UnpackSkipImages

    --------------------------------------------------------------------------------

    pixelStoreb :: GetPName -> PixelStore -> StateVar Bool
    pixelStoreb pn ps =
       makeStateVar
          (getBoolean1 unmarshalGLboolean pn)
          (glPixelStorei (marshalPixelStore ps) . marshalGLboolean)

    pixelStorei :: GetPName -> PixelStore -> StateVar GLint
    pixelStorei pn ps =
       makeStateVar
          (getInteger1 id pn)
          (glPixelStorei (marshalPixelStore ps))

    foreign import CALLCONV unsafe "glPixelStorei" glPixelStorei ::
       GLenum -> GLint -> IO ()