    -- #hide
    --------------------------------------------------------------------------------
    -- |
    -- Module      :  Graphics.Rendering.OpenGL.GL.Capability
    -- Copyright   :  (c) Sven Panne 2002-2009
    -- License     :  BSD-style (see the file libraries/OpenGL/LICENSE)
    --
    -- Maintainer  :  sven.panne@aedion.de
    -- Stability   :  stable
    -- Portability :  portable
    --
    -- This is a purely internal module for handling OpenGL capabilities, i.e.
    -- boolean state variables.
    --
    --------------------------------------------------------------------------------

    module Graphics.Rendering.OpenGL.GL.Capability (
       Capability(..), marshalCapability, unmarshalCapability,
       EnableCap(..), makeCapability, makeStateVarMaybe,

       IndexedEnableCap(..), makeIndexedCapability,
    ) where

    import Graphics.Rendering.OpenGL.GL.StateVar
    import Graphics.Rendering.OpenGL.GL.GLboolean
    import Graphics.Rendering.OpenGL.GL.QueryUtils
    import Graphics.Rendering.OpenGL.GLU.ErrorsInternal
    import Graphics.Rendering.OpenGL.Raw.ARB.Compatibility (
       gl_ALPHA_TEST, gl_AUTO_NORMAL, gl_COLOR_ARRAY, gl_COLOR_MATERIAL,
       gl_COLOR_SUM, gl_COLOR_TABLE, gl_CONVOLUTION_1D, gl_CONVOLUTION_2D,
       gl_EDGE_FLAG_ARRAY, gl_FOG, gl_FOG_COORD_ARRAY, gl_HISTOGRAM, gl_INDEX_ARRAY,
       gl_INDEX_LOGIC_OP, gl_LIGHTING, gl_LINE_STIPPLE, gl_MAP1_COLOR_4,
       gl_MAP1_INDEX, gl_MAP1_NORMAL, gl_MAP1_TEXTURE_COORD_1,
       gl_MAP1_TEXTURE_COORD_2, gl_MAP1_TEXTURE_COORD_3, gl_MAP1_TEXTURE_COORD_4,
       gl_MAP1_VERTEX_3, gl_MAP1_VERTEX_4, gl_MAP2_COLOR_4, gl_MAP2_INDEX,
       gl_MAP2_NORMAL, gl_MAP2_TEXTURE_COORD_1, gl_MAP2_TEXTURE_COORD_2,
       gl_MAP2_TEXTURE_COORD_3, gl_MAP2_TEXTURE_COORD_4, gl_MAP2_VERTEX_3,
       gl_MAP2_VERTEX_4, gl_MINMAX, gl_NORMALIZE, gl_NORMAL_ARRAY, gl_POINT_SMOOTH,
       gl_POINT_SPRITE, gl_POLYGON_STIPPLE, gl_POST_COLOR_MATRIX_COLOR_TABLE,
       gl_POST_CONVOLUTION_COLOR_TABLE, gl_RESCALE_NORMAL, gl_SECONDARY_COLOR_ARRAY,
       gl_SEPARABLE_2D, gl_TEXTURE_COORD_ARRAY, gl_TEXTURE_GEN_Q, gl_TEXTURE_GEN_R,
       gl_TEXTURE_GEN_S, gl_TEXTURE_GEN_T, gl_VERTEX_ARRAY,
       gl_VERTEX_PROGRAM_TWO_SIDE )
    import Graphics.Rendering.OpenGL.Raw.ARB.MatrixPalette ( gl_MATRIX_INDEX_ARRAY, gl_MATRIX_PALETTE )
    import Graphics.Rendering.OpenGL.Raw.ARB.VertexBlend ( gl_WEIGHT_SUM_UNITY, gl_VERTEX_BLEND, gl_WEIGHT_ARRAY )
    import Graphics.Rendering.OpenGL.Raw.Core31
    import Graphics.Rendering.OpenGL.Raw.EXT.DepthBoundsTest ( gl_DEPTH_BOUNDS_TEST )
    import Graphics.Rendering.OpenGL.Raw.EXT.SharedTexturePalette ( gl_SHARED_TEXTURE_PALETTE )
    import Graphics.Rendering.OpenGL.Raw.EXT.StencilTwoSide ( gl_STENCIL_TEST_TWO_SIDE )
    import Graphics.Rendering.OpenGL.Raw.NV.DepthClamp ( gl_DEPTH_CLAMP )

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

    data Capability =
         Disabled
       | Enabled
       deriving ( Eq, Ord, Show )

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

    marshalCapability :: Capability -> GLboolean
    marshalCapability = marshalGLboolean . (Enabled ==)

    unmarshalCapability :: GLboolean -> Capability
    unmarshalCapability x = if unmarshalGLboolean x then Enabled else Disabled

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

    data EnableCap =
         CapFog
       | CapLighting
       | CapTexture1D
       | CapTexture2D
       | CapTextureRectangle
       | CapLineStipple
       | CapPolygonStipple
       | CapCullFace
       | CapAlphaTest
       | CapBlend
       | CapIndexLogicOp
       | CapColorLogicOp
       | CapDither
       | CapStencilTest
       | CapDepthTest
       | CapClipPlane GLsizei
       | CapLight GLsizei
       | CapTextureGenS
       | CapTextureGenT
       | CapTextureGenR
       | CapTextureGenQ
       | CapMap1Vertex3
       | CapMap1Vertex4
       | CapMap1Color4
       | CapMap1Index
       | CapMap1Normal
       | CapMap1TextureCoord1
       | CapMap1TextureCoord2
       | CapMap1TextureCoord3
       | CapMap1TextureCoord4
       | CapMap2Vertex3
       | CapMap2Vertex4
       | CapMap2Color4
       | CapMap2Index
       | CapMap2Normal
       | CapMap2TextureCoord1
       | CapMap2TextureCoord2
       | CapMap2TextureCoord3
       | CapMap2TextureCoord4
       | CapPointSmooth
       | CapLineSmooth
       | CapPolygonSmooth
       | CapScissorTest
       | CapColorMaterial
       | CapNormalize
       | CapAutoNormal
       | CapPolygonOffsetPoint
       | CapPolygonOffsetLine
       | CapPolygonOffsetFill
       | CapVertexArray
       | CapNormalArray
       | CapColorArray
       | CapIndexArray
       | CapTextureCoordArray
       | CapEdgeFlagArray
       | CapFogCoordArray
       | CapSecondaryColorArray
       | CapMatrixIndexArray
       | CapConvolution1D
       | CapConvolution2D
       | CapSeparable2D
       | CapHistogram
       | CapMinmax
       | CapRescaleNormal
       | CapSharedTexturePalette
       | CapTexture3D
       | CapMultisample
       | CapSampleAlphaToCoverage
       | CapSampleAlphaToOne
       | CapSampleCoverage
       | CapColorTable
       | CapPostConvolutionColorTable
       | CapPostColorMatrixColorTable
       | CapColorSum
       | CapTextureCubeMap
       | CapWeightSumUnity
       | CapVertexBlend
       | CapWeightArray
       | CapMatrixPalette
       | CapDepthClamp
       | CapDepthBoundsTest
       | CapPrimitiveRestart
       | CapPointSprite
       | CapStencilTestTwoSide
       | CapRasterPositionUnclipped
       | CapRasterizerDiscard
       | CapTextureColorTable
       | CapVertexProgramPointSize
       | CapVertexProgramTwoSide

    marshalEnableCap :: EnableCap -> Maybe GLenum
    marshalEnableCap x = case x of
       CapFog -> Just gl_FOG
       CapLighting -> Just gl_LIGHTING
       CapTexture1D -> Just gl_TEXTURE_1D
       CapTexture2D -> Just gl_TEXTURE_2D
       CapTextureRectangle -> Just gl_TEXTURE_RECTANGLE
       CapLineStipple -> Just gl_LINE_STIPPLE
       CapPolygonStipple -> Just gl_POLYGON_STIPPLE
       CapCullFace -> Just gl_CULL_FACE
       CapAlphaTest -> Just gl_ALPHA_TEST
       CapBlend -> Just gl_BLEND
       CapIndexLogicOp -> Just gl_INDEX_LOGIC_OP
       CapColorLogicOp -> Just gl_COLOR_LOGIC_OP
       CapDither -> Just gl_DITHER
       CapStencilTest -> Just gl_STENCIL_TEST
       CapDepthTest -> Just gl_DEPTH_TEST
       CapClipPlane i -> clipPlaneIndexToEnum i
       CapLight i -> lightIndexToEnum i
       CapTextureGenS -> Just gl_TEXTURE_GEN_S
       CapTextureGenT -> Just gl_TEXTURE_GEN_T
       CapTextureGenR -> Just gl_TEXTURE_GEN_R
       CapTextureGenQ -> Just gl_TEXTURE_GEN_Q
       CapMap1Vertex3 -> Just gl_MAP1_VERTEX_3
       CapMap1Vertex4 -> Just gl_MAP1_VERTEX_4
       CapMap1Color4 -> Just gl_MAP1_COLOR_4
       CapMap1Index -> Just gl_MAP1_INDEX
       CapMap1Normal -> Just gl_MAP1_NORMAL
       CapMap1TextureCoord1 -> Just gl_MAP1_TEXTURE_COORD_1
       CapMap1TextureCoord2 -> Just gl_MAP1_TEXTURE_COORD_2
       CapMap1TextureCoord3 -> Just gl_MAP1_TEXTURE_COORD_3
       CapMap1TextureCoord4 -> Just gl_MAP1_TEXTURE_COORD_4
       CapMap2Vertex3 -> Just gl_MAP2_VERTEX_3
       CapMap2Vertex4 -> Just gl_MAP2_VERTEX_4
       CapMap2Color4 -> Just gl_MAP2_COLOR_4
       CapMap2Index -> Just gl_MAP2_INDEX
       CapMap2Normal -> Just gl_MAP2_NORMAL
       CapMap2TextureCoord1 -> Just gl_MAP2_TEXTURE_COORD_1
       CapMap2TextureCoord2 -> Just gl_MAP2_TEXTURE_COORD_2
       CapMap2TextureCoord3 -> Just gl_MAP2_TEXTURE_COORD_3
       CapMap2TextureCoord4 -> Just gl_MAP2_TEXTURE_COORD_4
       CapPointSmooth -> Just gl_POINT_SMOOTH
       CapLineSmooth -> Just gl_LINE_SMOOTH
       CapPolygonSmooth -> Just gl_POLYGON_SMOOTH
       CapScissorTest -> Just gl_SCISSOR_TEST
       CapColorMaterial -> Just gl_COLOR_MATERIAL
       CapNormalize -> Just gl_NORMALIZE
       CapAutoNormal -> Just gl_AUTO_NORMAL
       CapPolygonOffsetPoint -> Just gl_POLYGON_OFFSET_POINT
       CapPolygonOffsetLine -> Just gl_POLYGON_OFFSET_LINE
       CapPolygonOffsetFill -> Just gl_POLYGON_OFFSET_FILL
       CapVertexArray -> Just gl_VERTEX_ARRAY
       CapNormalArray -> Just gl_NORMAL_ARRAY
       CapColorArray -> Just gl_COLOR_ARRAY
       CapIndexArray -> Just gl_INDEX_ARRAY
       CapTextureCoordArray -> Just gl_TEXTURE_COORD_ARRAY
       CapEdgeFlagArray -> Just gl_EDGE_FLAG_ARRAY
       CapFogCoordArray -> Just gl_FOG_COORD_ARRAY
       CapSecondaryColorArray -> Just gl_SECONDARY_COLOR_ARRAY
       CapMatrixIndexArray -> Just gl_MATRIX_INDEX_ARRAY
       CapConvolution1D -> Just gl_CONVOLUTION_1D
       CapConvolution2D -> Just gl_CONVOLUTION_2D
       CapSeparable2D -> Just gl_SEPARABLE_2D
       CapHistogram -> Just gl_HISTOGRAM
       CapMinmax -> Just gl_MINMAX
       CapRescaleNormal -> Just gl_RESCALE_NORMAL
       CapSharedTexturePalette -> Just gl_SHARED_TEXTURE_PALETTE
       CapTexture3D -> Just gl_TEXTURE_3D
       CapMultisample -> Just gl_MULTISAMPLE
       CapSampleAlphaToCoverage -> Just gl_SAMPLE_ALPHA_TO_COVERAGE
       CapSampleAlphaToOne -> Just gl_SAMPLE_ALPHA_TO_ONE
       CapSampleCoverage -> Just gl_SAMPLE_COVERAGE
       CapColorTable -> Just gl_COLOR_TABLE
       CapPostConvolutionColorTable -> Just gl_POST_CONVOLUTION_COLOR_TABLE
       CapPostColorMatrixColorTable -> Just gl_POST_COLOR_MATRIX_COLOR_TABLE
       CapColorSum -> Just gl_COLOR_SUM
       CapTextureCubeMap -> Just gl_TEXTURE_CUBE_MAP
       CapWeightSumUnity -> Just gl_WEIGHT_SUM_UNITY
       CapVertexBlend -> Just gl_VERTEX_BLEND
       CapWeightArray -> Just gl_WEIGHT_ARRAY
       CapMatrixPalette -> Just gl_MATRIX_PALETTE
       CapDepthClamp -> Just gl_DEPTH_CLAMP
       CapDepthBoundsTest -> Just gl_DEPTH_BOUNDS_TEST
       CapPrimitiveRestart -> Just gl_PRIMITIVE_RESTART
       CapPointSprite -> Just gl_POINT_SPRITE
       CapStencilTestTwoSide -> Just gl_STENCIL_TEST_TWO_SIDE
       -- TODO: use RASTER_POSITION_UNCLIPPED_IBM from IBM_rasterpos_clip extension
       CapRasterPositionUnclipped -> Just 0x19262
       CapRasterizerDiscard -> Just gl_RASTERIZER_DISCARD
       -- TODO: use TEXTURE_COLOR_TABLE_SGI from SGI_texture_color_table extension
       CapTextureColorTable -> Just 0x80bc
       CapVertexProgramPointSize -> Just gl_VERTEX_PROGRAM_POINT_SIZE
       CapVertexProgramTwoSide -> Just gl_VERTEX_PROGRAM_TWO_SIDE

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

    makeCapability :: EnableCap -> StateVar Capability
    makeCapability cap = makeStateVar (isEnabled cap) (enable cap)

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

    isEnabled :: EnableCap -> IO Capability
    isEnabled =
       maybe (do recordInvalidEnum; return Disabled)
             (fmap unmarshalCapability . glIsEnabled) .
       marshalEnableCap

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

    enable :: EnableCap -> Capability -> IO ()
    enable cap state = maybe recordInvalidEnum (f state) (marshalEnableCap cap)
       where f Disabled = glDisable
             f Enabled  = glEnable

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

    makeStateVarMaybe :: IO EnableCap -> IO a -> (a -> IO ()) -> StateVar (Maybe a)
    makeStateVarMaybe getCap getAct setAct =
       makeStateVar
          (getStateVarMaybe getCap getAct)
          (setStateVarMaybe getCap setAct)

    getStateVarMaybe :: IO EnableCap -> IO a -> IO (Maybe a)
    getStateVarMaybe getCap act = do
       capability <- fmap makeCapability getCap
       state <- get capability
       if state == Enabled
          then fmap Just act
          else return Nothing

    setStateVarMaybe :: IO EnableCap -> (a -> IO ()) -> Maybe a -> IO ()
    setStateVarMaybe getCap act val = do
       capability <- fmap makeCapability getCap
       maybe (capability $= Disabled) (\x -> act x >> capability $= Enabled) val

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

    data IndexedEnableCap =
       BlendI

    marshalIndexedEnableCap :: IndexedEnableCap -> Maybe GLenum
    marshalIndexedEnableCap x = case x of
       BlendI -> Just gl_BLEND

    makeIndexedCapability ::(a -> GLuint) -> IndexedEnableCap ->  a
       -> StateVar Capability
    makeIndexedCapability f cap val = makeStateVar
       (isIndexedEnabled (f val) cap)
       (\state -> enableIndexed (f val) cap state)

    isIndexedEnabled :: GLuint -> IndexedEnableCap -> IO Capability
    isIndexedEnabled i =
       maybe (do recordInvalidEnum; return Disabled)
             (\cap -> fmap unmarshalCapability $ glIsEnabledi cap i) .
       marshalIndexedEnableCap

    enableIndexed :: GLuint -> IndexedEnableCap -> Capability -> IO ()
    enableIndexed i cap state =
       maybe recordInvalidEnum (f state) (marshalIndexedEnableCap cap)
          where f Enabled  = \c -> glEnablei c i
                f Disabled = \c -> glDisablei c i