    --------------------------------------------------------------------------------
    -- |
    -- Module      :  Graphics.Rendering.OpenGL.GLU.Initialization
    -- 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 chapter 2 (Initialization) of the GLU specs.
    --
    --------------------------------------------------------------------------------

    module Graphics.Rendering.OpenGL.GLU.Initialization (
       gluVersion, gluExtensions
    ) where

    import Foreign.Ptr ( Ptr, nullPtr, castPtr )
    import Foreign.C.String ( peekCString )
    import Graphics.Rendering.OpenGL.GL.BasicTypes ( GLenum, GLubyte )
    import Graphics.Rendering.OpenGL.GL.StateVar (
       GettableStateVar, makeGettableStateVar )

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

    gluVersion :: GettableStateVar String
    gluVersion = makeGettableStateVar (getString Version)

    gluExtensions :: GettableStateVar [String]
    gluExtensions = makeGettableStateVar (fmap words $ getString Extensions)

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

    data StringName =
         Version
       | Extensions
       deriving ( Eq, Ord, Show )

    marshalStringName :: StringName -> GLenum
    marshalStringName x = case x of
       Version -> 0x189c0
       Extensions -> 0x189c1

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

    getString :: StringName -> IO String
    getString n = do
       ptr <- gluGetString (marshalStringName n)
       if ptr == nullPtr
          then return ""
          else peekCString (castPtr ptr)

    foreign import CALLCONV unsafe "gluGetString" gluGetString ::
       GLenum -> IO (Ptr GLubyte)