    -- #hide
    --------------------------------------------------------------------------------
    -- |
    -- Module      :  Graphics.Rendering.OpenGL.GL.RenderMode
    -- 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 is a purely internal module related to the current render mode.
    --
    --------------------------------------------------------------------------------

    module Graphics.Rendering.OpenGL.GL.RenderMode (
       RenderMode(..), withRenderMode, renderMode
    ) where

    import Graphics.Rendering.OpenGL.GL.BasicTypes ( GLenum, GLint )
    import Graphics.Rendering.OpenGL.GL.Exception ( finallyRet )
    import Graphics.Rendering.OpenGL.GL.QueryUtils (
       GetPName(GetRenderMode), getEnum1 )
    import Graphics.Rendering.OpenGL.GL.StateVar (
       HasGetter(get), GettableStateVar, makeGettableStateVar )

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

    data RenderMode =
         Render
       | Feedback
       | Select
       deriving ( Eq, Ord, Show )

    marshalRenderMode :: RenderMode -> GLenum
    marshalRenderMode x = case x of
       Render -> 0x1c00
       Feedback -> 0x1c01
       Select -> 0x1c02

    unmarshalRenderMode :: GLenum -> RenderMode
    unmarshalRenderMode x
       | x == 0x1c00 = Render
       | x == 0x1c01 = Feedback
       | x == 0x1c02 = Select
       | otherwise = error ("unmarshalRenderMode: illegal value " ++ show x)

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

    withRenderMode :: RenderMode -> IO a -> IO (a, GLint)
    withRenderMode newMode action = do
       oldMode <- get renderMode
       setRenderMode newMode
       action `finallyRet` setRenderMode oldMode

    setRenderMode :: RenderMode -> IO GLint
    setRenderMode = glRenderMode . marshalRenderMode

    foreign import CALLCONV unsafe "glRenderMode" glRenderMode :: GLenum -> IO GLint

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

    renderMode :: GettableStateVar RenderMode
    renderMode = makeGettableStateVar $ getEnum1 unmarshalRenderMode GetRenderMode