    -- #hide
    --------------------------------------------------------------------------------
    -- |
    -- Module      :  Graphics.Rendering.OpenGL.GL.RenderMode
    -- 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 related to the current render mode.
    --
    --------------------------------------------------------------------------------

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

    import Graphics.Rendering.OpenGL.GL.StateVar
    import Graphics.Rendering.OpenGL.GL.Exception
    import Graphics.Rendering.OpenGL.GL.QueryUtils
    import Graphics.Rendering.OpenGL.Raw.ARB.Compatibility (
       glRenderMode, gl_FEEDBACK, gl_RENDER, gl_SELECT )
    import Graphics.Rendering.OpenGL.Raw.Core31

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

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

    marshalRenderMode :: RenderMode -> GLenum
    marshalRenderMode x = case x of
       Render -> gl_RENDER
       Feedback -> gl_FEEDBACK
       Select -> gl_SELECT

    unmarshalRenderMode :: GLenum -> RenderMode
    unmarshalRenderMode x
       | x == gl_RENDER = Render
       | x == gl_FEEDBACK = Feedback
       | x == gl_SELECT = 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

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

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