    {-# OPTIONS_HADDOCK hide #-}
    -----------------------------------------------------------------------------
    -- |
    -- Module      :  Graphics.UI.GLUT.Raw.Fonts
    -- Copyright   :  (c) Sven Panne 2013
    -- License     :  BSD3
    --
    -- Maintainer  :  Sven Panne <svenpanne@gmail.com>
    -- Stability   :  stable
    -- Portability :  portable
    --
    -- Our own functions to access font identifiers in a portable way.
    --
    -----------------------------------------------------------------------------

    module Graphics.UI.GLUT.Raw.Fonts (
       BitmapFont(..), GLUTbitmapFont, marshalBitmapFont,
       StrokeFont(..), GLUTstrokeFont, marshalStrokeFont
    ) where

    import Control.Monad.IO.Class ( MonadIO(..) )
    import Foreign.C.Types
    import Foreign.Ptr ( Ptr )

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

    -- | The bitmap fonts available in GLUT. The exact bitmap to be used is
    -- defined by the standard X glyph bitmaps for the X font with the given name.

    data BitmapFont
       = Fixed8By13   -- ^ A fixed width font with every character fitting in an 8
                      --   by 13 pixel rectangle.
                      --   (@-misc-fixed-medium-r-normal--13-120-75-75-C-80-iso8859-1@)
       | Fixed9By15   -- ^ A fixed width font with every character fitting in an 9
                      --   by 15 pixel rectangle.
                      --   (@-misc-fixed-medium-r-normal--15-140-75-75-C-90-iso8859-1@)
       | TimesRoman10 -- ^ A 10-point proportional spaced Times Roman font.
                      --   (@-adobe-times-medium-r-normal--10-100-75-75-p-54-iso8859-1@)
       | TimesRoman24 -- ^ A 24-point proportional spaced Times Roman font.
                      --   (@-adobe-times-medium-r-normal--24-240-75-75-p-124-iso8859-1@)
       | Helvetica10  -- ^ A 10-point proportional spaced Helvetica font.
                      --   (@-adobe-helvetica-medium-r-normal--10-100-75-75-p-56-iso8859-1@)
       | Helvetica12  -- ^ A 12-point proportional spaced Helvetica font.
                      --   (@-adobe-helvetica-medium-r-normal--12-120-75-75-p-67-iso8859-1@)
       | Helvetica18  -- ^ A 18-point proportional spaced Helvetica font.
                      --   (@-adobe-helvetica-medium-r-normal--18-180-75-75-p-98-iso8859-1@)
       deriving ( Eq, Ord, Show )

    -- Alas, fonts in GLUT are not denoted by some integral value, but by opaque
    -- pointers on the C side. Even worse: For WinDoze, they are simply small ints,
    -- casted to void*, for other platforms addresses of global variables are used.
    -- And all is done via ugly #ifdef-ed #defines... Aaaaargl! So the only portable
    -- way is using integers on the Haskell side and doing the marshaling via some
    -- small C wrappers around those macros. *sigh*
    type GLUTbitmapFont = Ptr ()

    marshalBitmapFont :: MonadIO m => BitmapFont -> m GLUTbitmapFont
    marshalBitmapFont x = liftIO $ case x of
       Fixed8By13 -> hs_GLUT_marshalBitmapFont 0
       Fixed9By15 -> hs_GLUT_marshalBitmapFont 1
       TimesRoman10 -> hs_GLUT_marshalBitmapFont 2
       TimesRoman24 -> hs_GLUT_marshalBitmapFont 3
       Helvetica10 -> hs_GLUT_marshalBitmapFont 4
       Helvetica12 -> hs_GLUT_marshalBitmapFont 5
       Helvetica18 -> hs_GLUT_marshalBitmapFont 6

    foreign import ccall unsafe "hs_GLUT_marshalBitmapFont"
       hs_GLUT_marshalBitmapFont :: CInt -> IO (Ptr a)

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

    -- | The stroke fonts available in GLUT.
    data StrokeFont
       = Roman     -- ^ A proportionally spaced Roman Simplex font for ASCII
                   --   characters 32 through 127. The maximum top character in the
                   --   font is 119.05 units; the bottom descends 33.33 units.
       | MonoRoman -- ^ A mono-spaced spaced Roman Simplex font (same characters as
                   --   'Roman') for ASCII characters 32 through 127. The maximum
                   --   top character in the font is 119.05 units; the bottom
                   --   descends 33.33 units. Each character is 104.76 units wide.
       deriving ( Eq, Ord, Show )

    -- Same remarks as for GLUTbitmapFont
    type GLUTstrokeFont = Ptr ()

    marshalStrokeFont :: MonadIO m => StrokeFont -> m GLUTstrokeFont
    marshalStrokeFont x = liftIO $ case x of
       Roman -> hs_GLUT_marshalStrokeFont 0
       MonoRoman -> hs_GLUT_marshalStrokeFont 1

    foreign import ccall unsafe "hs_GLUT_marshalStrokeFont"
       hs_GLUT_marshalStrokeFont :: CInt -> IO (Ptr a)