{-
   Font.hs  (adapted from font.c which is (c) Silicon Graphics, Inc)
   Copyright (c) Sven Panne 2002-2018 <svenpanne@gmail.com>
   This file is part of HOpenGL and distributed under a BSD-style license
   See the file libraries/GLUT/LICENSE

   Draws some text in a bitmapped font. Uses bitmap and other pixel routines.
   Also demonstrates use of display lists.
-}

import Control.Monad ( zipWithM_ )
import Data.List ( genericDrop, genericLength )
import Foreign.C.String ( castCharToCChar )
import Foreign.Marshal.Array ( withArray )
import System.Exit ( exitWith, ExitCode(ExitSuccess) )
import Graphics.UI.GLUT

space :: [GLubyte]
space = [
     0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 ]

letters :: [[GLubyte]]
letters = [
   [ 0x00, 0x00, 0xc3, 0xc3, 0xc3, 0xc3, 0xff, 0xc3, 0xc3, 0xc3, 0x66, 0x3c, 0x18 ],
   [ 0x00, 0x00, 0xfe, 0xc7, 0xc3, 0xc3, 0xc7, 0xfe, 0xc7, 0xc3, 0xc3, 0xc7, 0xfe ],
   [ 0x00, 0x00, 0x7e, 0xe7, 0xc0, 0xc0, 0xc0, 0xc0, 0xc0, 0xc0, 0xc0, 0xe7, 0x7e ],
   [ 0x00, 0x00, 0xfc, 0xce, 0xc7, 0xc3, 0xc3, 0xc3, 0xc3, 0xc3, 0xc7, 0xce, 0xfc ],
   [ 0x00, 0x00, 0xff, 0xc0, 0xc0, 0xc0, 0xc0, 0xfc, 0xc0, 0xc0, 0xc0, 0xc0, 0xff ],
   [ 0x00, 0x00, 0xc0, 0xc0, 0xc0, 0xc0, 0xc0, 0xc0, 0xfc, 0xc0, 0xc0, 0xc0, 0xff ],
   [ 0x00, 0x00, 0x7e, 0xe7, 0xc3, 0xc3, 0xcf, 0xc0, 0xc0, 0xc0, 0xc0, 0xe7, 0x7e ],
   [ 0x00, 0x00, 0xc3, 0xc3, 0xc3, 0xc3, 0xc3, 0xff, 0xc3, 0xc3, 0xc3, 0xc3, 0xc3 ],
   [ 0x00, 0x00, 0x7e, 0x18, 0x18, 0x18, 0x18, 0x18, 0x18, 0x18, 0x18, 0x18, 0x7e ],
   [ 0x00, 0x00, 0x7c, 0xee, 0xc6, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06 ],
   [ 0x00, 0x00, 0xc3, 0xc6, 0xcc, 0xd8, 0xf0, 0xe0, 0xf0, 0xd8, 0xcc, 0xc6, 0xc3 ],
   [ 0x00, 0x00, 0xff, 0xc0, 0xc0, 0xc0, 0xc0, 0xc0, 0xc0, 0xc0, 0xc0, 0xc0, 0xc0 ],
   [ 0x00, 0x00, 0xc3, 0xc3, 0xc3, 0xc3, 0xc3, 0xc3, 0xdb, 0xff, 0xff, 0xe7, 0xc3 ],
   [ 0x00, 0x00, 0xc7, 0xc7, 0xcf, 0xcf, 0xdf, 0xdb, 0xfb, 0xf3, 0xf3, 0xe3, 0xe3 ],
   [ 0x00, 0x00, 0x7e, 0xe7, 0xc3, 0xc3, 0xc3, 0xc3, 0xc3, 0xc3, 0xc3, 0xe7, 0x7e ],
   [ 0x00, 0x00, 0xc0, 0xc0, 0xc0, 0xc0, 0xc0, 0xfe, 0xc7, 0xc3, 0xc3, 0xc7, 0xfe ],
   [ 0x00, 0x00, 0x3f, 0x6e, 0xdf, 0xdb, 0xc3, 0xc3, 0xc3, 0xc3, 0xc3, 0x66, 0x3c ],
   [ 0x00, 0x00, 0xc3, 0xc6, 0xcc, 0xd8, 0xf0, 0xfe, 0xc7, 0xc3, 0xc3, 0xc7, 0xfe ],
   [ 0x00, 0x00, 0x7e, 0xe7, 0x03, 0x03, 0x07, 0x7e, 0xe0, 0xc0, 0xc0, 0xe7, 0x7e ],
   [ 0x00, 0x00, 0x18, 0x18, 0x18, 0x18, 0x18, 0x18, 0x18, 0x18, 0x18, 0x18, 0xff ],
   [ 0x00, 0x00, 0x7e, 0xe7, 0xc3, 0xc3, 0xc3, 0xc3, 0xc3, 0xc3, 0xc3, 0xc3, 0xc3 ],
   [ 0x00, 0x00, 0x18, 0x3c, 0x3c, 0x66, 0x66, 0xc3, 0xc3, 0xc3, 0xc3, 0xc3, 0xc3 ],
   [ 0x00, 0x00, 0xc3, 0xe7, 0xff, 0xff, 0xdb, 0xdb, 0xc3, 0xc3, 0xc3, 0xc3, 0xc3 ],
   [ 0x00, 0x00, 0xc3, 0x66, 0x66, 0x3c, 0x3c, 0x18, 0x3c, 0x3c, 0x66, 0x66, 0xc3 ],
   [ 0x00, 0x00, 0x18, 0x18, 0x18, 0x18, 0x18, 0x18, 0x3c, 0x3c, 0x66, 0x66, 0xc3 ],
   [ 0x00, 0x00, 0xff, 0xc0, 0xc0, 0x60, 0x30, 0x7e, 0x0c, 0x06, 0x03, 0x03, 0xff ]]

charToGLubyte :: Char -> GLubyte
charToGLubyte = fromIntegral . castCharToCChar

makeRasterFont :: IO DisplayList
makeRasterFont = do
   rowAlignment Unpack $= 1

   fontDisplayLists@(fontOffset:_) <- genObjectNames 128
   let listsStartingWith ch = genericDrop (charToGLubyte ch) fontDisplayLists
       makeLetter dl letter =
          defineList dl Compile $
             withArray letter $
                bitmap (Size 8 13) (Vertex2 0 2) (Vector2 10 0)

   zipWithM_ makeLetter (listsStartingWith 'A') letters
   makeLetter (head (listsStartingWith ' ')) space
   return fontOffset

myInit :: IO DisplayList
myInit = do
   shadeModel $= Flat
   makeRasterFont

printString :: DisplayList -> String -> IO ()
printString fontOffset s =
   preservingAttrib [ ListAttributes ] $ do
      listBase $= fontOffset
      withArray (map charToGLubyte s) $
         callLists (genericLength s) UnsignedByte

-- Everything above this line could be in a library
-- that defines a font.  To make it work, you've got
-- to call makeRasterFont before you start making
-- calls to printString.
display :: DisplayList -> DisplayCallback
display fontOffset = do
   let white = Color3 1 1 1

   clear [ ColorBuffer ]
   -- resolve overloading, not needed in "real" programs
   let color3f = color :: Color3 GLfloat -> IO ()
       rasterPos2i = rasterPos :: Vertex2 GLint -> IO ()
   color3f white

   rasterPos2i (Vertex2 20 60)
   printString fontOffset "THE QUICK BROWN FOX JUMPS"
   rasterPos2i (Vertex2 20 40)
   printString fontOffset "OVER A LAZY DOG"
   flush

reshape :: ReshapeCallback
reshape size@(Size w h) = do
   viewport $= (Position 0 0, size)
   matrixMode $= Projection
   loadIdentity
   ortho 0 (fromIntegral w) 0 (fromIntegral h) (-1) 1
   matrixMode $= Modelview 0

keyboard :: KeyboardMouseCallback
keyboard (Char '\27') Down _ _ = exitWith ExitSuccess
keyboard _            _    _ _ = return ()

-- Main Loop
-- Open window with initial window size, title bar,
-- RGBA display mode, and handle input events.
main :: IO ()
main = do
   (progName, _args) <- getArgsAndInitialize
   initialDisplayMode $= [ SingleBuffered, RGBMode ]
   initialWindowSize $= Size 300 100
   initialWindowPosition $= Position 100 100
   _ <- createWindow progName
   fontOffset <- myInit
   reshapeCallback $= Just reshape
   keyboardMouseCallback $= Just keyboard
   displayCallback $= display fontOffset
   mainLoop
