haskell で GLUT 使って hello work

gist.hs

import System.Exit ( exitWith, ExitCode(ExitSuccess) )  
-- http://hackage.haskell.org/package/GLUT  
import Graphics.UI.GLUT

intToFloat :: Int -> Float
intToFloat n = read (show n)::Float              

--scrx :: Int -> Float
scrx :: Fractional a => a -> a        
scrx x = 2 * x / 320.0 - 1.0
scry y = 1.0 - 2 * y / 400.0
color3i r g b = color (Color3 (r/255) (g/255) (b/255 :: GLfloat))    
  
display :: DisplayCallback
display = do
  clear [ColorBuffer]
  
  color3i 255 255 255  
  preservingMatrix $ do  
    translate (Vector3 (scrx 100) (scry 100) 0 ::Vector3 Float)
    scale 0.0007 0.0005 (1.0 :: Double)
    renderString Roman "hello work"

  putStrLn "display"
  swapBuffers

keyboardMouse :: KeyboardMouseCallback
keyboardMouse (Char 'q') _ _ _ = exitWith ExitSuccess
keyboardMouse (Char 'a') _ _ _ = putStrLn("key")
keyboardMouse (MouseButton LeftButton) _ _ _ = putStrLn("mouse")

screenWidth  = 320
screenHeight = 400
screenLeft   = 100
screenTop    = 100               

main :: IO()
main = do
  getArgsAndInitialize

  initialDisplayMode $= [ DoubleBuffered, RGBMode ]
  initialWindowSize $= Size screenWidth screenHeight
  initialWindowPosition $= Position screenLeft screenTop
  createWindow "hoge"

  displayCallback $= display
  keyboardMouseCallback $= Just keyboardMouse
  
  mainLoop