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{-
PickSquare.hs (adapted from picksquare.c which is (c) Silicon Graphics, Inc.)
Copyright (c) Sven Panne 2002-2005 <sven.panne@aedion.de>
This file is part of HOpenGL and distributed under a BSD-style license
See the file libraries/GLUT/LICENSE
Use of multiple names and picking are demonstrated. A 3x3 grid of squares is
drawn. When the left mouse button is pressed, all squares under the cursor
position have their color changed.
-}
import Data.Array ( Array, listArray, (!) )
import Data.IORef ( IORef, newIORef )
import System.Exit ( exitWith, ExitCode(ExitSuccess) )
import Graphics.UI.GLUT
type Board = Array (Int,Int) (IORef Int)
data State = State { board :: Board }
makeState :: IO State
makeState = do
refs <- sequence . replicate 9 . newIORef $ 0
return $ State { board = listArray ((0,0),(2,2)) refs }
-- Clear color value for every square on the board
myInit :: IO ()
myInit = do
clearColor $= Color4 0 0 0 0
-- The nine squares are drawn. Each square is given two names: one for the row
-- and the other for the column on the grid. The color of each square is
-- determined by its position on the grid, and the value in the board array.
-- Note: In contrast to the the original example, we always give names to
-- squares, regardless of the render mode. This simplifies the code a bit and
-- is even suggested by the Red Book.
drawSquares :: State -> IO ()
drawSquares state =
flip mapM_ [ 0 .. 2 ] $ \i -> do
loadName (Name (fromIntegral i))
flip mapM_ [ 0 .. 2 ] $ \j ->
withName (Name (fromIntegral j)) $ do
val <- get (board state ! (i,j))
-- resolve overloading, not needed in "real" programs
let color3f = color :: Color3 GLfloat -> IO ()
color3f (Color3 (fromIntegral i / 3.0)
(fromIntegral j / 3.0)
(fromIntegral val / 3.0))
let vertex2i :: Int -> Int -> Vertex2 GLint
vertex2i x y = Vertex2 (fromIntegral x) (fromIntegral y)
rect (vertex2i i j) (vertex2i (i + 1) (j + 1))
-- processHits prints the hit records and updates the board array.
processHits :: Maybe[HitRecord] -> State -> IO ()
processHits Nothing _ = putStrLn "selection buffer overflow"
processHits (Just hitRecords) state = do
putStrLn ("hits = " ++ show (length hitRecords))
mapM_ (\(HitRecord z1 z2 names) -> do
putStrLn (" number of names for this hit = " ++ show (length names))
putStr (" z1 is " ++ show z1)
putStrLn ("; z2 is " ++ show z2)
putStr " names are"
sequence_ [ putStr (" " ++ show n) | Name n <- names ]
putChar '\n'
let [i, j] = [ fromIntegral n | Name n <- names ]
(board state ! (i,j)) $~ (\x -> (x + 1) `mod` 3))
hitRecords
-- pickSquares sets up selection mode, name stack, and projection matrix for
-- picking. Then the objects are drawn.
bufSize :: GLsizei
bufSize = 512
pickSquares :: State -> KeyboardMouseCallback
pickSquares state (MouseButton LeftButton) Down _ (Position x y) = do
vp@(_, (Size _ height)) <- get viewport
(_, maybeHitRecords) <- getHitRecords bufSize $
withName (Name 0) $ do
matrixMode $= Projection
preservingMatrix $ do
loadIdentity
-- create 5x5 pixel picking region near cursor location
pickMatrix (fromIntegral x, fromIntegral height - fromIntegral y) (5, 5) vp
ortho2D 0 3 0 3
drawSquares state
flush
processHits maybeHitRecords state
postRedisplay Nothing
pickSquares _ (Char '\27') Down _ _ = exitWith ExitSuccess
pickSquares _ _ _ _ _ = return ()
display :: State -> DisplayCallback
display state = do
clear [ ColorBuffer ]
drawSquares state
flush
reshape :: ReshapeCallback
reshape size = do
viewport $= (Position 0 0, size)
matrixMode $= Projection
loadIdentity
ortho2D 0 3 0 3
matrixMode $= Modelview 0
loadIdentity
-- Main Loop
main :: IO ()
main = do
(progName, _args) <- getArgsAndInitialize
initialDisplayMode $= [ SingleBuffered, RGBMode ]
initialWindowSize $= Size 100 100
initialWindowPosition $= Position 100 100
createWindow progName
state <- makeState
myInit
reshapeCallback $= Just reshape
displayCallback $= display state
keyboardMouseCallback $= Just (pickSquares state)
mainLoop
|
