conways-game-of-life/Graphics/GlossUtils.hs

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module Graphics.GlossUtils (playYampa, InputEvent) where
-- A utility function to connect the FRP library Yampa to the
-- graphics library Gloss, from the library yampa-gloss
import Control.Monad (when)
import Data.IORef
( newIORef,
readIORef,
writeIORef,
)
import FRP.Yampa
( Event (..),
SF,
react,
reactInit,
)
import Graphics.Gloss
( Color,
Display,
Picture,
blank,
)
import qualified Graphics.Gloss
import Graphics.Gloss.Interface.IO.Game (playIO)
import qualified Graphics.Gloss.Interface.IO.Game as G
type InputEvent = G.Event
playYampa ::
-- | The display method
Display ->
-- | The background color
Color ->
-- | The refresh rate, in Hertz
Int ->
SF (Event InputEvent) Picture ->
IO ()
playYampa display color frequency mainSF = do
picRef <- newIORef blank
handle <-
reactInit
(return NoEvent)
( \_ updated pic ->
when updated (picRef `writeIORef` pic) >> return False
)
mainSF
let delta = 0.01 / fromIntegral frequency
toPic = const $ readIORef picRef
handleInput = (\e t -> react handle (delta, Just (Event e)) >> return (t + delta))
stepWorld =
( \d t ->
let delta' = realToFrac d - t
in if delta' > 0
then react handle (delta', Just NoEvent) >> return 0.0
else return (- delta')
)
playIO display color frequency 0 toPic handleInput stepWorld