htanks/GLDriver.hs

{-# LANGUAGE ExistentialQuantification, DeriveDataTypeable #-}

module GLDriver ( Driver(..)
                , Event
                , SomeEvent(..)
                , QuitEvent(..)
                , fromEvent
                ) where

import Data.Typeable


class Driver a where
    initialized :: a -> Bool
    
    initGL :: a -> IO a
    deinitGL :: a -> IO ()
    
    nextEvent :: a -> IO (Maybe SomeEvent)


class Typeable a => Event a

data SomeEvent = forall a. Event a => SomeEvent a

fromEvent :: Event a => SomeEvent -> Maybe a
fromEvent (SomeEvent a) = cast a


data QuitEvent = QuitEvent deriving Typeable

instance Event QuitEvent