module main(main) where

import CGA.SpinBox
import CGA.Window

main = cgaBegin $ do
  myInt <- newMVar MyInt 4 [] --The initial value of int variable
  doOnChange myInt (do
                       a <- getVal myInt
                       putStr (show a)
                    ) --This shows myInt on the screen whenever it is changed
  -- The following two lines put the MyInt interface in a window
  interface <- make_interface myInt 
  window <- newWindow [ title := "spinbox test", addChild := interface ]

class Object a where
  make_interface :: MVar a -> Widget b
  doOnChange-    :: MVar a -> (IO ()) -> IO ()

data MyInt = MyInt Int [(IO())]

getVal :: MVar MyInt -> IO( Int )
getVal theint =
  MyInt a _ <- readMVar theint
  return a

setVal :: MVar MyInt -> Int -> IO ()
setVal theint t = do
  modifyMVar theint (\(MyInt _ b) -> return (MyInt t b))
  MyInt _ callbackList <- readMVar theint
  sequence_ callbackList
  return ()
  
instance Object Int where
  make_interface theint = do 
    i <- getVal theint 
    widget <- SpinBox [ value := i, onSpinChange := (setVal i) ]
    doOnChange theint (do
                         a <- getVal theint
                         set widget [ value := a ]
                         return () --Just in case )
  doOnChange theint callback = do
    modifyMVar theint (\(MyInt a b) -> return (MyInt a (callback:b)))