type Nick = Int
data Pos = Pos Double Double
data Sz = Sz Double Double
data Box = Box Pos Sz

data Doodle =
  Doodle { titled :: Text
         , sized :: Sz
         , widgets :: Map Nick Widget
         , displayed :: Nick
         , kbFocus :: KbFocus
         }

data KbFocus = KbFocus [Nick] Int -- which has focus

data Render c => Widget b c =
  Widget { box :: Box
         , thing :: c
         , handleKey :: Key -> c -> (b, c)
         , handleMouse :: Mouse -> c -> (b, c)
         }

kbFocused :: DoodleIO -> Nick
kbFocused io = do

 d <- readIORef io
  return (case kbFocus d of
            KbFocus ns i -> ns !! i)

runDoodle :: Doodle -> IO ()
runDoodle doodle = do
  let doodleIO = newIORef doodle
  in bananaSDL (titled doodle) $ \ah -> do
  sdl <- fromAddHandler ah
  keys <- filter isKey sdl
  mice <- filter isMouse sdl

  doodleB <- doodleIO

  -- a behavior meant to be the widget to recieve key events
  kbw <- kbFocused <@> doodleB

  (h1, lens1) <- lookupKeyHandler kbw <$> doodleB
  applyHandler lens1 h1 doodleB
    -- the handler gives the new value
    -- the doodleB is updated by the lens with the new value

  -- figure out who is hit
  hby <- whoHitBy <@> mice
  (h2, lens2) <- lookupMouseHandler doodleB

  -- lookup hit widgets handler and state
  -- apply the handler to the state with the event
  -- return the events raised and the new state
  applyHandler lens2 h2 doodleB

  reactimate' $ draw <$> changes doodleB