{-----------------------------------------------------------------------------
reactive-banana-wx
Example: Emit a wave of lights.
Demonstrates that reactive-banana is capable of emitting timed events,
even though it has no built-in notion of time.
------------------------------------------------------------------------------}
{-# LANGUAGE ScopedTypeVariables #-}
-- allows pattern signatures like
-- do
-- (b :: Behavior Int) <- stepper 0 ...
{-# LANGUAGE RecursiveDo #-}
-- allows recursive do notation
-- mdo
-- ...
import Control.Monad
import qualified Data.List as List
import Data.Ord
import Graphics.UI.WX hiding (Event)
import Reactive.Banana
import Reactive.Banana.WX
{-----------------------------------------------------------------------------
Main
------------------------------------------------------------------------------}
lightCount :: Int
lightCount = 15 -- number of lights that comprise the wave
waveLength :: Int
waveLength = 4 -- number of lights that are lit at once
dt :: Int
dt = 70 -- half the cycle duration
main :: IO ()
main = start $ do
-- create window and widgets
f <- frame [text := "Waves of Light"]
left <- button f [text := "Left"]
right <- button f [text := "Right"]
lights <- replicateM lightCount $ staticText f [text := "•"]
set f [layout := margin 10 $
column 10 [row 5 [widget left, widget right],
row 5 $ map widget lights]
]
-- we're going to need a timer
t <- timer f []
let networkDescription :: MomentIO ()
networkDescription = do
eLeft <- event0 left command
eRight <- event0 right command
-- event describing all the lights
eWave <- scheduleQueue t $ unionWith (++)
(waveLeft <$ eLeft )
(waveRight <$ eRight)
-- animate the lights
forM_ [1 .. lightCount] $ \k -> do
let
bulb = lights !! (k-1)
colorize True = red
colorize False = black
bBulb <- stepper False $ snd <$> filterE ((== k) . fst) eWave
sink bulb [ color :== colorize <$> bBulb ]
network <- compile networkDescription
actuate network
type Index = Int
type Action = (Index, Bool)
-- describe wave pattern as a list
wave :: (Index -> Index) -> [(Duration, Action)]
wave f = deltas $ merge ons offs
where
merge xs ys = List.sortBy (comparing fst) $ xs ++ ys
deltas xs = zipWith relativize (0 : map fst xs) xs
where relativize dt1 (dt2,x) = (dt2-dt1, x)
ons = [(k*2*dt, (f k, True)) | k <- [1..lightCount]]
offs = [(dt+(waveLength+k)*2*dt, (f k, False)) | k <- [1..lightCount]]
waveLeft :: [(Duration, Action)]
waveLeft = wave id
waveRight :: [(Duration, Action)]
waveRight = wave (\k -> lightCount - k + 1)
{-----------------------------------------------------------------------------
Timer magic
------------------------------------------------------------------------------}
type Duration = Int -- in milliseconds
type Queue a = [(Duration, a)] -- [(time to wait, occurrence to happen)]
type Enqueue a = Queue a
-- Schedule events to happen after a given duration from their occurrence
-- However, new events will *not* be scheduled before the old ones have finished.
scheduleQueue :: Timer -> Event (Enqueue a) -> MomentIO (Event a)
scheduleQueue t e = mdo
liftIO $ set t [ enabled := False ]
eAlarm <- event0 t command
-- (Queue that keeps track of events to schedule
-- , duration of the new alarm if applicable)
(eSetNewAlarmDuration, bQueue)
<- mapAccum [] $ unionWith const (remove <$ eAlarm) (add <$> e)
let
-- change queue and change timer
remove (_:[]) = (stop, [])
remove (_:xs) = (wait (fst $ head xs), xs)
add ys [] = (wait (fst $ head ys), ys)
add ys xs = (idle, xs ++ ys)
wait dt = set t [ enabled := True, interval := dt ]
stop = set t [ enabled := False ]
idle = return ()
-- Return topmost value from the queue whenever the alarm rings.
-- The queue is never empty when the alarm rings.
eout = fmap (snd . head) $ bQueue <@ eAlarm
reactimate eSetNewAlarmDuration
return eout