Add music support

src/Sound.hs

@@ -11,6 +11,7 @@ Uses SDL.Mixer.
 module Sound (
     -- * Simple (One-Shot) Playback
       playSoundQueue
+    , playPositionalSoundQueue
     -- * Complex Playback
     , playAndUpdate
     ) where
@@ -24,6 +25,7 @@ import Control.Monad
 import Control.Monad.Trans
 import Control.Monad.Trans.Maybe
 import Control.Lens
+import Data.Int (Int16)
 {- | Start playing new sounds and update sound specifications.
 A Map of new sound specifications is merged with a Map of already playing sounds, 
 then sounds in the merged Map are updated.
@@ -120,18 +122,29 @@ cleanupHalted s = do
 
 -----------------------------------------------------------------
 {- | Play sounds from a list of indices.
-Each sound starts playing (and will not repeat) if there is a free channel.
+For each index, the corresponding sound starts playing if there is a free channel.
 Use this if you don't care about timing, overlapping, fading, or sound positions.
 -}
 playSoundQueue :: IM.IntMap Mix.Chunk -> [Int] -> IO ()
-playSoundQueue chunkMap ns = forM_ ns $ \n -> playIfFree (chunkMap IM.! n) Mix.Once
+playSoundQueue chunkMap ns = forM_ ns $ \n -> runMaybeT $ playIfFree (chunkMap IM.! n) Mix.Once
 {- | Given a chunk, attempt to play this on a free channel a given number of
 times. Returns 'Just' the channel if succeeds.
 -}
-playIfFree :: Mix.Chunk -> Mix.Times -> IO (Maybe Mix.Channel)
-playIfFree c times = do
-    mayChan <- Mix.getAvailable Mix.DefaultGroup
-    case mayChan of
-        Nothing -> return Nothing
-        Just i  -> Just <$> Mix.playOn i times c
 
+playIfFree :: Mix.Chunk -> Mix.Times -> MaybeT IO Mix.Channel
+playIfFree c times = do
+    i <- MaybeT $ Mix.getAvailable Mix.DefaultGroup
+    liftIO $ Mix.playOn i times c
+
+-----------------------------------------------------------------
+{- | Play sounds from a list of index/position pairs.
+As for 'playSoundQueue', but with positional information in the form of an Int16.
+-}
+playPositionalSoundQueue :: IM.IntMap Mix.Chunk -> [(Int,Int16)] -> IO ()
+playPositionalSoundQueue chunkMap ns = forM_ ns $ \(n,a) -> 
+    runMaybeT $ playIfFree (chunkMap IM.! n) Mix.Once >>= setChannelPos a
+
+setChannelPos :: Int16 -> Mix.Channel -> MaybeT IO Mix.Channel
+setChannelPos a i = do
+    liftIO $ Mix.effectPosition i a 0 
+    return i