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|
-----------------------------------------------------------------------------
-- |
-- Module : W.hs
-- Copyright : (c) Spencer Janssen 2007
-- License : BSD3-style (see LICENSE)
--
-- Maintainer : sjanssen@cse.unl.edu
-- Stability : unstable
-- Portability : not portable, uses cunning newtype deriving
--
-----------------------------------------------------------------------------
--
-- The W monad, a state monad transformer over IO, for the window
-- manager state, and support routines.
--
module W where
import Data.Sequence
import Control.Monad.State
import System.IO (hFlush, hPutStrLn, stderr)
import Graphics.X11.Xlib
--
-- | WState, the window manager state.
-- Just the display, width, height and a window list
--
data WState = WState
{ display :: Display
, screenWidth :: !Int
, screenHeight :: !Int
, windows :: Seq Window
}
-- | The W monad, a StateT transformer over IO encapuslating the window
-- manager state
--
newtype W a = W (StateT WState IO a)
deriving (Functor, Monad, MonadIO)
-- | Run the W monad, given a chunk of W monad code, and an initial state
-- Return the result, and final state
--
runW :: W a -> WState -> IO (a, WState)
runW (W m) = runStateT m
withIO :: (forall b. (a -> IO b) -> IO b) -> (a -> W c) -> W c
withIO f g = do
s <- W get
(y, t) <- io (f (flip runW s . g))
W (put t)
return y
--
-- | Lift an IO action into the W monad
--
io :: IO a -> W a
io = liftIO
--
-- | Lift an IO action into the W monad, discarding any result
--
io_ :: IO a -> W ()
io_ f = liftIO f >> return ()
--
-- | A 'trace' for the W monad
--
trace :: String -> W ()
trace msg = io $ do
hPutStrLn stderr msg
hFlush stderr
--
-- | Run an action forever
--
forever :: (Monad m) => m a -> m b
forever a = a >> forever a
-- ---------------------------------------------------------------------
-- Getting at the window manager state
-- | Return the current dispaly
getDisplay :: W Display
getDisplay = W (gets display)
-- | Return the current windows
getWindows :: W (Seq Window)
getWindows = W (gets windows)
-- | Return the screen width
getScreenWidth :: W Int
getScreenWidth = W (gets screenWidth)
-- | Return the screen height
getScreenHeight :: W Int
getScreenHeight = W (gets screenHeight)
-- | Set the current window list
setWindows :: Seq Window -> W ()
setWindows x = W (modify (\s -> s {windows = x}))
-- | Modify the current window list
modifyWindows :: (Seq Window -> Seq Window) -> W ()
modifyWindows f = W (modify (\s -> s {windows = f (windows s)}))
|
