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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 WMonad where
import StackSet
import Control.Monad.State
import System.IO
import System.Process (runCommand)
import Graphics.X11.Xlib (Display,Window)
-- | WState, the window manager state.
-- Just the display, width, height and a window list
data WState = WState
{ display :: Display
, screenWidth :: {-# UNPACK #-} !Int
, screenHeight :: {-# UNPACK #-} !Int
, workspace :: {-# UNPACK #-} !WorkSpace -- ^ workspace list
}
type WorkSpace = StackSet Window
-- | The W monad, a StateT transformer over IO encapuslating the window
-- manager state
newtype W a = W { unW :: StateT WState IO a }
deriving (Functor, Monad, MonadIO, MonadState WState)
-- | Run the W monad, given a chunk of W monad code, and an initial state
-- Return the result, and final state
runW :: WState -> W a -> IO (a, WState)
runW st a = runStateT (unW a) st
-- | 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 ()
-- | Run an action forever
forever :: (Monad m) => m a -> m b
forever a = a >> forever a
-- | spawn. Launch an external application
spawn :: String -> W ()
spawn = io_ . runCommand
-- | A 'trace' for the W monad. Logs a string to stderr. The result may
-- be found in your .xsession-errors file
trace :: String -> W ()
trace msg = io $ do
hPutStrLn stderr msg
hFlush stderr
-- | Run a monad action with the current display settings
withDisplay :: (Display -> W ()) -> W ()
withDisplay f = gets display >>= f
-- | Run a monadic action with the display, screen width and height
withScreen :: ((Display,Int,Int) -> W ()) -> W ()
withScreen f = do
d <- gets display
sw <- gets screenWidth
sh <- gets screenHeight
f (d,sw,sh)
-- | Modify the workspace list.
modifyWorkspace :: (WorkSpace -> WorkSpace) -> W ()
modifyWorkspace f = do
modify $ \s -> s { workspace = f (workspace s) }
ws <- gets workspace
trace (show ws) -- log state changes to stderr
-- | Run a side effecting action with the current workspace. Like 'when' but
-- for (WorkSpace -> Maybe a).
whenJust :: (WorkSpace -> Maybe a) -> (a -> W ()) -> W ()
whenJust mg f = do
ws <- gets workspace
case mg ws of
Nothing -> return ()
Just w -> f w
|
