content: {-# LANGUAGE ExistentialQuantification, FlexibleInstances, GeneralizedNewtypeDeriving,
               MultiParamTypeClasses, TypeSynonymInstances, CPP, DeriveDataTypeable #-}
  
  -----------------------------------------------------------------------------
  -- |
  -- Module      :  XMonad.Core
  -- Copyright   :  (c) Spencer Janssen 2007
  -- License     :  BSD3-style (see LICENSE)
  --
  -- Maintainer  :  spencerjanssen@gmail.com
  -- Stability   :  unstable
  -- Portability :  not portable, uses cunning newtype deriving
  --
  -- The 'X' monad, a state monad transformer over 'IO', for the window
  -- manager state, and support routines.
  --
  -----------------------------------------------------------------------------
  
  module XMonad.Core (
      X, WindowSet, WindowSpace, WorkspaceId,
      ScreenId(..), ScreenDetail(..), XState(..),
      XConf(..), XConfig(..), LayoutClass(..),
      Layout(..), readsLayout, Typeable, Message,
      SomeMessage(..), fromMessage, LayoutMessages(..),
      StateExtension(..), ExtensionClass(..),
      runX, catchX, userCode, userCodeDef, io, catchIO, installSignalHandlers, uninstallSignalHandlers,
      withDisplay, withWindowSet, isRoot, runOnWorkspaces,
      getAtom, spawn, spawnPID, xfork, getXMonadDir, recompile, trace, whenJust, whenX,
      atom_WM_STATE, atom_WM_PROTOCOLS, atom_WM_DELETE_WINDOW, ManageHook, Query(..), runQuery
    ) where
  
  import XMonad.StackSet hiding (modify)
  
  import Prelude hiding ( catch )
  import Codec.Binary.UTF8.String (encodeString)
  import Control.Exception.Extensible (catch, fromException, try, bracket, throw, finally, SomeException(..))
  import Control.Applicative
  import Control.Monad.State
  import Control.Monad.Reader
  import System.FilePath
  import System.IO
  import System.Info
  import System.Posix.Process (executeFile, forkProcess, getAnyProcessStatus, createSession)
  import System.Posix.Signals
  import System.Posix.IO
  import System.Posix.Types (ProcessID)
  import System.Process
  import System.Directory
  import System.Exit
  import Graphics.X11.Xlib
  import Graphics.X11.Xlib.Extras (Event)
  import Data.Typeable
  import Data.List ((\\))
  import Data.Maybe (isJust,fromMaybe)
  import Data.Monoid
  
  import qualified Data.Map as M
  import qualified Data.Set as S
  
  -- | XState, the (mutable) window manager state.
  data XState = XState
      { windowset        :: !WindowSet                     -- ^ workspace list
      , mapped           :: !(S.Set Window)                -- ^ the Set of mapped windows
      , waitingUnmap     :: !(M.Map Window Int)            -- ^ the number of expected UnmapEvents
      , dragging         :: !(Maybe (Position -> Position -> X (), X ()))
      , numberlockMask   :: !KeyMask                       -- ^ The numlock modifier
      , extensibleState  :: !(M.Map String (Either String StateExtension))
      -- ^ stores custom state information.
      --
      -- The module "XMonad.Utils.ExtensibleState" in xmonad-contrib
      -- provides additional information and a simple interface for using this.
      }
  
  -- | XConf, the (read-only) window manager configuration.
  data XConf = XConf
      { display       :: Display        -- ^ the X11 display
      , config        :: !(XConfig Layout)       -- ^ initial user configuration
      , theRoot       :: !Window        -- ^ the root window
      , normalBorder  :: !Pixel         -- ^ border color of unfocused windows
      , focusedBorder :: !Pixel         -- ^ border color of the focused window
      , keyActions    :: !(M.Map (KeyMask, KeySym) (X ()))
                                        -- ^ a mapping of key presses to actions
      , buttonActions :: !(M.Map (KeyMask, Button) (Window -> X ()))
                                        -- ^ a mapping of button presses to actions
      , mouseFocused :: !Bool           -- ^ was refocus caused by mouse action?
      , mousePosition :: !(Maybe (Position, Position))
                                        -- ^ position of the mouse according to
                                        -- the event currently being processed
      }
  
  -- todo, better name
  data XConfig l = XConfig
      { normalBorderColor  :: !String              -- ^ Non focused windows border color. Default: \"#dddddd\"
      , focusedBorderColor :: !String              -- ^ Focused windows border color. Default: \"#ff0000\"
      , terminal           :: !String              -- ^ The preferred terminal application. Default: \"xterm\"
      , layoutHook         :: !(l Window)          -- ^ The available layouts
      , manageHook         :: !ManageHook          -- ^ The action to run when a new window is opened
      , handleEventHook    :: !(Event -> X All)    -- ^ Handle an X event, returns (All True) if the default handler
                                                   -- should also be run afterwards. mappend should be used for combining
                                                   -- event hooks in most cases.
      , workspaces         :: ![String]            -- ^ The list of workspaces' names
      , modMask            :: !KeyMask             -- ^ the mod modifier
      , keys               :: !(XConfig Layout -> M.Map (ButtonMask,KeySym) (X ()))
                                                   -- ^ The key binding: a map from key presses and actions
      , mouseBindings      :: !(XConfig Layout -> M.Map (ButtonMask, Button) (Window -> X ()))
                                                   -- ^ The mouse bindings
      , borderWidth        :: !Dimension           -- ^ The border width
      , logHook            :: !(X ())              -- ^ The action to perform when the windows set is changed
      , startupHook        :: !(X ())              -- ^ The action to perform on startup
      , focusFollowsMouse  :: !Bool                -- ^ Whether window entry events can change focus
      }
  
  
  type WindowSet   = StackSet  WorkspaceId (Layout Window) Window ScreenId ScreenDetail
  type WindowSpace = Workspace WorkspaceId (Layout Window) Window
  
  -- | Virtual workspace indices
  type WorkspaceId = String
  
  -- | Physical screen indices
  newtype ScreenId    = S Int deriving (Eq,Ord,Show,Read,Enum,Num,Integral,Real)
  
  -- | The 'Rectangle' with screen dimensions
  data ScreenDetail   = SD { screenRect :: !Rectangle } deriving (Eq,Show, Read)
  
  ------------------------------------------------------------------------
  
  -- | The X monad, 'ReaderT' and 'StateT' transformers over 'IO'
  -- encapsulating the window manager configuration and state,
  -- respectively.
  --
  -- Dynamic components may be retrieved with 'get', static components
  -- with 'ask'. With newtype deriving we get readers and state monads
  -- instantiated on 'XConf' and 'XState' automatically.
  --
  newtype X a = X (ReaderT XConf (StateT XState IO) a)
      deriving (Functor, Monad, MonadIO, MonadState XState, MonadReader XConf, Typeable)
  
  instance Applicative X where
    pure = return
    (<*>) = ap
  
  instance (Monoid a) => Monoid (X a) where
      mempty  = return mempty
      mappend = liftM2 mappend
  
  type ManageHook = Query (Endo WindowSet)
  newtype Query a = Query (ReaderT Window X a)
      deriving (Functor, Monad, MonadReader Window, MonadIO)
  
  runQuery :: Query a -> Window -> X a
  runQuery (Query m) w = runReaderT m w
  
  instance Monoid a => Monoid (Query a) where
      mempty  = return mempty
      mappend = liftM2 mappend
  
  -- | Run the 'X' monad, given a chunk of 'X' monad code, and an initial state
  -- Return the result, and final state
  runX :: XConf -> XState -> X a -> IO (a, XState)
  runX c st (X a) = runStateT (runReaderT a c) st
  
  -- | Run in the 'X' monad, and in case of exception, and catch it and log it
  -- to stderr, and run the error case.
  catchX :: X a -> X a -> X a
  catchX job errcase = do
      st <- get
      c <- ask
      (a, s') <- io $ runX c st job `catch` \e -> case fromException e of
                          Just x -> throw e `const` (x `asTypeOf` ExitSuccess)
                          _ -> do hPrint stderr e; runX c st errcase
      put s'
      return a
  
  -- | Execute the argument, catching all exceptions.  Either this function or
  -- 'catchX' should be used at all callsites of user customized code.
  userCode :: X a -> X (Maybe a)
  userCode a = catchX (Just `liftM` a) (return Nothing)
  
  -- | Same as userCode but with a default argument to return instead of using
  -- Maybe, provided for convenience.
  userCodeDef :: a -> X a -> X a
  userCodeDef def a = fromMaybe def `liftM` userCode a
  
  -- ---------------------------------------------------------------------
  -- Convenient wrappers to state
  
  -- | Run a monad action with the current display settings
  withDisplay :: (Display -> X a) -> X a
  withDisplay   f = asks display >>= f
  
  -- | Run a monadic action with the current stack set
  withWindowSet :: (WindowSet -> X a) -> X a
  withWindowSet f = gets windowset >>= f
  
  -- | True if the given window is the root window
  isRoot :: Window -> X Bool
  isRoot w = (w==) <$> asks theRoot
  
  -- | Wrapper for the common case of atom internment
  getAtom :: String -> X Atom
  getAtom str = withDisplay $ \dpy -> io $ internAtom dpy str False
  
  -- | Common non-predefined atoms
  atom_WM_PROTOCOLS, atom_WM_DELETE_WINDOW, atom_WM_STATE :: X Atom
  atom_WM_PROTOCOLS       = getAtom "WM_PROTOCOLS"
  atom_WM_DELETE_WINDOW   = getAtom "WM_DELETE_WINDOW"
  atom_WM_STATE           = getAtom "WM_STATE"
  
  ------------------------------------------------------------------------
  -- LayoutClass handling. See particular instances in Operations.hs
  
  -- | An existential type that can hold any object that is in 'Read'
  --   and 'LayoutClass'.
  data Layout a = forall l. (LayoutClass l a, Read (l a)) => Layout (l a)
  
  -- | Using the 'Layout' as a witness, parse existentially wrapped windows
  -- from a 'String'.
  readsLayout :: Layout a -> String -> [(Layout a, String)]
  readsLayout (Layout l) s = [(Layout (asTypeOf x l), rs) | (x, rs) <- reads s]
  
  -- | Every layout must be an instance of 'LayoutClass', which defines
  -- the basic layout operations along with a sensible default for each.
  --
  -- Minimal complete definition:
  --
  -- * 'runLayout' || (('doLayout' || 'pureLayout') && 'emptyLayout'), and
  --
  -- * 'handleMessage' || 'pureMessage'
  --
  -- You should also strongly consider implementing 'description',
  -- although it is not required.
  --
  -- Note that any code which /uses/ 'LayoutClass' methods should only
  -- ever call 'runLayout', 'handleMessage', and 'description'!  In
  -- other words, the only calls to 'doLayout', 'pureMessage', and other
  -- such methods should be from the default implementations of
  -- 'runLayout', 'handleMessage', and so on.  This ensures that the
  -- proper methods will be used, regardless of the particular methods
  -- that any 'LayoutClass' instance chooses to define.
  class Show (layout a) => LayoutClass layout a where
  
      -- | By default, 'runLayout' calls 'doLayout' if there are any
      --   windows to be laid out, and 'emptyLayout' otherwise.  Most
      --   instances of 'LayoutClass' probably do not need to implement
      --   'runLayout'; it is only useful for layouts which wish to make
      --   use of more of the 'Workspace' information (for example,
      --   "XMonad.Layout.PerWorkspace").
      runLayout :: Workspace WorkspaceId (layout a) a
                -> Rectangle
                -> X ([(a, Rectangle)], Maybe (layout a))
      runLayout (Workspace _ l ms) r = maybe (emptyLayout l r) (doLayout l r) ms
  
      -- | Given a 'Rectangle' in which to place the windows, and a 'Stack'
      -- of windows, return a list of windows and their corresponding
      -- Rectangles.  If an element is not given a Rectangle by
      -- 'doLayout', then it is not shown on screen.  The order of
      -- windows in this list should be the desired stacking order.
      --
      -- Also possibly return a modified layout (by returning @Just
      -- newLayout@), if this layout needs to be modified (e.g. if it
      -- keeps track of some sort of state).  Return @Nothing@ if the
      -- layout does not need to be modified.
      --
      -- Layouts which do not need access to the 'X' monad ('IO', window
      -- manager state, or configuration) and do not keep track of their
      -- own state should implement 'pureLayout' instead of 'doLayout'.
      doLayout    :: layout a -> Rectangle -> Stack a
                  -> X ([(a, Rectangle)], Maybe (layout a))
      doLayout l r s   = return (pureLayout l r s, Nothing)
  
      -- | This is a pure version of 'doLayout', for cases where we
      -- don't need access to the 'X' monad to determine how to lay out
      -- the windows, and we don't need to modify the layout itself.
      pureLayout  :: layout a -> Rectangle -> Stack a -> [(a, Rectangle)]
      pureLayout _ r s = [(focus s, r)]
  
      -- | 'emptyLayout' is called when there are no windows.
      emptyLayout :: layout a -> Rectangle -> X ([(a, Rectangle)], Maybe (layout a))
      emptyLayout _ _ = return ([], Nothing)
  
      -- | 'handleMessage' performs message handling.  If
      -- 'handleMessage' returns @Nothing@, then the layout did not
      -- respond to the message and the screen is not refreshed.
      -- Otherwise, 'handleMessage' returns an updated layout and the
      -- screen is refreshed.
      --
      -- Layouts which do not need access to the 'X' monad to decide how
      -- to handle messages should implement 'pureMessage' instead of
      -- 'handleMessage' (this restricts the risk of error, and makes
      -- testing much easier).
      handleMessage :: layout a -> SomeMessage -> X (Maybe (layout a))
      handleMessage l  = return . pureMessage l
  
      -- | Respond to a message by (possibly) changing our layout, but
      -- taking no other action.  If the layout changes, the screen will
      -- be refreshed.
      pureMessage :: layout a -> SomeMessage -> Maybe (layout a)
      pureMessage _ _  = Nothing
  
      -- | This should be a human-readable string that is used when
      -- selecting layouts by name.  The default implementation is
      -- 'show', which is in some cases a poor default.
      description :: layout a -> String
      description      = show
  
  instance LayoutClass Layout Window where
      runLayout (Workspace i (Layout l) ms) r = fmap (fmap Layout) `fmap` runLayout (Workspace i l ms) r
      doLayout (Layout l) r s  = fmap (fmap Layout) `fmap` doLayout l r s
      emptyLayout (Layout l) r = fmap (fmap Layout) `fmap` emptyLayout l r
      handleMessage (Layout l) = fmap (fmap Layout) . handleMessage l
      description (Layout l)   = description l
  
  instance Show (Layout a) where show (Layout l) = show l
  
  -- | Based on ideas in /An Extensible Dynamically-Typed Hierarchy of
  -- Exceptions/, Simon Marlow, 2006. Use extensible messages to the
  -- 'handleMessage' handler.
  --
  -- User-extensible messages must be a member of this class.
  --
  class Typeable a => Message a
  
  -- |
  -- A wrapped value of some type in the 'Message' class.
  --
  data SomeMessage = forall a. Message a => SomeMessage a
  
  -- |
  -- And now, unwrap a given, unknown 'Message' type, performing a (dynamic)
  -- type check on the result.
  --
  fromMessage :: Message m => SomeMessage -> Maybe m
  fromMessage (SomeMessage m) = cast m
  
  -- X Events are valid Messages.
  instance Message Event
  
  -- | 'LayoutMessages' are core messages that all layouts (especially stateful
  -- layouts) should consider handling.
  data LayoutMessages = Hide              -- ^ sent when a layout becomes non-visible
                      | ReleaseResources  -- ^ sent when xmonad is exiting or restarting
      deriving (Typeable, Eq)
  
  instance Message LayoutMessages
  
  -- ---------------------------------------------------------------------
  -- Extensible state
  --
  
  -- | Every module must make the data it wants to store
  -- an instance of this class.
  --
  -- Minimal complete definition: initialValue
  class Typeable a => ExtensionClass a where
      -- | Defines an initial value for the state extension
      initialValue :: a
      -- | Specifies whether the state extension should be
      -- persistent. Setting this method to 'PersistentExtension'
      -- will make the stored data survive restarts, but
      -- requires a to be an instance of Read and Show.
      --
      -- It defaults to 'StateExtension', i.e. no persistence.
      extensionType :: a -> StateExtension
      extensionType = StateExtension
  
  -- | Existential type to store a state extension.
  data StateExtension =
      forall a. ExtensionClass a => StateExtension a
      -- ^ Non-persistent state extension
    | forall a. (Read a, Show a, ExtensionClass a) => PersistentExtension a
      -- ^ Persistent extension
  
  -- ---------------------------------------------------------------------
  -- | General utilities
  --
  -- Lift an 'IO' action into the 'X' monad
  io :: MonadIO m => IO a -> m a
  io = liftIO
  
  -- | Lift an 'IO' action into the 'X' monad.  If the action results in an 'IO'
  -- exception, log the exception to stderr and continue normal execution.
  catchIO :: MonadIO m => IO () -> m ()
  catchIO f = io (f `catch` \(SomeException e) -> hPrint stderr e >> hFlush stderr)
  
  -- | spawn. Launch an external application. Specifically, it double-forks and
  -- runs the 'String' you pass as a command to \/bin\/sh.
  --
  -- Note this function assumes your locale uses utf8.
  spawn :: MonadIO m => String -> m ()
  spawn x = spawnPID x >> return ()
  
  -- | Like 'spawn', but returns the 'ProcessID' of the launched application
  spawnPID :: MonadIO m => String -> m ProcessID
  spawnPID x = xfork $ executeFile "/bin/sh" False ["-c", encodeString x] Nothing
  
  -- | A replacement for 'forkProcess' which resets default signal handlers.
  xfork :: MonadIO m => IO () -> m ProcessID
  xfork x = io . forkProcess . finally nullStdin $ do
                  uninstallSignalHandlers
                  createSession
                  x
   where
      nullStdin = do
          fd <- openFd "/dev/null" ReadOnly Nothing defaultFileFlags
          dupTo fd stdInput
          closeFd fd
  
  -- | This is basically a map function, running a function in the 'X' monad on
  -- each workspace with the output of that function being the modified workspace.
  runOnWorkspaces :: (WindowSpace -> X WindowSpace) -> X ()
  runOnWorkspaces job = do
      ws <- gets windowset
      h <- mapM job $ hidden ws
      c:v <- mapM (\s -> (\w -> s { workspace = w}) <$> job (workspace s))
               $ current ws : visible ws
      modify $ \s -> s { windowset = ws { current = c, visible = v, hidden = h } }
  
  -- | Return the path to @~\/.xmonad@.
  getXMonadDir :: MonadIO m => m String
  getXMonadDir = io $ getAppUserDataDirectory "xmonad"
  
  -- | 'recompile force', recompile @~\/.xmonad\/xmonad.hs@ when any of the
  -- following apply:
  --
  --      * force is 'True'
  --
  --      * the xmonad executable does not exist
  --
  --      * the xmonad executable is older than xmonad.hs or any file in
  --        ~\/.xmonad\/lib
  --
  -- The -i flag is used to restrict recompilation to the xmonad.hs file only,
  -- and any files in the ~\/.xmonad\/lib directory.
  --
  -- Compilation errors (if any) are logged to ~\/.xmonad\/xmonad.errors.  If
  -- GHC indicates failure with a non-zero exit code, an xmessage displaying
  -- that file is spawned.
  --
  -- 'False' is returned if there are compilation errors.
  --
  recompile :: MonadIO m => Bool -> m Bool
  recompile force = io $ do
      dir <- getXMonadDir
      let binn = "xmonad-"++arch++"-"++os
          bin  = dir </> binn
          base = dir </> "xmonad"
          err  = base ++ ".errors"
          src  = base ++ ".hs"
          lib  = dir </> "lib"
      libTs <- mapM getModTime . Prelude.filter isSource =<< allFiles lib
      srcT <- getModTime src
      binT <- getModTime bin
      if force || any (binT <) (srcT : libTs)
        then do
          -- temporarily disable SIGCHLD ignoring:
          uninstallSignalHandlers
          status <- bracket (openFile err WriteMode) hClose $ \h ->
              waitForProcess =<< runProcess "ghc" ["--make", "xmonad.hs", "-i", "-ilib", "-fforce-recomp", "-v0", "-o",binn] (Just dir)
                                      Nothing Nothing Nothing (Just h)
  
          -- re-enable SIGCHLD:
          installSignalHandlers
  
          -- now, if it fails, run xmessage to let the user know:
          when (status /= ExitSuccess) $ do
              ghcErr <- readFile err
              let msg = unlines $
                      ["Error detected while loading xmonad configuration file: " ++ src]
                      ++ lines (if null ghcErr then show status else ghcErr)
                      ++ ["","Please check the file for errors."]
              -- nb, the ordering of printing, then forking, is crucial due to
              -- lazy evaluation
              hPutStrLn stderr msg
              forkProcess $ executeFile "xmessage" True ["-default", "okay", msg] Nothing
              return ()
          return (status == ExitSuccess)
        else return True
   where getModTime f = catch (Just <$> getModificationTime f) (\(SomeException _) -> return Nothing)
         isSource = flip elem [".hs",".lhs",".hsc"]
         allFiles t = do
              let prep = map (t</>) . Prelude.filter (`notElem` [".",".."])
              cs <- prep <$> catch (getDirectoryContents t) (\(SomeException _) -> return [])
              ds <- filterM doesDirectoryExist cs
              concat . ((cs \\ ds):) <$> mapM allFiles ds
  
  -- | Conditionally run an action, using a @Maybe a@ to decide.
  whenJust :: Monad m => Maybe a -> (a -> m ()) -> m ()
  whenJust mg f = maybe (return ()) f mg
  
  -- | Conditionally run an action, using a 'X' event to decide
  whenX :: X Bool -> X () -> X ()
  whenX a f = a >>= \b -> when b f
  
  -- | A 'trace' for the 'X' monad. Logs a string to stderr. The result may
  -- be found in your .xsession-errors file
  trace :: MonadIO m => String -> m ()
  trace = io . hPutStrLn stderr
  
  -- | Ignore SIGPIPE to avoid termination when a pipe is full, and SIGCHLD to
  -- avoid zombie processes, and clean up any extant zombie processes.
  installSignalHandlers :: MonadIO m => m ()
  installSignalHandlers = io $ do
      installHandler openEndedPipe Ignore Nothing
      installHandler sigCHLD Ignore Nothing
      (try :: IO a -> IO (Either SomeException a))
        $ fix $ \more -> do
          x <- getAnyProcessStatus False False
          when (isJust x) more
      return ()
  
  uninstallSignalHandlers :: MonadIO m => m ()
  uninstallSignalHandlers = io $ do
      installHandler openEndedPipe Default Nothing
      installHandler sigCHLD Default Nothing
      return ()
  