content: {-# LANGUAGE TypeSynonymInstances, DeriveDataTypeable, MultiParamTypeClasses, FlexibleContexts, FlexibleInstances, PatternGuards #-}
  -----------------------------------------------------------------------------
  -- |
  -- Module      :  XMonad.Layout.ComboP
  -- Copyright   :  (c) Konstantin Sobolev <konstantin.sobolev@gmail.com>
  -- License     :  BSD-style (see LICENSE)
  --
  -- Maintainer  :  Konstantin Sobolev <konstantin.sobolev@gmail.com>
  -- Stability   :  unstable
  -- Portability :  unportable
  --
  -- A layout that combines multiple layouts and allows to specify where to put
  -- new windows.
  --
  -----------------------------------------------------------------------------
  
  module XMonad.Layout.ComboP (
                               -- * Usage
                               -- $usage
                               combineTwoP,
                               CombineTwoP,
                               SwapWindow(..),
                               Property(..)
                              ) where
  
  import Data.List ( delete, intersect, (\\) )
  import Data.Maybe ( isJust )
  import Control.Monad
  import XMonad hiding (focus)
  import XMonad.StackSet ( Workspace (..), Stack(..) )
  import XMonad.Layout.WindowNavigation
  import XMonad.Util.WindowProperties
  import qualified XMonad.StackSet as W
  
  -- $usage
  -- You can use this module with the following in your @~\/.xmonad\/xmonad.hs@:
  --
  -- > import XMonad.Layout.ComboP
  --
  -- and add something like
  --
  -- > combineTwoP (TwoPane 0.03 0.5) (tabbed shrinkText defaultTConf) (tabbed shrinkText defaultTConf) (ClassName "Firefox")
  --
  -- to your layouts. This way all windows with class = \"Firefox\" will always go
  -- to the left pane, all others - to the right.
  --
  -- For more detailed instructions on editing the layoutHook see:
  --
  -- "XMonad.Doc.Extending#Editing_the_layout_hook"
  --
  -- 'combineTwoP' is a simple layout combinator based on 'combineTwo' from Combo, with
  -- addition of a 'Property' which tells where to put new windows. Windows mathing
  -- the property will go into the first part, all others will go into the second
  -- part. It supports @Move@ messages as 'combineTwo' does, but it also introduces
  -- 'SwapWindow' message which sends focused window to the other part. It is
  -- required because @Move@ commands don't work when one of the parts is empty.
  -- To use it, import \"XMonad.Layout.WindowNavigation\", and add the following key
  -- bindings (or something similar):
  --
  -- >    , ((modm .|. controlMask .|. shiftMask, xK_Right), sendMessage $ Move R)
  -- >    , ((modm .|. controlMask .|. shiftMask, xK_Left ), sendMessage $ Move L)
  -- >    , ((modm .|. controlMask .|. shiftMask, xK_Up   ), sendMessage $ Move U)
  -- >    , ((modm .|. controlMask .|. shiftMask, xK_Down ), sendMessage $ Move D)
  -- >    , ((modm .|. controlMask .|. shiftMask, xK_s    ), sendMessage $ SwapWindow)
  --
  -- For detailed instruction on editing the key binding see
  -- "XMonad.Doc.Extending#Editing_key_bindings".
  
  data SwapWindow =  SwapWindow        -- ^ Swap window between panes
                   | SwapWindowN Int   -- ^ Swap window between panes in the N-th nested ComboP. @SwapWindowN 0@ equals to SwapWindow
                   deriving (Read, Show, Typeable)
  instance Message SwapWindow
  
  data CombineTwoP l l1 l2 a = C2P [a] [a] [a] l (l1 a) (l2 a) Property
                                  deriving (Read, Show)
  
  combineTwoP :: (LayoutClass super(), LayoutClass l1 Window, LayoutClass l2 Window) =>
                  super () -> l1 Window -> l2 Window -> Property -> CombineTwoP (super ()) l1 l2 Window
  combineTwoP = C2P [] [] []
  
  instance (LayoutClass l (), LayoutClass l1 Window, LayoutClass l2 Window) =>
      LayoutClass (CombineTwoP (l ()) l1 l2) Window where
      doLayout (C2P f w1 w2 super l1 l2 prop) rinput s =
          let origws = W.integrate s           -- passed in windows
              w1c = origws `intersect` w1      -- current windows in the first pane
              w2c = origws `intersect` w2      -- current windows in the second pane
              new = origws \\ (w1c ++ w2c)     -- new windows
              superstack = Just Stack { focus=(), up=[], down=[()] }
              f' = focus s:delete (focus s) f  -- list of focused windows, contains 2 elements at most
          in do
              matching <- (hasProperty prop) `filterM` new  -- new windows matching predecate
              let w1' = w1c ++ matching                     -- updated first pane windows
                  w2' = w2c ++ (new \\ matching)            -- updated second pane windows
                  s1 = differentiate f' w1'                 -- first pane stack
                  s2 = differentiate f' w2'                 -- second pane stack
              ([((),r1),((),r2)], msuper') <- runLayout (Workspace "" super superstack) rinput
              (wrs1, ml1') <- runLayout (Workspace "" l1 s1) r1
              (wrs2, ml2') <- runLayout (Workspace "" l2 s2) r2
              return  (wrs1++wrs2, Just $ C2P f' w1' w2' (maybe super id msuper')
                  (maybe l1 id ml1') (maybe l2 id ml2') prop)
  
      handleMessage us@(C2P f ws1 ws2 super l1 l2 prop) m
          | Just SwapWindow      <- fromMessage m = swap us
          | Just (SwapWindowN 0) <- fromMessage m = swap us
          | Just (SwapWindowN n) <- fromMessage m = forwardToFocused us $ SomeMessage $ SwapWindowN $ n-1
  
          | Just (MoveWindowToWindow w1 w2) <- fromMessage m,
            w1 `elem` ws1,
            w2 `elem` ws2 = return $ Just $ C2P f (delete w1 ws1) (w1:ws2) super l1 l2 prop
  
          | Just (MoveWindowToWindow w1 w2) <- fromMessage m,
            w1 `elem` ws2,
            w2 `elem` ws1 = return $ Just $ C2P f (w1:ws1) (delete w1 ws2) super l1 l2 prop
  
          | otherwise = do ml1' <- handleMessage l1 m
                           ml2' <- handleMessage l2 m
                           msuper' <- handleMessage super m
                           if isJust msuper' || isJust ml1' || isJust ml2'
                              then return $ Just $ C2P f ws1 ws2
                                                   (maybe super id msuper')
                                                   (maybe l1 id ml1')
                                                   (maybe l2 id ml2') prop
                              else return Nothing
  
      description (C2P _ _ _ super l1 l2 prop) = "combining " ++ description l1 ++ " and "++
                                  description l2 ++ " with " ++ description super ++ " using "++ (show prop)
  
  -- send focused window to the other pane. Does nothing if we don't
  -- own the focused window
  swap :: (LayoutClass s a, LayoutClass l1 Window, LayoutClass l2 Window) =>
          CombineTwoP (s a) l1 l2 Window -> X (Maybe (CombineTwoP (s a) l1 l2 Window))
  swap (C2P f ws1 ws2 super l1 l2 prop) = do
      mst <- gets (W.stack . W.workspace . W.current . windowset)
      let (ws1', ws2') = case mst of
              Nothing -> (ws1, ws2)
              Just st -> if foc `elem` ws1
                             then (foc `delete` ws1, foc:ws2)
                             else if foc `elem` ws2
                                 then (foc:ws1, foc `delete` ws2)
                                 else (ws1, ws2)
                         where foc = W.focus st
      if (ws1,ws2) == (ws1',ws2')
          then return Nothing
          else return $ Just $ C2P f ws1' ws2' super l1 l2 prop
  
  
  -- forwards the message to the sublayout which contains the focused window
  forwardToFocused :: (LayoutClass l1 Window, LayoutClass l2 Window, LayoutClass s a) =>
                      CombineTwoP (s a) l1 l2 Window -> SomeMessage -> X (Maybe (CombineTwoP (s a) l1 l2 Window))
  forwardToFocused (C2P f ws1 ws2 super l1 l2 prop) m = do
      ml1 <- forwardIfFocused l1 ws1 m
      ml2 <- forwardIfFocused l2 ws2 m
      ms <- if isJust ml1 || isJust ml2
              then return Nothing
              else handleMessage super m
      if isJust ml1 || isJust ml2 || isJust ms
          then return $ Just $ C2P f ws1 ws2 (maybe super id ms) (maybe l1 id ml1) (maybe l2 id ml2) prop
          else return Nothing
  
  -- forwards message m to layout l if focused window is among w
  forwardIfFocused :: (LayoutClass l Window) => l Window -> [Window] -> SomeMessage -> X (Maybe (l Window))
  forwardIfFocused l w m = do
      mst <- gets (W.stack . W.workspace . W.current . windowset)
      maybe (return Nothing) send mst where
      send st = if (W.focus st) `elem` w
                  then handleMessage l m
                  else return Nothing
  
  -- code from CombineTwo
  -- given two sets of zs and xs takes the first z from zs that also belongs to xs
  -- and turns xs into a stack with z being current element. Acts as
  -- StackSet.differentiate if zs and xs don't intersect
  differentiate :: Eq q => [q] -> [q] -> Maybe (Stack q)
  differentiate (z:zs) xs | z `elem` xs = Just $ Stack { focus=z
                                                       , up = reverse $ takeWhile (/=z) xs
                                                       , down = tail $ dropWhile (/=z) xs }
                          | otherwise = differentiate zs xs
  differentiate [] xs = W.differentiate xs
  
  -- vim:ts=4:shiftwidth=4:softtabstop=4:expandtab:foldlevel=20:
  