    -----------------------------------------------------------------------------
    -- |
    -- Module      :  XMonad.Actions.CycleRecentWS
    -- Copyright   :  (c) Michal Janeczek <janeczek@gmail.com>
    -- License     :  BSD3-style (see LICENSE)
    --
    -- Maintainer  :  Michal Janeczek <janeczek@gmail.com>
    -- Stability   :  unstable
    -- Portability :  unportable
    --
    -- Provides bindings to cycle through most recently used workspaces
    -- with repeated presses of a single key (as long as modifier key is
    -- held down). This is similar to how many window managers handle
    -- window switching.
    --
    -----------------------------------------------------------------------------

    module XMonad.Actions.CycleRecentWS (
                                    -- * Usage
                                    -- $usage
                                    cycleRecentWS,
                                    cycleWindowSets
    ) where

    import XMonad hiding (workspaces)
    import XMonad.StackSet

    -- $usage
    -- You can use this module with the following in your @~\/.xmonad\/xmonad.hs@ file:
    --
    -- > import XMonad.Actions.CycleRecentWS
    -- >
    -- >   , ((modm, xK_Tab), cycleRecentWS [xK_Alt_L] xK_Tab xK_grave)
    --
    -- For detailed instructions on editing your key bindings, see
    -- "XMonad.Doc.Extending#Editing_key_bindings".

    -- | Cycle through most recent workspaces with repeated presses of a key, while
    --   a modifier key is held down. The recency of workspaces previewed while browsing
    --   to the target workspace is not affected. That way a stack of most recently used
    --   workspaces is maintained, similarly to how many window managers handle window
    --   switching. For best effects use the same modkey+key combination as the one used
    --   to invoke this action.
    cycleRecentWS :: [KeySym] -- ^ A list of modifier keys used when invoking this action.
                              --   As soon as one of them is released, the final switch is made.
                  -> KeySym   -- ^ Key used to switch to next (less recent) workspace.
                  -> KeySym   -- ^ Key used to switch to previous (more recent) workspace.
                              --   If it's the same as the nextWorkspace key, it is effectively ignored.
                  -> X ()
    cycleRecentWS = cycleWindowSets options
     where options w = map (view `flip` w) (recentTags w)
           recentTags w = map tag $ tail (workspaces w) ++ [head (workspaces w)]

    cycref :: [a] -> Int -> a
    cycref l i = l !! (i `mod` length l)

    -- | Cycle through a finite list of WindowSets with repeated presses of a key, while
    --   a modifier key is held down. For best effects use the same modkey+key combination
    --   as the one used to invoke this action.
    cycleWindowSets :: (WindowSet -> [WindowSet]) -- ^ A function used to create a list of WindowSets to choose from
                    -> [KeySym]                   -- ^ A list of modifier keys used when invoking this action.
                                                  --   As soon as one of them is released, the final WindowSet is chosen and the action exits.
                    -> KeySym                     -- ^ Key used to preview next WindowSet from the list of generated options
                    -> KeySym                     -- ^ Key used to preview previous WindowSet from the list of generated options.
                                                  --   If it's the same as nextOption key, it is effectively ignored.
                    -> X ()
    cycleWindowSets genOptions mods keyNext keyPrev = do
      options <- gets $ genOptions . windowset
      XConf {theRoot = root, display = d} <- ask
      let event = allocaXEvent $ \p -> do
                    maskEvent d (keyPressMask .|. keyReleaseMask) p
                    KeyEvent {ev_event_type = t, ev_keycode = c} <- getEvent p
                    s <- keycodeToKeysym d c 0
                    return (t, s)
      let setOption n = do windows $ const $ options `cycref` n
                           (t, s) <- io event
                           case () of
                             () | t == keyPress   && s == keyNext  -> setOption (n+1)
                                | t == keyPress   && s == keyPrev  -> setOption (n-1)
                                | t == keyRelease && s `elem` mods -> return ()
                                | otherwise                        -> setOption n
      io $ grabKeyboard d root False grabModeAsync grabModeAsync currentTime
      setOption 0
      io $ ungrabKeyboard d currentTime