    {-# LANGUAGE FlexibleContexts, FlexibleInstances, MultiParamTypeClasses #-}

    -----------------------------------------------------------------------------
    -- |
    -- Module      :  XMonad.Layout.LayoutScreens
    -- Copyright   :  (c) David Roundy <droundy@darcs.net>
    -- License     :  BSD3-style (see LICENSE)
    --
    -- Maintainer  :  none
    -- Stability   :  unstable
    -- Portability :  unportable
    --
    -----------------------------------------------------------------------------

    module XMonad.Layout.LayoutScreens (
                                        -- * Usage
                                        -- $usage
                                        layoutScreens, fixedLayout
                                       ) where

    import XMonad
    import qualified XMonad.StackSet as W

    -- $usage
    -- This module allows you to pretend that you have more than one screen by
    -- dividing a single screen into multiple screens that xmonad will treat as
    -- separate screens.  This should definitely be useful for testing the
    -- behavior of xmonad under Xinerama, and it's possible that it'd also be
    -- handy for use as an actual user interface, if you've got a very large
    -- screen and long for greater flexibility (e.g. being able to see your
    -- email window at all times, a crude mimic of sticky windows).
    --
    -- You can use this module with the following in your
    -- @~\/.xmonad\/xmonad.hs@ file:
    --
    -- > import XMonad.Layout.LayoutScreens
    -- > import XMonad.Layout.TwoPane
    --
    -- Then add some keybindings; for example:
    --
    -- >   , ((modMask x .|. shiftMask,                 xK_space), layoutScreens 2 (TwoPane 0.5 0.5))
    -- >   , ((modMask x .|. controlMask .|. shiftMask, xK_space), rescreen)
    --
    -- Another example use would be to handle a scenario where xrandr didn't
    -- work properly (e.g. a VNC X server in my case) and you want to be able
    -- to resize your screen (e.g. to match the size of a remote VNC client):
    --
    -- > import XMonad.Layout.LayoutScreens
    --
    -- >   , ((modMask x .|. shiftMask, xK_space),
    -- >        layoutScreens 1 (fixedLayout [Rectangle 0 0 1024 768]))
    -- >   , ((modMask x .|. controlMask .|. shiftMask, xK_space), rescreen)
    --
    -- For detailed instructions on editing your key bindings, see
    -- "XMonad.Doc.Extending#Editing_key_bindings".

    layoutScreens :: LayoutClass l Int => Int -> l Int -> X ()
    layoutScreens nscr _ | nscr < 1 = trace $ "Can't layoutScreens with only " ++ show nscr ++ " screens."
    layoutScreens nscr l =
        do rtrect <- asks theRoot >>= getWindowRectangle
           (wss, _) <- runLayout (W.Workspace "" l (Just $ W.Stack { W.focus=1, W.up=[],W.down=[1..nscr-1] })) rtrect
           windows $ \ws@(W.StackSet { W.current = v, W.visible = vs, W.hidden = hs }) ->
               let (x:xs, ys) = splitAt nscr $ map W.workspace (v:vs) ++ hs
                   s:ss = map snd wss
               in  ws { W.current = W.Screen x 0 (SD s)
                      , W.visible = zipWith3 W.Screen xs [1 ..] $ map SD ss
                      , W.hidden  = ys }

    getWindowRectangle :: Window -> X Rectangle
    getWindowRectangle w = withDisplay $ \d ->
        do a <- io $ getWindowAttributes d w
           return $ Rectangle (fromIntegral $ wa_x a)     (fromIntegral $ wa_y a)
                              (fromIntegral $ wa_width a) (fromIntegral $ wa_height a)

    data FixedLayout a = FixedLayout [Rectangle] deriving (Read,Show)

    instance LayoutClass FixedLayout a where
        doLayout (FixedLayout rs) _ s = return (zip (W.integrate s) rs, Nothing)

    fixedLayout :: [Rectangle] -> FixedLayout a
    fixedLayout = FixedLayout