{-# LANGUAGE FlexibleInstances, MultiParamTypeClasses #-}

-----------------------------------------------------------------------------
-- |
-- Module      :  XMonad.Layout.Grid
-- Copyright   :  (c) Lukas Mai
-- License     :  BSD-style (see LICENSE)
--
-- Maintainer  :  <l.mai@web.de>
-- Stability   :  unstable
-- Portability :  unportable
--
-- A simple layout that attempts to put all windows in a square grid.
--
-----------------------------------------------------------------------------

module XMonad.Layout.Grid (
    -- * Usage
    -- $usage
    Grid(..), arrange
) where

import XMonad
import XMonad.StackSet

-- $usage
-- You can use this module with the following in your @~\/.xmonad\/xmonad.hs@:
--
-- > import XMonad.Layout.Grid
--
-- Then edit your @layoutHook@ by adding the Grid layout:
--
-- > myLayouts = Grid ||| Full ||| etc..
-- > main = xmonad defaultConfig { layoutHook = myLayouts }
--
-- For more detailed instructions on editing the layoutHook see:
--
-- "XMonad.Doc.Extending#Editing_the_layout_hook"

data Grid a = Grid deriving (Read, Show)

instance LayoutClass Grid a where
    pureLayout Grid r s = arrange r (integrate s)

arrange :: Rectangle -> [a] -> [(a, Rectangle)]
arrange (Rectangle rx ry rw rh) st = zip st rectangles
    where
    nwins = length st
    ncols = max 1 . round . sqrt $ fromIntegral nwins * 9 * fromIntegral rw / (16 * fromIntegral rh :: Double)
    mincs = nwins `div` ncols
    extrs = nwins - ncols * mincs
    chop :: Int -> Dimension -> [(Position, Dimension)]
    chop n m = ((0, m - k * fromIntegral (pred n)) :) . map (flip (,) k) . tail . reverse . take n . tail . iterate (subtract k') $ m'
        where
        k :: Dimension
        k = m `div` fromIntegral n
        m' = fromIntegral m
        k' :: Position
        k' = fromIntegral k
    xcoords = chop ncols rw
    ycoords = chop mincs rh
    ycoords' = chop (succ mincs) rh
    (xbase, xext) = splitAt (ncols - extrs) xcoords
    rectangles = combine ycoords xbase ++ combine ycoords' xext
        where
        combine ys xs = [Rectangle (rx + x) (ry + y) w h | (x, w) <- xs, (y, h) <- ys]