content: {-# LANGUAGE FlexibleInstances, MultiParamTypeClasses, TypeSynonymInstances #-}
  
  -----------------------------------------------------------------------------
  -- |
  -- Module      :  XMonad.Layout.Circle
  -- Copyright   :  (c) Peter De Wachter
  -- License     :  BSD-style (see LICENSE)
  --
  -- Maintainer  :  Peter De Wachter <pdewacht@gmail.com>
  -- Stability   :  unstable
  -- Portability :  unportable
  --
  -- Circle is an elliptical, overlapping layout, by Peter De Wachter
  --
  -----------------------------------------------------------------------------
  
  module XMonad.Layout.Circle (
                               -- * Usage
                               -- $usage
                               Circle (..)
                              ) where -- actually it's an ellipse
  
  import Data.List
  import XMonad
  import XMonad.StackSet (integrate, peek)
  
  -- $usage
  -- You can use this module with the following in your @~\/.xmonad\/xmonad.hs@:
  --
  -- > import XMonad.Layout.Circle
  --
  -- Then edit your @layoutHook@ by adding the Circle layout:
  --
  -- > myLayout = Circle ||| Full ||| etc..
  -- > main = xmonad def { layoutHook = myLayout }
  --
  -- For more detailed instructions on editing the layoutHook see:
  --
  -- "XMonad.Doc.Extending#Editing_the_layout_hook"
  
  data Circle a = Circle deriving ( Read, Show )
  
  instance LayoutClass Circle Window where
      doLayout Circle r s = do layout <- raiseFocus $ circleLayout r $ integrate s
                               return (layout, Nothing)
  
  circleLayout :: Rectangle -> [a] -> [(a, Rectangle)]
  circleLayout _ []     = []
  circleLayout r (w:ws) = master : rest
      where master = (w, center r)
            rest   = zip ws $ map (satellite r) [0, pi * 2 / fromIntegral (length ws) ..]
  
  raiseFocus :: [(Window, Rectangle)] -> X [(Window, Rectangle)]
  raiseFocus xs = do focused <- withWindowSet (return . peek)
                     return $ case find ((== focused) . Just . fst) xs of
                                Just x  -> x : delete x xs
                                Nothing -> xs
  
  center :: Rectangle -> Rectangle
  center (Rectangle sx sy sw sh) = Rectangle x y w h
      where s = sqrt 2 :: Double
            w = round (fromIntegral sw / s)
            h = round (fromIntegral sh / s)
            x = sx + fromIntegral (sw - w) `div` 2
            y = sy + fromIntegral (sh - h) `div` 2
  
  satellite :: Rectangle -> Double -> Rectangle
  satellite (Rectangle sx sy sw sh) a = Rectangle (sx + round (rx + rx * cos a))
                                                  (sy + round (ry + ry * sin a))
                                                  w h
      where rx = fromIntegral (sw - w) / 2
            ry = fromIntegral (sh - h) / 2
            w = sw * 10 `div` 25
            h = sh * 10 `div` 25
  
  