[SPIRAL] add spiral tiling layout

Spiral.hs

@@ -0,0 +1,58 @@
+module Spiral (spiral) where
+
+import Graphics.X11.Xlib
+import Operations
+import Data.Ratio
+import XMonad
+
+--
+-- Spiral layout
+--
+-- eg,
+--    defaultLayouts :: [Layout]
+--    defaultLayouts = [ full,
+--                       tall defaultWindowsInMaster defaultDelta (1%2),
+--                       wide defaultWindowsInMaster defaultDelta (1%2),
+--                       spiral (1000 % 1618) ]
+--
+spiral :: Rational -> Layout
+spiral rat = Layout { doLayout = \sc ws -> return $ zip ws (divideRects rat (length ws) East $ sc),
+                      modifyLayout = \m -> fmap resize (fromMessage m)}
+
+    where resize Expand = let newRat = ((numerator rat + 10) % (denominator rat))
+                              normRat = if numerator newRat > denominator newRat then rat else newRat in
+                          spiral normRat
+          resize Shrink = let newRat = ((numerator rat - 10) % (denominator rat))
+                              normRat = if numerator newRat < 0 then rat else newRat in
+                          spiral normRat
+
+data Direction = East | South | West | North
+
+nextDir :: Direction -> Direction
+nextDir East = South
+nextDir South = West
+nextDir West = North
+nextDir North = East
+
+divideRects :: Rational -> Int -> Direction -> Rectangle -> [Rectangle]
+divideRects r n dir rect | n <= 1 = [rect]
+                         | otherwise = case divideRect r dir rect of
+                                     (r1, r2) -> r1 : (divideRects r (n - 1) (nextDir dir) r2)
+
+divideRect :: Rational -> Direction -> Rectangle -> (Rectangle, Rectangle)
+divideRect ratio East (Rectangle x y w h) = let (w1, w2) = chop ratio (fromIntegral w) in
+                                            (Rectangle x y (fromIntegral w1) h,
+                                             Rectangle (x + (fromIntegral w1)) y (fromIntegral w2) h)
+divideRect ratio South (Rectangle x y w h) = let (h1, h2) = chop ratio (fromIntegral h) in
+                                             (Rectangle x y w (fromIntegral h1),
+                                              Rectangle x (y + (fromIntegral h1)) w (fromIntegral h2))
+divideRect ratio West (Rectangle x y w h) = let (w1, w2) = chop (1 - ratio) (fromIntegral w) in
+                                            (Rectangle (x + (fromIntegral w1)) y (fromIntegral w2) h,
+                                             Rectangle x y (fromIntegral w1) h)
+divideRect ratio North (Rectangle x y w h) = let (h1, h2) = chop (1 - ratio) (fromIntegral h) in
+                                             (Rectangle x (y + (fromIntegral h1)) w (fromIntegral h2),
+                                              Rectangle x y w (fromIntegral h1))
+
+chop :: Rational -> Integer -> (Integer, Integer)
+chop rat n = let f = ((fromIntegral n) * (numerator rat)) `div` (denominator rat) in
+             (f, n - f)