add "Square" layout.

This is probably only ever useful in combination with Combo.
It sticks one window in a square region, and makes the rest
of the windows live with what's left (in a full-screen sense).

Square.hs

@@ -0,0 +1,30 @@
+-- A layout that splits the screen into a square area and the rest of the
+-- screen.
+
+
+-- An example layout using square to make the very last area square:
+
+--  , combo [(tabbed,3),(tabbed,30),(tabbed,1),(tabbed,1)]
+--              (combo [(twoPane 0.03 0.2,1)
+--                     ,(combo [(twoPane 0.03 0.8,1),(square,1)]
+--                                 (mirror $ twoPane 0.03 0.85),1)] (twoPane 0.03 0.5) )
+
+module XMonadContrib.Square ( square ) where
+
+import XMonad
+import Graphics.X11.Xlib
+
+square :: Layout
+square = Layout { doLayout = arrange, modifyLayout = message }
+ where
+    arrange rect ws@(_:_) = do
+        let (rest, sq) = splitSquare rect
+        return (map (\w->(w,rest)) (init ws) ++ [(last ws,sq)])
+    arrange _ [] = return []
+
+    message _ = return Nothing
+
+splitSquare :: Rectangle -> (Rectangle, Rectangle)
+splitSquare (Rectangle x y w h)
+    | w > h = (Rectangle x y (w - h) h, Rectangle (x+fromIntegral (w-h)) y h h)
+    | otherwise = (Rectangle x y w (h-w), Rectangle x (y+fromIntegral (h-w)) w w)