Add ConstrainedResize module

Constrain the aspect ratio of floated windows by holding down shift

ConstrainedResize.hs

@@ -0,0 +1,54 @@
+-----------------------------------------------------------------------------
+-- |
+-- Module      :  XMonadContrib.ConstrainedResize
+-- Copyright   :  (c) Dougal Stanton
+-- License     :  BSD3-style (see LICENSE)
+-- 
+-- Maintainer  :  <dougal@dougalstanton.net>
+-- Stability   :  unstable
+-- Portability :  unportable
+--
+-- Lets you constrain the aspect ratio of a floating
+-- window by holding shift while you resize.
+--
+-- Useful for making a nice circular XClock window.
+--
+-----------------------------------------------------------------------------
+
+module XMonadContrib.ConstrainedResize (
+	-- * Usage
+	-- $usage
+	XMonadContrib.ConstrainedResize.mouseResizeWindow
+) where
+
+import XMonad
+import Operations
+import Graphics.X11.Xlib
+import Graphics.X11.Xlib.Extras
+
+-- $usage
+-- Put something like this in your Config.hs file:
+--
+-- > import qualified XMonadContrib.ConstrainedResize as Sqr
+-- > mouseBindings = M.fromList
+-- >     [ ...
+-- >     , ((modMask, button3),               (\w -> focus w >> Sqr.mouseResizeWindow w False))
+-- >     , ((modMask .|. shiftMask, button3), (\w -> focus w >> Sqr.mouseResizeWindow w True )) ]
+
+-- %import qualified XMonadContrib.ConstrainedResize as Sqr
+-- %mousebind , ((modMask, button3), (\\w -> focus w >> Sqr.mouseResizeWindow w False))
+
+-- | Resize (floating) window with optional aspect ratio constraints.
+mouseResizeWindow :: Window -> Bool -> X ()
+mouseResizeWindow w c = whenX (isClient w) $ withDisplay $ \d -> do
+    io $ raiseWindow d w
+    wa <- io $ getWindowAttributes d w
+    sh <- io $ getWMNormalHints d w
+    io $ warpPointer d none w 0 0 0 0 (fromIntegral (wa_width wa)) (fromIntegral (wa_height wa))
+    mouseDrag (\ex ey -> do
+                 let x = ex - fromIntegral (wa_x wa)
+                     y = ey - fromIntegral (wa_y wa)
+                     sz = if c then (max x y, max x y) else (x,y)
+                 io $ resizeWindow d w `uncurry`
+                    applySizeHints sh sz)
+              (float w)