Make border width configurable

Config.hs

@@ -111,6 +111,10 @@ normalBorderColor, focusedBorderColor :: String
 normalBorderColor  = "#dddddd"
 focusedBorderColor = "#ff0000"
 
+-- Width of the window border in pixels
+borderWidth :: Dimension
+borderWidth = 1
+
 -- What layout to start in, and what the default proportion for the
 -- left pane should be in the tiled layout.  See LayoutDesc and
 -- friends in XMonad.hs for options.

Config.hs-boot

@@ -1,3 +1,5 @@
 module Config where
 import XMonad (LayoutDesc)
+import Graphics.X11.Xlib.Types (Dimension)
 defaultLayoutDesc :: LayoutDesc
+borderWidth :: Dimension

Operations.hs

@@ -161,7 +161,7 @@ manage w = do
     withDisplay $ \d -> io $ do
         selectInput d w $ structureNotifyMask .|. enterWindowMask .|. propertyChangeMask
         mapWindow d w
-        setWindowBorderWidth d w 1
+        setWindowBorderWidth d w borderWidth
     windows $ W.push w
 
 -- | unmanage. A window no longer exists, remove it from the window