new module NoBorders to let a given layout have windows without borders.

This is designed for layouts like full and tabbed, where the red square
around the screen actually conveys no information (except for weird windows
that use the shape extension or something, so that more than one window is
actually visible).  Save some real estate at no cost.

MetaModule.hs

@@ -23,6 +23,7 @@ import XMonadContrib.HintedTile ()
 import XMonadContrib.LayoutHints ()
 import XMonadContrib.Mosaic ()
 import XMonadContrib.NamedWindows ()
+import XMonadContrib.NoBorders ()
 import XMonadContrib.RotView ()
 import XMonadContrib.SimpleDate ()
 import XMonadContrib.Spiral ()

NoBorders.hs

@@ -0,0 +1,36 @@
+module XMonadContrib.NoBorders ( noBorders, withBorder ) where
+
+-- Make a given layout display without borders.  This is useful for
+-- full-screen or tabbed layouts, where you don't really want to waste a
+-- couple of pixels of real estate just to inform yourself that the visible
+-- window has focus.
+
+-- Usage:
+
+-- import XMonadContrib.NoBorders
+
+-- layouts = [ noBorders full, tall, ... ]
+
+import Control.Monad.State ( gets )
+import Graphics.X11.Xlib
+
+import XMonad
+import Operations ( UnDoLayout(UnDoLayout) )
+import qualified StackSet as W
+import {-# SOURCE #-} Config (borderWidth)
+
+noBorders :: Layout -> Layout
+noBorders = withBorder 0
+
+withBorder :: Dimension -> Layout -> Layout
+withBorder bd l = l { doLayout = \r x -> setborders bd >> doLayout l r x
+                    , modifyLayout = ml }
+    where ml m | Just UnDoLayout == fromMessage m
+                   = do setborders borderWidth
+                        fmap (withBorder bd) `fmap` (modifyLayout l) m
+               | otherwise = fmap (withBorder bd) `fmap` (modifyLayout l) m
+
+setborders :: Dimension -> X ()
+setborders bw = withDisplay $ \d ->
+                do ws <- gets (W.integrate . W.stack . W.workspace . W.current . windowset)
+                   mapM_ (\w -> io $ setWindowBorderWidth d w bw) ws