add DynamicLog.hs

DynamicLog.hs

@@ -0,0 +1,49 @@
+-- 
+-- DynamicLog
+--
+-- Log events in:
+--
+--      1 2 [3] 4 8
+--
+-- format. suitable to pipe into dzen.
+--
+-- To use, set:
+--
+--      import XMonadContrib.DynamicLog
+--      logHook = dynamicLog
+--
+-- Don Stewart
+
+module XMonadContrib.DynamicLog where
+
+-- 
+-- Useful imports
+--
+import XMonad
+import Data.List
+import qualified StackSet as S
+
+--
+-- Perform an arbitrary action on each state change.
+-- Examples include:
+--      * do nothing
+--      * log the state to stdout
+
+--
+-- An example logger, print a status bar output to dzen, in the form:
+--
+--  1 2 [3] 4 7
+--  
+
+dynamicLog :: X ()
+dynamicLog = withWindowSet $ io . putStrLn . ppr
+  where
+    ppr s =  concatMap fmt $ sortBy tags
+                (map S.workspace (S.current s : S.visible s) ++ S.hidden s)
+
+       where tags a b = S.tag a `compare` S.tag b
+             this     = S.tag (S.workspace (S.current s))
+             pprTag   = show . (+(1::Int)) . fromIntegral . S.tag
+             fmt w | S.tag w == this      = "[" ++ pprTag w ++ "]"
+                   | S.stack w /= S.Empty = " " ++ pprTag w ++ " "
+                   | otherwise            = ""