X.H.StatusBar.PP: Clarify ppOutput doc + minor cleanups

XMonad/Hooks/StatusBar.hs

@@ -335,9 +335,8 @@ statusBarPipe cmd xpp = do
     return $ def
         { sbStartupHook = io (writeIORef hRef . Just =<< spawnPipe cmd)
         , sbLogHook     = do
-              pp <- xpp
               h' <- io (readIORef hRef)
-              whenJust h' $ \h -> dynamicLogWithPP pp { ppOutput = hPutStrLn h }
+              whenJust h' $ \h -> io . hPutStrLn h =<< dynamicLogString =<< xpp
         , sbCleanupHook = io
                           $   readIORef hRef
                           >>= (`whenJust` hClose)

XMonad/Hooks/StatusBar/PP.hs

@@ -128,7 +128,9 @@ data PP = PP { ppCurrent :: WorkspaceId -> String
                -- output it.  Can be used to specify an alternative
                -- output method (e.g. write to a pipe instead of
                -- stdout), and\/or to perform some last-minute
-               -- formatting.
+               -- formatting. Note that this is only used by
+               -- 'dynamicLogWithPP'; it won't work with 'dynamicLogString' or
+               -- "XMonad.Hooks.StatusBar".
              }
 
 -- | The default pretty printing options:
@@ -179,7 +181,7 @@ dynamicLogString pp = do
     let ws = pprWindowSet sort' urgents pp winset
 
     -- run extra loggers, ignoring any that generate errors.
-    extras <- mapM (`catchX` return Nothing) $ ppExtras pp
+    extras <- mapM (userCodeDef Nothing) $ ppExtras pp
 
     -- window title
     wt <- maybe (pure "") (fmap show . getName) . S.peek $ winset