Add submapDefaultWithKey.

This is useful for when we want to decide what to do in the default
action based on the key that failed to match in the submap.

XMonad/Actions/Submap.hs

@@ -16,7 +16,8 @@ module XMonad.Actions.Submap (
                              -- * Usage
                              -- $usage
                              submap,
-                             submapDefault
+                             submapDefault,
+                             submapDefaultWithKey
                             ) where
 import Data.Bits
 import Data.Maybe (fromMaybe)
@@ -63,7 +64,14 @@ submap = submapDefault (return ())
 
 -- | Like 'submap', but executes a default action if the key did not match.
 submapDefault :: X () -> M.Map (KeyMask, KeySym) (X ()) -> X ()
-submapDefault defAction keys = do
+submapDefault = submapDefaultWithKey . const
+
+-- | Like 'submapDefault', but sends the unmatched key to the default
+-- action as argument.
+submapDefaultWithKey :: ((KeyMask, KeySym) -> X ())
+                     -> M.Map (KeyMask, KeySym) (X ())
+                     -> X ()
+submapDefaultWithKey defAction keys = do
     XConf { theRoot = root, display = d } <- ask
 
     io $ grabKeyboard d root False grabModeAsync grabModeAsync currentTime
@@ -80,4 +88,4 @@ submapDefault defAction keys = do
 
     io $ ungrabKeyboard d currentTime
 
-    fromMaybe defAction (M.lookup (m', s) keys)
+    fromMaybe (defAction (m', s)) (M.lookup (m', s) keys)