Added updateName and removeName to X.A.DynamicWorkspaceOrder

This adds the possibility to maintain the ordering of workspaces after
they are renamed and to remove them from sorting when they are deleted.

CHANGES.md

@@ -282,6 +282,11 @@
     - Added optional `ppVisibleNoWindows` to differentiate between empty
       and non-empty visible workspaces in pretty printing.
 
+  * `XMonad.Actions.DynamicWorkspaceOrder`
+
+    - Added `updateName` and `removeName` to better control ordering when
+      workspace names are changed or workspaces are removed.
+
 ## 0.13 (February 10, 2017)
 
 ### Breaking Changes

XMonad/Actions/DynamicWorkspaceOrder.hs

@@ -23,6 +23,8 @@ module XMonad.Actions.DynamicWorkspaceOrder
       getWsCompareByOrder
     , getSortByOrder
     , swapWith
+    , updateName
+    , removeName
 
     , moveTo
     , moveToGreedy
@@ -152,6 +154,21 @@ swapOrder w1 w2 = do
   XS.modify (withWSO (M.insert w1 i2 . M.insert w2 i1))
   windows id  -- force a status bar update
 
+-- | Update the name of a workspace in the stored order.
+updateName :: WorkspaceId -> WorkspaceId -> X ()
+updateName oldId newId = XS.modify . withWSO $ changeKey oldId newId
+
+-- | Remove a workspace from the stored order.
+removeName :: WorkspaceId -> X ()
+removeName = XS.modify . withWSO . M.delete
+
+-- | Update a key in a Map.
+changeKey :: Ord k => k -> k -> M.Map k a -> M.Map k a
+changeKey oldKey newKey oldMap =
+  case M.updateLookupWithKey (\_ _ -> Nothing) oldKey oldMap of
+    (Nothing, _) -> oldMap
+    (Just val, newMap) -> M.insert newKey val newMap
+
 -- | View the next workspace of the given type in the given direction,
 -- where \"next\" is determined using the dynamic workspace order.
 moveTo :: Direction1D -> WSType -> X ()
@@ -175,4 +192,4 @@ withNthWorkspace job wnum = do
   ws <- gets (map W.tag . sort . W.workspaces . windowset)
   case drop wnum ws of
     (w:_) -> windows $ job w
-    []    -> return ()
+    []    -> return ()