X.Operations: Fix mouse in Tabbed decorations (revert broadcastMessage refactor)

Turns out there was another aspect of `broadcastMessage` behaviour that
I missed in my review of the refactor: X.L.Tabbed updates the windowset
during handleMessage (via `X.O.focus`) and expects that change to
persist (by returning `Nothing` and hoping no other layout or layout
modifier returns `Just`). That's quite a hack, but the LayoutClass
interface doesn't allow a cleaner way to do this (well, some extensible
state plus a custom event hook might work, but then the layout isn't
self-contained any more).

And since rereading workspace layouts during `modifyLayouts` would force
this back into O(n²), we might as well revert the whole refactor. :-/

Fixes: https://github.com/xmonad/xmonad/issues/329

CHANGES.md

@@ -65,11 +65,6 @@
     it easier for us to clean up the codebase. These can still be suppressed
     manually using an `OPTIONS_GHC` pragma with `-Wno-deprecations`.
 
-  * `runOnWorkspaces` changed to first run the action on the current
-    workspace, then the visible workspaces and then hidden, to match the order
-    of processing messages in `broadcastMessage`. Previously,
-    `runOnWorkspaces` processed the hidden workspaces first.
-
   * Added `withUnfocused` function to `XMonad.Operations`, allowing for
     `X` operations to be applied to unfocused windows.
 

src/XMonad/Core.hs

@@ -470,9 +470,9 @@ xmessage msg = void . xfork $ do
 runOnWorkspaces :: (WindowSpace -> X WindowSpace) -> X ()
 runOnWorkspaces job = do
     ws <- gets windowset
+    h <- mapM job $ hidden ws
     c:v <- mapM (\s -> (\w -> s { workspace = w}) <$> job (workspace s))
              $ current ws : visible ws
-    h <- mapM job $ hidden ws
     modify $ \s -> s { windowset = ws { current = c, visible = v, hidden = h } }
 
 -- | All the directories that xmonad will use.  They will be used for

src/XMonad/Operations.hs

@@ -440,24 +440,22 @@ sendMessage a = windowBracket_ $ do
 
 -- | Send a message to all layouts, without refreshing.
 broadcastMessage :: Message a => a -> X ()
-broadcastMessage = filterMessageWithNoRefresh (const True)
+broadcastMessage a = withWindowSet $ \ws -> do
+    -- this is O(n²), but we can't really fix this as there's code in
+    -- xmonad-contrib that touches the windowset during handleMessage
+    -- (returning Nothing for changes to not get overwritten), so we
+    -- unfortunately need to do this one by one and persist layout states
+    -- of each workspace separately)
+    let c = W.workspace . W.current $ ws
+        v = map W.workspace . W.visible $ ws
+        h = W.hidden ws
+    mapM_ (sendMessageWithNoRefresh a) (c : v ++ h)
 
 -- | Send a message to a layout, without refreshing.
 sendMessageWithNoRefresh :: Message a => a -> WindowSpace -> X ()
 sendMessageWithNoRefresh a w =
-    filterMessageWithNoRefresh (((==) `on` W.tag) w) a
-
--- | Send a message to the layouts of some workspaces, without refreshing.
-filterMessageWithNoRefresh :: Message a => (WindowSpace -> Bool) -> a -> X ()
-filterMessageWithNoRefresh p a = modifyLayouts $ \wrk ->
-    if p wrk
-      then userCodeDef Nothing $ W.layout wrk `handleMessage` SomeMessage a
-      else pure Nothing
-
--- | Modify the layouts of some workspaces.
-modifyLayouts :: (WindowSpace -> X (Maybe (Layout Window))) -> X ()
-modifyLayouts f = runOnWorkspaces $ \ wrk ->
-    maybe wrk (\l -> wrk{ W.layout = l }) <$> f wrk
+    handleMessage (W.layout w) (SomeMessage a) `catchX` return Nothing >>=
+    updateLayout  (W.tag w)
 
 -- | Update the layout field of a workspace.
 updateLayout :: WorkspaceId -> Maybe (Layout Window) -> X ()