X.H.{EwmhDesktops,ManageHelpers}: Add _NET_WM_DESKTOP-handling ManageHook

Useful for restoring browser windows to where they were before restart
(which is something one should do several times a week as security
updates get released).

CHANGES.md

@@ -246,6 +246,10 @@
       `XMonad.Actions.ToggleFullFloat` for a float-restoring implementation of
       fullscreening.
 
+    - Added `ewmhDesktops(Maybe)ManageHook` that places windows in their
+      preferred workspaces. This is useful when restoring a browser session
+      after a restart.
+
   * `XMonad.Hooks.StatusBar`
 
     - Added `startAllStatusBars` to start the configured status bars.

XMonad/Hooks/EwmhDesktops.hs

@@ -24,6 +24,8 @@ module XMonad.Hooks.EwmhDesktops (
     -- $usage
     ewmh,
     ewmhFullscreen,
+    ewmhDesktopsManageHook,
+    ewmhDesktopsMaybeManageHook,
 
     -- * Customization
     -- $customization
@@ -481,6 +483,31 @@ ewmhDesktopsEventHook'
         mempty
 ewmhDesktopsEventHook' _ _ = mempty
 
+-- | A 'ManageHook' that shifts windows to the workspace they want to be in.
+-- Useful for restoring browser windows to where they were before restart.
+--
+-- To only use this for browsers (which might be a good idea, as many apps try
+-- to restore their window to their original position, but it's rarely
+-- desirable outside of security updates of multi-window apps like a browser),
+-- use this:
+--
+-- > stringProperty "WM_WINDOW_ROLE" =? "browser" --> ewmhDesktopsManageHook
+ewmhDesktopsManageHook :: ManageHook
+ewmhDesktopsManageHook = maybeToDefinite ewmhDesktopsMaybeManageHook
+
+-- | 'ewmhDesktopsManageHook' as a 'MaybeManageHook' for use with
+-- 'composeOne'. Returns 'Nothing' if the window didn't indicate any desktop
+-- preference, otherwise 'Just' (even if the preferred desktop was out of
+-- bounds).
+ewmhDesktopsMaybeManageHook :: MaybeManageHook
+ewmhDesktopsMaybeManageHook = desktop >>= traverse doShiftI
+  where
+    doShiftI :: Int -> ManageHook
+    doShiftI d = do
+        sort' <- liftX . XC.withDef $ \EwmhDesktopsConfig{workspaceSort} -> workspaceSort
+        ws <- liftX . gets $ map W.tag . sort' . W.workspaces . windowset
+        maybe idHook doShift $ ws !? d
+
 -- | Add EWMH fullscreen functionality to the given config.
 ewmhFullscreen :: XConfig a -> XConfig a
 ewmhFullscreen c = c { startupHook     = startupHook c <> fullscreenStartup

XMonad/Hooks/ManageHelpers.hs

@@ -52,6 +52,7 @@ module XMonad.Hooks.ManageHelpers (
     isMinimized,
     isDialog,
     pid,
+    desktop,
     transientTo,
     maybeToDefinite,
     MaybeManageHook,
@@ -202,6 +203,15 @@ pid = ask >>= \w -> liftX $ getProp32s "_NET_WM_PID" w <&> \case
     Just [x] -> Just (fromIntegral x)
     _        -> Nothing
 
+-- | This function returns 'Just' the @_NET_WM_DESKTOP@ property for a
+-- particular window if set, 'Nothing' otherwise.
+--
+-- See <https://specifications.freedesktop.org/wm-spec/wm-spec-1.5.html#idm46181547492704>.
+desktop :: Query (Maybe Int)
+desktop = ask >>= \w -> liftX $ getProp32s "_NET_WM_DESKTOP" w <&> \case
+    Just [x] -> Just (fromIntegral x)
+    _        -> Nothing
+
 -- | A predicate to check whether a window is Transient.
 -- It holds the result which might be the window it is transient to
 -- or it might be 'Nothing'.