X.L.IndependentScreens: Add workspacesOn, withScreen, fix marshallPP always sorting lexically

- Added `workspacesOn` for filtering workspaces on the current screen.

- Added `withScreen` to specify names for a given single screen.

- Added new aliases `PhysicalWindowSpace` and `VirtualWindowSpace`
  for a `WindowSpace` for easier to read function signatures.

- Fixed a bug where `marshallPP` always sorted workspace names
  lexically.

Fixes: https://github.com/xmonad/xmonad-contrib/issues/420

CHANGES.md

@@ -609,6 +609,22 @@
     - The decoration window now sets a `WM_CLASS` property.  This allows
       other applications, like compositors, to properly match on it.
 
+  * `XMonad.Layout.IndependentScreens`
+
+    - Fixed a bug where `marshallPP` always sorted workspace names
+      lexically.  This changes the default behaviour of `marshallPP`—the
+      given `ppSort` now operates in the _physical_ workspace names.
+      The documentation of `marshallSort` contains an example of how to
+      get the old behaviour, where `ppSort` operates in virtual names,
+      back.
+
+    - Added `workspacesOn` for filtering workspaces on the current screen.
+
+    - Added `withScreen` to specify names for a given single screen.
+
+    - Added new aliases `PhysicalWindowSpace` and `VirtualWindowSpace`
+      for a `WindowSpace` for easier to read function signatures.
+
 ## 0.16
 
 ### Breaking Changes

XMonad/Actions/CopyWindow.hs

@@ -18,7 +18,7 @@ module XMonad.Actions.CopyWindow (
                                  -- * Usage
                                  -- $usage
                                  copy, copyToAll, copyWindow, runOrCopy
-                                 , killAllOtherCopies, kill1
+                                 , killAllOtherCopies, kill1, taggedWindows, copiesOfOn
                                  -- * Highlight workspaces containing copies in logHook
                                  -- $logHook
                                  , wsContainingCopies

XMonad/Config/Dmwit.hs

@@ -25,7 +25,7 @@ import XMonad.Hooks.DynamicLog
 import XMonad.Hooks.ManageDocks
 import XMonad.Hooks.ManageHelpers
 import XMonad.Layout.Grid
-import XMonad.Layout.IndependentScreens
+import XMonad.Layout.IndependentScreens hiding (withScreen)
 import XMonad.Layout.Magnifier
 import XMonad.Layout.NoBorders
 import XMonad.Prelude

XMonad/Layout/IndependentScreens.hs

@@ -17,15 +17,18 @@ module XMonad.Layout.IndependentScreens (
     -- * Usage
     -- $usage
     VirtualWorkspace, PhysicalWorkspace,
+    VirtualWindowSpace, PhysicalWindowSpace,
     workspaces',
-    withScreens, onCurrentScreen,
+    withScreen, withScreens,
+    onCurrentScreen,
     marshallPP,
     whenCurrentOn,
     countScreens,
+    workspacesOn,
     -- * Converting between virtual and physical workspaces
     -- $converting
     marshall, unmarshall, unmarshallS, unmarshallW,
-    marshallWindowSpace, unmarshallWindowSpace, marshallSort
+    marshallWindowSpace, unmarshallWindowSpace, marshallSort,
 ) where
 
 -- for the screen stuff
@@ -33,7 +36,7 @@ import Control.Arrow ((***))
 import Graphics.X11.Xinerama
 import XMonad
 import XMonad.Prelude
-import XMonad.StackSet hiding (filter, workspaces)
+import qualified XMonad.StackSet as W
 import XMonad.Hooks.DynamicLog
 
 -- $usage
@@ -78,6 +81,11 @@ import XMonad.Hooks.DynamicLog
 type VirtualWorkspace  = WorkspaceId
 type PhysicalWorkspace = WorkspaceId
 
+-- | A 'WindowSpace' whose tags are 'PhysicalWorkspace's.
+type PhysicalWindowSpace = WindowSpace
+-- | A 'WindowSpace' whose tags are 'VirtualWorkspace's.
+type VirtualWindowSpace = WindowSpace
+
 -- $converting
 -- You shouldn't need to use the functions below very much. They are used
 -- internally. However, in some cases, they may be useful, and so are exported
@@ -100,13 +108,20 @@ unmarshallW = snd . unmarshall
 workspaces' :: XConfig l -> [VirtualWorkspace]
 workspaces' = nub . map unmarshallW . workspaces
 
+-- | Specify workspace names for each screen
+withScreen :: ScreenId            -- ^ The screen to make workspaces for
+           -> [VirtualWorkspace]  -- ^ The desired virtual workspace names
+           -> [PhysicalWorkspace] -- ^ A list of all internal physical workspace names
+withScreen n vws = [marshall n pws | pws <- vws]
+
+-- | Make all workspaces across the monitors bear the same names
 withScreens :: ScreenId            -- ^ The number of screens to make workspaces for
             -> [VirtualWorkspace]  -- ^ The desired virtual workspace names
             -> [PhysicalWorkspace] -- ^ A list of all internal physical workspace names
-withScreens n vws = [marshall sc pws | pws <- vws, sc <- [0..n-1]]
+withScreens n vws = concatMap (`withScreen` vws) [0..n-1]
 
 onCurrentScreen :: (VirtualWorkspace -> WindowSet -> a) -> (PhysicalWorkspace -> WindowSet -> a)
-onCurrentScreen f vws = screen . current >>= f . flip marshall vws
+onCurrentScreen f vws = W.screen . W.current >>= f . flip marshall vws
 
 -- | In case you don't know statically how many screens there will be, you can call this in main before starting xmonad.  For example, part of my config reads
 --
@@ -121,20 +136,25 @@ onCurrentScreen f vws = screen . current >>= f . flip marshall vws
 countScreens :: (MonadIO m, Integral i) => m i
 countScreens = fmap genericLength . liftIO $ openDisplay "" >>= liftA2 (<*) getScreenInfo closeDisplay
 
--- | This turns a naive pretty-printer into one that is aware of the
--- independent screens. That is, you can write your pretty printer to behave
--- the way you want on virtual workspaces; this function will convert that
--- pretty-printer into one that first filters out physical workspaces on other
--- screens, then converts all the physical workspaces on this screen to their
--- virtual names.
+-- | This turns a pretty-printer into one that is aware of the independent screens. The
+-- converted pretty-printer first filters out physical workspaces on other screens, then
+-- converts all the physical workspaces on this screen to their virtual names.
+-- Note that 'ppSort' still operates on physical (marshalled) workspace names,
+-- otherwise functions from "XMonad.Util.WorkspaceCompare" wouldn't work.
+-- If you need to sort on virtual names, see 'marshallSort'.
 --
--- For example, if you have handles @hLeft@ and @hRight@ for bars on the left and right screens, respectively, and @pp@ is a pretty-printer function that takes a handle, you could write
+-- For example, if you have have two bars on the left and right screens, respectively, and @pp@ is
+-- a pretty-printer, you could apply 'marshallPP' when creating a @StatusBarConfig@ from "XMonad.Hooks.StatusBar".
+--
+-- A sample config looks like this:
+--
+-- > mySBL = statusBarProp "xmobar" $ pure (marshallPP (S 0) pp)
+-- > mySBR = statusBarProp "xmobar" $ pure (marshallPP (S 1) pp)
+-- > main = xmonad $ withEasySB (mySBL <> mySBR) defToggleStrutsKey def
 --
--- > logHook = let log screen handle = dynamicLogWithPP . marshallPP screen . pp $ handle
--- >           in log 0 hLeft >> log 1 hRight
 marshallPP :: ScreenId -> PP -> PP
 marshallPP s pp = pp { ppRename = ppRename pp . unmarshallW
-                     , ppSort = fmap (marshallSort s) (ppSort pp) }
+                     , ppSort = (. workspacesOn s) <$> ppSort pp }
 
 -- | Take a pretty-printer and turn it into one that only runs when the current
 -- workspace is one associated with the given screen. The way this works is a
@@ -161,7 +181,7 @@ whenCurrentOn s pp = pp
     { ppSort = do
         sortWs <- ppSort pp
         return $ \xs -> case xs of
-            x:_ | unmarshallS (tag x) == s -> sortWs xs
+            x:_ | unmarshallS (W.tag x) == s -> sortWs xs
             _ -> []
     , ppOrder = \i@(wss:_) -> case wss of
         "" -> ["\0"] -- we got passed no workspaces; this is the signal from ppSort that this is a boring case
@@ -171,11 +191,31 @@ whenCurrentOn s pp = pp
         _ -> ppOutput pp out
     }
 
--- | If @vSort@ is a function that sorts 'WindowSpace's with virtual names, then @marshallSort s vSort@ is a function which sorts 'WindowSpace's with physical names in an analogous way -- but keeps only the spaces on screen @s@.
-marshallSort :: ScreenId -> ([WindowSpace] -> [WindowSpace]) -> ([WindowSpace] -> [WindowSpace])
+-- | Filter workspaces that are on current screen.
+workspacesOn :: ScreenId -> [PhysicalWindowSpace] -> [PhysicalWindowSpace]
+workspacesOn s = filter (\ws -> unmarshallS (W.tag ws) == s)
+
+-- | @vSort@ is a function that sorts 'VirtualWindowSpace's with virtual names.
+-- @marshallSort s vSort@ is a function which sorts 'PhysicalWindowSpace's with virtual names,
+-- but keeps only the 'WindowSpace'\'s on screen @s@.
+--
+-- NOTE: @vSort@ operating on virtual names comes with some caveats, see
+-- <https://github.com/xmonad/xmonad-contrib/issues/420 this issue> for
+-- more information. You can use 'marshallSort' like in the following example:
+--
+-- === __Example__
+--
+-- > pp' :: ScreenId -> PP -> PP
+-- > pp' s pp = (marshallPP s pp) { ppSort = fmap (marshallSort s) (ppSort pp) }
+-- >
+-- > mySBL = statusBarProp "xmobar" $ pure (pp' (S 0) pp)
+-- > mySBR = statusBarProp "xmobar" $ pure (pp' (S 1) pp)
+-- > main = xmonad $ withEasySB (mySBL <> mySBR) defToggleStrutsKey def
+--
+-- In this way, you have a custom virtual names sort on top of 'marshallPP'.
+marshallSort :: ScreenId -> ([VirtualWindowSpace] -> [VirtualWindowSpace]) -> ([PhysicalWindowSpace] -> [PhysicalWindowSpace])
 marshallSort s vSort = pScreens . vSort . vScreens where
-    onScreen ws = unmarshallS (tag ws) == s
-    vScreens    = map unmarshallWindowSpace . filter onScreen
+    vScreens    = map unmarshallWindowSpace . workspacesOn s
     pScreens    = map (marshallWindowSpace s)
 
 -- | Convert the tag of the 'WindowSpace' from a 'VirtualWorkspace' to a 'PhysicalWorkspace'.
@@ -183,5 +223,5 @@ marshallWindowSpace   :: ScreenId -> WindowSpace -> WindowSpace
 -- | Convert the tag of the 'WindowSpace' from a 'PhysicalWorkspace' to a 'VirtualWorkspace'.
 unmarshallWindowSpace :: WindowSpace -> WindowSpace
 
-marshallWindowSpace s ws = ws { tag = marshall s  (tag ws) }
-unmarshallWindowSpace ws = ws { tag = unmarshallW (tag ws) }
+marshallWindowSpace s ws = ws { W.tag = marshall s  (W.tag ws) }
+unmarshallWindowSpace ws = ws { W.tag = unmarshallW (W.tag ws) }