X.U.PureX: Add focusWindow and focusNth

This can be used to reduce flicker in noop focus actions.

CHANGES.md

@@ -243,6 +243,11 @@
 
     - Export `Minimize` type constructor.
 
+  * `XMonad.Util.PureX`
+
+    - Added `focusWindow` and `focusNth` which don't refresh (and thus
+      possibly flicker) when they happen to be a no-op.
+
 ## 0.16
 
 ### Breaking Changes

XMonad/Util/PureX.hs

@@ -44,6 +44,7 @@ module XMonad.Util.PureX (
   withWindowSet', withFocii,
   modify'', modifyWindowSet',
   getStack, putStack, peek,
+  focusWindow, focusNth,
   view, greedyView, invisiView,
   shift, curScreen, curWorkspace,
   curTag, curScreenId,
@@ -52,6 +53,7 @@ module XMonad.Util.PureX (
 -- xmonad
 import XMonad
 import qualified XMonad.StackSet as W
+import qualified XMonad.Actions.FocusNth
 
 -- mtl
 import Control.Monad.State
@@ -272,5 +274,21 @@ shift tag = withFocii $ \ctag fw ->
     mfw' <- peek
     return (Any $ Just fw /= mfw')
 
+-- | Internal. Refresh-tracking logic of focus operations.
+focusWith :: XLike m => (WindowSet -> WindowSet) -> m Any
+focusWith focuser = do
+    old <- peek
+    modifyWindowSet' focuser
+    new <- peek
+    return (Any $ old /= new)
+
+-- | A refresh-tracking version of @W.focusWindow@.
+focusWindow :: XLike m => Window -> m Any
+focusWindow w = focusWith (W.focusWindow w)
+
+-- | A refresh-tracking version of @XMonad.Actions.FocusNth.focusNth@.
+focusNth :: XLike m => Int -> m Any
+focusNth i = focusWith (W.modify' (XMonad.Actions.FocusNth.focusNth' i))
+
 -- }}}