X.A.{Grid,Tree}Select: Fix keybindings in secondary kbd layouts

We didn't clean XKB group bits out of the KeyPress events' state so key
bindings only worked in the primary keyboard layout (first XKB group).
To fix this, this adds a `cleanKeyMask` function to X.Prelude which is
analogous to `cleanMask` but aimed at cleaning regular KeyPress states
(as opposed to just KeyPresses from passive key grabs), and this is then
used instead of `cleanMask`.

Related: https://github.com/xmonad/xmonad-contrib/issues/290
Related: https://github.com/xmonad/xmonad-contrib/pull/590

XMonad/Prelude.hs

@@ -24,6 +24,7 @@ module XMonad.Prelude (
     safeGetWindowAttributes,
     keyToString,
     keymaskToString,
+    cleanKeyMask,
 ) where
 
 import Foreign (alloca, peek)
@@ -116,3 +117,18 @@ keymaskToString numLockMask msk =
 -- pair, into a string.
 keyToString :: (KeyMask, KeySym) -> [Char]
 keyToString = uncurry (++) . bimap (keymaskToString 0) keysymToString
+
+-- | Strip numlock, capslock, mouse buttons and XKB group from a 'KeyMask',
+-- leaving only modifier keys like Shift, Control, Super, Hyper in the mask
+-- (hence the \"Key\" in \"cleanKeyMask\").
+--
+-- Core's 'cleanMask' only strips the first two because key events from
+-- passive grabs (key bindings) are stripped of mouse buttons and XKB group by
+-- the X server already for compatibility reasons. For more info, see:
+-- <https://www.x.org/releases/X11R7.7/doc/kbproto/xkbproto.html#Delivering_a_Key_or_Button_Event_to_a_Client>
+cleanKeyMask :: X (KeyMask -> KeyMask)
+cleanKeyMask = cleanKeyMask' <$> gets numberlockMask
+
+cleanKeyMask' :: KeyMask -> KeyMask -> KeyMask
+cleanKeyMask' numLockMask mask =
+    mask .&. complement (numLockMask .|. lockMask) .&. (button1Mask - 1)