vanadium/xmonad: use event handling to set master pane count

nix/configurations/vanadium/home/xmonad/lib/XMonad/Layout/SetMasterNTall.hs

@@ -0,0 +1,30 @@
+{-# LANGUAGE FlexibleInstances, MultiParamTypeClasses #-}
+
+-- Wraps ResizableTall, allows setting master count to a number directly
+module XMonad.Layout.SetMasterNTall
+  ( SetMasterNTall(..)
+  , SetMasterN(..)
+  ) where
+
+import XMonad
+import qualified XMonad.StackSet as W
+import XMonad.Layout.ResizableTile
+
+-- Message
+data SetMasterN = SetMasterN Int
+instance Message SetMasterN
+
+-- Layout
+newtype SetMasterNTall a = SetMasterNTall { unSetMasterNTall :: ResizableTall a }
+    deriving (Read, Show)
+
+instance LayoutClass SetMasterNTall a where
+  runLayout (W.Workspace t l s) =
+    let ws' = W.Workspace t (unSetMasterNTall l) s
+    in  (fmap . fmap . fmap) SetMasterNTall . runLayout ws'
+
+  handleMessage (SetMasterNTall l@(ResizableTall _n0 d f s)) mess
+      | Just (SetMasterN n) <- fromMessage mess = pure $ Just $ SetMasterNTall $ ResizableTall n d f s
+      | otherwise = (fmap . fmap) SetMasterNTall . handleMessage l $ mess
+
+  description (SetMasterNTall l) = description l