From f8c8240793a9992db68f07e75281e7f549406648 Mon Sep 17 00:00:00 2001
From: Josh Rahm <rahm@google.com>
Date: Tue, 12 Apr 2022 13:07:17 -0600
Subject: Add type-static way to get the length of a LayoutList

---
 src/Rahm/Desktop/Keys.hs        |  9 +++++++--
 src/Rahm/Desktop/Layout.hs      | 17 ++++++++++++-----
 src/Rahm/Desktop/Layout/List.hs | 35 +++++++++++++++++++++++++++++------
 3 files changed, 48 insertions(+), 13 deletions(-)

diff --git a/src/Rahm/Desktop/Keys.hs b/src/Rahm/Desktop/Keys.hs
index 87f88cf..321d185 100644
--- a/src/Rahm/Desktop/Keys.hs
+++ b/src/Rahm/Desktop/Keys.hs
@@ -53,7 +53,8 @@ import Rahm.Desktop.PassMenu
 import Rahm.Desktop.Logger
 import Rahm.Desktop.RebindKeys
 import Rahm.Desktop.Swallow
-import Rahm.Desktop.Layout.List (toNextLayout, toPreviousLayout, toFirstLayout)
+import Rahm.Desktop.Layout.List (
+  toNextLayout, toPreviousLayout, toFirstLayout, toIndexedLayout)
 import Rahm.Desktop.Layout.Hole (toggleHole)
 import Rahm.Desktop.Layout.Pop (togglePop)
 import Rahm.Desktop.Layout.Flip (flipHorizontally, flipVertically)
@@ -438,10 +439,14 @@ keymap = runKeys $ do
         (noMod -|- justMod) $ doc "Rotate the layout 90 degrees" $
           sendMessage rotateLayout
 
-      bind xK_t $
+      bind xK_c $
         (noMod -|- justMod) $ doc "Toggle the pop window" $
           sendMessage togglePop
 
+      bind xK_t $
+        (noMod -|- justMod) $ doc "Jump to the middle layout." $
+          sendMessage (toIndexedLayout (nLayouts `div` 2))
+
       bind xK_x $
         (noMod -|- justMod) $ doc "Toggle the hole" $
           sendMessage toggleHole
diff --git a/src/Rahm/Desktop/Layout.hs b/src/Rahm/Desktop/Layout.hs
index b416111..bd875d0 100644
--- a/src/Rahm/Desktop/Layout.hs
+++ b/src/Rahm/Desktop/Layout.hs
@@ -37,13 +37,17 @@ import Rahm.Desktop.Layout.Hole
 import qualified Data.Map as M
 import qualified XMonad.StackSet as W
 
-withSpacing = spacingRaw True (Border 5 5 5 5) True (Border 5 5 5 5) True
-mods =
-  withSpacing . poppable . flippable . rotateable . hole
-
 myLayout =
   fullscreenFull $
-    avoidStruts $
+    avoidStruts myLayoutList
+
+mySpacing = spacingRaw True (Border 5 5 5 5) True (Border 5 5 5 5) True
+
+
+mods =
+  mySpacing . poppable . flippable . rotateable . hole
+
+myLayoutList =
         layoutList $
           mods (reinterpretIncMaster $ spiral (6/7)) |:
           mods (modifyMosaic (MosaicAlt M.empty :: MosaicAlt Window)) |:
@@ -55,6 +59,9 @@ myLayout =
           mods (reinterpretIncMaster $ D.Dwindle D.R D.CW 1.5 1.1) |:
           nil
 
+nLayouts :: Int
+nLayouts = layoutListLength myLayoutList
+
 -- Mosaic doesn't have the concept of a "Master Space", so reinterpret messages
 -- intended to modify the master space and instead have those messages expand
 -- and shrink the current window.
diff --git a/src/Rahm/Desktop/Layout/List.hs b/src/Rahm/Desktop/Layout/List.hs
index 96f9be5..f533ea2 100644
--- a/src/Rahm/Desktop/Layout/List.hs
+++ b/src/Rahm/Desktop/Layout/List.hs
@@ -1,4 +1,4 @@
-{-# LANGUAGE UndecidableInstances #-}
+{-# LANGUAGE UndecidableInstances, TypeOperators #-}
 
 {-
  - This module provides a more powerful version of the "Choose" layout that can
@@ -15,18 +15,22 @@ module Rahm.Desktop.Layout.List (
   toNextLayout,
   toPreviousLayout,
   toFirstLayout,
+  toIndexedLayout,
   (|:),
-  nil
+  nil,
+  layoutListLength,
+  layoutListLengthProxy
   )where
 
 import Control.Applicative ((<|>))
-import Data.Void
+import Control.Arrow (second, (>>>))
 import Control.Monad.Identity (runIdentity)
 import Data.Maybe (fromMaybe, fromJust)
-import Control.Arrow (second)
+import Data.Proxy
+import Data.Void
+import GHC.TypeLits
 import XMonad
 import qualified XMonad.StackSet as W
-import Data.Proxy
 
 -- Type-level lists. LNil is the final of the list. LCons contains a layout and a
 -- tail.
@@ -156,6 +160,20 @@ data LayoutList l a where
 deriving instance (LayoutSelect l a) => Show (LayoutList l a)
 deriving instance (LayoutSelect l a) => Read (LayoutList l a)
 
+-- Type family to get the LengthOf a ConsList.
+type family LengthOf (x :: * -> *) :: Nat where
+  LengthOf LNil = 0
+  LengthOf (LCons l t) = 1 + LengthOf t
+
+-- Length of a LayoutList. This is calculated at Compile-time using
+-- typefamilies and Nat TypeLits.
+layoutListLength :: forall l n a. (LengthOf l ~ n, KnownNat n) => LayoutList l a -> Int
+layoutListLength = fromIntegral . natVal . layoutListLengthProxy
+
+-- Proxy for the type-level Nat length of a LayoutList.
+layoutListLengthProxy :: (LengthOf l ~ n) => LayoutList l a -> Proxy n
+layoutListLengthProxy _ = Proxy
+
 -- Cons two LayoutSelect types together.
 (|:) :: (LayoutSelect t a, LayoutClass l a) => l a -> t a -> LCons l t a
 (|:) = LCons
@@ -189,10 +207,15 @@ toNextLayout = NavigateLayout $ addSelector (intToSelector 1)
 toPreviousLayout :: NavigateLayout
 toPreviousLayout = NavigateLayout $ \c -> fromMaybe c (decrement c <|> final)
 
--- NavigateLayotu instance to move to the first layout.
+-- NavigateLayout instance to move to the first layout.
 toFirstLayout :: NavigateLayout
 toFirstLayout = NavigateLayout (`fromMaybe` initial)
 
+-- NavigateLayout instance to go to an indexed layout.
+toIndexedLayout :: Int -> NavigateLayout
+toIndexedLayout i = NavigateLayout $
+  (`fromMaybe` initial) >>> addSelector (intToSelector i)
+
 instance Message NavigateLayout where
 
 -- LayoutSelect class Describes a type that can be used to select a layout using
-- 
cgit