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{-# LANGUAGE GADTs, RankNTypes, FlexibleInstances, MultiParamTypeClasses,
FlexibleContexts, UndecidableInstances, ViewPatterns, StandaloneDeriving,
RankNTypes, TupleSections, TypeFamilies #-}
{- This module provides a more powerful version of the choose layout, using a
- list to store the layouts, and thus the list is navigatable. -}
module Internal.LayoutZipper where
import Data.Void
import Control.Monad.Identity (runIdentity)
import Data.Maybe (fromMaybe)
import Control.Arrow (second)
import XMonad
import qualified XMonad.StackSet as W
import Data.Proxy
data LNil a = LNil deriving (Read, Show)
data LCons l t a = LCons (l a) (t a) deriving (Read, Show)
data IsSelected l = Selected | NotSelected l
deriving (Read, Show)
-- Combinator for combining layouts together into a LayoutList. This amy then be
-- used with the layoutZipper to create a layout zipper.
class SelectionClass c where
nextSelection :: c -> c
prevSelection :: c -> c
firstSelection :: Maybe c
isSelected :: c -> Bool
instance (SelectionClass t) => SelectionClass (IsSelected t) where
nextSelection (NotSelected l) = NotSelected (nextSelection l)
nextSelection Selected = maybe Selected NotSelected firstSelection
firstSelection = Just Selected
prevSelection (NotSelected t) =
if isSelected t
then Selected
else NotSelected (prevSelection t)
prevSelection Selected = Selected
isSelected Selected = True
isSelected _ = False
instance SelectionClass Void where
nextSelection = absurd
prevSelection = absurd
firstSelection = Nothing
isSelected = const False
data LayoutZipper l a where
LayoutZipper :: (LayoutSelect l a) => Selection l -> l a -> LayoutZipper l a
deriving instance (LayoutSelect l a) => Show (LayoutZipper l a)
deriving instance (LayoutSelect l a) => Read (LayoutZipper l a)
(|:) :: (LayoutSelect t a, LayoutClass l a) => l a -> t a -> LCons l t a
(|:) = LCons
infixr 5 |:
layoutZipper :: (LayoutSelect l a, Selection l ~ IsSelected n) => l a -> LayoutZipper l a
layoutZipper = LayoutZipper Selected
-- The termination of a layout zipper.
nil :: LNil a
nil = LNil
-- Message to navigate to a layout.
newtype NavigateLayout =
-- Sets the layout based on the given function.
NavigateLayout {
changeLayoutFn :: forall c. (SelectionClass c) => c -> c
}
deriving (Typeable)
-- NavigateLayout instance to move to the next layout, circularly.
toNextLayout :: NavigateLayout
toNextLayout = NavigateLayout nextSelection
-- NavigateLayout instance to move to the previous layout, circularly.
toPreviousLayout :: NavigateLayout
toPreviousLayout = NavigateLayout prevSelection
-- NavigateLayotu instance to move to the first layout.
toFirstLayout :: NavigateLayout
toFirstLayout = NavigateLayout (`fromMaybe` firstSelection)
instance Message NavigateLayout where
class (
Show (l a),
Read (l a),
Read (Selection l),
Show (Selection l),
SelectionClass (Selection l)) => LayoutSelect l a where
type Selection l :: *
update :: forall r m. (Monad m) =>
Selection l ->
l a ->
(forall l'. (LayoutClass l' a) => l' a -> m (r, Maybe (l' a))) ->
m (Maybe (r, l a))
nLayouts :: l a -> Int
instance (
Read (l a),
LayoutClass l a,
LayoutSelect t a,
Show (Selection t),
Read (Selection t)) =>
LayoutSelect (LCons l t) a where
-- This is something
type Selection (LCons l t) = IsSelected (Selection t)
update Selected (LCons layout t) fn = do
(r, layout') <- fn layout
return $ Just (r, LCons (fromMaybe layout layout') t)
update (NotSelected s) (LCons l t) fn =
fmap (second $ \t' -> LCons l t') <$> update s t fn
nLayouts (LCons _ t) = 1 + nLayouts t
instance LayoutSelect LNil a where
type Selection LNil = Void -- Cannot be selected
update _ _ _ = return Nothing
nLayouts _ = 0
instance (Show (l a), Typeable l, LayoutSelect l a) => LayoutClass (LayoutZipper l) a where
runLayout (W.Workspace i (LayoutZipper idx l) ms) r = do
r <- update idx l $ \layout ->
runLayout (W.Workspace i layout ms) r
case r of
Nothing -> return ([], Nothing)
Just (r, la) -> return (r, Just (LayoutZipper idx la))
pureLayout (LayoutZipper idx l) r s = runIdentity $ do
r <- update idx l $ \layout -> return (pureLayout layout r s, Nothing)
case r of
Nothing -> return []
Just (r, a) -> return r
emptyLayout (LayoutZipper idx l) r = do
r <- update idx l $ \layout -> emptyLayout layout r
case r of
Nothing -> return ([], Nothing)
Just (r, la) -> return (r, Just (LayoutZipper idx la))
handleMessage (LayoutZipper idx l) (fromMessage -> Just (NavigateLayout fn)) =
return $ Just (LayoutZipper (fn idx) l)
handleMessage (LayoutZipper idx l) m = do
r <- update idx l $ \layout -> ((),) <$> handleMessage layout m
return $ LayoutZipper idx . snd <$> r
pureMessage (LayoutZipper idx l) m = runIdentity $ do
r <- update idx l $ \layout -> return ((), pureMessage layout m)
return $ LayoutZipper idx . snd <$> r
description (LayoutZipper idx l) = runIdentity $ do
r <- update idx l $ \l -> return (description l, Nothing)
return $
case r of
Nothing -> "No Layout"
Just (descr, _) -> descr
|
