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https://github.com/xmonad/xmonad-contrib.git
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30a78d51e3
Changed the interface of X.U.ExtensibleState to resemble that of Control.Monad.State and modified the modules that use it accordingly.
40 lines
1.3 KiB
Haskell
40 lines
1.3 KiB
Haskell
{-# LANGUAGE DeriveDataTypeable #-}
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-----------------------------------------------------------------------------
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-- |
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-- Module : XMonad.Util.ExtensibleState
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-- Copyright : (c) Spencer Janssen 2009
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-- License : BSD3-style (see LICENSE)
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--
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-- Maintainer : spencerjanssen@gmail.com
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-- Stability : unstable
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-- Portability : not portable
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--
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-- A module for spawning a command once, and only once. Useful to start
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-- status bars and make session settings inside startupHook.
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--
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-----------------------------------------------------------------------------
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module XMonad.Util.SpawnOnce (spawnOnce) where
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import XMonad
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import Data.Set as Set
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import qualified XMonad.Util.ExtensibleState as XS
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import Control.Monad
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data SpawnOnce = SpawnOnce { unspawnOnce :: (Set String) }
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deriving (Read, Show, Typeable)
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instance ExtensionClass SpawnOnce where
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initialValue = SpawnOnce Set.empty
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extensionType = PersistentExtension
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-- | The first time 'spawnOnce' is executed on a particular command, that
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-- command is executed. Subsequent invocations for a command do nothing.
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spawnOnce :: String -> X ()
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spawnOnce xs = do
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b <- XS.gets (Set.member xs . unspawnOnce)
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when (not b) $ do
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spawn xs
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XS.modify (SpawnOnce . Set.insert xs . unspawnOnce)
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