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Diffstat (limited to 'XMonad')
-rw-r--r-- | XMonad/Util/SpawnOnce.hs | 39 |
1 files changed, 39 insertions, 0 deletions
diff --git a/XMonad/Util/SpawnOnce.hs b/XMonad/Util/SpawnOnce.hs new file mode 100644 index 0000000..edb3b5f --- /dev/null +++ b/XMonad/Util/SpawnOnce.hs @@ -0,0 +1,39 @@ +{-# LANGUAGE DeriveDataTypeable #-} + +----------------------------------------------------------------------------- +-- | +-- Module : XMonad.Util.ExtensibleState +-- Copyright : (c) Spencer Janssen 2009 +-- License : BSD3-style (see LICENSE) +-- +-- Maintainer : spencerjanssen@gmail.com +-- Stability : unstable +-- Portability : not portable +-- +-- A module for spawning a command once, and only once. Useful to start +-- status bars and make session settings inside startupHook. +-- +----------------------------------------------------------------------------- + +module XMonad.Util.SpawnOnce (spawnOnce) where + +import XMonad +import Data.Set as Set +import XMonad.Util.ExtensibleState +import Control.Monad + +data SpawnOnce = SpawnOnce { unspawnOnce :: (Set String) } + deriving (Read, Show, Typeable) + +instance ExtensionClass SpawnOnce where + initialValue = SpawnOnce $ Set.empty + extensionType = PersistentExtension + +-- | The first time 'spawnOnce' is executed on a particular command, that +-- command is executed. Subsequent invocations for a command do nothing. +spawnOnce :: String -> X () +spawnOnce xs = do + b <- fmap (Set.member xs . unspawnOnce) $ getState + when (not b) $ do + spawn xs + modifyState (SpawnOnce . Set.insert xs . unspawnOnce) |