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X.L.OnHost: Query gethostname if $HOST lookup fails #901

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Sep 4, 2024
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X.L.OnHost: Query gethostname if $HOST lookup fails #901

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X.L.OnHost: Query gethostname if $HOST lookup fails
slotThe Aug 27, 2024
ed85394
fixup! X.L.OnHost: Query gethostname if $HOST lookup fails
slotThe Aug 27, 2024
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37 changes: 28 additions & 9 deletions XMonad/Layout/OnHost.hs
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Original file line number Diff line number Diff line change
@@ -1,5 +1,6 @@
{-# LANGUAGE FlexibleInstances, MultiParamTypeClasses #-}

{-# LANGUAGE FlexibleInstances #-}
{-# LANGUAGE LambdaCase #-}
{-# LANGUAGE MultiParamTypeClasses #-}
-----------------------------------------------------------------------------
-- |
-- Module : XMonad.Layout.OnHost
Expand Down Expand Up @@ -27,10 +28,12 @@ module XMonad.Layout.OnHost (-- * Usage

import XMonad
import qualified XMonad.StackSet as W
import XMonad.Prelude

import XMonad.Layout.LayoutModifier

import Data.Maybe (fromMaybe)
import Foreign (allocaArray0)
import Foreign.C
import System.Posix.Env (getEnv)

-- $usage
Expand All @@ -56,11 +59,13 @@ import System.Posix.Env (getEnv)
--
-- > layoutHook = A ||| B ||| onHost "foo" D C
--
-- Note that we rely on '$HOST' being set in the environment, as is true on most
-- modern systems; if it's not, you may want to use a wrapper around xmonad or
-- perhaps use 'System.Posix.Env.setEnv' (or 'putEnv') to set it in 'main'.
-- This is to avoid dragging in the network package as an xmonad dependency.
-- If '$HOST' is not defined, it will behave as if the host name never matches.
-- Note that we rely on either @$HOST@ being set in the environment, or
-- <https://linux.die.net/man/2/gethostname gethostname> returning something
-- useful, as is true on most modern systems; if this is not the case for you,
-- you may want to use a wrapper around xmonad or perhaps use
-- 'System.Posix.Env.setEnv' (or 'putEnv') to set @$HOST@ in 'main'. If
-- neither of the two methods work, the module will behave as if the host name
-- never matches.
--
-- Also note that '$HOST' is usually a fully qualified domain name, not a short name.
-- If you use a short name, this code will try to truncate $HOST to match; this may
Expand Down Expand Up @@ -116,7 +121,7 @@ data OnHost l1 l2 a = OnHost [String]

instance (LayoutClass l1 a, LayoutClass l2 a, Show a) => LayoutClass (OnHost l1 l2) a where
runLayout (W.Workspace i p@(OnHost hosts _ lt lf) ms) r = do
h <- io $ getEnv "HOST"
h <- io $ getEnv "HOST" <|> getHostName
if maybe False (`elemFQDN` hosts) h
then do (wrs, mlt') <- runLayout (W.Workspace i lt ms) r
return (wrs, Just $ mkNewOnHostT p mlt')
Expand Down Expand Up @@ -154,3 +159,17 @@ eqFQDN a b
| '.' `elem` a = takeWhile (/= '.') a == b
| '.' `elem` b = a == takeWhile (/= '.') b
| otherwise = a == b

-----------------------------------------------------------------------
-- cbits

foreign import ccall "gethostname" gethostname :: CString -> CSize -> IO CInt

getHostName :: IO (Maybe String)
getHostName = allocaArray0 size $ \cstr -> do
throwErrnoIfMinus1_ "getHostName" $ gethostname cstr (fromIntegral size)
peekCString cstr <&> \case
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"" -> Nothing
s -> Just s
where
size = 256
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