1 files changed, 134 insertions, 0 deletions
diff --git a/src/Xmobar/System/Signal.hs b/src/Xmobar/System/Signal.hs
new file mode 100644
index 0000000..ce39e10
--- /dev/null
+++ b/src/Xmobar/System/Signal.hs
@@ -0,0 +1,134 @@
+{-# LANGUAGE DeriveDataTypeable, CPP #-}
+
+-----------------------------------------------------------------------------
+-- |
+-- Module      :  Signal
+-- Copyright   :  (c) Andrea Rosatto
+--             :  (c) Jose A. Ortega Ruiz
+--             :  (c) Jochen Keil
+-- License     :  BSD-style (see LICENSE)
+--
+-- Maintainer  :  Jose A. Ortega Ruiz <jao@gnu.org>
+-- Stability   :  unstable
+-- Portability :  unportable
+--
+-- Signal handling, including DBUS when available
+--
+-----------------------------------------------------------------------------
+
+module Xmobar.System.Signal where
+
+import Data.Foldable (for_)
+import Data.Typeable (Typeable)
+import Control.Concurrent
+import Control.Concurrent.STM
+import Control.Exception
+import System.Posix.Signals
+import Graphics.X11.Types (Button)
+import Graphics.X11.Xlib.Types (Position)
+import System.IO
+
+#ifdef DBUS
+import DBus (IsVariant(..))
+import Control.Monad ((>=>))
+#endif
+
+safeHead :: [a] -> Maybe a
+safeHead    [] = Nothing
+safeHead (x:_) = Just x
+
+data WakeUp = WakeUp deriving (Show,Typeable)
+instance Exception WakeUp
+
+data SignalType = Wakeup
+                | Reposition
+                | ChangeScreen
+                | Hide   Int
+                | Reveal Int
+                | Toggle Int
+                | TogglePersistent
+                | Action Button Position
+    deriving (Read, Show)
+
+#ifdef DBUS
+instance IsVariant SignalType where
+    toVariant   = toVariant . show
+    fromVariant = fromVariant >=> parseSignalType
+#endif
+
+parseSignalType :: String -> Maybe SignalType
+parseSignalType = fmap fst . safeHead . reads
+
+-- | Signal handling
+setupSignalHandler :: IO (TMVar SignalType)
+setupSignalHandler = do
+   tid   <- newEmptyTMVarIO
+   installHandler sigUSR2 (Catch $ updatePosHandler tid) Nothing
+   installHandler sigUSR1 (Catch $ changeScreenHandler tid) Nothing
+   return tid
+
+updatePosHandler :: TMVar SignalType -> IO ()
+updatePosHandler sig = do
+   atomically $ putTMVar sig Reposition
+   return ()
+
+changeScreenHandler :: TMVar SignalType -> IO ()
+changeScreenHandler sig = do
+   atomically $ putTMVar sig ChangeScreen
+   return ()
+
+
+-- | Ensures that the given IO action runs its cleanup actions ('bracket' etc.),
+-- even if a signal is caught.
+--
+-- An exception will be thrown on the thread that called this function when a
+-- signal is caught.
+withDeferSignals :: IO a -> IO a
+withDeferSignals thing = do
+  threadId <- myThreadId
+  caughtSignal <- newEmptyMVar
+
+  let signals =
+        filter (not . flip inSignalSet reservedSignals)
+          [ sigQUIT
+          , sigTERM
+          --, sigINT -- Handler already installed by GHC
+          --, sigPIPE -- Handler already installed by GHC
+          --, sigUSR1 -- Handled by setupSignalHandler
+          --, sigUSR2 -- Handled by setupSignalHandler
+
+          -- One of the following appears to cause instability, see #360
+          --, sigHUP
+          --, sigILL
+          --, sigABRT
+          --, sigFPE
+          --, sigSEGV
+          --, sigALRM
+          --, sigBUS
+          --, sigPOLL
+          --, sigPROF
+          --, sigSYS
+          --, sigTRAP
+          --, sigVTALRM
+          --, sigXCPU
+          --, sigXFSZ
+          ]
+
+  for_ signals $ \s ->
+
+      installHandler s
+        (Catch $ do
+          tryPutMVar caughtSignal s
+          hPutStrLn stderr ("xmobar: Caught signal "++show s++"; exiting...")
+          throwTo threadId ThreadKilled)
+        Nothing
+
+  thing `finally` do
+        s0 <- tryReadMVar caughtSignal
+        case s0 of
+          Nothing -> pure ()
+          Just s -> do
+            -- Run the default handler for the signal
+            -- hPutStrLn stderr ("xmobar: Running default handler for signal "++show s)
+            installHandler s Default Nothing
+            raiseSignal s