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+-----------------------------------------------------------------------------
+-- |
+-- Module : Plugins.MarqueePipeReader
+-- Copyright : (c) Reto Habluetzel
+-- License : BSD-style (see LICENSE)
+--
+-- Maintainer : Jose A. Ortega Ruiz <jao@gnu.org>
+-- Stability : unstable
+-- Portability : unportable
+--
+-- A plugin for reading from named pipes for long texts with marquee
+--
+-----------------------------------------------------------------------------
+
+module Xmobar.Plugins.MarqueePipeReader where
+
+import System.IO (openFile, IOMode(ReadWriteMode), Handle)
+import Xmobar.Environment
+import Xmobar.Plugins (tenthSeconds, Exec(alias, start), hGetLineSafe)
+import System.Posix.Files (getFileStatus, isNamedPipe)
+import Control.Concurrent(forkIO, threadDelay)
+import Control.Concurrent.STM (TChan, atomically, writeTChan, tryReadTChan, newTChan)
+import Control.Exception
+import Control.Monad(forever, unless)
+import Control.Applicative ((<$>))
+
+type Length = Int -- length of the text to display
+type Rate = Int -- delay in tenth seconds
+type Separator = String -- if text wraps around, use separator
+
+data MarqueePipeReader = MarqueePipeReader String (Length, Rate, Separator) String
+ deriving (Read, Show)
+
+instance Exec MarqueePipeReader where
+ alias (MarqueePipeReader _ _ a) = a
+ start (MarqueePipeReader p (len, rate, sep) _) cb = do
+ (def, pipe) <- split ':' <$> expandEnv p
+ unless (null def) (cb def)
+ checkPipe pipe
+ h <- openFile pipe ReadWriteMode
+ line <- hGetLineSafe h
+ chan <- atomically newTChan
+ forkIO $ writer (toInfTxt line sep) sep len rate chan cb
+ forever $ pipeToChan h chan
+ where
+ split c xs | c `elem` xs = let (pre, post) = span (c /=) xs
+ in (pre, dropWhile (c ==) post)
+ | otherwise = ([], xs)
+
+pipeToChan :: Handle -> TChan String -> IO ()
+pipeToChan h chan = do
+ line <- hGetLineSafe h
+ atomically $ writeTChan chan line
+
+writer :: String -> Separator -> Length -> Rate -> TChan String -> (String -> IO ()) -> IO ()
+writer txt sep len rate chan cb = do
+ cb (take len txt)
+ mbnext <- atomically $ tryReadTChan chan
+ case mbnext of
+ Just new -> writer (toInfTxt new sep) sep len rate chan cb
+ Nothing -> tenthSeconds rate >> writer (drop 1 txt) sep len rate chan cb
+
+toInfTxt :: String -> String -> String
+toInfTxt line sep = concat (repeat $ line ++ " " ++ sep ++ " ")
+
+checkPipe :: FilePath -> IO ()
+checkPipe file = handle (\(SomeException _) -> waitForPipe) $ do
+ status <- getFileStatus file
+ unless (isNamedPipe status) waitForPipe
+ where waitForPipe = threadDelay 1000 >> checkPipe file