New Plugin MarqueePipeReader

    Display a long text from a pipe with marquee. It wraps around
    with a given separator and the length may be specified as well
    as the delay in 10th seconds. See readme for an example.

1 files changed, 68 insertions, 0 deletions

diff --git a/src/Plugins/MarqueePipeReader.hs b/src/Plugins/MarqueePipeReader.hs
new file mode 100644
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+++ b/src/Plugins/MarqueePipeReader.hs
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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 Plugins.MarqueePipeReader where
+
+import System.IO (openFile, IOMode(ReadWriteMode), Handle)
+import 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)
+
+type Length = Int       -- length of the text to display
+type Rate = Int         -- delay in tenth seconds 
+type Seperator = String -- if text wraps around, use separator
+
+data MarqueePipeReader = MarqueePipeReader String (Length, Rate, Seperator) String
+    deriving (Read, Show)
+
+instance Exec MarqueePipeReader where
+    alias (MarqueePipeReader _ _ a)    = a
+    start (MarqueePipeReader p (len, rate, sep) _) cb = do
+        let (def, pipe) = split ':' 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 -> Seperator -> 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