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-- Example of concurrent Haskell and Gtk.
--
-- As long as GHC does not support OS level threads by default, a trick has
-- to be used to let Haskell programs continue while the GUI is running.
-- We attach a call to the Haskell function "yield" to the timeout handler of
-- Gtk's main loop. Thus GHC regularly gets a chance to execute Haskell
-- threads.
import Graphics.UI.Gtk
import Control.Applicative
import Prelude
import Control.Concurrent
main :: IO ()
main = do
initGUI
dia <- dialogNew
dialogAddButton dia stockClose ResponseClose
contain <- castToBox <$> dialogGetContentArea dia
pb <- progressBarNew
boxPackStart contain pb PackNatural 0
widgetShowAll dia
forkIO (doTask pb)
-- 50ms timeout, so GHC will get a chance to scheule about 20 times a second
-- which gives reasonable latency without the polling generating too much
-- cpu load.
timeoutAddFull (yield >> return True) priorityDefaultIdle 50
dialogRun dia
return ()
doTask :: ProgressBar -> IO ()
doTask pb = do
progressBarPulse pb
threadDelay 100000
doTask pb
|
