Hi, I've been playing around with Control.Concurrent lately, and ran into a problem with xmonad as it stands: it usually blocks inside XNextEvent() in the main loop, so the Haskell runtime system never gets a chance to run any other lightweight threads. The attached patch uses threadWaitRead to tell the runtime system to wait for the X file descriptor to become ready before calling XNextEvent. This works for me: I've now got a couple of forkIO threads happily updating my status bar periodically. I'm not entirely convinced it's correct, though. Is it possible for the X server to send more than one event in a single communication? If so, it would be necessary to call nextEvent to handle the subsequent events before the file descriptor becomes ready again (which'd be easy if there's a way to find out whether there are any events pending without blocking). Thanks, -- Adam Sampson http://offog.org/