import Control.Monad (when, forever)
import qualified Graphics.X11.Xlib as X
import qualified Graphics.X11.Xlib.Extras as X

main = do
  dpy <- X.openDisplay ""
  let scr = X.defaultScreen dpy
      h   = fromIntegral (X.displayHeight dpy scr)
      w   = fromIntegral (X.displayWidth dpy scr)
  root <- X.rootWindow dpy scr
  X.allocaSetWindowAttributes $ \attr -> do
    X.set_event_mask attr X.substructureNotifyMask
    X.changeWindowAttributes dpy root X.cWEventMask attr
  forever $ X.allocaXEvent $ \event -> do
    X.nextEvent dpy event
    eventType <- X.get_EventType event
    when (eventType == X.mapNotify) $ do
      win <- X.get_Window event
      X.moveResizeWindow dpy win 0 0 h w