Simple image viewer in Haskell

Main.hs

module Main where

import qualified Data.ByteString.Char8 as B -- bad
import qualified Graphics.UI.Gtk as Gtk
import           System.Environment
import qualified System.GIO as GIO

updateImage :: Gtk.ImageClass o => o -> Maybe GIO.File -> Maybe GIO.File -> GIO.FileMonitorEvent -> IO ()
updateImage image (Just file) _ GIO.FileMonitorEventChanged = do
  pixbuf <- Gtk.pixbufNewFromFile . B.unpack $ GIO.filePath file
  Gtk.set (Gtk.toImage image)
    [ Gtk.imagePixbuf Gtk.:= pixbuf
    ]
updateImage _ _ _ _ = pure ()

main :: IO ()
main = do
  [ path ] <- getArgs
  let file = GIO.fileFromPath $ B.pack path
  _ <- Gtk.initGUI
  fileMonitor <- GIO.fileMonitor file [] Nothing
  window <- Gtk.windowNew
  image <- Gtk.imageNew
  Gtk.on fileMonitor GIO.fileMonitorChanged (updateImage image)
  Gtk.set window
    [ Gtk.containerChild Gtk.:= image
    ]
  Gtk.on window Gtk.objectDestroy Gtk.mainQuit
  Gtk.widgetShowAll window
  Gtk.mainGUI