getCurrentHeight :: EventM Int
getCurrentHeight = EventM $ do
  heightRef <- asks eventEnvCurrentHeight
  liftIO $ readIORef heightRef
getCurrentHeight :: EventM Int
getCurrentHeight = EventM $ do
  heightRef <- asks eventEnvCurrentHeight
  liftIO $ readIORef heightRef
getCurrentHeight = EventM $ do
  heightRef <- asks eventEnvCurrentHeight
  liftIO $ readIORef heightRef