Hey! I'm currently looking into how to re-implement my PositionStore in a way that is more suited to go into xmonad's mainline. As mentioned before, I currently plan to base this on Daniel Schoepe's extensible state patch [1]. Then use a ManageHook to fill the PositionStore with information about windows as they are created. However, I also need to delete those entries once a window is closed again, so that the PositionStore doesn't accumulate junk over time. One way could be to check from time to time (e.g. every time a new window appears) all the entries if the associated windows still exist. But that seems unnecessary expensive. So I was thinking of adding an 'UnManageHook' as a counter part to ManageHooks so that modules from contrib can be notified when a window is unmapped. Any objections against this? Or is there an alternative way, which I didn't consider? Regards, Jan [1] http://article.gmane.org/gmane.comp.lang.haskell.xmonad/8126