My situation is that I'm using Thunderbird and its External Editor plug-in to write mail. When I invoke the external editor, it brings up an emacs window (calling through emacsclient). I have a manage hook that puts emacs windows into a particular workspace, but I don't want e-mail composition emacs windows to go there. I thought I could handle this by looking at an emacs window's WM_NAME in my ManageHook, but unfortunately, it seems at this point that the title is still just "emacs@<myhost>", which is not helpful. It seems that the useful title (which is of the form "<something-or-other>.eml") gets created a little later. So, I thought I would put in a general eventhandler to watch for a property change, and to then do the shift to the appropriate workspace. So, I added handleEventHook = mappend myhandlePropEvent (handleEventHook defaultConfig) to my modifications of the default config. I then have myhandlePropEvent ev = case ev of PropertyEvent {} -> let w = ev_window ev ... Through calls to trace, I can see that I am indeed picking up on the desired event (the change in the window's name), and I have a window (w above) to hand, but I don't know how to do things to it. My cursory examination of the relevant APIs suggested I could do action <- runQuery (doShift "mail") w giving me a handle on an Endo Windowset, but I don't know how to lift that into the X monad (where I have to eventually return $ All True). Can I use the withWindowSet function somehow? Michael