On Wed, Aug 29, 2007 at 12:16:35PM -0400, David Roundy wrote:
You can see the problem (yes, I'm spending even more time on this...) in
sendMessage :: Message a => a -> X () sendMessage a = do n <- (W.tag . W.workspace . W.current) `fmap` gets windowset Just (l,ls) <- M.lookup n `fmap` gets layouts ml' <- modifyLayout l (SomeMessage a) `catchX` return (Just l) whenJust ml' $ \l' -> do modify $ \s -> s { layouts = M.insert n (l',ls) (layouts s) } refresh
We read the current layout l, then we call modifyLayout, and if that gives us a new layout, we proceed to update the layout using the return value of modifyLayout. But if modifyLayout itself *already* changed the layout, that change will be lost!
So what we've got is a rather complicated and unchecked constraint on layout behavior. :(
My best guess as to a solution would be to enable a simple locking mechanism such that we can keep layouts from being modified or used while they're already being modified.
I had the feeling that I was hitting a limit but I could not track down its origin. Now I understand the problem. Thanks for your time. I hoped it could be possible to modify the layout, refresh and return the modified layout *within* modifyLayout... I think I'll try to find a solution myself. I doubt I'll actually find it... Andrea