* Konstantin Sobolev
I'm trying to implement my own LayoutClass which mixes the ideas of IM and CombineTwo. It has to contain some predicate as a part of it's state, which will tell where to put new windows. As I see IM uses WindowProperties for this purpose, but I wouldn't like to use it for 2 reasons: 1. Property essentially duplicates Query Bool. 2. Property isn't flexible enough. For instance, I can't match a window by title substring, while I can easily do it with Query. However, there's one problem (and I guess that's why Property was introduced): Query doesn't derive Read and Show, and as far as I understand it's not so easy to implement them.
You are right.
So what should I use, Query Bool with empty (Read, Show) implementations, losing state between restarts; or Property losing flexibility that I'd like to have?
You should use Property. Concerning flexibility, if you can not discriminate windows by exact matches, it's typically a problem with that application and is a reason to submit a bug report. -- Roman I. Cheplyaka (aka Feuerbach @ IRC) http://ro-che.info/docs/xmonad.hs