I'm recently working on adding support for client-side window decorations, and this should make it easier to add arbitrary widgets into the window frame area. I've got a branch up, but I was intending to wait until it's further along before I post much about it and ask for review. But just figured I'd chime in and let you know there's some work going on for this.
Only one question: Why don't we use the window header for the
application menu? IMO the window border has not sense, only a lot of
space without any useful feature (only close and, sometimes, the title)