These changes are interesting and I don't see any problem with new needs but I think these changes carry some complexities to window system that can kept outside in new programs or libraries. Rio runs in your windows a terminal as default that I think too, and I believe that is possible, to kept outside the window system and called into. (This if I want reduce the code that I known by window system). I can see the need for a window have an owner and stay on the screen only if your owner stays, but I think this feature could be put in a GUI library with a control called Window (a pseudo-window) that can have an owner (other Window). The terminal code (colors etc.) can be put in a terminal program etc. Noborder feature are a small and interesting feature to have within the window system (programs that run inside rio windows can so control entire window look).