shell companion windows

To some extent, it isn't necessary to write a whole new application for the futureshell. What we need is a connection to a "graphical tty" that is associated with the current shell, so that e.g. if I want to offer a preview of an image or show graphical relationships between items, timelines, etc., all I have to do is sending "drawing commands" to that companion window. Where the companion stands, whether it sticks and move along, what's its size, etc. can be managed by the window manager. That may not be as sweet as having "file descriptor #4" ready by default, but that'll certainly be easier to evolve to.