Screwtape at
For my own edification, I'm trying to get work done with an X11 port of the Plan 9 editor sam.
I'm not stressing it particularly hard; I'm just writing documentation so I don't need much more than copy/paste and finding text by regex. Still, I'm already annoyed by the way sam has its own custom window-management system (instead of just opening multiple top-level windows I can manage with my normal window-manager), and its own custom clipboard (Both of those are true to the original Plan 9 version, although the custom-window-management thing is slightly more idiomatic there).
I keep wondering how difficult it would be to try and bolt structural-regular-expression handling and multiple-cursors onto something like a GTK text-box widget...