- Is it worth splitting off display-font independent stuff
  from display dependent stuff. How do we do that?

- Can we abandon XIM? Can we support XIM in backwards-compatibility
  mode? Just in RootWindow mode?

- Are input methods windowing system independent? What do
  we gain/lose?

- Do we need to worry about glyph changes at line breaks?

- Do we ever need to break clusters on line breaks?

- Do input methods need attributed strings for displaying
  feedback? If so, do we build such support into GDK?
  Into GTK+?

- How do we index positions in a string 
  (By character? By byte?)