🚀 go-pugleaf

Does anyone know how I can get troff to save the current horizontal position
on the output line?  My documentation says that the ".k" register hold the
current input line, which is close to what I need, but it won't compensate for
the filling that takes place when the line is output.  In fact, I don't
understand what use it is to have the horizontal position on the input line.

On a side note, the book "Unix Text Processing" by Dale Dougherty and Tim
O'Reilly mentions an escape sequence "\jx" which is supposed to mark the
horizontal place in the output line in register x (as opposed to "\kx" which
marks the horizontal place in the input line in register x).  My troff (from
Elan) doesn't understand "\j".  Does anyone know of a troff which does
understand this escape sequence?  Considering the large number of errors in
this book, I wouldn't be surprised if no troff has "\j" (I haven't seen this
many errors in a technical book in a long time!).

Thanks in advance,

  Michael Morrell