...
On the subject of implementing Heirloom troff's paragraph-at-once
formatting and associated goodies, I wrote Gunnar about it. Here's
what he had to say:
"Sorry, but I haven't done anything related to those topics for
several years. I've never looked much into the groff code. From
what I remember, the fact that it was in C++ alone made it so
different though that there were few if any similarities at a
superficial glance.
Implementing paragraph based line breaking took me several weeks
back when I was intimately familiar with the surrounding code.
The algorithm itself is complex and takes some time to understand.
And then there is the task of rewriting large portions of an
existing environment that assumes line based formatting."
Which is by way of saying it's going to be a big job, and we *must*,
as a group, figure out how to attract programmers interested in
tackling it. Line-by-line formatting is, IMO, the single biggest
stumbling block to more widespread adoption of groff as a
typesetting system.
...
GROFF MISSION STATEMENT, 2014, 2nd draft
...
Backend
The biggest challenge facing groff is the implementation of
paragraph-at-once formatting based on the Knuth-Plass algorithm.
Already present in Heirloom troff, this is a high-priority next step
in groff's evolution, along with the addition of typesetting
features modelled after Heirloom troff.
...