Re: Parallel Typesetting

[Douglas McIlroy]

I don't see how to typeset a multilingual text
parallel by page strictly within groff.
However, suppose

1. the input comes from two different files
that contain synch points.
2  corresponding synch points must appear
on facing pages.
3. segments between successive sync points
always fit on one page.

Then a small non-troff program can merge
synchronized segments alternately from the
two files.

To process the merged file, direct segments
by pairs into diversions named, say,
A1, B1, A2, B2, ... When the sums of lengths
of either Ai or Bi overflow a page, emit
the diversions in order A1, A2 ... .bp
B1, B2 ... .bp. Rename the overflowing pair
A1, B1 and continue.

Synch-point macros end, measure, and
start diversions, invoking an overflow
macro as necessary.