[Groff] tbl peculiarity

[Werner LEMBERG]

Folks,


if you have a table like this and process it with -Tascii:

  .ll 40n
  .TS
  tab(;);
  lw(10n) l lw(10n).
  test;T{
  test
  T};test
  .TE

What's the expected width for the middle column?  If you read the
documentation, you could think that the column width is 10n too, using
the formula LxC/(N+1) for blocks which don't have a `w' modifier
(L=40n, C=1, N=3).  However, you get a different result:

  test         test   test

Since the column separation is 3n it can easily be seen that the
middle column width is 4n.  BTW, heirloom tbl gives exactly the same
result.

The solution is easy, but not really documented: The line width is
indeed set to 10n while processing the block diversion, but the
*actual width* of the diversion (given in register \n[dl]) is used
finally.

I'll update the documentation accordingly.


    Werner