Re: [Groff] widow/orphan control

[Werner LEMBERG]

> If you prefer to have paragraphs demarcated by
> blank lines, you can set the blank line macro
> 
> .blm pp
> 
> but then *all* blank lines would start a new paragraph.

Not necessarily.  Just use the `.ns' request to disable further
spacing if there are multiple blank lines.

> The first one (the one that doesn't work) is to use an
> "active" margin character to increment a line counter.
> But it seems that the character is only evaluated at the
> .mc request, and not again when it is actually used, so the
> counter gets incremented only once, and not with every line.
> [Is it desirable to change this behaviour?  Opinions?]

I won't change that.  The right way is to introduce the already
discussed `beginning-of-line macro' in GNU troff.

> (The usual bottom-margin page traps can't prevent a line
> with excessive height or depth from intruding into the bottom
> margin, because the trap is sprung *after* the line is output,
> and then it's already too late.  This seems to be a fundamental
> flaw in the design of troff.  It would be much more useful if
> the trap were sprung *before* a line sweeping beyond the trap
> position were output.  [Am I right in assuming this won't be
> changed in the near future?])

You are right, I won't change this.  Instead, I'll probably activate
the widow protection support in gtroff (see the WIDOW_CONTROL macro in
the source files).  The basic idea is to save the last (formatted)
output line(s) and defer its output if necessary -- a kind of built-in
diversion.

Unfortunately, it doesn't work yet in all cases; since the saved
output lines are never again processed, there is no interaction with
data emitted by traps.  For example, the effect of `.ns' invoked in a
header macro is delayed until saved lines are already output; with
other words, `.ns' suppresses vertical spacing at the wrong place.


    Werner