Re: [Groff] .mk/.rt not work across a page?

[Mike Bianchi]

On Thu, Sep 04, 2014 at 03:35:25PM +0100, Anton Shterenlikht wrote:
> >Date: Thu, 4 Sep 2014 12:31:09 +0200 (CEST)
> >From: Carsten Kunze <address@hidden>
> >To: address@hidden
> >
> >You could try
> >
> >.mk A
> >
> >and on the next page
> >
> >.sp |\nA
> >
> >(have not tested that.)
> 
> In UNIX Text Processing, p. 462, the advice is
> 
> .mk Q
> .sp |\nQu
> 
> Neither your form nor theirs (with "u" at the end) work.
> I guess this is because this feature is used
> to affect vertical position on a single page,
> not across pages.
> 
> Anton

If you are doing this at the top a page, the "no-space mode" is probably turned
on.   See  .ns  and  .rs  in  man 7 groff . 

In theory, issuing an  .rs  should make it work, but I find with the  mm
macros it is not reliable.

Rather than figuring out precisely why it doesn't alway work, I just output
a  \&  (Non-printable, zero-width glyph) which seems to reliably cancel the
no-space mode and then it does work.  E.g. 

        \&
        .nr Q 0.5i
        .sp |\n[Q]u
        Hi there


(I put all my register, string and character references inside [ ] so they
stand out.  Just a matter of style.)

Give it a try.
I used:
         groff -mm /tmp/i  | gv -
for these experiments.


>>  Gurus of groff internals <<    look at this!
Using MM macros.

        \&
        .nr Q \n[.ns]
        .sp |0.5i
        Q = \n[Q]

prints
        Q = 1
That says to me "no-space mode is ON".  Yes?

Now
        .rs
        .nr Q \n[.ns]
        .sp |0.5i
        Q = \n[Q]

Prints
        Q = 0
1.0 inch down from the top edge, which is where MM normally starts normal text.
That says to me "no-space mode is OFF",
so position of the  Q = [01]  text is opposite of what I expect.
Am I confused about something?


Oddly, this works as expected.
        .br
        .rs
        .nr Q \n[.ns]
        .sp |0.5i
        Q = \n[Q]

Prints
        Q = 0
0.5 inch down from the top edge.


So there is some odd relationship between no-space and whether the line buffer
has been flushed?

What is going on?


-- 
 Mike Bianchi
 Foveal Systems

 973 822-2085

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