On Fri, Jun 02, 2023 at 01:35:22PM -0500, G. Branden Robinson wrote: > Subject: drawing commands have no impact on diversion height > > I find myself offended by the fact that \D drawing commands update the > diversion width register `dl`, but have no impact on the diversion > height register `dn`. > > Nevertheless, all of DWB 3.3, Heirloom Doctools, and GNU troff behave > this way. > > But it seems pretty unhelpful to me. If a drawing command inside a > diversion increases its maximum vertical extent, the formatter should > tell me that, but it doesn't. Instead it appears to count only text > baselines. > > Can someone defend this behavior?
I haven't seen any responses to this yet, but it seems pretty
important to me.
As far as I can tell, the height of a diversion is only
calculated by \n[.v] values. If spacing is reversed within the
diversion and the end of the diversion occurs before the
high-water mark in the diversion, \n[dn] seems to contain only
the difference between the vertical starting point of the
diversion and the vertical position of the last output line.
Nothing I tried with either \D commands or even \H (to
artificially increase the height of the current font) made a
difference to the value of \n[dn]; it only registered values in
terms of \n[.v].
I modified the following for testing:
> Hello, world.
> .sp
> Pardon me a moment while I create a diversion.
> .br
> .di DD
> \D'c 1i'
> .br
> .di
> Okay, I'm back.
> .sp
> Now, let's have a look at that diversion;
> it's \n(dn tall by \n(dl wide. \" 12000, 72000 in PostScript
> .sp 0.5i-0.5v
> .DD
> .sp 0.5i
> All done.
------------------------------------------------------------
.sp 1i
Hello, world.
.sp
Pardon me a moment while I create a diversion.
.br
.di DD
' \" \D'c 1i'
.nf
\H'72'This is a test.\H'0'
Line 2 of this test.
.sp -2v
Line 3 of this test.
.br
.di
.fi
Okay, I'm back.
.sp
Now, let's have a look at that diversion;
it's \n(dn tall by \n(dl wide. \" 12000, 72000 in PostScript
.sp 0.5i-0.5v
.DD
This line starts after the output of the diversion.
.sp 0.5i
All done.
------------------------------------------------------------
Note the .sp -2v, which caused the diversion to end above the
high-water mark and resulted in \n[dn] registering only 1 line
height.
*But* the ending of the diversion seemed to swallow the EOL of
the diversion's last output line, or the .br, or something. As a
result, the first line after the diversion acts as if it's a
continuation of the input to the diversion (see attached PS
file). If I add a .br immediately after the .DD, I get the
expected results, but that seems unnecessary and unpredictable to
me, almost as if a .chop got silently applied by .di
Using groff 1.22.4 on Debian Bullseye.
-- Steve
--
Steve Izma
-
Home: 35 Locust St., Kitchener, Ontario, Canada N2H 1W6
E-mail: si...@golden.net phone: 519-745-1313
cell (text only; not frequently checked): 519-998-2684
==
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therefore never scrutinize or question.
-- Stephen Jay Gould, *Full House: The Spread of Excellence
from Plato to Darwin*, 1996
test.ps
Description: PostScript document
