bugGNU troff - Bugs: bug #61507, want mechanism for more reliable...

 
 

bug #61507: want mechanism for more reliable absolute vertical positioning

Submitter:  Dave <barx>
Submitted:  Fri 19 Nov 2021 09:40:19 AM UTC
 
Category:  Core Severity:  1 - Wish
Item Group:  Feature change Status:  Need Info
Privacy:  Public Assigned to:  None
Open/Closed:  Open Planned Release:  None
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Mon 28 Feb 2022 10:51:06 PM UTC, comment #6: 

Thanks, Dave.

I tried to cover some of this material in an earlier commit.

commit 1228acc430b2b9638c598a223496ceebfed778af
Author: G. Branden Robinson <g.branden.robinson@gmail.com>
Date:   Thu Feb 3 04:05:14 2022 +1100

    [docs]: Present several fundamental concepts.

    * doc/groff.texi (Page Geometry):
    * man/roff.7.man (Concepts): Add new node/section defining concepts.
      - device resolution
      - basic units
      - drawing position
      - text baseline
      - page offset
      - vertical spacing
      - vee
      - page break

G. Branden Robinson <gbranden>
Project Administrator
Mon 28 Feb 2022 08:00:59 PM UTC, comment #5: 

comment #4:

> 1) the escape sequence '\v' is for local motions (are contained within a
> line, see CSTR #54, paragraph 11.1).
>   The absolute position indicator '|' does not make sense there.


The groff manual says that \v can take the | modifier; it describes \v as: "Move vertically; usually from the current location on the page (if no absolute position operator '|' is used)."

> 2) The absolute position '0' (zero) is the first usable printable line,
> not the distance from the edge of the paper.
> The edge can't be a printable line.


Thank you, this is useful information, though it seems to apply more to bug #60820, which seeks to clarify how | works, than to this bug, which requests a reliable way (separate from |, which has an entrenched troff history) to measure from the page boundary.

Dave <barx>
Project Member
Mon 14 Feb 2022 02:41:52 AM UTC, comment #4: 

  Some comments:

1) the escape sequence '\v' is for local motions (are contained within a
line, see CSTR #54, paragraph 11.1).
  The absolute position indicator '|' does not make sense there.

2) The absolute position '0' (zero) is the first usable printable line,
not the distance from the edge of the paper.
The edge can't be a printable line.
Traps at position '0' are thus always sprung.

  A test case

.pl 5v
.vs 10p
.ps 12
Word
.sp |0c
Second

Bjarni Ingi Gislason <bjarniig>
Wed 24 Nov 2021 07:34:12 AM UTC, comment #3: 

comment #2:

> Rather conceitedly, I like to think of myself as somewhat above novice level, but I still find the vertical "|" semantics unintelligible.


Fair point--I also feel my grasp on them is not quite solid.  Once I've done my experiments and written my planned "Drawing Position" Texinfo node, maybe that will change.  Maybe I should have said "non-masters".  :D

G. Branden Robinson <gbranden>
Project Administrator
Wed 24 Nov 2021 06:40:42 AM UTC, comment #2: 

Rather conceitedly, I like to think of myself as somewhat above novice level, but I still find the vertical "|" semantics unintelligible.

Dave <barx>
Project Member
Sat 20 Nov 2021 10:28:10 AM UTC, comment #1: 

Thanks for logging this, Dave.

Marking as "Need Info" since there is still some design work to do.  I have some ideas coming together regarding a "Drawing Position" section for Chapter 5 of our Texinfo manual.  Possibly, once I actually get that composed and pushed, it can help continue the discussion from a common basis of understanding (since I'm sure people will point out any erroneous claims I might make), and even if it doesn't do that, a presentation of how the page geometry is discretized might make the weird semantics of "|" more intelligible to novices.

G. Branden Robinson <gbranden>
Project Administrator
Fri 19 Nov 2021 09:40:19 AM UTC, original submission:  

The | modifier for absolute vertical positioning is less than ideal.

One drawback, pointed out in bug #60820, is that it is not quite the absolute-position indicator it purports to be, when used with, e.g., the \v escape.

Another -- pointed out in an October email thread (http://lists.gnu.org/r/groff/2021-10/msg00016.html) and, as of Sunday's commit f7bbcd8f, documented in Texinfo (though alluded to for many years before that, by the existence of the example "y-from-top-down" macro in the .sp section) -- is that when used in an .sp request, the motion unavoidably goes 1v further down than requested.  (There is a related issue with .mk/.rt.)

Brainstorming took place in the aforementioned thread, but whether the new mechanism should be a new request, a new distance modifier akin to |, or something else, has not been decided.

Dave <barx>
Project Member

 

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    Date Changed by Updated Field Previous Value => Replaced by
    2021-11-20 gbranden StatusNone Need Info
    2021-11-19 barx Carbon-Copy- Added ptpi

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