[bug #64206] [mm] indexing system paginates badly

[G. Branden Robinson]

URL:
  <https://savannah.gnu.org/bugs/?64206>

                 Summary: [mm] indexing system paginates badly
                   Group: GNU roff
               Submitter: gbranden
               Submitted: Wed 17 May 2023 09:02:57 AM UTC
                Category: Macro mm
                Severity: 3 - Normal
              Item Group: Incorrect behaviour
                  Status: None
                 Privacy: Public
             Assigned to: None
             Open/Closed: Open
         Discussion Lock: Any
         Planned Release: None


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Follow-up Comments:


-------------------------------------------------------
Date: Wed 17 May 2023 09:02:57 AM UTC By: G. Branden Robinson <gbranden>
Affects groff 1.22.4.


$ cat EXPERIMENTS/use-index.mm 
.INITI N myindex
.P
This is my document.
.IND "first item"
.IND "item, first"
.bp
.P
Here is some more stuff.
.IND "second item"
.IND "item, second"
This concludes our regularly scheduled programming.
.INDP
$ mmroff -Tascii EXPERIMENTS/use-index.mm | cat -s

                                   - 1 -

       This is my document.

                                   - 2 -

       Here  is  some  more  stuff.   This  concludes our regularly

                                   - 3 -

       scheduled programming.

                                   - 4 -

                                  INDEX

       first item      1
       item, first     1
       item, second    2
       second item     2

                                   - 5 -



I see two problems here.

A.  The page is being broken before the index without flushing the pending
output line first.  This smells like a missing `br` request to me.

B.  The page is being broken after the index even if there is no further
content.

One can apparently redefine `TYIND` to get around the first problem.  It would
be better to use `TXIND` for this purpose, and if it is not defined, call `SK`
(or something similar) as the fallback for `TYIND` currently does.


.de INDP
.ie \\n[Ref] .tm .\\\\" Index: \\*[ind*file]
.el \{\
.       if !\\n[Cp] .pg@next-page
.       \" print INDEX
.       \" execute user-defined macros
.       if d TXIND .TXIND
.       ie d TYIND .TYIND
.       el \{\
.               SK
.               ce
\\*[Index]
.               SP 3
.               2C
.               nf
.       \}
'       so  \\*[ind*file]
.       ie d TZIND .TZIND
.       el \{\
.               fi
.               1C
.       \}
.\}
.rm ind*file
..


It's a shame the default operation wastes a page at the end of the document in
(what I assume is) the common case of having no material in the document after
the index.  (I assume not _everybody_ sticks on a colophon or whatever.)

Possibly `INDP` could take a pair of arguments controlling whether the page is
broken before and after, respectively.  It would of course pass these
arguments to the appropriate hook macros.







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