[bug #64005] [ms] fix for Savannah #62688 suppresses page breaks between displays

[G. Branden Robinson]

URL:
  <https://savannah.gnu.org/bugs/?64005>

                 Summary: [ms] fix for Savannah #62688 suppresses page breaks
between displays
                   Group: GNU roff
               Submitter: gbranden
               Submitted: Wed 05 Apr 2023 11:02:47 PM UTC
                Category: Macro ms
                Severity: 3 - Normal
              Item Group: Incorrect behaviour
                  Status: Confirmed
                 Privacy: Public
             Assigned to: gbranden
             Open/Closed: Open
         Discussion Lock: Any
         Planned Release: None


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Follow-up Comments:


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Date: Wed 05 Apr 2023 11:02:47 PM UTC By: G. Branden Robinson <gbranden>
The fix for bug #62688, to get more authentic-to-AT&T-ms spacing between
displays, unfortunately also defeats user-requested page breaks between
displays.

This was [https://lists.gnu.org/archive/html/groff/2023-04/msg00022.html
reported by Michał Kruszewski to the groff development list].

Here is some sample input.


.LP
Hello.
This is page \n%.
.DS
display goes here
.DE
.bp
.LP
This is page \n%.
.pl \n(nlu


All of groff 1.22.4 ms, DWB 3.3 ms, Heirloom Doctools ms, and Version 7 Unix
ms honor the page break.  groff Git does not.

I had implemented the fix by simply kicking the formatter into no-space mode
after displays and equations.  It was the simplest solution I could think of.

Unfortunately, it was too simple.

Come up with something better, and add a regression test.

An only slightly less simple remedy might be to wrap the `bp` request, forcing
no-space on, invoking the "real" `bp`, and then restoring no-space mode (if it
was enabled).







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