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

[Deri James]

Update of bug #64005 (group groff):

                  Status:                   Fixed => Need Info              
             Open/Closed:                  Closed => Open                   

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Follow-up Comment #7:

I think there may be a problem with this fix.

The fix:-

+.\" Wrap the `bp` request so that we disregard the enablement of
+.\" no-space mode, which we enter after displays and equations to
+.\" prevent multiple sources of vertical space (like the DD and PD
+.\" registers) from incorrectly accumulating.  Thus, if the user
+.\" requests a page break, we honor it.  See Savannah #62688 & #64005.
+.als @break-page bp
+.de bp
+.      nr @saved-no-space-mode \\n[.ns]
+.      rs
+.      ie \\n[.br] '@break-page \\$1
+.      el          .@break-page \\$1
+.      if \\n[@saved-no-space-mode] .ns
+.      rr @saved-no-space-mode
+..
+.

In the groff_book the documentation of the .br register has this code
snippet:-

.als bp*orig bp
.de bp
. tm before bp
. ie \\n[.br] .bp*orig
. el ’bp*orig
. tm after bp
..

Very similar, but the break/non-break versions of bp are round the other way.
This seems to cause a problem:-

[derij@pip build (jpeg)]$ printf "
What is Lorem Ipsum?

Lorem Ipsum is simply dummy text of the printing and typesetting industry.
Lorem Ipsum has been the industry's standard dummy text ever since the 1500s,
when an unknown printer took a galley of type and scrambled it to make a type
specimen book. It has survived not only five centuries, but also the leap into
electronic typesetting, remaining essentially unchanged. It was popularised in
the 1960s with the release of Letraset sheets containing Lorem Ipsum passages,
and more recently with desktop publishing software like Aldus PageMaker.
.bp\nPage 2"|groff -ms -a

Results in:-

<beginning of page>
What is Lorem Ipsum?
Lorem Ipsum is simply dummy text of the printing and typesetting industry.
Lorem Ipsum has been the industry's
standard dummy text ever since the 1500s, when an unknown printer took a
galley of type and scrambled it to make
a type specimen book. It has survived not only five centuries, but also the
leap into electronic typesetting, remaining
essentially unchanged. It was popularised in the 1960s with the release of
Letraset sheets containing Lorem Ipsum
  
<beginning of page>
 -2- 
passages, and more recently with desktop publishing software like Aldus
PageMaker. Page 2

The partial line ending in "Aldus PageMaker" should be on page 1, it isn't. I
have not looked at the regression test associated with this bug, but it does
not seem to detect this issue.


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