[latex3-commits] [git/LaTeX3-latex3-latex2e] copyedits-chris: ltpara more temporary local stuff (1bacc248)

[Chris Rowley]

Repository : https://github.com/latex3/latex2e
On branch  : copyedits-chris
Link       : https://github.com/latex3/latex2e/commit/1bacc2484cf06bfe03892f28ebe200bf106925bd

>---------------------------------------------------------------

commit 1bacc2484cf06bfe03892f28ebe200bf106925bd
Author: Chris Rowley <car222222 at users.noreply.github.com>
Date:   Mon Sep 20 13:04:21 2021 +0700

    ltpara more temporary local stuff
    
    Incorporating change from kern to glue


>---------------------------------------------------------------

1bacc2484cf06bfe03892f28ebe200bf106925bd
 base/ltpara.dtx | 27 ++++++++++++++-------------
 1 file changed, 14 insertions(+), 13 deletions(-)

diff --git a/base/ltpara.dtx b/base/ltpara.dtx
index c07e74da..f01b03b2 100644
--- a/base/ltpara.dtx
+++ b/base/ltpara.dtx
@@ -928,7 +928,7 @@
 %    \end{itemize}
 %
 %    Unfortunately, \TeX{} has some (these days) unnecessary
-%    optimisations: if a \cs{vbox} ends and \TeX{} is still in
+%    optimizations: if a \cs{vbox} ends and \TeX{} is still in
 %    horizontal mode it simply exercises the paragraph builder instead
 %    of issuing a \cs{par}. It is therefore necessary for \LaTeX{} to
 %    ensure that this case doesn't happen and all boxes internally
@@ -1034,12 +1034,12 @@
          \mode_if_horizontal:TF {
 %    \end{macrocode}
 %    The final action (before getting to the point where
-%    \cs{tex_par:D} is called) is to add a kern item XXXX DC so that the
-%    primitive is prevented from removing glue (if there was some). If
-%      we don't do this and the
-%    horizontal list ended in several glue items we would end up  with
-%    removing two glue items instead of just the last one, which would be wrong.
-%    We use a kern as that is minimally faster.  XXX DC
+%    \cs{tex_par:D} is called) is to add an extra glue item so that the
+%    primitive is prevented from removing intended glue 
+%    (if there was some). If we don't do this and the
+%    horizontal list ends in several glue items we would end up 
+%    removing two glue items instead of just the last one, which would be wrong.  XXX DC needs more rewriting
+%    We use glue (rather than a kern) so that  is minimally faster.  XXX DC
 %
 %    There is however one other \TeX{} optimization that hurts: in a
 %    sequence like this \verb=$$ ... $$ \par=  \TeX{} will be in
@@ -1052,14 +1052,15 @@
 %    simply goes silently to vmode. Now if we would had added something (to
 %    prevent glue removal) that would look to \TeX{} like material
 %    after the display and so we would end up with an empty paragraph
-%    just containing \cs{parfillskip}.   XXX not needed!! 
+%    just containing \cs{parfillskip}.   XXX not needed!! Bad text also.
 %
-%    We therefore check if the current hlist is empty  XXX DC but add nonempty
-%    (\cs{tex_lastnodetype:D} has the value \texttt{-1} and
-%    only if not we add our kern.  XXX  See DC but use “if so add extra zero skip”
+%    We therefore check whether the current hlist ends with a glue item  XXX DC add nonempty?? 
+%    (\cs{tex_lastnodetype:D} has the value \texttt{-1}) and
+%    if it does then we add an extra zero-length glue item as a guard, 
+%    so that only this extra glue is removed by the primitive.  XXX  See DC too 
 %    \begin{macrocode}
-           \if_int_compare:w 0 < \tex_lastnodetype:D
-             \tex_kern:D \c_zero_dim
+           \if_int_compare:w 11 = \tex_lastnodetype:D
+             \tex_hskip:D \c_zero_dim
            \fi:
 %    \end{macrocode}
 %    To run the \hook{para/after} hook we first end the