Re: [NTG-context] Blank page added after pagecolumns

16 May 2020

      All right, I've found a tentative solution that appears to work in all
cases, but I'd like to know more about why the code I'm patching was
implemented in the first place, because I don't want to break anything
else. According to the code in page-pcl.mkiv, the \stoppagecolumns macro
has two implementations, \page_col_stop_yes and \page_col_stop_nop. The
choice of which implementation is used is determined by which of two
implementations of \startpagecolumns (\page_col_start_yes
and \page_col_start_nop) is used. That choice, in turn, is made in
the \page_col_start macro, in the following lines:

```
\c_page_col_n_of_columns\pagecolumnsparameter\c!n\relax
   \ifnum\c_page_col_n_of_columns>\plusone
     \expandafter\page_col_start_yes
   \else
     \expandafter\page_col_start_nop
   \fi
```

so if the number of columns (i.e., the n option for the
pagecolumns environment) is more than one, the "yes" implementation of the
start and stop commands is used.

But this seems wrong. The naming convention for the two implementations
("yes" and "nop") suggests that they should be related the parameters
"page=yes" and "page=no" (hence, no page, which is what I think "nop"
abbreviates), but the choice of which implementation to use is determined
not by the page parameter, but by the n parameter. Is this an error in the
code, or am I just understanding this incorrectly? Is there some reason why
a layout with more than one column would need special instructions to add a
blank page after stopping the environment?

In any event, I was able to solve the problem by patching the
\page_col_start_yes macro to invoke the \page_col_start_nop macro as
follows:

```

\unprotect

\def\page_col_stop_yes

{\page_col_stop_nop}

\protect
```

With this fix, the MWE I provided works regardless of which column the text
ends in. I'm content to consider the problem solved, but I would certainly
appreciate any feedback on my thoughts and questions about page-pcl.mkiv.

Joey

On Thu, May 14, 2020 at 5:03 PM Joey McCollum 
wrote:
...
Okay, I think I'm getting close, but I'm not quite there yet. The
pagecolumns source code is found in page-pcl.mkiv (
source.contextgarden.net/tex/context/base/mkiv/page-pcl.mkiv), and in
that code, the \page_col_stop_yes macro seems to have something to do with
the issue:
```
\unexpanded\def\page_col_stop_yes
  {\column % \page_otr_eject_page
   \page
   \endgroup
 % \setupoutputroutine[\s!singlecolumn]%
   \page_otr_command_set_vsize
   \page_otr_command_set_hsize
   \page
   \endgroup}
```
If I redefine this macro in my MWE as follows, I can remove the extra page
that is added when the last page ends with text in the last column:
```
\unprotect
\def\page_col_stop_yes
{\column %\page_otr_eject_page
%\page
\endgroup
% \setupoutputroutine[\s!singlecolumn]%
\page_otr_command_set_vsize
\page_otr_command_set_hsize
%\page
\endgroup}
\protect
```
Commenting out the \page calls does the trick in this case, but now, if
the last page ends with its text in a column before the last one, then the
last page is not typeset at all, and a blank page takes its place.
On Sun, May 10, 2020 at 8:34 PM Thangalin  wrote:
...
Bump.
See also: https://tex.stackexchange.com/q/542993/2148
On Mon, May 4, 2020 at 11:46 AM Joey McCollum
 wrote:
...
After continuing to look into this a bit, I noticed that a similar
issue involving the insertion of a blank page after a columnset environment
has been discussed on the mailing list in the thread "Blank page inserted
when text reaches column's end" (dated 08 Dec 2019). In that thread, a
proposed solution was to redefine the \page_grd_stop macro found in
page-cst.mkiv as follows:
...
```
\unprotect
\def\page_grd_stop{%
  \endgraf % needed, else wrong vsize in one par case
  \vfill % otherwise weird \placenotes[endnotes]
  \page_grd_command_set_vsize % needed
  \penalty\c_page_otr_eject_penalty
  %\page_grd_command_flush_page
  \page_otr_fill_and_eject_page
  \page_grd_command_set_vsize % why here
  \egroup
  \page_otr_command_set_vsize
  \page_otr_command_set_hsize
}
\protect
```
Unfortunately, this approach was found to have potential issues in that
thread, and it does not fix the problem with pagecolumns in my MWE. Are
pagecolumns commands aliased to pagegrid commands like columnset commands
are, or are they defined somewhere else? I checked page-col.mkiv, but it
seems to be too short to be the file that defines pagecolumns behavior.
...
Joey
On Sat, May 2, 2020 at 11:46 AM Joey McCollum <
...
...
I recently found the pagecolumns manual (
http://www.pragma-ade.com/general/manuals/pagecolumns.pdf), and in
several of the examples (including those for side floats and footnotes),
...
...
Joey
On Tue, Apr 28, 2020 at 1:40 PM Joey McCollum <
jmccollum20140511@gmail.com> wrote:
...
...
I am typesetting a document using pagecolumns to ensure that my
footnotes are set ragged-bottom in columns. I have observed some unexpected
behavior whenever the last column on a page is left incomplete: a blank
...
...
...
```
\starttext
\startpagecolumns[n=2]
\dorecurse{3}{\par\input zapf}
\stoppagecolumns
\stoptext
```
I typeset this using ConTeXt version 2020.03.10, as released with
TeXLive 2020. Notably, if \dorecurse{3} is changed to \dorecurse{2} or
\dorecurse{6} (so that the text ends in the first column of a page), then
jmccollum20140511@gmail.com> wrote:
the addition of a blank page after the end of the pagecolumns environment
also seems to occur. So when the manual says, "We always start at a new
page and end on a new one," does it mean that this is a feature of
pagecolumns? And if so, is there any way to disable it? I have no problem
with a page break after the end of the pagecolumns environment, but an
empty page added after the break seems unnecessary. I checked for a wiki
page on the \definepagecolumns command to get more information on its
accepted inputs, but there doesn't appear to be a page for this command.
page is added at the end of the document. A minimal working example follows:
there is no problem. I have tried to fix this by specifying page=no in the
\startpagecolumns arguments, but it did not change anything. Is there
something else I am missing?
...
...
...
Thank you,
Joey
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If your question is of interest to others as well, please add an entry to
the Wiki!
maillist : ntg-context@ntg.nl /
http://www.ntg.nl/mailman/listinfo/ntg-context
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archive  : https://bitbucket.org/phg/context-mirror/commits/
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