Joey McCollum schrieb am 16.05.2020 um 05:45:
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?
Why do you think "yes" and "nop" are related to the page-key?
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.
You broke now now normal single columns text after the pagecolumns
environment. A better fix is to add a check for the \column command at
the end of the environment and add it only when we aren't in the last
column.
\unexpanded\def\page_col_stop_yes
{%\column % \page_otr_eject_page
\ifnum\c_page_col_current<\c_page_col_n_of_columns
\column
\fi
\page
\endgroup
% \setupoutputroutine[\s!singlecolumn]%
\page_otr_command_set_vsize
\page_otr_command_set_hsize
\page
\endgroup}
Wolfgang
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