support identical page numbering as option for print/online pdf

[kcrisman]

An interesting case not currently supported by PTX is to have a version of the "electronic pdf" (with lots of hyperlinks, no page numbers for hyperlinks, etc.) but with identical page numbering to a two-sided one suitable for printing (margins alternating, blank pages so chapters begin on the right-hand side, etc.).

The idea behind this is the classroom case where some students are using a tablet, where the one-sided pages really are necessary to avoid distraction, but some students will have a printed copy, where it's nice to have the slightly wider margin at the binding edge. Students find it (in my experience) much more natural to go to a page number than a specific theorem or even chapter number, so having the same page numbers is crucial.

My solution was to use the standard pdf compiling, but to add the following code from a very helpful Tex.SE post in the preamble and then (manually) switch the document class to twoside after compiling the oneside version.

\makeatletter
% Update \cleardoublepage to be similar in oneside and twoside
\if@twoside\else
  \def\cleardoublepage{%
    \clearpage
    \ifodd\c@page\else
      \hbox{}\newpage
      \if@twocolumn
        \hbox{}\newpage
      \fi
    \fi
  }
\fi
\makeatother

Plopping this in just before \begin{document} worked well.

---

(@rbeezer suggested in drop-in hours today that this would be useful to have as an issue for possible eventual usage, so here it is.)

[rbeezer]

Review potential attribute value names at thread starting with:

https://groups.google.com/g/pretext-support/c/Yk129zjN_Hc/m/VfVpFOaLBQAJ

[kcrisman]

👍

[rbeezer]

See #1020 as well.

[rbeezer]

This has effectively happened at #2034. Thanks, @kcrisman for your work on this - @jjrsylvestre simply got in line ahead of you by working up a pull request, so I went with that. If any of that misbehaves, we can always revisit the solution here.

[kcrisman]

This has effectively happened at #2034 https://github.com/PreTeXtBook/pretext/pull/2034. Thanks, @kcrisman https://github.com/kcrisman for your work on this - @jjrsylvestre https://github.com/jjrsylvestre simply got in line ahead of you by working up a pull request, so I went with that. If any of that misbehaves, we can always revisit the solution here.

I had already forgotten I'd done this issue! I'm sure the other solution will be fine too, and a great addition.

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