[tex-eplain] Problem with marks and \doublecolumns

[Karl Berry]

Hi Laurence - I'm close to releasing a new version of Eplain (nothing
big, just minor fixes and updates), and thought I'd finally look at the
\mark + \doublecolumns bug you reported last August.
https://tug.org/pipermail/tex-eplain/2021/001001.html
https://tug.org/pipermail/tex-eplain/2021/001003.html

In short:

    I think it would be nicer if the first version, with \topmark, would work. 

I agree.

    However, if the multiple columns macros use \output, 

Which they do. Calling \singlecolumn or whatever \...columns invokes
\output to collect the material so far.
    
    I doubt that it would be possible to solve this problem with a
    reasonable amount of work.

I agree, unfortunately. It's not at all clear to me how to preserve the
mark information in the face of all the crazy partial pages that Eplain
tries to manipulate. (Just reading the comments in xeplain.tex about it
gives the flavor of how painful it all is.)

Presumably it is possible somehow, but unfortunately it's been a lot of
years since I first wrote that code, and lots of other people have
changed it since to fix the succession of bugs related to it, so it
would be quite a project to look into it now.

If you or someone else wants to undertake it, I'm all for it, and more
power to you. But I'm afraid this one is going to remain unfixed by me.
Sorry.

Best,
Karl