[latexrefman] node \par

[Vincent Belaïche]

Thanks, I did an update to the English to clarify this. I also
clarified that the paragraph separator can be of serval blank lines,
and these lines may contain blanks (not be strictly empty).
Double checking the English is welcome.
   V.

Le mer. 11 août 2021 à 03:26, Karl Berry <karl at freefriends.org> a écrit :
>
>     ``horizontal mode'' and ``unrestrcited horizontal mode'' are
>     synonyms. Simlarly ``vertical mode'' and `\outer vertical mode''. The
>     latters are just as opposed to restrcited horizontal mode, resp. inner
>     vertical mode.
>
> Yes.
>
> LaTeX's renaming of TeX's modes is one of the most irritating and
> unnecessary things done by Lamport, IMHO. It's just a constant source of
> confusion, as far as I can see.  I've never looked at what's said in
> latex2e.texi about them. I don't doubt additional clarity would be welcome.
>
>     @dfn{Paragraph mode} is what @LaTeX{} is in when processing ordinary
>     text.  It breaks the input text into lines and breaks the lines into
>     pages.
>
> Well, "paragraph mode" is simply an unclarity introduced by Lamport. It
> is true that the default operation of (La)TeX is to read words, break
> them into lines of paragraphs, and break the lines into pages, which is
> what he's trying to describe. However, this conflates what's really
> going on, which is two different things, as you say: horizontal mode
> (words into paragraphs) and vertical mode (lines into pages). So as soon
> as you get beyond the most superficial level of understanding how TeX
> works, it just makes things things to speak of this "paragraph mode".
>
> However, since Lamport described it this way, it is hard to say what to
> do in latex2e.texi.
>
>     paragraph line breaking process
>
> It's not during the breaking-words-into-paragraphs per se, but then the
> line breaks have been chosen and the lines are being added to the page
> (aka "main vertical list").
>
>     TeX keeps track of the potential good break points positions.
>
> When a paragraph is broken into lines, each line is a potential point
> for a page break. More generally, most items added in vertical mode are
> potential page breaks.
>
>     Then, is there some way to retrieve explicitely these good positions
>
> Not at the TeX level (except maybe in LuaTeX), but TeX will output every
> potential page break in the log file if you ask it (% lines and %%
> lines). The TeXbook goes into quite some detail about this.
>
> (I suspect you already know all this, but )
>     https://github.com/olpa/tex/issues/6
>
> To get a page break in the middle of a tall cell, you somehow have to
> make the contents of that cell be at the top level of the page (again,
> the "main vertical list"). That would mean unhboxing the line and
> unvboxing the cell, I'm guessing. It sounds pretty impossible.
>
> In LuaTeX, it may be possible to play around with the boxing after the
> table is built and then trigger the page builder, but I don't actually
> know. --best, karl.