Thanks.

The problem happens in a case where there are no paragraph split between 2 pages. All pars are entirely either in page 1 or page 2 (these numbers are not actual page numbers, but it’s for clarity).

I am trying to create a MWE but it’s not trivial. The situation as far as I understand it is like the following :

I’ve added tracers for vspacing.synchronizepage function.

When page 1 ships, there are 2 paragraphs (1 + 3 lines) still pending because they do not fit in page 1 so they will be shipped in page 2 (I think that what is in texlists.page_head variable). Hence tex.prevgraf which was 0 is set to 4 (see this from traces in output log).

vspacing        > page 4, prevdepth 2.56577pt => 2.56577pt, prevgraf 0 => 4

vspacing        > list glue:topskip hlist:line penalty:userpenalty penalty:userpenalty glue:baselineskip hlist:line penalty:linebreakpenalty glue:baselineskip hlist:line penalty:linebreakpenalty glue:baselineskip hlist:line glue:userskip

Next paragraph after the 2 pending pars I refer to above has a non zero \hangindent and \hangafter (set to -1) and when it starts being processed (in horizontal mode) prevgraf is already 4 so I think this cancels out that hanging (that’s the effect I see in output, there is no indent in 1st line of 3rd par), as IIRC TEX considers par has already 4 lines but in actuality it has 0. If I read correctly the TeXBook, prevgraf value has some impact on \hangafter / \hangindent

The value of \prevgraf affects line breaking only when TEX

is dealing with nonstandard \parshape or \hangindent.

Joseph

De : Hans Hagen
Envoyé le :jeudi 19 juillet 2018 00:00
À : Joseph Canedo; mailing list for ConTeXt users
Objet :Re: [NTG-context] Issues with vertical spacing in simple case

On 7/18/2018 10:33 PM, Joseph Canedo wrote:

> Thanks Hans.

>

> Picked up today beta and some code I have relying on value of

> tex.prevgraf starts breaking. This is lettrine related code that sets

> hangafter for 1st paragraph and eventually subsequent if lettrine is

> larger than 1st par.

>

> I see the function vspacing.synchronizepage() sets prevgraf value I

> guess to avoid bleeding also paragraph lines.

>

> Is there any possibility to get original unchanged tex.prevgraf value,

> possibly using some callback or some other tex.<Something> ?

you cannot rely on prevgraf crossing pages (so you get e.g. 8 at the top

of a page with 5 lines

where/how does it fail

Hans

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