Emanuel Han via ntg-context schrieb am 28.02.2024 um 20:51:
> Thank you all for your suggestions and contributions to the wiki.
>
> I don't intend to nag, but when looking at what ConTeXt is producing, 
> I need to state that the result is still far away from a properly 
> typeset Japanese text.
>
> So the nihongo script which comes with ConTeXt handles *line breaks / 
> line wrapping*. But the line break rules defined in it need a rework, 
> because they don't follow the standards. The standards are documented 
> here: 
> https://www.w3.org/TR/jlreq/#possibilities_for_linebreaking_between_characters 
> , and all affected characters are listed here: 
> https://www.w3.org/TR/jlreq/tables/table_en3.pdf
>
> We have different rules, depending what kind of character is 
> surpassing the text width (or is in its last position).
>
> Rule 1:
>
> Before closing brackets, closing quotation marks, iteration marks, the 
> Prolonged sound mark and small Kana, line breaking is prohibited.
>
> ’”）〕］｝〉》」』】ヽヾゝゞ々ーぁぃぅぇぉァィゥェォっゃゅょッャュョ etc.
>
> The actual programmed behaviour by the nihongo script is that, if in 
> the position which exceeds the line width,  these characters jump to 
> the next line and take the previous character with them. If they're in 
> the last position of the line, they stay where they are. This 
> behaviour is correct.
>
> Rule 2:
>
> After opening Brackets and opening quotation marks, line breaking is 
> prohibited (but not before).
>
> ‘“（〔［｛〈《「『【
>
> The actual programmed behaviour by the nihongo script is that these 
> characters jump to the next line and take the previous character with 
> them. This behaviour is wrong. They should jump to the next line 
> without taking the previous character with them, just like any regular 
> character. The difference to a regular character is that they jump 
> already when still within the line length, and they're in the last 
> position of the line. The correct behaviour can be seen in LibreOffice 
> Writer in action.

Can you provide a minimal example because this should be correct and if 
not it's a bug.

> Rule 3:
> Comma (tōten), full width comma, full stop
>
> 、，。
>
> The actual programmed behaviour by the nihongo script is that, if in 
> the position which exceeds the line width, these characters jump to 
> the next line and take the previous character with them. This 
> behaviour is wrong.
> They have to be put back to the end of the previous line, but beyond 
> the specified line length. (JIS Z 8125) (Search for "Line adjustment 
> by hanging punctuation" under https://www.w3.org/TR/jlreq/ )
> If they're in the last position of the line, they stay where they are. 
> The correct behaviour can be seen in LibreOffice Writer in action.

This is handled by the protrusion mechanism and enabled with paragraph 
alignment.

> Rules 4, 5, ...:
> Combinations of inseparable characters... (see 
> https://www.w3.org/TR/jlreq/#possibilities_for_linebreaking_between_character 
> ) and eventually more, which I didn't test.
>
> It might be useful to define three scripts nihongo_loose, 
> nihongo_strict and nihongo_very_strict which each implement one of the 
> 3 cases described here: https://www.w3.org/TR/jlreq/#addendum_a
>
> According the *line gap* (Otared uses \setupwhitespace[big], which is 
> exceeding common line gaps), I'd like to quote from 
> https://www.w3.org/TR/jlreq/ :
>
> /It is common that the line gap for the kihon-hanmen is set to a value 
> between half-em spacing and the one em spacing of the character frame 
> used for the kihon-hanmen. Half-em spacing can be chosen in cases 
> where the line length is short, but one em spacing or close to it is 
> more appropriate when the line length is longer than 35 characters./
>
> I like the standard line gap which is provided by ConTeXt, which is 
> equivalent to \setupwhitespace/[0pt]/. Even when using ruby, it works 
> well. I found the best voffset for ruby to be -1.7ex.

The \setupwhitespace setting controls the distance between paragraphs 
but you're looking for the \setuplinespace command.

> The *line adjustment* provided by ConTeXt by default is not meeting 
> the needs for Japanese  (and Chinese) text, which follow a grid 
> pattern. Especially the last line of a paragraph is squeezed, which is 
> "hurting the eye".
> When characters need to jump to the next line due to previously 
> discussed line breaking rules, ConTeXt seems to apply "Line adjustment 
> by inter-character spacing expansion", which is a valid method 
> according to https://www.w3.org/TR/jlreq/#line_adjustment , although 
> "Line adjustment by inter-character spacing reduction" is preferred.
>
> The last point which ConTeXt is missing, when talking about Japanese 
> typesetting, is vertical writing.

Vertical typesetting is possible but only for small text blocks which 
fit on a single page. Typesetting text which spans multiple pages isn't 
supported yet (it was possible ages ago with MkII) because nobody needed 
it yet.

Wolfgang