[tex-eplain] TeX--XeT

[terry.s at Safe-mail.net]

Hi Laurence

> > Are you refering to LTR/RTL *directionality*? When languages are typeset RTL, the characters aren't flipped, the text just *runs* RTL ...
> 
> No.  If you rotated the characters by 90° clockwise or counterclockwise and turn a row sidewise to turn it into a column, it will either go up or down, and if you rotate it in the other, it will go the other way.  So, one way, you would have to typeset it rtl and the other ltr.  I haven't tried to visualize exactly what will happen, but in my experience, this sort of thing often doesn't work the way one expects and requires some experimentation.

Ah ... I didn't realize you were discussing vertical text in this case. You're correct the glyphs would have to flip (for text that would normally end up sideways, like English).

With Asian engines, I thought the text flowed vertically (could be a brain fart). Regardless every glyph *in SOME fonts* (my mistake) has a companion specifically designed for vertical typesetting which is a little differnent (I assume just dimensions that look better). All kanji or kana are the exact same width in Japanese. In horizontal text, certain punctuation (like parentheses or brackets) are narrower. The algorithms must insert a little extra glue only on the "outside" of delimiters. (It appears to have less space "inside", which is false, and more space "outside" which is true, so the same space is taken as any other character in the total of glyph and glue (excepting space between sentences or foreign-language words). There is no text-justification (or maybe between sentences electronically). In vertical mode, I forget if punctuation glyphs are the same width as regular characters (if there are companion glyphs) or if that doesn't matter. Where there is extra glue, it obviously goes above or below.

The result is Japanese has no interword spacing. There's a little space before opening- and after closing-punctuation, which are narrower, and around foreign words (represented by a different phonetic syllabary than Japanese particles, etc). There's more space between sentences. Foreign phrases also use a raised dot (typed with a dash, '-') between the individual words.

I'm not highly technical in this fashion as you are, but in my search for pTeX/upTeX documentation, I came across a document on the proper typesettting and electronic design of Japanese, which I read some time ago. I attached it in case you are curious.

It's "pTeX and Japanese Typsetting" by Prof. Haruhiko Okumura 奥村 晴彦, for the Asian Journal of TeX (2008)

Sincerely,
Terry S.
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