Re: Vertical BIDI

From: John Cowan (
Date: Wed May 19 2004 - 08:24:34 CDT

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    Andrew C. West scripsit:

    > The only thing that is certain is that Ogham must be rendered BTT in
    > vertical contexts. For Ogham text in isolation this is fairly easy to
    > accomplish by simple rotation, and one could expect "writing-mode
    > : bt-rl" or "writing-mode : bt-lr" to accomplish this in a CSS
    > stylesheet. Whether the columns should run LTR or RTL across the page
    > is another question, although LTR would be simplest to implement as
    > it would only involve rotating a whole block of horizontal LTR Ogham
    > text 90 degrees anticlockwise. At any rate, vertical presentation is
    > a matter for a higher protocol, and not a Unicode matter.

    I think it's clear by now that bt-lr is the Right Thing. (A great pity
    that the Irish monks didn't record horizontal Ogham RTL! If you are
    standing in front of an Ogham-inscribed archway, the curve of the text
    does pass from your right side to your left side (and the same for a
    standing stone if you in imagination flatten out the sides), and the
    monks must have had *some* familiarity with Hebrew or Arabic.)

    > However, Ogham text embedded in Mongolian may be a different matter. If
    > a plain text editor renders everything horizontally, as most do, then
    > both Mongolian and Ogham should be rendered LTR thus <mongolian ogham
    > mongolian>, but if you then select vertical presentation (assuming
    > your text editor has this option) Mongolian should be rendered TTB and
    > Ogham BTT thus <mongolian mahgo mongolian>. I still have no idea as
    > to how this should be achieved. My "hack" of using a custom rotated
    > Ogham font and RLO/PDF codes would achieve the desired result for
    > vertical presentation, but would make the Ogham text RTL for horizontal
    > presentation, which is apparently unacceptable. But what alternatives
    > are there ?

    To introduce a concept of bidi override into stylesheet languages.
    You need something like this anyway to handle the case of lr Latin
    with embedded Han, where the Latin reads BTT and the Han reads TTB.

    Fundamentally, vertical scripts like Han and Mongolian and Ogham have
    an essential vertical directionality and a preferred horizontal one
    (but they can sometimes tolerate the other direction: RTL Han is not
    unknown). Horizontal scripts have an essential horizontal directionality
    and may or may not have a preferred vertical one.

    Long-short-short, long-short-short / Dactyls in dimeter,
    Verse form with choriambs / (Masculine rhyme):
    One sentence (two stanzas) / Hexasyllabically
    Challenges poets who / Don't have the time.     --robison who's at texas dot net

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