From: Ken Whistler (email@example.com)
Date: Mon May 16 2011 - 18:44:07 CDT
On 5/16/2011 3:33 PM, fantasai wrote:
> I'd drop the "using digital layout" part but otherwise, yes, that's a
> good definition. If we had such a property it would need to state for
> each script:
First of all, the Unicode Standard does not have any formal notion of
properties for *scripts*. The properties in the Unicode Character Database
are properties for *characters* (and/or code points).
That doesn't mean that there isn't a need for such, or that people don't
in practice talk about scripts as if they had enumerated properties,
both in the text of the standard (i.e., talking about alphabets versus
abjads versus abugidas versus logosyllabaries, etc., talking about
complex scripts versus simple scripts, talking about script layout
directionality, talking about "Indic scripts") and in informal discussion
about the standard and its implementation.
But the pushback you are encountering in this thread stems in part
from the fact that the Unicode Standard is *not* a writing system
or orthographical standard, and does not attempt to standardize issues
of text layout, beyond the minimum required for plain text layout
legibility. Hence the systematic lack of properties relating to
any issues of vertical layout.
Even the horizontal directionality property values of the Bidi_Class
are *character* properties, not script properties. And although
the standard talks about "right-to-left scripts", what that really means
is scripts whose alphabetic characters have bc=R (or bc=AL) predominantly.
> - what vertical directionality it has (if any). Horizontal scripts
> would be none. Most vertical scripts would be top-to-bottom. Going
> by Michael Everson's answer, Ogham would be bottom-to-top.
Ogham is not bottom-to-top. It is left-to-right in preferred directionality.
(Which again is spelled out by its alphabetic characters having bc=L.)
It only has an appearance of bottom-to-top in that in the monumental
ogham inscriptions, the convention was to start at the bottom lefthand
side of a stone, incising along the edge, then across the top edge,
and then continuing down the righthand side. This is more like Andrew's
example of laying out text in a spiral -- it is a conceptual line
laid out along the various edges of a three-dimensional object.
> - If it has vertical directionality, how the text is transformed from
> horizontal to vertical, i.e. are grapheme clusters rotated (laid
> sideways wrt horizontal) or translated (kept upright like CJK).
I don't think that is sufficient. You also need to answer the question
of how scripts which on their own are always laid out in horizontal
lines behave when mixed laid out in vertical text as text inclusions.
This is the problem of which way to rotate Latin (or other) text
when incorporated in Japanese (or Chinese) text laid out vertically.
But that might be answered in terms of the predominant direction
of the script in question. So a left-to-right script will typically be
rotated 90 degrees clockwise, while a right-to-left script will
typically be rotated 90 degrees anti-clockwise, so that the overall
text flow will match the vertical flow of the embedding text. To do
otherwise adds bidi complexity on top of the horizontal -> vertical
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