<please excuse if this is a double post, but i think the original gots
swallowed on the way to the newsgroup>
I would like to get some feedback on how we should handle glyphs
("letter pictures") when the read-direction attribute is set to Asian or
Mongolian.
In this case glyphs in the "native" script are usually rendered upright,
but words in other scripts, namely in latin alphabet are sometimes
rotated by 90Â clockwise (tilt your head to the right to read). Now, in
unicode there is a "asian-width" property assigned to each symbol
("letter") this property in some way relates to our orientation problem
in that you have narrow, wide, half-width and full-width versions of
US-ASCII characters. And all CJK letters tagged as wide or full-width
are always upright. But the problem is that you cannot say, ok then we
rotate all tagged as narrow or half-width. For one, there are CJK
characters tagged as one of those as well. Then you have Mongolian (any
maybe other Scripts to be upright) that are tagged as narrow but they
need to be upright. Also there are a lot of narrow or ambiguous tagged
misc symbols, punctuation that may have to be upright or rotated or even
depending on context. And finally you would want to write a western word
in upright manner that contains letter that have no wide/full-width
tagged representation (for example containing an umlaut or accent).
For this reason i think for a solution where decision on orientation is
made from the character code (any maybe its neighbour characters) it is
very difficult to define a satisfactory set of rules (let alone a
complete and final solution).
Therefore i now think the "best" approach is to introduce an attribute
that defines the orientation of glyphs. This should be a fontstyle
attribute in order to allow adjusting the representation of a single
word within a longer run in a subtitle text by using the attribute in a
<font> tag, or refer to a style defining the orientation by specifying
that style also in a <font> tag around the word in question.
It is probably safe to ignore that attribute when the read-direction is
Western or Arabic. However if it is not ignored you could create funny
things here, especially if that tag is interpreted to turn the character
90Â counter-clockwise instead of clockwise. Or the attributes could
allow values "+90", "0", "-90" and maybe more instead of a simple
boolean flag such as "upright"|"rotated".
The attribute should not be required, therefore it should default to the
most used setting. I think this is "upright" (else you have to specify
it on all text in CJK/Mongolian when using Asian/Mongolian read-direction!).
If the attribute is to be an amount of rotation rather than a boolean
flag, the default should be "0"(Â) and is interpreted as upright in
Asian/Mongolian read-direction. For simplicity, i think the attribute
values in this case should (at least for a start) be restricted to
multiples of 90Â. Intermediate values allow for fancy effects, but
proper positioning of such glyphs may pose a problem because the
"effective" bounding box had to non-orthogonal to the text baseline.
Comments are welcome.
<style name="tilt"> <fontstyle glyph-rot="-90"> </style>
regards, unmei
