From: Peter Kirk (peterkirk@qaya.org)
Date: Wed Apr 28 2004 - 17:52:30 EDT
On 28/04/2004 14:34, Ernest Cline wrote:
>
>
>>[Original Message]
>>From: Peter Kirk <peterkirk@qaya.org>
>>
>>On 28/04/2004 12:00, Ernest Cline wrote:
>>
>>
>>
>>>There will always be scripts that Unicode will not support, either
>>>
>>>
>because
>
>
>>>they are constructed scripts with no real use, rare or ancient scripts
>>>
>>>
>that
>
>
>>>lack sufficient examples to determine how the script should be encoded,
>>>or are picture fonts. This last we can discount, because the existing
>>>private use area supports them adequately. ...
>>>
>>>
>>>
>>Don't count on it. The PUA as Ken envisages it doesn't provide adequate
>>support for anything at all.
>>
>>
>
>Oh? How does the existing PUA fail to support a picture font adequately?
>
>
My point is that, according to what Ken has written, the PUA can be used
for a picture font only if not only the end users but also the software
developers have come to a specific agreement about that picture font and
the identity of each character in it. He seemed to reject my suggestion
that developers might sensibly support the PUA apart from such specific
agreements with end users, by supporting default character properties
for each PUA character and allowing the glyph to be specified in the font.
>- Pictures don't have casing.
>- While a Bidi Class of ON would suit them better, L is adequate.
>- They don't have any need for any of the minor properties of PropList.txt.
>- The Line Break class does not usually matter for these characters either,
> because of their usual positions and because XX is usually treated as
> if it were AL, which they would have if they were given a more precise
>value.
>
>Given the typical uses of picture fonts, the lack of the optimum Bidi Class
>for the characters a picture font contains is not significant enough to
>worry
>about it in itself, especially with bidirectional override characters
>available
>in the rare cases where multiple symbols from a picture font are used in
>sequence in the middle of a stretch of RTL text. ...
>
Or, within RTL text, a picture symbol is followed by punctuation or any
other neutral or not strongly directional character. Directional
overrides might need to be used more often than you think.
>... ZWSP and WJ can handle
>the few cases where the default line breaking behavior of Line Break
>class XX is inadequate. The existing PUA is adequate for picture fonts
>precisely because they don't need very much. A case can be made for
>improving the Private Use repertoire, but picture fonts have at best a
>non-speaking role in the chorus line in that production.
>
>
>
Agreed, but only if the PUA works in the kind of way which you and I
envisage. If it works as Ken envisages, which is very close to saying
that it doesn't work at all, you would be wrong to expect any support
for any of the properties you have listed, because applications should
not even try to support PUA characters of which they have no specific
knowledge.
-- Peter Kirk peter@qaya.org (personal) peterkirk@qaya.org (work) http://www.qaya.org/
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