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Re: [css-text] I18N-ISSUE-331: No kashida style or relationship to styles 'distribute' and 'inter-word'

From: Richard Ishida <ishida@w3.org>
Date: Tue, 27 May 2014 16:56:13 +0100
Message-ID: <5384B59D.5050204@w3.org>
To: www International <www-international@w3.org>, W3C Style <www-style@w3.org>
I suspect we should say as little as possible for now in the spec about 
text elongation in Arabic script for justification of running text in 
paragraphs, since I believe that in the end the requirements will be 
somewhat complex, and we are a long way from understanding them yet.

For example, it appears that some font types (eg. Ruqah style fonts) 
should not be used with elongation at all - all the justification is 
therefore done by manipulating space.  Also, it's looking to me as if 
justification in, say, a naskh type font is likely to involve adjusting 
spacing a lot of the time, but may occasionally involve that plus some 
elongation when the spaces get too wide (eg. when a url is embedded in a 
narrow column). In other cases, however, a greater amount of elongation 
may be favoured in a naskh type font.  Nastaliq font types, on the other 
hand, seem to rely more on elongation (and ligation and other shortening 
techniques) than naskh (since spaces are seen in a somewhat different 
light for nastaliq script). Also, btw, the rules for elongation are 
somewhat different in nastaliq than for naskh.

Like detection of conjunct behaviour in indic scripts, the determination 
of the correct behaviour seems to be font dependent, and it's not clear 
to me how to handle that.  Note that all this therefore also raises 
questions about how to do the right thing when a user changes the font 
by design or a font is substituted due to availability of fonts on a 
particular device).  It suggests that maybe we need special controls for 
elongation that say something like: apply elongation if the font is X or 
Y only.

(By the way, in passing, note that in Tasmeem it is possible to 
independently set parameters for the size of spaces inside a word (ie. 
where a letter doesn't join to the left) as well as outside a word.)

I guess we can say that inter-word turns off elongation, since that is 
the purpose of that value.  I'm not sure we can say much yet, until we 
understand things better, of the relationship between distribute and 
elongation, since elongation seems to involve far too many, poorly 
understood, complications.

The current text says "Justification adjusts spacing between each pair 
of adjacent visually-perceived characters", which may be sufficient to 
deal with elongations, since joined cursive letters don't have any 
spaces between them. I suppose it introduces a question about stretching 
of gaps inside a word where letters don't join to the left, though.



PS: For a discussion of nastaliq justification in Urdu see 
http://www.cle.org.pk/Publication/papers/2004/rule-based-expert-system.pdf


> Resent-Date: Fri, 09 May 2014 00:30:14 +0000
> Resent-From: www-style@w3.org
> Date: Thu, 08 May 2014 17:29:44 -0700
> From: fantasai <fantasai.lists@inkedblade.net>
> To: www-style@w3.org
>
> On 01/24/2014 10:30 AM, Phillips, Addison wrote:
>> State:
>>      OPEN WG Comment
>> Product:
>>      CSS3-text
>> Raised by:
>>      Addison Phillips
>> Opened on:
>>      2014-01-23
>> Description:
>>      Section 7.3: Surprisingly there is no keyword specifically
>> associated
>>      with kashida (other than "auto"). Shouldn't there be?
>
> There is no special keyword for it, just as there is no special keyword
> for standard Japanese justification.
>
>>      Or is it a special case of "distribute"?
>
> No. It is most definitely not a special case of "distribute".
>
>>      Some WG members [1] thought that "inter-word" implies turning
>> kashida off.
>
> This is true. It turns it off, because it only allows expansion
> at spaces.
>
> ~fantasai
>
>
>
>
Received on Tuesday, 27 May 2014 15:56:42 UTC

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