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Re: Fwd: Re: [css-text] I18N-ISSUE-334: 'letter-spacing' and Indic

From: Richard Ishida <ishida@w3.org>
Date: Fri, 25 Apr 2014 17:41:55 +0100
Message-ID: <535A9053.8090003@w3.org>
To: W3C Style <www-style@w3.org>, www International <www-international@w3.org>
> On Jan 25, 2014, at 9:07, Peter Moulder <pjrm@mail.internode.on.net> wrote:
>
>> On Sat, Jan 25, 2014 at 10:30:00AM +1100, I wrote:
>>
>>> I would thus be careful about specifying that this bar should always
>>> have visible gaps when letter-spacing is non-zero.
>>
>> More practically in terms of how to word the spec when addressing this
>> issue (if indeed we don't wish to specify that this bar should always have
>> visible gaps): the spec might merely say where letter-spacing is applied
>> (namely at syllable boundaries), without necessarily even mentioning the bar.  If
>> gaps in the bar are mentioned, then the requirement might be on where gaps
>> should/must not appear.
>
> Hm, I agree to leave things that we’re not certain undefined.
>
> Is the “syllable boundaries” different from the current grapheme cluster
> definitions? If no, I suppose there’s no need to update the spec.
>
> If different, is it possible to change Unicode grapheme cluster, or is
> it something that letter-spacing point needs to be different from
> grapheme cluster boundaries?

I have sent a note to the Indic Layout Task Force list asking for 
clarification, and will report back what they say.

My current understanding is that the units around which letter-spacing 
applies are different depending on which font is used. If the font 
indicates consonant clusters without showing the virama, then the unit 
is the whole consonant cluster plus vowel-signs, diacritics etc. This is 
very often likely to NOT coincide with extended grapheme clusters.

If the font does show the virama explicitly, then the stretching appears 
just after the virama.  I think that this DOES map to grapheme clusters 
as defined by Unicode.

As i said, I'll let you know if the indic experts get back to me to 
confirm this one way or another.

RI
Received on Friday, 25 April 2014 16:42:23 UTC

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