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

From: Richard Ishida <ishida@w3.org>
Date: Wed, 08 Oct 2014 16:30:58 +0100
Message-ID: <543558B2.4060505@w3.org>
To: fantasai <fantasai.lists@inkedblade.net>, "Phillips, Addison" <addison@lab126.com>, "CSS WWW Style (www-style@w3.org)" <www-style@w3.org>
CC: www International <www-international@w3.org>
On 10/05/2014 19:39, fantasai wrote:
> On 01/24/2014 10:32 AM, Phillips, Addison wrote:
>> State:
>>      OPEN WG Comment
>> Product:
>>      CSS3-text
>> Raised by:
>>      Addison Phillips
>> Opened on:
>>      2014-01-23
>> Description:
>>      Section 8.2: The section on "tracking" ('letter-spacing') may
>>      need to consider the effect on scripts such as Indic. The I18N
>>      WG asked for guidance from various Indic language contributors [1].
>>
>>      It was reported to use that 'letter-spacing' is not a native
>>      typographic style to these languages, however it is used in
>>      several languages, such as Hindi, for visual effect--if only rarely.
>>
>>      The guidance we received, which is consistent with our
>> understanding,
>>      is that letter-spacing should "break" the joining "bar" (shirorekha)
>>      in those scripts that use a "bar" and that the separation should be
>>      on syllable boundaries. These boundaries do not necessarily
>> correspond
>>      to Unicode's default grapheme cluster boundaries, making proper
>>      description more complicated.
>>
>>      [1] See thread:
>> http://lists.w3.org/Archives/Public/public-i18n-indic/2013OctDec/
>
> Indeed, and this is why the spec explicitly allows for tailoring the units
> used for letter-spacing.
>
> Since we have no references on exactly how such units should be tailored,
> we cannot add any normative guidance on this.
>
> Unless you can provide such references, I am marking this issue as
> Closed No Change, since it does not seem to reflect a deficiency
> in the spec.

For additional information on this topic see the thread that starts at 
http://lists.w3.org/Archives/Public/public-i18n-indic/2013OctDec/0001.html

In summary, letter-spacing does apparently occur in Indic scripts such 
as Hindi, and the line is broken.

There is still no authoritative pronouncement on whether the text unit 
around which spacing occurs is different when the virama is visible, but 
certainly when the virama is not visible the appropriate text unit is a 
syllable/akshar, which is not always equivalent to a grapheme cluster.

There is a section in the draft of Indic Layout Requirements doc that 
refers to letter spacing 
(http://www.w3.org/International/docs/indic-layout/#letter-spacing), and 
it points to the section which describe indic syllables 
(http://www.w3.org/International/docs/indic-layout/#abnf-valid-segmentation-proposed-solution-for-layout-issues-in-indian-languages).

hth
ri
Received on Wednesday, 8 October 2014 15:31:33 UTC

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