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Re: [css-text] i18n-ISSUE-354: Questions about letter-spacing for Arabic script

From: Richard Ishida <ishida@w3.org>
Date: Thu, 23 Oct 2014 11:08:30 +0100
Message-ID: <5448D39E.9030901@w3.org>
To: fantasai <fantasai.lists@inkedblade.net>, W3C Style <www-style@w3.org>, www International <www-international@w3.org>
On 01/08/2014 15:02, fantasai wrote:
> On 07/25/2014 07:57 PM, Richard Ishida wrote:
>> 8.2 Tracking: the letter-spacing property
>> http://dev.w3.org/csswg/css-text/#letter-spacing-property
>> Editor’s Draft, 20 March 2014
>>
>> The length value has the description:
>>
>> "Specifies additional spacing between visually-perceived characters.
>> Values may be negative, but there may be implementation-dependent
>> limits."
>>
>> For cursive text the spec says:
>>
>> "If it is able, the UA may apply letter-spacing to cursive scripts by
>> translating the total spacing distributed to a run of such letters
>> into some form of cursive elongation for that run."
>>
>> Does this mean that if tracking length is set to 1em for a word that
>> is 6 letters long, that the total length of the resulting text will
>> be 6em plus the letter widths, and that therefore if there are some
>> letters that are not allowed to elongate the others will elongate
>> wider than 1em? Or does it mean that those letters that can stretch
>> will each stretch by 1em (possibly resulting in less than 6em overall
>> width)?
>
> The former.
>
>> If values are negative, does this have any meaning for cursive scripts,
>> or is it a hint to use ligatures if any are available
>> (which will result in different effects per font)?
>
> This would allow the use of shortening ligatures or contextual forms,
> yes.
>
>> And then there are Arabic font styles that don't elongate, such as
>> ruq'a. Does the application have to disable letter-spacing  if the
>> user or the device chooses a ruq'a-style font, or is that the
>> responsibility of the author? It seems that it might be
>> hard for authors to signal what to do in the case of fallback fonts.
>
> The application should disable any elongation, yes. It seems unlikely
> for a ruqu'a-style font to be a fallback font, however: system fonts
> are much more likely to be the newspaper style of writing.


The i18n WG is hoping that you can add some of the above clarifications 
to the spec, so that we can close this issue.

thanks,
ri
Received on Thursday, 23 October 2014 10:09:00 UTC

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