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

[Phillips, Addison-2]

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/

[fantasai]

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.

~fantasai

[r12a]

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

[r12a]

On 24/01/2014 18:32, 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/

The i18n WG discussed this at our last telecon. We agree that the text
around the definition of typographic character units helps address this
issue.

We suggest however, in view of current implementations of
letter-spacing[1], the addition of a short note near the top of the
letter-spacing section to remind implementers that "typographic
charactere units" are not glyphs.

thanks
ri



[1]
http://192.168.0.4/International/tests/repository/css3-text/letter-spacing/css3-text-i18n-letter-spacing-001.html

[fantasai]

On 10/23/2014 03:03 AM, Richard Ishida wrote:
>
> We suggest however, in view of current implementations of letter-spacing[1], the addition of a short note near the top of the
> letter-spacing section to remind implementers that "typographic charactere units" are not glyphs.

Given current implementations are based on earlier specs like
CSS2.1 and my impression that “typographic character unit”
is sufficiently scary that an implementer reading *this* spec
will want to look it up, I think this reminder is not really
necessary here, and I would therefore prefer not to add it. :)

~fantasai