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Re: [SVGMobile12] Lack of BIDI 'direction' (ISSUE-2058)

From: fantasai <fantasai.lists@inkedblade.net>
Date: Tue, 28 Oct 2008 11:10:14 -0700
Message-ID: <49075586.7050402@inkedblade.net>
To: Doug Schepers <schepers@w3.org>
CC: www-style@w3.org, public-i18n-core@w3.org, www-svg <www-svg@w3.org>

Doug Schepers wrote:
> Hi, fantasai-
> 
> fantasai wrote (on 9/17/08 7:51 PM):
>> There's discussion in http://www.w3.org/TR/SVGMobile12/text.html about
>> bidirectional text, but there is no definition for a 'direction' property
>> that I can find, nor any mention of any substitute for it (such as a 'dir'
>> attribute).
>>
>> This is a problem because the Unicode bidirectional algorithm needs a
>> base direction for each "paragraph" that it operates on. For plain text
>> it guesses based on the first character in the text, but this is not
>> always accurate. Applying this rule to SVG Tiny would be incompatible
>> with an implementation that supported SVG Tiny plus the 'direction'
>> property because 'direction' defaults to 'ltr', not to 'guess a direction'.
>>
>> The lack of a 'direction' affects both bidi reordering and other properties
>> like 'text-align', whose values' behavior depends on 'direction'.
>>
>> I therefore strongly recommend that SVG Tiny include the 'direction'
>> property.
> 
> Thanks for your suggestion.  We agree with you and the I18N WG, and have
> added both 'direction' and 'unicode-bidi' properties. [1]
> 
> Please let us know if this satisfies your comment.
> 
> [1] http://dev.w3.org/SVG/profiles/1.2T/publish/text.html#DirectionProperty

   # For the 'direction' property to have any effect, the 'unicode-bidi'
   # property's value must be embed or bidi-override.

This is false. As I explained before, the 'direction' property alone has an
effect when set at the paragraph level ("paragraph" being the unit of text
the bidi algorithm operates on).

   # The 'direction' property applies only to glyphs oriented perpendicular
   # to the inline-progression-direction, which includes the usual case of
   # horizontally-oriented Latin or Arabic text and the case of narrow-cell
   # Latin or Arabic characters rotated 90 degrees clockwise relative to a
   # top-to-bottom inline-progression-direction.

This doesn't make any sense. The 'direction' property does not apply to
glyphs, it applies to text runs. (Although when combined with "bidi-override"
it does also apply to characters.)

~fantasai
Received on Tuesday, 28 October 2008 18:11:00 GMT

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