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[Bug 28266] [webvtt] 6.2.1 processing model handling of bidi [I18N-ISSUE-432]

From: <bugzilla@jessica.w3.org>
Date: Thu, 01 Oct 2015 19:04:22 +0000
To: www-international@w3.org
Message-ID: <bug-28266-4285-dC9UzfCkDN@http.www.w3.org/Bugs/Public/>
https://www.w3.org/Bugs/Public/show_bug.cgi?id=28266

--- Comment #21 from Glenn Adams <glenn@skynav.com> ---
(In reply to Silvia Pfeiffer from comment #20)
> (In reply to Glenn Adams from comment #19)
> >
> > > > It would also be helpful if the author could set the base direction for each
> > > > cue explicitly, since the Unicode paragraph detection algorithm can be
> > > > fooled by a paragraph that starts with a strong LTR character, but is
> > > > actually a RTL paragraph (or vice versa), eg. "نشاط التدويل is how you say
> > > > 'i18n Activity' in Arabic."
> > > 
> > > This problem has been acknowledged. However, there is already a means to
> > > address this by using the UTF-8 RLO, LRO, RLE and LRE characters. These do
> > > explicit directionality overrides in contrast to &lrm; and &rlm; which
> > > provide only hints to the algorithm.
> > 
> > While it is true that each cue's text could be wrapped in a RLE/PDF or
> > LRE/PDF pair, this does not actually affect the cue's default
> > directionality, but merely the embedding level of the text so wrapped.
> 
> If the resulting rendering is correct, what's the difference in it being
> called an overall "default directionality" and "the default direction of
> text on that embedding level"?
> 
> 
> > If there are style properties that apply to the cue as a whole, and those
> > properties require the use of a default directionality to resolve their
> > computed value, e.g., the computed value resolved from 'start', 'end', etc.,
> > then use of Bidi controls in the text will not suffice.
> 
> The writing direction in WebVTT is not determined from the cue text, but
> through cue settings. The resolution of 'start' and 'end' alignments and
> positioning is dependent on the paragraph directionality as determined by
> BIDI, which in fact is the direction of the paragraph embedding level, so
> we're good on that, too.

I'm afraid I don't agree. You are suggesting that the default bidi level for
the paragraph is determined by the embedding level of the text content of the
paragraph. However, that is not how the Unicode Bidi Algorithm works: the
default bidi level of the paragraph is an input parameter to be used to
determine the resolved levels of the paragraph's content, and not the other way
around.

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Received on Thursday, 1 October 2015 19:04:24 UTC

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