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

https://www.w3.org/Bugs/Public/show_bug.cgi?id=28266

--- Comment #23 from Glenn Adams <glenn@skynav.com> ---
(In reply to Silvia Pfeiffer from comment #22)
> (In reply to Glenn Adams from comment #21)
> >
> > > > 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.
> 
> No, I'm not suggesting any such thing.
> 
> I'm saying that the default bidi level for the paragraph is irrelevant for
> WebVTT cues, because we have the writing direction.
> 
> If you read how the cue text alignment works:
> http://dev.w3.org/html5/webvtt/#dfn-webvtt-cue-text-alignment
> you find that it depends on the writing direction (determined by a cue
> setting) and on the BIDI paragraph direction (which according to
> http://www.unicode.org/reports/tr9/ is specified as follows: "The direction
> of the paragraph embedding level is called the paragraph direction.").

ok, if writing mode is specified by and applied to individual cues, as opposed
to, say specified by a region regardless of the cues associated with that
region, then i would agree you can infer the default paragraph from the cue
specific writing mode;

however, if VTT allows specifying a writing mode on a region, and the cues
obtain their writing mode from the region's writing mode, then there should be
a way to override the region's writing mode on a cue by cue basis, at least
with respect to overriding the inline directionality

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Received on Friday, 2 October 2015 00:52:12 UTC