Re: ISSUE-406 + #lineBreak-uax14

Hi Glenn,

I appreciate the clarifications. I am checking with folks to see if
CFF-TT implementations typically implement #lineBreak-uax14.

Best,

-- Pierre

On Mon, Sep 21, 2015 at 4:31 PM, Glenn Adams <glenn@skynav.com> wrote:
>
> On Mon, Sep 21, 2015 at 3:43 PM, Pierre-Anthony Lemieux <pal@sandflow.com>
> wrote:
>>
>> HI Glenn,
>>
>> > I presumed that by listing feature designators, you were specifying
>> > whether the features so designated may be used in a document.
>>
>> Yes. This is the intent.
>>
>> > it appears you may in addition consider the presence of a designator in
>> > these sections as indicating whether
>> > a feature can be required in a document specific profile over and above
>> > the use of an IMSC profile.
>>
>> No. That is not the intent.
>>
>> I was merely curious why, as opposed to other TTML parameter that
>> impact processor behavior, #lineBreak-uax14 is not controlled using a
>> ttp attribute.
>
>
> I don't believe anyone ever suggested defining a parameter, since it would
> not be something typically changed on a document by document basis (in a
> given profile). Instead, we felt such a requirement was closely aligned to
> profile definitions, and that a profile could specify this requirement or
> not.
>
>>
>>
>> > Given the focus on reproducible behavior, e.g., defining the use of
>> > specific glyph metrics, I would expect that UAX14 be mandated by IMSC1.
>>
>> Ok. To confirm, unless IMSC1 requires that processor implement
>> #lineBreak-uax14, a processor may or may not do so.
>
>
> That is correct. In other words, the default is that you have no idea which
> line break algorithm is used. If you specify #lineBreak-uax14 as required in
> a standard or per-document profile, then at least you know what algorithm is
> used (provided the implementation heeds #profile).
>
>>
>>
>> Best,
>>
>> -- Pierre
>>
>> On Mon, Sep 21, 2015 at 2:15 PM, Glenn Adams <glenn@skynav.com> wrote:
>> > I was not sufficiently clear in my description. Of course, the
>> > #lineBreak-uax14 designator can be listed in a document defined profile
>> > based on IMSC1 text profile as the base profile.
>> >
>> > What I had apparently not understood was what was meant by "The Document
>> > Instance shall conform to the following table:" in Sections 6.10, 7.4,
>> > and
>> > 8.4. I presumed that by listing feature designators, you were specifying
>> > whether the features so designated may be used in a document. In the
>> > case of
>> > most features, there is a syntactic feature that corresponds to a
>> > designator. However, that is not true for #lineBreak-uax14, which may be
>> > used by an application to signal whether a particular algorithm is used
>> > or
>> > not by the implementation, as opposed to whether a syntactic feature is
>> > used
>> > in the document.
>> >
>> > From your question, it appears you may in addition consider the presence
>> > of
>> > a designator in these sections as indicating whether a feature can be
>> > required in a document specific profile over and above the use of an
>> > IMSC
>> > profile.
>> >
>> > This doesn't seem a legitimate requirement. If an application of IMSC1
>> > also
>> > wants to require an implementation to support a superset of IMSC1, then
>> > they
>> > should be able to additional require features not required by IMSC1.
>> >
>> > Furthermore, I wonder if the fact that absent a generic requirement for
>> > UAX14 line break support, then there is no guarantee of reproducibility
>> > of
>> > line breaks even given the same font metrics, same resolution, and same
>> > region extents?
>> >
>> > Given the focus on reproducible behavior, e.g., defining the use of
>> > specific
>> > glyph metrics, I would expect that UAX14 be mandated by IMSC1.
>> >
>> >
>> >
>> >
>> >
>> >
>> >
>> > On Mon, Sep 21, 2015 at 9:35 AM, Pierre-Anthony Lemieux
>> > <pal@sandflow.com>
>> > wrote:
>> >>
>> >> Hi Glenn,
>> >>
>> >> Couple of questions related to #lineBreak-uax14 and ISSUE-406 [1].
>> >>
>> >> - why can #lineBreak-uax14 only be signaled through a profile
>> >> declaration and cannot be set through a ttp attribute?
>> >>
>> >> - what is the default value of #lineBreak-uax14 in absence of a
>> >> profile declaration?
>> >>
>> >> Thanks,
>> >>
>> >> -- Pierre
>> >>
>> >> [1] http://www.w3.org/AudioVideo/TT/tracker/issues/406
>> >>
>> >
>
>

Received on Monday, 21 September 2015 23:43:41 UTC