Re: TTML writingMode vs CSS Writing Modes Level 3 writing-mode

Hi Glenn,

Ok. To determine precedence between tts:writingMode and tts:direction,
the following prose from XSL 7.29.1 applies, right?

"""To insure consistency with the "writing-mode" property, the
"direction" property is initialized to the value that sets the same
inline-progression-direction as is set by the "writing-mode" property
whenever that "writing-mode" property sets that direction. If the
"direction" property is explicitly specified on the same formatting
object the value of the "direction" property will override the
inline-progression-direction set by the "writing-mode"."""

Best,

-- Pierre

On Sat, Nov 5, 2016 at 8:43 AM, Glenn Adams <glenn@skynav.com> wrote:
>
>
> On Sat, Nov 5, 2016 at 12:19 AM, Pierre-Anthony Lemieux <pal@sandflow.com>
> wrote:
>>
>> Hi Glenn,
>>
>> Thanks! So is writingMode="rltb" in TTML equivalent to {writing-mode:
>> "horizontal-tb", direction: "rtl"} in CSS? In other words,
>> writingMode="rltb" sets the default to default paragraph embedding
>> level to "RTL" just as {direction: "rtl"} does?
>
>
> Yes. But keep in mind that WM applies at a higher context (region) than
> direction (p/span). So it can be viewed as a special case of semantic
> inheritance.
>
>>
>>
>> Best,
>>
>> -- Pierre
>>
>> On Fri, Nov 4, 2016 at 11:00 PM, Glenn Adams <glenn@skynav.com> wrote:
>> >
>> >
>> > On Fri, Nov 4, 2016 at 11:13 PM, Pierre-Anthony Lemieux
>> > <pal@sandflow.com>
>> > wrote:
>> >>
>> >> Hi all,
>> >>
>> >> TTML allows both 'lrtb' and 'rltb' as values for writingMode, and
>> >> references Section 7.29.7 at XSL.
>> >>
>> >> CSS Writing Modes Level 3 [1] states that both 'lr-tb' and 'rl-tb' (as
>> >> defined in SVG) are both replaced by 'horizontal-tb'.
>> >>
>> >> Why would 'lr-tb' and 'rl-tb' be redundant?
>> >
>> >
>> > They aren't (in XSL-FO or TTML), since they have the added effect of
>> > indicating the default paragraph embedding level (of LTR or RTL) for all
>> > content targeted to a region. Keep in mind that XSL-FO defined writing
>> > mode
>> > before CSS3 WM took it up for consideration. Apparently, CSS3 WM prefers
>> > to
>> > use the direction property and/or character properties exclusively for
>> > this
>> > purpose.
>> >
>> > In TTML, a paragraph's default embedding level can be influenced by the
>> > computed value of tts:writingMode, the computed value of tts:direction,
>> > and
>> > the character content of the paragraph.
>> >
>> >>
>> >>
>> >> Thanks,
>> >>
>> >> -- Pierre
>> >>
>> >
>
>

Received on Saturday, 5 November 2016 20:10:01 UTC