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

yes; i.e.,

if region specifies writingMode but not direction, then direction on region
is initialized to the WM's inline direction; while if both writingMode and
direction are specified on region, then the value of direction will
override the WM's inline direction;

we should probably note this in TTML

On Sat, Nov 5, 2016 at 2:09 PM, Pierre-Anthony Lemieux <pal@sandflow.com>
wrote:

> 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
> >> >>
> >> >
> >
> >
>