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

as I said above:

if region specifies writingMode but not direction, then direction on region
> is initialized to the WM's inline direction


so, yes, we need to document this special behavior regarding how the
initial value of direction is determined

On Tue, Nov 8, 2016 at 6:29 PM, Pierre-Anthony Lemieux <pal@sandflow.com>
wrote:

>   while if both writingMode and direction are specified on region, then the
> > value of direction will override the WM's inline direction;
>
> Style inheritance propagates direction="ltr" (the initial value) on
> all elements (unless explicitly specified as "rtl" somewhere), thereby
> overriding any right-to-left direction specified using writingMode on
> region.
>
> It sounds like the style resolution process should have an exception
> for 'direction', which mimics XSL (7.29.1 Second Bullet) and, whenever
> writingMode is specified, also sets the value of 'direction' to the
> horizontal direction implied by writingMode.
>
> Best,
>
> -- Pierre
>
> On Sat, Nov 5, 2016 at 2:03 PM, Glenn Adams <glenn@skynav.com> wrote:
> > 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
> >> >> >>
> >> >> >
> >> >
> >> >
> >
> >
>