Re: ISSUE-331 (forcedDisplay region background note): An advisory note on the use of backgrounds on regions in combination with forcedDisplay [TTML IMSC 1.0]

Keep in mind that if some element E is not visible, then all of its
children are not visible regardless of their visibility property.


On Fri, Aug 1, 2014 at 11:17 AM, Pierre-Anthony Lemieux <pal@sandflow.com>
wrote:

> Hi Glenn,
>
> Thanks. Sounds good.
>
> Per Nigel's earlier question: is specifying "inherited:yes" in the
> attribute definition sufficient to enable inheritance similar to that
> of tts:display?
>
> Thanks,
>
> -- Pierre
>
>
> On Fri, Aug 1, 2014 at 6:51 PM, Glenn Adams <glenn@skynav.com> wrote:
> >
> > On Fri, Aug 1, 2014 at 10:21 AM, Pierre-Anthony Lemieux <
> pal@sandflow.com>
> > wrote:
> >>
> >> Hi Glenn,
> >>
> >> > Then it needs to be changed.
> >>
> >> What about the following:
> >>
> >> "If the value of displayForcedOnlyMode is "true", a content element
> >> with a itts:forcedDisplay computed value of "false" shall be invisible
> >> (fully transparent), but still affects layout, regardless of the value
> >> of tts:visibility."
> >
> >
> > s/shall be invisible (fully transparent)/shall not produce any visible
> > rendering/
> >
> >>
> >>
> >> Thanks,
> >>
> >> -- Pierre
> >>
> >> On Fri, Aug 1, 2014 at 5:59 PM, Glenn Adams <glenn@skynav.com> wrote:
> >> >
> >> >
> >> > On Fri, Aug 1, 2014 at 9:19 AM, Nigel Megitt <nigel.megitt@bbc.co.uk>
> >> > wrote:
> >> >>
> >> >> On 01/08/2014 16:01, "Glenn Adams" <glenn@skynav.com> wrote:
> >> >>
> >> >>
> >> >> On Fri, Aug 1, 2014 at 7:51 AM, Timed Text Working Group Issue
> Tracker
> >> >> <sysbot+tracker@w3.org> wrote:
> >> >>>
> >> >>> ISSUE-331 (forcedDisplay region background note): An advisory note
> on
> >> >>> the
> >> >>> use of backgrounds on regions in combination with forcedDisplay
> [TTML
> >> >>> IMSC
> >> >>> 1.0]
> >> >>>
> >> >>> http://www.w3.org/AudioVideo/TT/tracker/issues/331
> >> >>>
> >> >>> Raised by: Nigel Megitt
> >> >>> On product: TTML IMSC 1.0
> >> >>>
> >> >>> This issue is created to fulfil Action-314.
> >> >>>
> >> >>> Rationale:
> >> >>>
> >> >>> Since forcedDisplay affects the computed value of the tts:visibility
> >> >>> property
> >> >>
> >> >>
> >> >> Actually it doesn't change the computed value of tts:visibility (or
> >> >> shouldn't). It qualifies how the computed value is used, e.g., by
> doing
> >> >> something like:
> >> >>
> >> >> if (computedValue('tts:visibility') == 'visible') {
> >> >>   if (!displayForcedOnlyMode || (computedValue('itts:forcedDisplay')
> !=
> >> >> 'false')) {
> >> >>     renderContent()
> >> >>   }
> >> >> }
> >> >>
> >> >>
> >> >>
> >> >> That would be one way to do it, but the current spec does seem to
> state
> >> >> that the tts:visibility computed value should change.
> >> >
> >> >
> >> > Then it needs to be changed.
> >> >
> >> >>
> >> >>
> >> >> Aren't they completely equivalent though?
> >> >
> >> >
> >> > No, since computed values are referenced elsewhere, e.g., inheritance.
> >> >
> >> >>
> >> >> I don't see what the difference would be between your algorithm and:
> >> >>
> >> >> if (!displayForcedOnlyMode || (computedValue('itts:forcedDisplay')
> >> >> !='false')) {
> >> >>    setComputedValue('tts:visibility', 'visible')
> >> >> }
> >> >>
> >> >> if (computedValue('tts:visibility')=='visible') {
> >> >>    renderContent()
> >> >> }
> >> >
> >> >
> >> > The problem is that computed value is referenced elsewhere, and this
> >> > logic
> >> > shouldn't impact it.
> >> >
> >> >>
> >> >>
> >> >>> it has no effect on whether or not the hidden/visible content is
> >> >>> temporally active. This means that if non-forced content is assigned
> >> >>> to a
> >> >>> region with a background colour then the background will be shown
> >> >>> whenever
> >> >>> the content is active even if it is hidden. This is likely to be
> >> >>> unexpected
> >> >>> behaviour for some readers of the specification, who may imagine
> that
> >> >>> by
> >> >>> using a setting of tts:showBackground of "whenActive" they can
> prevent
> >> >>> this
> >> >>> effect.
> >> >>>
> >> >>> (incidentally they'd be correct in thinking this if forcedDisplay
> were
> >> >>> changed to do what its name suggests and affect tts:display, which
> >> >>> arguably
> >> >>> would be more useful functionality)
> >> >>>
> >> >>> Proposal:
> >> >>>
> >> >>> Include a non-normative note such as the following:
> >> >>> <--
> >> >>> NOTE
> >> >>>
> >> >>> If the forcedDisplay attribute is used for content in combination
> with
> >> >>> regions that have a non-transparent computed background color then
> >> >>> authors
> >> >>> should be aware that those regions' backgrounds will be drawn
> whenever
> >> >>> the
> >> >>> selected content is active, even if the computed tts:visibility of
> >> >>> that
> >> >>> content is "none".
> >> >>
> >> >>
> >> >> Note that the two legal values of tts:visibility are 'visible' and
> >> >> 'hidden'. The values 'none' and 'false' and 'true' are not legal.
> [IMSC
> >> >> ED
> >> >> currently refers to an illegal value 'true'.
> >> >>
> >> >>
> >> >> Yes, sorry, my mistake – as Pierre also pointed out I meant "hidden"
> in
> >> >> place of "none".
> >> >>
> >> >>
> >> >> BTW, I'd still like to see the name changed to itts:forced in order
> to
> >> >> avoid the display vs visibility confusion.
> >> >>
> >> >>
> >> >>
> >> >> I'd like to see it changed to itts:forcedVisibility to make it even
> >> >> clearer, if we're going to change the name at all.
> >> >>
> >> >>
> >> >>> One strategy for avoiding this scenario would be to assign content
> >> >>> elements only to regions that have the same value of forcedDisplay.
> >> >>> -->
> >> >>>
> >> >>>
> >> >>>
> >> >>>
> >> >>
> >> >
> >
> >
>