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]

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.
>> >>> -->
>> >>>
>> >>>
>> >>>
>> >>>
>> >>
>> >
>
>

Received on Friday, 1 August 2014 17:18:32 UTC