RE: TTML2 anonymous inline region creation

I believe your proposal is more in line with users expectations.

Viz: A user probably has the expectation that a region style attribute that is specified on a p element has an effect on the region that is associated with that p element.

Changing display align dynamically could be useful in the case of a simplistic document using a 'full screen' 'transparent' region. Similarly changing writingMode to support mixed Arabic / Latin might be useful.
Consequently I don't think restricting the scope to specific style attributes is necessary... some cases might be somewhat limited in utility, but it is probably easier to apply the anonymous set concept to all region style attributes.


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P Before printing, think about the environment-----Original Message-----
From: Nigel Megitt []
Sent: 20 October 2015 15:48
To: Timed Text Working Group
Subject: TTML2 anonymous inline region creation


Right now in TTML2 if a style attribute is specified on a p element that only has an effect on regions then an anonymous inline region is created.
The style attribute inheritance chain is:

>initial values -> anonymous region -> body -> div ... -> p -> span ...

In considering how to fix tts:disparity it occurred to me that this isn't always what document authors might want or indeed expect.

Another idea that I'm considering is: change from creating an anonymous inline region to creating an anonymous inline <set> element whose target is the region that applies to the element on which it applies and whose timing is coincident with the timing of the same element.

In case of temporally overlapping elements that set the same style attributes to different values I would resolve the conflict using a begin-time-then-document-order rule, where last one wins.

This would apply to the following style attributes that only have an effect on regions: tts:disparity, tts:extent, tts:origin, tts:position and tts:zIndex. I would probably exclude tts:displayAlign, tts:overflow, tts:showBackground and tts:writingMode because changing those on the fly would be weird.

I'm just thinking this through right now, not definitively proposing it.
The main thing I'm worried about is how the current solution interacts with issue-341 and issue-368. Even if we do go down the route of creating anonymous inline regions I imagine that authors will want a semantic like "just like a template region but with the specified style attributes differing", where the template region is the one that would have applied in the absence of the region-based style attributes on the p. That would also require a change to the inheritance chain, which would then be:

Initial values -> specified region (if any) ... -> anonymous region -> body -> div … -> p -> span …

Any thoughts on this appreciated, even if they're "Aargh don't change it now"!



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Received on Wednesday, 21 October 2015 08:44:33 UTC