TTML Agenda for 21/9/12

We will hold a special technical meeting today 21/9/12 at 3pm PST, 11 pm European, to discuss positioning of block elements


Zakim Bridge +1.617.761.6200, conference 88651 ("TTML1")
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Agenda

Chair: Sean Hayes

Agenda+    Introduction by Sean of http://www.w3.org/wiki/TTML/changeProposal002 

Agenda+  Proposed amendment of Section 9.3.3. step 6

 for each body, div, and p element that is not associated with a tts:display
 style property with the value none, map the element to the equivalent of a
 distinct fo:block element, additionally if the element has an origin or
 extent attribute, place the mapped block element inside an 
 fo:block-container element with an absolute-position attribute with value
 fixed, and where the element's position and extent are mapped to equivalent
 top, left, width, and height attributes; populating the style properties of
 the fo:block-container element if created, or alternately, the fo:block by 
 using the computed style set associated with each original TTML content   
 element;

Agenda+ Proposed additional prose for section 8.2.14 on how the feature works: 

The presence of tts:origin, tts:extent or both on a block element will cause an anonymous region to be created, into which the block element is placed., This anonymous region has the same active duration as the block from which it was constructed.

During layout the computed style set of the element is applied to the block container corresponding to this anonymous region, rather than the block corresponding to the element.  

NOTE: The creation of anonymous regions happens after timing and the computation of the computed style set, and thus the anonymous region receives the entire computed style set of the block element, including any animated attributes.

The generated block container and the block are still part of the flow content of the named region into which it would have flowed, or the default region, if no named regions are present.

NOTE this means that the element must, in order to remain after the pruning algorithm, be selected into a named region if any exist; thus the anonymous region inherits from the region into which the block was originally flowed, and the block inherits from the anonymous region.

This does not affect the flow of any sibling block elements, which continue to be flowed into the named region as blocks.


Agenda+ Issues to be considered:

1- Is the anonymous region triggered by just origin, either origin or extent, just extent, or are both required? 

Either.

2 - It does not appear to be possible to apply attributes that are defined to only have semantics on <region> or can't be inherited,  e.g. tts:opacity, tts:showBackground, etc.  It seems that we would have to change all these attribute descriptions to explain how they can be applied to anonymous regions. I don't think it would be acceptable to preclude their use.

They would be moved to the region and inherited by the block. If it were essential to have the block use a different attribute, then nested blocks should be used. 


3 - Without an identifier (xml:id), there doesn't appear to be any way to animate these anonymous regions. Maybe it is not needed (in which case we should explicitly note the shortfall).  But if it is, perhaps we could come up with some derived region id's such as the <p> id appended with a number or something - e.g. using the example, the first anonymous region would be "p1.1".

Animation applied to the block would be copied to the region. 

[[ Note the time at which set animation is not considered in [1] which is an error, an issue has been raised]]


4 - When are these regions active exactly?  Do they inherit begin/end/dur including settings on the block element that invokes the creation of the region?

They are created after the timing pruning phase, and thus have the same active duration as the block that creates them.

5 - When are these regions visible exactly?  Are they the same as explicit regions (and thus under control of tts:showBackground - see #3 above)?  

Yes. However note their restricted duration.

6- This would imply that (using the initial value of showBackground) that they are visible for the entire duration of the document per an external timeline. This means a presentation processor will need to scan the <body> and actually create all the regions in advance of dealing with the active timing, just as if they were in the <head>.

No, they are visible precisely when the block they were created from is visible.

Change proposal:
http://www.w3.org/wiki/TTML/changeProposal002 

TTML Wiki 
http://www.w3.org/wiki/TimedText

[1] Second edition draft:
http://dvcs.w3.org/hg/ttml/raw-file/tip/ttml10/spec/ttaf1-dfxp.html

Received on Friday, 21 September 2012 15:46:53 UTC