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ISSUE-380 (Content area width is unclear): The width of content elements' areas is unclear, especially looking at the examples [TTML2]

From: Timed Text Working Group Issue Tracker <sysbot+tracker@w3.org>
Date: Thu, 26 Mar 2015 16:32:21 +0000
To: public-tt@w3.org
Message-Id: <E1YbAhh-000EHd-BG@deneb.w3.org>
ISSUE-380 (Content area width is unclear): The width of content elements' areas is unclear, especially looking at the examples [TTML2]

http://www.w3.org/AudioVideo/TT/tracker/issues/380

Raised by: Nigel Megitt
On product: TTML2

The size of content elements relative to their parent elements and generated content elements is unclear. It is neither specified in §10.2.1 Style Attribute Vocabulary nor in §8.1 Content Element Vocabulary. It perhaps is specified in §11.3.1.4 Synchronic Flow Processing however there are no forward references directing the reader there. Even if it is in fact specified by a normative reference to XSL-FO and/or CSS, it would be helpful to add non-normative Notes where the information is most relevant, i.e. on style attributes whose effect is bounded by the applicable rectangular area.

The terms "block display", "inline display" and "inline block display" are usefully defined in TTML2 but those definitions are not referenced everywhere they apply.

Specifically, the implementation of the tts:backgroundColor, tts:backgroundImage and tts:border style attributes depends on the correct calculation of the rectangle to which they apply, and that rectangle is computed differently for spans than for the other content elements: only for spans is the size in the inline progression dimension related to the text content width; all the other elements' size in the inline progression dimension relates to the parent element's content rectangle minus any padding applied.

The example for tts:backgroundColor is ambiguous and possibly misleading in this respect, because the width of the text has been chosen to be exactly the same as the width of the content area of the p that is coloured purple, making it appear to the casual observer that the purple box is shrunk to the maximum width of the inline areas generated for the text.

Proposed resolutions:

1. EITHER include normative text that specifies how the calculation of the rectangle to which the above listed attributes apply differs between spans and other content elements OR (if somehow the normative text is already strong enough) add non-normative notes to each attribute calling out the difference, or add the note to the introductory part of §10.2 and then reference it from the attributes.

2. Add a diagram showing the width and height calculation (possibly this relates also to the resolution for Issue-302) that applies to each content element, and reference it from tts:backgroundColor, tts:backgroundImage and tts:border. This could be in the introductory part of §10.2 for example.

3. Change the example for tts:backgroundColor to make it use a longest line length that is shorter than the width of the content area of the parent p element, or add a new example or a second p where that is the case.

4. Ensure that the examples for tts:border do not reproduce the ambiguity.
Received on Thursday, 26 March 2015 16:32:23 UTC

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