RE: [webvtt] comments from the CSS WG on WD-webvtt1-20141111

A concept that IMHO is related to 'balanced text' is 'multi-row alignment' - as introduced by EBU-TT (see https://tech.ebu.ch/docs/tech/tech3350.pdf Annex A). It might be useful to consider how the concepts of  'text-wrap:balancing' and 'multi-row alignment' interact?

Best regards,
John

John Birch | Strategic Partnerships Manager | Screen
Main Line : +44 1473 831700 | Ext : 2208 | Direct Dial : +44 1473 834532
Mobile : +44 7919 558380 | Fax : +44 1473 830078
John.Birch@screensystems.tv | www.screensystems.tv | https://twitter.com/screensystems

Visit us at
NAB, Las Vegas Convention Center 13-16 April 2015 Stand No. SU9610

P Before printing, think about the environment-----Original Message-----
From: Bert Bos [mailto:bert@w3.org]
Sent: 09 April 2015 10:21
To: public-tt@w3.org
Subject: [webvtt] comments from the CSS WG on WD-webvtt1-20141111

The CSS WG looked at the first draft of webvtt and these are the comments we came up with:

1) The example in section 1.1 is possibly a use case for a new property and keyword for CSS, tentatively called 'text-wrap: balance', whose goals are to avoid that the last line of a paragraph is much shorter than the other lines. (The property appeared in an example in a WD once, but no definition has been published yet).

1a) Further investigation may be needed to see if and how this balancing (and the CSS property) applies to different scripts.

1b) And if the WebVTT use case and the CSS property are indeed the same feature, we'll need to see how precisely we want to define it: is it a good idea to specify a formula? (E.g., minimize a function that adds up a number of things like the total number of lines, the (absolute value or square of) each line's difference from the mean length, each line's difference from the available width, each line's difference from the previous line, each space's difference from the normal space width, the difference between the amount of stretching/shrinking in each line's spaces compared to the previous line, the difference in the amount of letter spacing in each line compared to the previous line, the occurrences of "rivers", etc.); or is it better to just give hints about possible factors to take into account and leave room for implementations to do better (but slower) or worse (but faster)?

2) Section 5.5: Some people wonder if HTMLElement is the right type to use for all the nodes, or if it is better to use more specific subclasses.

3) The list in that section doesn't match with the description of how Selectors work; in particularly, Class, Voice, and Lang objects are all "span" elements here, but are "c", "v", and "lang" elements in Selectors.
Selectors is written on top of the DOM, though, so these should match. (But we hear this difference is intentional?)

4) Related to the previous, this section doesn't seem to apply the IDs of region objects.

5) Section 6.2.3.1: "group of selectors" has no defined meaning. You probably want either "compound selector list" or "complex selector list".

6) You can remove the entire section about how to evaluate the selector once section 5.5 defines an accurate DOM mapping; just specify that it matches over the equivalent DOM defined in 5.5. Or are there (intentional) differences between selecting against a WebVTT DOM and the mapped HTML DOM?

7) Section 6.2.3.3: It looks like cue regions are basically blocks that get filled with cues. Why not just make those an element selectable by ::cue()?
You're limited to the same styles that apply to ::cue anyway.

8) Even though regions have an ID, it looks like you can't select by it. All you can do is apply styles to all regions. What's the purpose of this, then? It seems equivalent to ::cue with no argument, except maybe the background property would apply over a wider box.

9) Regarding external stylesheets, several people recommend against trying to use sheets from the outer document (except for style rules that use ::cue()). Can WebVTT be extended to ref an external stylesheet?



For the CSS WG,
Bert
--
  Bert Bos                                ( W 3 C ) http://www.w3.org/
  http://www.w3.org/people/bos                               W3C/ERCIM
  bert@w3.org                             2004 Rt des Lucioles / BP 93
  +33 (0)4 92 38 76 92            06902 Sophia Antipolis Cedex, France

This message may contain confidential and/or privileged information. If you are not the intended recipient you must not use, copy, disclose or take any action based on this message or any information herein. If you have received this message in error, please advise the sender immediately by reply e-mail and delete this message. Thank you for your cooperation. Screen Subtitling Systems Ltd. Registered in England No. 2596832. Registered Office: The Old Rectory, Claydon Church Lane, Claydon, Ipswich, Suffolk, IP6 0EQ

Received on Thursday, 9 April 2015 10:45:51 UTC