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

Thank you Bert, and please relay our thanks to the CSS WG for these thoughtful and helpful comments.

I suggest we turn to the editors for initial triage and entering the appropriate bugs etc.  Is that OK by the editors and everyone?


> On Apr 9, 2015, at 2:21 , Bert Bos <bert@w3.org> wrote:
> 
> 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

David Singer
Manager, Software Standards, Apple Inc.

Received on Thursday, 9 April 2015 15:50:28 UTC