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

Hi Bert,

Thanks very much for all these comments.

I've put references inline below to bugs that are either related to
the identified issues or that I have registered newly as a consequence
of your feedback. Feel free to encourage anyone in the CSS WG
interested in these bugs to follow the bugs and to provide feedback in
the discussions. We will, of course, also provide a summary response
once the discussions on the bugs and mailing lists have come to a
conclusion.

On Thu, Apr 9, 2015 at 7:21 PM, 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)?

The original reason that the CSS group created the 'text-wrap:
balance' feature was actually as a consequence of WebVTT needs, see
https://www.w3.org/Bugs/Public/show_bug.cgi?id=19458 . We're very
happy that this feature exists now. If it's not finalized in its
specification, where would be the best way to get involved?

Incidentally: we now have a bug to apply 'text-wrap: balance' to the
WebVTT spec: https://www.w3.org/Bugs/Public/show_bug.cgi?id=28432 . It
will replace step 11 of "apply WebVTT cue settings"
http://dev.w3.org/html5/webvtt/#dfn-apply-webvtt-cue-settings where it
starts with "Text runs must be wrapped...".


> 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.

Registered at https://www.w3.org/Bugs/Public/show_bug.cgi?id=28469 .


> 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?)

Yes, this is intentional, but I've still registered
https://www.w3.org/Bugs/Public/show_bug.cgi?id=28470 .


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

Registered at https://www.w3.org/Bugs/Public/show_bug.cgi?id=28471


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

Registered at https://www.w3.org/Bugs/Public/show_bug.cgi?id=28472


> 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?

Added this to https://www.w3.org/Bugs/Public/show_bug.cgi?id=28470


> 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.

Registered at https://www.w3.org/Bugs/Public/show_bug.cgi?id=28473


> 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.

Registered at https://www.w3.org/Bugs/Public/show_bug.cgi?id=28474


> 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?

@import can be used to include external stylesheets once we have
internal stylesheet support, which is part of
https://www.w3.org/Bugs/Public/show_bug.cgi?id=15023


Best Regards,
Silvia.


> 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

Received on Sunday, 12 April 2015 11:32:17 UTC