Re: <track> and WebVTT in Opera Next

On Thu, 09 Aug 2012 10:27:11 +0200, Julien Villetorte  
<j.villetorte@gmail.com> wrote:

> 2012/8/8 Philip Jägenstedt<philipj@opera.com <mailto:philipj@opera.com>>
>
>         I found a couple of (maybe known) issues related to WebVTT
>         classes and
>         settings.
>         Taking this video as an
>         example:http://www.delphiki.com/html5/playr/
>         <http://www.delphiki.com/html5/playr/>
>         The first cue (see webvtt file:
>         http://www.delphiki.com/html5/playr/examples/dw_trailer_low.vtt
>         <http://www.delphiki.com/html5/playr/examples/dw_trailer_low.vtt>)
>         does not
>         render properly, multiples classes seems to be the problem.
>
>
>     I investigated a bit and it turns out that the problem is
>     position:0%. Per spec, that means that the maximum size of the cue
>     should be 0, which is really strange. I filed a
>     bug:https://www.w3.org/Bugs/Public/show_bug.cgi?id=18501
>     <https://www.w3.org/Bugs/Public/show_bug.cgi?id=18501>
>
>     If you try position:0% line:0 you'll see where the rest of the text
>     ended up -- one word per line! The reason that the cue wasn't moved
>     up into the viewport is because the cue box has width 0 and it's not
>     really clear if that should be considered intersecting the viewport
>     or not :/
>
>
> In this case, I may have misinterpreted the spec about position.
> I thought this was the way it should behave:
> http://leanbackplayer.com/other/webvtt.html#cue-settings-textposition
> I think I get the general idea now.
> Anyway this isn't the clearest part of the spec.

Actually, I also didn't really understand how position was supposed to  
work until I investigated your problem. I hope we can just change the spec  
on this point, so feedback from authors (you) and other implementors on  
that bug would be appreciated.

>         ::cue:past & ::cue:future pseudo-classes don't seem to be  
> supported.
>
>
>     Those have been implemented and tested, can you give an example of
>     something that doesn't work?
>
>
> I haven't been able to make them work.
> I may not have done it the right way, see the last 2 selectors in this
> file: http://www.delphiki.com/html5/playr/style.css

There are a few problems here. First, the syntax should be

::cue(:future){
 opacity:0;
}

::cue(:past){
 opacity:1;
 color:yellow;
}

Second, opacity isn't on the white list of CSS properties allowed for  
::cue, so I've filed  
<https://www.w3.org/Bugs/Public/show_bug.cgi?id=18519> to allow that.

Finally, :past and :future don't work if you just have text between the  
timestamps, see <https://www.w3.org/Bugs/Public/show_bug.cgi?id=16875>.  
This is a really bad bug, but a workaround is wrapping text in <c>...

-- 
Philip Jägenstedt
Core Developer
Opera Software

Received on Friday, 10 August 2012 09:07:01 UTC