WebVTT wrapping

On Mon, Dec 5, 2011 at 11:37 PM, Glenn Maynard <glenn@zewt.org> wrote:

> On Mon, Dec 5, 2011 at 7:38 PM, Ian Hickson <ian@hixie.ch> wrote:
>
>> > If wrapping to similar line lengths is what's wanted, then the VTT
>> > renderer (and so CSS) should support that.
>>
>> Possibly. It's not currently. It would require a new 'white-space' value.
>> Given that, it would be easy to support in VTT; just have authors not use
>> line breaks at all, and let the renderer do it.
>>
>
> I think this is much better than having people do it by hand.
>

As a real example of this sort of approach causing problems, see the
attached, which is from the YouTube Android app.  When the caption font
size is set to "extra large", it falls apart.  (In case the archive breaks
attachments: http://i.imgur.com/IaGNv.png, http://i.imgur.com/zcgTv.png.)

This could also be triggered by differences in font engines, different
fonts being used (for any number of reasons), differences in word-breaking
and hyphenization rules (both of which are left to the UA), the stylesheet
used during authoring not being loaded, and so on.

It also makes manual editing of captions harder, since you need to view the
final output in order to adjust wrapping.  It complicates tools
significantly: *every* tool that modifies caption text will need some way
to update wrapping, which means every tool effectively needs access to a
complete parser, renderer, the fonts (assumed to be) in use, and so on.  If
you want to change the line width, you have to re-wrap the entire
document.  Allowing a user-adjustable maximum width (as any eBook reader
supports) is probably impossible.

WebVTT inherited this problem from SRT.  This was already solved by SSA
(which has entirely replaced SRT, in my experience, not that I particularly
like the SSA format as a whole), so this feels like a big step back.  I
hope this can be fixed, with a new default wrapping mode, eg. text-wrap:
balanced and text-space-collapse: collapse, and an explicit <br> tag for
when it's really needed.

-- 
Glenn Maynard