Re: Multiple Settings in a Cue

On Tue, Nov 27, 2012 at 2:49 AM, Simon Pieters <simonp@opera.com> wrote:

> On Tue, 27 Nov 2012 03:13:26 +0100, Kyle Barnhart <kyle@barnhart.ca>
> wrote:
>
>  Hello. I'm part of the Seneca College student who are implementing the
>> WebVTT spec for Mozilla.
>>
>> The syntax rules state, "Each component must not be included more than
>> once
>> per WebVTT cue settings string." The parsing rules allow for duplicate
>> settings implicitly because it makes no such check. The splitting on a
>> space creates a list, not an ordered list.
>>
>
> Why would it not be ordered?


Because the entire paragraph says:

The WebVTT cue settings part of a WebVTT
cue<http://dev.w3.org/html5/webvtt/#webvtt-cue>consists of zero or
more of the following components, in any order,
separated from each other by one or more U+0020 SPACE characters or U+0009
CHARACTER TABULATION (tab) characters. Each component must not be included
more than once per WebVTT cue
settings<http://dev.w3.org/html5/webvtt/#webvtt-cue-settings>string.

So the cue settings components can be in any order.


>
>
>  That means a cue with duplicate
>> settings will parse but with unpredictable results.
>>
>
> The results are predictable if the list is ordered, which I have
> understood the spec to mean. Maybe it should be more explicit about that in
> the common microsyntax section.
>
>
>  Question. Should this simply be left as unpredictable behaviour? Or should
>> the parser make the behaviour predictable? If the settings could be
>> tokenized in to an ordered list then either it could use the first or last
>> duplicate setting (last should be easier).
>>
>> My feeling is that it should remain unpredictable because the syntax
>> states
>> only one is allowed and therefore duplicate settings should not be
>> supported.
>>
>
> No, that's not how things work. That something is invalid does not mean
> that the behavior should be unpredictable. Behavior should generally always
> be predictable.
>
>
>  If this is the case, it might be useful to have a note in the
>> setting paring section stating that while duplicate settings will be
>> parsed, the behaviour will be unpredictable.
>>
>> http://dev.w3.org/html5/**webvtt/#parse-the-webvtt-**settings<http://dev.w3.org/html5/webvtt/#parse-the-webvtt-settings>
>> http://dev.w3.org/html5/spec//**common-microsyntaxes.html#**
>> split-a-string-on-spaces<http://dev.w3.org/html5/spec//common-microsyntaxes.html#split-a-string-on-spaces>
>>
>> Thank you,
>> Kyle Barnhart
>>
>
> FTR, http://w3c-test.org/html/**tests/submission/Opera/media/**
> track/webvtt/parsing/001.html<http://w3c-test.org/html/tests/submission/Opera/media/track/webvtt/parsing/001.html>tests duplicate settings.
>
> --
> Simon Pieters
> Opera Software
>
>