Re: File headers

Hi Glenn,

Allowing empty lines in headers will require us to make non-backwards
compatible changes to WebVTT. Or do you have an idea on how to achieve that?

I'm tempted to only allow one-line metadata and everything that needs more
should be an external sheet (such as external style sheets). That makes the
format simpler. Other than CSS, what would need multi-line metadata?

On Sat, Mar 9, 2013 at 11:52 AM, Glenn Maynard <glenn@zewt.org> wrote:

> On Wed, Oct 24, 2012 at 3:11 AM, Silvia Pfeiffer <
> silviapfeiffer1@gmail.com> wrote:
>
>> I'm now quite keen to use the following specification for multi-line cues:
>> * if a metadata field has no value in the same line as the metadata
>> field name, assume it's a multi-line metadata header
>> * multi-line metadata headers ends when a line is parsed that only
>> contains "##"
>> * no empty lines are allowed within the multi-line metadata header (if
>> people have a long CSS file with many empty lines to add, they should
>> use external stylesheets through the @import directive)
>>
>
> Comments:
>
> - If I have an editor that gives people a text box and lets them type in
> CSS, and the user uses blank lines, they shouldn't disappear when they load
> the file again later.  We should be able to store simple plain-text strings
> without odd exceptions like "can't represent blank lines" or "can't
> represent ## on a line by itself".  (Also, blank lines don't mean long
> files; I use blank lines for readability in my stylesheets regardless of
> size.  It's also not obvious to me that large stylesheets should
> necessarily always be imports.)
>


Do you have a suggestion for how to resolve this in a backwards compatible
way?


 - Currently, the suggested format means that if I edit a file that says
>
> Author: Glenn
> Language: en
>
> and remove my name, giving
>
> Author:
> Language: en
>
> then we end up with a header named "Author" with a value of "Language: en"
> and everything that follows.  That's a confusing way to fail.  We discussed
> a marker to indicate a multi-line header, eg. "Style: |", to help avoid
> this.
>

That's fine by me, but other than CSS what multi-line metadata do we need?
So, should we even bother?


- We still have the "-->" issue: current parsers will stop at the first
> "-->", assuming it's a cue (http://dev.w3.org/html5/webvtt/#parsing step
> 14).  We should be able to represent "-->" in headers.  The options seem to
> be:
>
> 1. Escape it, eg. "--&gt;".  That works, but it then means we need to
> escape &, which is pretty annoying.
> 2. Change the parser's error handling to understands the header format, so
> it only triggers when not within a real header.  I don't know if we can
> still do this.  This doesn't affect existing WebVTT files, so there
> shouldn't be a problem with web-compatibility.


I agree with 2, since it's backwards compatible. But we do need to figure
out how to make the header work. Any ideas welcome!

Silvia.