[webvtt] Definition of "text alignment" doesn't match processing requirements

zcorpan has just created a new issue for 
https://github.com/w3c/webvtt:

== Definition of "text alignment" doesn't match processing 
requirements ==
https://w3c.github.io/webvtt/#webvtt-cue-text-alignment

> A text alignment
An alignment for all lines of text within the cue box, in the 
dimension of the writing direction and the paragraph direction [BIDI],
 one of:

> Start alignment
The text is aligned towards the paragraph direction start side of the 
cue box.

As far as I can tell, this text is wrong. The [processing 
model](https://w3c.github.io/webvtt/#applying-css-properties) sets 
'unicode-bidi' to `plaintext` which isolates paragraphs, and then sets
 'text-align' to `start` for "Start alignment", and the behavior of 
CSS in that case does not match the description above.

See
http://software.hixie.ch/utilities/js/live-dom-viewer/saved/3719
and flip the value of 'text-align' between `start` and `end` (in Gecko
 or WebKit or Blink), to see what the effect of the processing 
requirements are.

So for start alignment, each line is aligned to the start edge for 
that line, which is separate from the **cue**'s "paragraph direction".

My understanding is that @r12a is happy with the effect of the 
processing requirements, so I suggest we fix the description here to 
match.

See https://github.com/w3c/webvtt/issues/232

Received on Friday, 30 October 2015 07:07:26 UTC