[Bug 20037] WebVTT: Redesign the positioning mechanism

https://www.w3.org/Bugs/Public/show_bug.cgi?id=20037

Silvia Pfeiffer <silviapfeiffer1@gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|---                         |FIXED

--- Comment #66 from Silvia Pfeiffer <silviapfeiffer1@gmail.com> ---
(In reply to Silvia Pfeiffer from comment #44)
> (In reply to David Singer from comment #37)
> >  In
> > the c15 proposal, that will flip the two boxes to the other sides of the
> > screen, so the captions are now under the wrong person.  This is wrong.
> 
> Right. I think you have a point - I didn't intend a change of position to be
> necessary for internationalizing text. Let's see if we can fix that.
> 
> If we separate the text directionality from the align setting, i.e. change
> the align setting from referring to the text anchoring to referring to a box
> anchoring, I think that would work. I believe that's the same proposal that
> Philip made in #c38 .
> 
> BTW: the way CSS background-position works was exactly as we had it before
> and that caused problems, because in contrast to background images, text can
> be left, middle or right aligned within its box. We need all the 0-100%
> positions of background position at work for all 3 positions of the box.
> 
> So, we need text directionality to work independent of position. E.g., a
> start aligned text box can still have rtl text aligned at the right edge of
> the box, but with box anchoring at the left edge.

I have just committed a change that resolves this and makes "text position"
refer to the position of the cue box:
https://dvcs.w3.org/hg/text-tracks/rev/bb753d2a2739

This now means the following:

* the cue box is positioned within the video viewport like CSS
background-position but at all 0-100% of the viewport. This is as it was in the
old version of the spec (the one Ian [1] wrote) with the position referring to
a x% point within the cue box when positioning at x% of the video viewport.
This is for backwards compatibility. Bug 23404 will give us other options for
positioning (left, center, right edge of cue box for measurement).

[1] Last version of WebVTT spec as written by Ian:
http://dev.w3.org/cvsweb/html5/webvtt/Overview.html?rev=1.62;content-type=text%2Fhtml

* the positioning is independent of the alignment, except that if no
positioning is given, the default depends on alignment.

* note that if you choose to create a cue box "template" into which you will
render either ltr or rtl text and your box is not 100% width and you are not
specifying "middle" as the alignment, it is indeed possible that your box may
flip sides. This is expected, since you are leaving positioning within the full
width of the viewport up to the browser. You need to provide an explicit
position to get the cue box into a fixed place.

This closes this bug (minus any typos I have introduced). All changes made in
this bug can be seen in:
http://dev.w3.org/cvsweb/html5/webvtt/Overview.html.diff?r1=text&tr1=1.75&r2=text&tr2=1.74


In the interest of readability, please open a new bug if you come across any
further issues or disagree with the patches etc. 66 comments is a lot to scroll
through. ;-)

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Received on Monday, 28 October 2013 03:52:37 UTC