Re: Alternative approach to scrolling, with demos

On Mon, Mar 31, 2014 at 11:06 PM, Philip Jägenstedt <philipj@opera.com>wrote:

> Hi Rick! The simple answer is that I still don't know exactly what


Hello Philip!


> syntax and API changes I would propose, I'm still trying to figure out
> precisely what the 608/708 model is at the lowest level and whether or
> not making that model blend with WebVTT is something I could get
> behind. However, to support things as in the final absolute.html
> example, the changes would be something like this:
>
>  * Reduce VTTRegion to just scroll and lines


How would this work if you want to confine the cues in the region to a
particular place on the video? If we're removing the width setting then the
cues within the region could be all kinds of different lengths depending on
their own settings. How would that be resolved?

Also, one of the use cases for regions was using them to specify a place
for a set of cues to be displayed on the video regardless if they have a
scroll setting so that you don't have to write the same syntax for the,
potentially, hundreds of cues being displayed in that area. It sounds like
you're planning on removing this feature?

 * Make scrolling part of the overlap avoidance algorithms
>

I think this is an awesome idea. The algorithm already has a lot of the
necessary pieces needed to make this happen. It's just a few tweaks to get
this new behaviour as well.


>  * Maybe some change to how backgrounds are handled
>  * A mode of clipping scrolling cues that is more complex that the
> current spec, which AFAICT is necessary to make cues keep scrolling
> once the region is full.
>

I think this is a good idea as well. I feel like when and where cues should
be clipped is a little hard to tell and slightly ambiguous in the current
spec. Clarification would be good.


> To avoid later being accused of less-than-fair play, I'll note that I
> still think it's more sane for this stuff to be done using JavaScript,
> but I'm hedging my bets in case some browser vendor feel obligated to
> support these features declaratively. (If so, speak up!)
>

Good thing Firefox is using JavaScript! Chrome JavaScript that is ;-). More
seriously though, I get what you're saying. I do think scroll up is a good
feature to have. Especially when we want to start doing live WebVTT, if
that ever happens.

I think taking a minimal approach like this to modifying the current spec
as little as possible for region support is a good tradeoff to be compliant
with 608/708.


>
> Philip
>
> On Tue, Apr 1, 2014 at 4:58 AM, Richard Eyre <rick.eyre@outlook.com>
> wrote:
> > This looks good Philip. Regions would still have to exist in markup
> though,
> > correct? In order to comply with 608/708, I forget which one.
> >
> > Do you have an example of how the specification would change to implement
> > this new method?
> >
> >
> > On Sun, Mar 30, 2014 at 1:41 AM, Philip Jägenstedt <philipj@opera.com>
> > wrote:
> >>
> >> Hi all,
> >>
> >> As promised, I have put together demos to illustrate how the
> >> alternative approach to scrolling [1,2] would work in practice. The
> >> way I have gone about this is to assume a baseline of WebVTT without
> >> regions, and to try to solve each problem in the simplest way I could
> >> find. The demos make use of basic TextTrack and WebVTT support. I've
> >> tested them in Opera, Safari and Chrome.
> >>
> >> == Scrolling as an overlap avoidance ==
> >>
> >> Demo: http://people.opera.com/philipj/2014/03/vttscroll/simple.html
> >>
> >> When a cue overlaps, it's moved down until it doesn't overlap, then
> >> all the cues are moved up. Scrolling is implemented by moving cues,
> >> not their container.
> >>
> >> This approach makes things much more similar to the regular overlap
> >> avoidance. You will end up with cues occupying approximately the same
> >> space in both modes, the only difference is the order.
> >>
> >> == Background box tweaking ==
> >>
> >> Demo: http://people.opera.com/philipj/2014/03/vttscroll/background.html
> >>
> >> WebVTT doesn't do a good job with the cue background right now. The
> >> only thing you can put a background on is the line box. One small
> >> improvement to this would be to allow a background on the cue box
> >> instead. This demo does exactly that, and visually it looks the same
> >> as a single region background.
> >>
> >> == Clipping to a maximum number of lines ==
> >>
> >> Demo: http://people.opera.com/philipj/2014/03/vttscroll/clip.html
> >>
> >> In the demo captions there can be 4 lines visible at the same time,
> >> but the top line is a bit distracting. This demo implements a possible
> >> solution for this problem, by clipping the group of cues to a maximum
> >> number of lines.
> >>
> >> == Absolute positioning and scrolling ==
> >>
> >> Demo: http://people.opera.com/philipj/2014/03/vttscroll/absolute.html
> >>
> >> Finally, an idea for how scrolling might work with absolutely
> >> positioned cues. You simply position all the cues at the point where
> >> scrolling should begin, and they'll scroll up from there.
> >>
> >> [1]
> >> http://lists.w3.org/Archives/Public/public-texttracks/2013Nov/0012.html
> >> [2]
> >> http://lists.w3.org/Archives/Public/public-texttracks/2014Jan/0025.html
> >>
> >> Philip
> >>
> >
>
>