Re: What is the use case for two levels of background colors?

On Mon, May 12, 2014 at 10:16 PM, Philip Jägenstedt <philipj@opera.com> wrote:
> On Mon, May 12, 2014 at 10:24 AM, Silvia Pfeiffer
> <silviapfeiffer1@gmail.com> wrote:
>> On Mon, May 12, 2014 at 6:12 PM, Philip Jägenstedt <philipj@opera.com> wrote:
>>> Using the cue box as the background box was what I did in
>>> http://people.opera.com/philipj/2014/03/vttscroll/background.html
>>
>> There's a difference: you're putting a background on the individual
>> cues while the background on the region is putting a background on the
>> group of cues in one go. There is no chance of a gap appearing between
>> the cues because of this.
>
> Yes, that is true. (Trying to emulate a grid-based format should have
> similar problems.)
>
>>> However, I've realized that this creates a bit of a tension between
>>> two goals: in order to "look nice" the background should not be much
>>> bigger than the cue text, but to give the cue size to grow when the
>>> font size changes, it should be as big as possible.
>>>
>>> This would likely cause authors to create boxes that are too small,
>>> causing unnecessary line wrapping when the font size increases. Note
>>> that using a font-relative unit like em doesn't eliminate the problem,
>>> as illustrated here:
>>> http://jsfiddle.net/zLB3N/
>>>
>>> If the use case was to provide a common background for a number of
>>> lines (possibly from different cues) simply taking the bounding box of
>>> those lines and adding some padding would be enough.
>>
>> That's what the region is for.
>
> Doesn't regions have exactly the problem I describe? Not that I have a
> solution, I don't know how this could be made reliably when fonts and
> their sizes is under user control...

Yes, the bounding box around a couple of lines/captions is always big
and has some whitespace in it. That's, however, not a problem, but
rather expected, IIUC.

Also, Christian just made a very good point about why such a bounding
box is important: it allows users to override the background on the
group of captions with a single setting (
::cue-region(){background-color: red;} ).


>>> However, if the background needs to be unchanging over time
>>
>> What do you mean by "unchanging"?
>
> I mean a background which isn't just the bounding box of the cues
> current showing, but those that will be shown. The author cannot know
> what that box is, and calculating it at runtime would require
> rendering all cues once and assuming scripts won't change them...

I don't think I've seen that requirement nor did I read that out of
CEA708 nor the FCC.

Cheers,
Silvia.

Received on Monday, 12 May 2014 12:26:21 UTC