W3C home > Mailing lists > Public > public-texttracks@w3.org > September 2012

Re: Yet Another Scroll-Up Idea (YASUI) in VTT

From: Simon Pieters <simonp@opera.com>
Date: Fri, 07 Sep 2012 01:02:47 +0200
To: public-texttracks <public-texttracks@w3.org>, "David Singer" <singer@apple.com>
Message-ID: <op.wj8kyx0gidj3kv@device-23f190>
On Fri, 07 Sep 2012 00:08:18 +0200, David Singer <singer@apple.com> wrote:

>> Woah! I was unaware of that wiki page.
>> Why can't such UAs just support the subset of CSS that they want to  
>> support, like 'color' and 'background-color'?
> I think the amount of work to support general CSS parsing and so on is  
> not insignificant.  It's like trying to pull one thread of spaghetti off  
> your plate…you very easily end up with all of it in your lap :-(

I'm not convinced that's true. Things that want to support a limited  
subset of HTML can be expected to implement all of the parsing rules (or  
use an off-the-shelf HTML parser) and then implement only the stuff they  
care about without ending up with implementing a full browser rendering  
engine. It might be the case the off-the-shelf CSS parsers aren't readily  
available yet, though.

Even if I'm wrong, for WebVTT the set *allowed* CSS properties is very  

>> The WebVTT rendering rules don't really work like "divs" at all.
> But regions could work pretty much like them (in a restricted sense).
>> The rendering rules do things like avoid overlapping. What happens if a  
>> rollup cue and a positioned cue within a region overlap?
> At the moment, what I wrote was that when text is addressed into line N  
> of a roll-up region, then the (each) line of arriving text causes the  
> contents of lines N and above to move up a line; can collision still  
> occur?

This assumes that you can only position cues vertically with integers, not  
with %?

Simon Pieters
Opera Software
Received on Thursday, 6 September 2012 23:03:31 UTC

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