RE: Timed tracks

When TTML was being defined, XSL:FO was ahead. And a lot of the CSS3 work was either in a very rough state or not there at all. 
When CSS3 gets a little more mature, in say 10 years. Then TTML could migrate to it. But to be clear, TTML is *defined* in terms of the semantics of XSL:FO, which is *defined* largely in terms of CSS; but it is its own thing, and it does not require either a full XSL:FO processor or a CSS one.

We deliberately did not define an applicative model for styling in TTML, although we discussed it for a long time. Neither did we include either full CSS or XSL:FO in order to keep implementation cost down.

-----Original Message-----
From: public-html-request@w3.org [mailto:public-html-request@w3.org] On Behalf Of Philippe Le Hegaret
Sent: Thursday, May 06, 2010 7:24 PM
To: Geoff Freed
Cc: HTML WG
Subject: Re: Timed tracks

On Thu, 2010-05-06 at 13:49 -0400, Geoff Freed wrote:
>         But since XSL:FO is based on CSS, would it be such a large
>         amount of work to define mappings of the former to the
>         latter?  In the TTML spec, links are provided to the XSL:FO
>         elements, which themselves are linked to the appropriate CSS
>         references.

There are differences between XSL FO and CSS. Several values provided in the XSL FO aren't supported in the CSS specifications and are thus impossible to map into a HTML+CSS engine, like in text-decoration. In addition, the innovation happening in CSS isn't happening in the XSL FO world as far as I know and XSL FO is no where to have the same numbers of properties that one can find in CSS. For example, you can't use text-shadow, advanced box model, border-radius, transition effects, or media queries in TTML. There is no support for selectors or @font-face either.

Philippe

Received on Thursday, 6 May 2010 22:01:53 UTC