On Apr 11, 2010, at 2:59 PM, Jonas Sicking wrote:
On Sun, Apr 11, 2010 at 5:30 AM, Silvia Pfeiffer
<[email protected]> wrote:
f>> Is it expected that all of TTML will be required? The proposal
suggests
That is also something that still has to be discussed further.
Initial
feedback from browser vendors was that the full TTML spec is too
complicated and too much to support from the start. Thus, the
implementation path with the TTML profiles is being suggested.
However, it is as yet unclear if there should be a native parsing
implementation of TTML implemented in browsers or simply a mapping of
TTML markup to HTML/CSS/JavaScript. My gut feeling is that the latter
would be easier, in particular since such a mapping has been started
already with Philippe's implementation, see
http://www.w3.org/2009/02/ThisIsCoffee.html . The mapping would need
to be documented.
Personally I'm concerned that if we start heading down the TTML path,
browsers are ultimately going to end up forced to implement the whole
thing. Useful parts as well as parts less so. We see this time and
again where if we implement part of a spec we end up forced to
implement the whole thing.
I'm especially concerned that TTML presentation is formally defined in
terms of XSL-FO, itself an extremely complicated spec that is in many
ways at odds with the CSS formatting model in browser engines. I am
not at all enthusiastic about implementing a second layout engine just
for captions.
While some have claimed that it's probably possible to translate TTML
presentation requirements to CSS, I don't really buy this without
seeing a normative specification for how to do so.
Regards,
Maciej
