Re: SVG and getCurrentTime

Hi Cyril,

I mainly wanted to respond to one thing:

 This part is yet to be spec'ed but I *think* the arrangement we will end
>> up with may be something like this:
>>
>> * Each Document has a timeline (the 'document timeline').
>>
>> The document timeline is not seekable/pauseable. This is because pausing
>> the document timeline, for example, would cause all UI transitions to stop
>> playing which is generally not what you want.
>>
> I understand the problem, but I would rather have UI transitions not
> locked onto the document timeline. Having the ability to expose controls
> (as with a video) to control the document timeline would be very useful.


Do you have any solid use cases for this? I'm struggling to think of any.
The performance implications of a seekable document timeline are pretty
monstrous - essentially every transition that ever occurs on a page must be
kept for the page's lifetime.

I'd also question whether it makes sense to pause or reverse a transition
via the document timeline. What happens if a transition occurs, then the
timeline is reversed and another transition is triggered partway through
the reversed playback of the previous transition? Does the new transition
get entered into the timeline backwards? Does the new transition start form
the current animation state, or the "real" state of the element?

If you've got some good use cases then we should definitely work them
through. One alternative (to cover debugging style use cases) is to be able
to throw the page into a debug or playback mode and keep a buffer of recent
transitions that can then be scrubbed in a read-only fashion. This
preserves an immutable flow of time for the page but still allows
fine-grained inspection of the behaviour.

Cheers,
    -Shane