585874 - SVG SMIL: Set and use the timestamp on events with event-base timing

Status: NEW

(Core :: SVG, defect)

Description

[Brian Birtles (:birtles)]

For SMIL's event base timing SMIL recommends basing the generated instance time on the timestamp of the event. This prevents synchronisation slew, particularly when several animations are configured to start in response to the same event.

Furthermore, there are specific rules for setting the timestamp for TimeEvents:

  In order to make the model operate consistently and remove the effects of synchronization slew in a chain of event times, the timestamp value associated with events such as the beginEvent,  endEvent, and repeat events is not (necessarily) the actual time that the event is raised, nor is it the time when a time dependent is actually notified of the event. Rather the event timestamp is the earliest time that the event could be raised (given the timing model semantics, and assuming that elements would begin and end precisely when they are defined to).
  http://www.w3.org/TR/SMIL/smil-timing.html#q135

Currently (see bug 485157) we simply use the time the event was received which is obviously suboptimal.

Fixing this however involves setting the timestamp correctly (and hopefully consistently) on all events that we might receive (see bug 77992 and bug 238041).