A document that belongs to an iframe that is display:none as no associated pres
context from which to get a refresh driver. However, in this case
document.timeline.currentTime should still never go backwards (since document
timelines are supposed to be monotonically increasing).
This patch makes AnimationTimeline record the last value returned for the
current time so that if the document becomes display:none we can still return
the most recently used time.
This patch changes the order in which we look for matches when updating existing
animations. Previously we would iterate through new animations in a forwards
direction but match old animations by going through the list of animations
backwards.
This patch makes us iterate through both lists in a backwards direction. That
means that if we have:
animation: anim 100s
and later we make it
animation: anim 100s, anim 100s
Then the new animation will be added to the *start* of the list, i.e. prepended,
and the resulting animation will not restart.
Previously when updating animations we'd generate a new list of animation
objects then try to match up animations from the existing list and copy across
state such as start times and notification flags. However, this means that from
the API we end up returning different objects.
This patch makes us maintain the same object identity when updating an existing
animation. It does this by looking for matching animations in both lists. If it
finds a match it copies the necessary information from the *new* animation to
the *existing* animation (but preserving the start time, last notification
etc.). Then, finally, it puts the *existing* animation in the list of *new*
animations and removes the corresponding *new* animation. The existing
animation is also removed from the list of existing animations so that it only
matches once.
The method used for matching is probably not intuitive but this is addressed in
a subsequent patch in this series.
This patch simply factors out the conversion from a TimeStamp value to
a nullable-double value relative to the start of the timeline. This is so that,
in a subsequent patch, this functionality can be reused by ElementAnimation
when it reports its start time (which is currently recorded as a TimeStamp).
AnimationTimeline::GetCurrentTime returns the time value of the timeline as
a double. For internal calculations however it is more useful to get this as
a mozilla::TimeStamp.
This patch splits the calculation of the current time into two stages:
calculation as a timestamp then conversion to a double.
