Animation enhancements

Brian Hudson brian.r.hudson at
Tue Sep 11 15:49:49 UTC 2018

Async: started, cycleStarted, cycleEnded, ended, paused, resumed

A "starting" event would have to be synchronous to work as I described. The
other "-ing" events probably aren't useful an cause the complications you

On Tue, Sep 11, 2018 at 10:11 AM Nir Lisker <nlisker at> wrote:

> So the "-ed" events are synchronous? That is, in case of "started", the
> animation needs to wait until the event handling finished and then start.
> In the case of "starting", the animation would start and call the event
> handler asynchronously (like "finished" does now).
> Synchronous events can be problematic because they interfere with the
> running of the animation. A "cycleStarting" (for example) handler will need
> to suspend the animation somehow before each cycle for an unknown duration
> (because it can't know what you put in the handler code). This can be done
> in practice via something like Future, but I'm skeptical about how much
> this would fit with the current animation semantics.
> There is a case for "starting" though, which is that it doesn't interfere
> with a running animation, and that it can be used as a
> "prepare-then-start", as you said. But what happens when the animation is
> embedded in a sequential and parallel transitions?
> I agree that other "-ed" events are not that useful. We can discuss a
> "prepare-then-start" mechanism.
> On Tue, Sep 11, 2018 at 4:09 PM Brian Hudson <brian.r.hudson at>
> wrote:
>> starting: Indicates that the animation is about to start. This is the
>> last opportunity to change an aspect of the animation that cannot be
>> changed once the animation has started. PathTransition duration for example.
>> started: The animation has started.
>> The "-ed" actions are really what I've had a need for, other than
>> "starting" I can't really think of use cases for the other "-ing" events
>> On Tue, Sep 11, 2018 at 4:42 AM Nir Lisker <nlisker at> wrote:
>>> Hi Brian,
>>> Thanks for the input. How is "starting" different from "started" etc.?
>>> On Mon, Sep 10, 2018 at 6:23 PM Brian Hudson <brian.r.hudson at>
>>> wrote:
>>>> I would love to see "Animation needs more events" resolved [1].
>>>> Maybe following events: started, paused, resumed, cycleStarted,
>>>> cycleEnded,
>>>> stopped/ended? These additional life cycle events would allow me to do
>>>> some
>>>> things with animations/transitions that I've been struggling to do.
>>>> There may even be use cases events for starting, pausing, resuming,
>>>> cycleStarting, cycleEnding, stopping/ending.
>>>> [1]:

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