Re: Updated versions of Apple's transforms/animations/transitions proposals

On Thu, Apr 17, 2008 at 3:58 AM, Maciej Stachowiak <mjs@apple.com> wrote:

>
> On Apr 15, 2008, at 4:24 AM, Robert O'Callahan wrote:
>
> On Tue, Apr 15, 2008 at 9:31 PM, Mikko Rantalainen <
> mikko.rantalainen@peda.net> wrote:
>
> >
> > This means that if the current position is not "fully zoomed" (in case
> > of fisheye demo), the transition (the speed of the movement/zooming) is
> > slower than it would be normally but it takes as long as the full
> > movement would take.
>
>
> That may look OK in some cases but in other cases it won't. I hope that's
> not what gets specified.
>
> For really smooth handling of reversing a transition only a short way in,
> it may be desirable to specify transition velocity rather than duration.
>

Duration is simpler for authors than velocity, especially since CSS can't
express division easily. What I was thinking of have authors specify
duration, but compute the velocity by dividing the distance from the old
target value to the new target value by the duration, and use the velocity
internally instead of the duration, so if our current actual value is closer
to the new target than expected, the animation is shorter than the specified
duration, or if the actual value is further away than expected the animation
lasts longer than the specified duration.

Or maybe you allow the former case but not the latter, so the actual
duration can be less than the specified duration but not greater.

Another possibility is Hyatt's suggestion of detecting reversal, since that
> is typically the only way you see a very small transition over a long
> duration.
>

That sounds a bit fragile. For example an element might have multiple states
and we want to animate the transitions between them; we might be
transitioning from state A to state B and then suddenly decide we want state
C instead, which is closer to A than B on some property axis.

I'm hoping you are objecting only to the "full duration" part of the above,
> not starting from the current (possibly mid-transition) state when beginning
> a new transition.
>

Of course! Continuity is essential.

Rob
-- 
"He was pierced for our transgressions, he was crushed for our iniquities;
the punishment that brought us peace was upon him, and by his wounds we are
healed. We all, like sheep, have gone astray, each of us has turned to his
own way; and the LORD has laid on him the iniquity of us all." [Isaiah
53:5-6]