Add support for "flinging" the animation timeline with a spring force. So far,

Add support for "flinging" the animation timeline with a spring force. So far,
Drawer uses this when you fling it.

I refactored Timeline to be based on AnimatedSimulation. When playing normally,
we use a TweenSimulation, which just gives values linearly in a range. You can
optionally replace this simulation with one of your choice (in Drawer's case, a
SpringSimulation).

R=abarth@chromium.org

Committed: https://chromium.googlesource.com/external/mojo/+/a02eb74b7deb52526b6152f208632e233846b8f6

[Matt Perry, 2015-07-15 19:22:40]

mpcomplete@chromium.org changed reviewers:
+ abarth@chromium.org

[abarth-chromium, 2015-07-15 19:38:12]

https://codereview.chromium.org/1233653003/diff/60001/sky/sdk/lib/animation/t...
File sky/sdk/lib/animation/timeline.dart (right):

https://codereview.chromium.org/1233653003/diff/60001/sky/sdk/lib/animation/t...
sky/sdk/lib/animation/timeline.dart:70: final double duration; // in seconds
We should probably push the Duration type further into the system

https://codereview.chromium.org/1233653003/diff/60001/sky/sdk/lib/animation/t...
sky/sdk/lib/animation/timeline.dart:71: final double begin; // 0 to 1.
What does this comment mean?  It looks like these can be any value.

https://codereview.chromium.org/1233653003/diff/60001/sky/sdk/lib/animation/t...
sky/sdk/lib/animation/timeline.dart:74: TweenSimulation(this.duration,
this.begin, this.end);
const

https://codereview.chromium.org/1233653003/diff/60001/sky/sdk/lib/animation/t...
sky/sdk/lib/animation/timeline.dart:76: @override
We're not using @override annotations yet because they aren't enforced by the
analyzer.

https://codereview.chromium.org/1233653003/diff/60001/sky/sdk/lib/animation/t...
sky/sdk/lib/animation/timeline.dart:132: mass: 1.0, springConstant: 500.0,
ratio: 1.0);
Should this code be shared with scroll_behavior.dart?  There the springConstant
is 170.0 and the ratio is 1.1.

[abarth-chromium, 2015-07-15 19:40:22]

https://codereview.chromium.org/1233653003/diff/60001/sky/sdk/lib/animation/t...
File sky/sdk/lib/animation/timeline.dart (right):

https://codereview.chromium.org/1233653003/diff/60001/sky/sdk/lib/animation/t...
sky/sdk/lib/animation/timeline.dart:8: import
'package:sky/animation/animated_simulation.dart';
This import introduces a circular dependency between these two files.  We should
just merge them into one file instead of having a circular dependency.

https://codereview.chromium.org/1233653003/diff/60001/sky/sdk/lib/animation/t...
sky/sdk/lib/animation/timeline.dart:9: import
'package:sky/animation/scroll_behavior.dart';
It seems wrong for timeline.dart to depend on scroll_behavior.dart.  What are
you using form this library?  Maybe we should factor that code into this library
instead.

[hansmuller, 2015-07-15 19:42:47]

hansmuller@chromium.org changed reviewers:
+ hansmuller@chromium.org

[hansmuller, 2015-07-15 19:42:48]

https://codereview.chromium.org/1233653003/diff/60001/sky/sdk/lib/animation/t...
File sky/sdk/lib/animation/timeline.dart (right):

https://codereview.chromium.org/1233653003/diff/60001/sky/sdk/lib/animation/t...
sky/sdk/lib/animation/timeline.dart:132: mass: 1.0, springConstant: 500.0,
ratio: 1.0);
On 2015/07/15 19:38:12, abarth-chromium wrote:
> Should this code be shared with scroll_behavior.dart?  There the
springConstant
> is 170.0 and the ratio is 1.1.

Chinmay and I arrived at the SpringDescription parameters in
scroll_behavior.dart by experimenting with different values for a while. See
https://codereview.chromium.org/1241733002

Using 170.0 for the spring constant seemed provide the right amount
of snap.

Perhaps a const SpringDescription belongs in view_configuration.dart.

[Matt Perry, 2015-07-15 20:17:58]

https://codereview.chromium.org/1233653003/diff/60001/sky/sdk/lib/animation/t...
File sky/sdk/lib/animation/timeline.dart (right):

https://codereview.chromium.org/1233653003/diff/60001/sky/sdk/lib/animation/t...
sky/sdk/lib/animation/timeline.dart:8: import
'package:sky/animation/animated_simulation.dart';
On 2015/07/15 19:40:22, abarth-chromium wrote:
> This import introduces a circular dependency between these two files.  We
should
> just merge them into one file instead of having a circular dependency.

I just moved Ticker for now. Let me know if you think we should merge them
further.

https://codereview.chromium.org/1233653003/diff/60001/sky/sdk/lib/animation/t...
sky/sdk/lib/animation/timeline.dart:9: import
'package:sky/animation/scroll_behavior.dart';
On 2015/07/15 19:40:22, abarth-chromium wrote:
> It seems wrong for timeline.dart to depend on scroll_behavior.dart.  What are
> you using form this library?  Maybe we should factor that code into this
library
> instead.

That's a mistake. removed.

https://codereview.chromium.org/1233653003/diff/60001/sky/sdk/lib/animation/t...
sky/sdk/lib/animation/timeline.dart:70: final double duration; // in seconds
On 2015/07/15 19:38:12, abarth-chromium wrote:
> We should probably push the Duration type further into the system

Done.

https://codereview.chromium.org/1233653003/diff/60001/sky/sdk/lib/animation/t...
sky/sdk/lib/animation/timeline.dart:71: final double begin; // 0 to 1.
On 2015/07/15 19:38:12, abarth-chromium wrote:
> What does this comment mean?  It looks like these can be any value.

Got rid of the comment and added an assert

https://codereview.chromium.org/1233653003/diff/60001/sky/sdk/lib/animation/t...
sky/sdk/lib/animation/timeline.dart:74: TweenSimulation(this.duration,
this.begin, this.end);
On 2015/07/15 19:38:12, abarth-chromium wrote:
> const

Done.

https://codereview.chromium.org/1233653003/diff/60001/sky/sdk/lib/animation/t...
sky/sdk/lib/animation/timeline.dart:76: @override
On 2015/07/15 19:38:12, abarth-chromium wrote:
> We're not using @override annotations yet because they aren't enforced by the
> analyzer.

OK I removed them, but that seems like a silly reason not to use something :)
(e.g. comments aren't enforced either, but are still helpful)

https://codereview.chromium.org/1233653003/diff/60001/sky/sdk/lib/animation/t...
sky/sdk/lib/animation/timeline.dart:132: mass: 1.0, springConstant: 500.0,
ratio: 1.0);
On 2015/07/15 19:42:48, hansmuller wrote:
> On 2015/07/15 19:38:12, abarth-chromium wrote:
> > Should this code be shared with scroll_behavior.dart?  There the
> springConstant
> > is 170.0 and the ratio is 1.1.
> 
> Chinmay and I arrived at the SpringDescription parameters in
> scroll_behavior.dart by experimenting with different values for a while. See
> https://codereview.chromium.org/1241733002
> 
> Using 170.0 for the spring constant seemed provide the right amount
> of snap.
> 
> Perhaps a const SpringDescription belongs in view_configuration.dart.

I twiddled with the values a bunch to make it look just right for the Drawer. I
suspect we'll need different constants for each type of thing we're animating.

BTW https://www.desmos.com/calculator/unqmkyqrcd was helpful in figuring out the
right values.

[Matt Perry, 2015-07-15 20:45:23]

I changed Dismissable to use fling() as well. Hans, you might want to take a
look there.

[abarth-chromium, 2015-07-15 20:49:26]

lgtm

https://codereview.chromium.org/1233653003/diff/100001/sky/sdk/lib/animation/...
File sky/sdk/lib/animation/timeline.dart (right):

https://codereview.chromium.org/1233653003/diff/100001/sky/sdk/lib/animation/...
sky/sdk/lib/animation/timeline.dart:10: const  double _kEpsilon = 0.001;
Does this mean we'll simulate down to the 1000th of a pixel?  Does the drawer
animation stop ticking at a reasonable point?

https://codereview.chromium.org/1233653003/diff/100001/sky/sdk/lib/animation/...
sky/sdk/lib/animation/timeline.dart:73: mass: 1.0, springConstant: 500.0, ratio:
1.0);
I'm not quite sure where this should live...  I guess here is ok for now until
we learn how many different springs we're going to need.

[hansmuller, 2015-07-15 20:57:50]

https://codereview.chromium.org/1233653003/diff/100001/sky/sdk/lib/widgets/di...
File sky/sdk/lib/widgets/dismissable.dart (right):

https://codereview.chromium.org/1233653003/diff/100001/sky/sdk/lib/widgets/di...
sky/sdk/lib/widgets/dismissable.dart:130: _performance.fling(velocity:
event.velocityX.abs() / _width);
I think you need to set _dragX here, as before. Otherwise we'll always be
flinging to the right.

[Matt Perry, 2015-07-15 21:00:08]

https://codereview.chromium.org/1233653003/diff/100001/sky/sdk/lib/widgets/di...
File sky/sdk/lib/widgets/dismissable.dart (right):

https://codereview.chromium.org/1233653003/diff/100001/sky/sdk/lib/widgets/di...
sky/sdk/lib/widgets/dismissable.dart:130: _performance.fling(velocity:
event.velocityX.abs() / _width);
On 2015/07/15 20:57:50, hansmuller wrote:
> I think you need to set _dragX here, as before. Otherwise we'll always be
> flinging to the right.

Flinging left still works - I think because all my fling gestures are preceeded
by a "move pointer to the left" gesture. But maybe I can't rely on that..

[Matt Perry, 2015-07-15 21:07:46]

Committed patchset #8 (id:120001) manually as
a02eb74b7deb52526b6152f208632e233846b8f6 (presubmit successful).