Card "swipe-away" dismiss

An example prototype of adding support for
Material-style card dismissal. Many things remain to be done:

- Track event.dx sum; don't listen to the card container
- Make this a feature of Card
- Support dismissing to the left (too)
- Animate the layout change caused by dismissing the card
- Deal with many cards animating away at the same time
- Integrate with TBD VariableHeightScrollable

This version just exists to collect a little feedback,
including about the use of AnimationPerformance

R=abarth@chromium.org

Committed: https://chromium.googlesource.com/external/mojo/+/e7433cf734504a38b030734a31d7c920e9df6e8c

[hansmuller, 2015-07-08 20:46:09]

hansmuller@chromium.org changed reviewers:
+ abarth@google.com, mpcomplete@chromium.org

[hansmuller, 2015-07-08 20:48:14]

Patchset #1 (id:1) has been deleted

[hansmuller, 2015-07-08 20:51:15]

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

[hansmuller, 2015-07-08 20:51:15]

PTAL

[abarth-chromium, 2015-07-08 21:12:01]

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

[abarth-chromium, 2015-07-08 21:12:02]

LGTM

https://codereview.chromium.org/1231603003/diff/20001/sky/sdk/example/widgets...
File sky/sdk/example/widgets/card_collection.dart (right):

https://codereview.chromium.org/1231603003/diff/20001/sky/sdk/example/widgets...
sky/sdk/example/widgets/card_collection.dart:74: _activeCardAnchorX = event.x -
event.dx;
Unfortunately, the dx property gives you the delta since the last event, not the
total delta since the down.

[hansmuller, 2015-07-08 21:22:51]

https://codereview.chromium.org/1231603003/diff/20001/sky/sdk/example/widgets...
File sky/sdk/example/widgets/card_collection.dart (right):

https://codereview.chromium.org/1231603003/diff/20001/sky/sdk/example/widgets...
sky/sdk/example/widgets/card_collection.dart:74: _activeCardAnchorX = event.x -
event.dx;
On 2015/07/08 21:12:02, abarth-chromium wrote:
> Unfortunately, the dx property gives you the delta since the last event, not
the
> total delta since the down.

I assumed that, in this case, the last event was the pointer-down. I verified as
much experimentally :-).

In my next CL I'll just accumulate event.dx values. And I'll allow one to
dismiss to the left or right.

[hansmuller1, 2015-07-08 21:31:35]

Committed patchset #1 (id:20001) manually as
e7433cf734504a38b030734a31d7c920e9df6e8c (presubmit successful).

[Matt Perry, 2015-07-08 22:21:59]

https://codereview.chromium.org/1231603003/diff/20001/sky/sdk/example/widgets...
File sky/sdk/example/widgets/card_collection.dart (right):

https://codereview.chromium.org/1231603003/diff/20001/sky/sdk/example/widgets...
sky/sdk/example/widgets/card_collection.dart:51: if
(_activeCardAnimation.isCompleted && !_activeCardDragUnderway)
would this be simpler if AnimationPerformance supplied an "animationComplete"
callback?

https://codereview.chromium.org/1231603003/diff/20001/sky/sdk/example/widgets...
sky/sdk/example/widgets/card_collection.dart:114: Matrix4 transform = new
Matrix4.identity();
This'll get a little nicer once I check in my AnimatedContainer:
https://codereview.chromium.org/1223073002/

[hansmuller, 2015-07-08 23:07:15]

https://codereview.chromium.org/1231603003/diff/20001/sky/sdk/example/widgets...
File sky/sdk/example/widgets/card_collection.dart (right):

https://codereview.chromium.org/1231603003/diff/20001/sky/sdk/example/widgets...
sky/sdk/example/widgets/card_collection.dart:51: if
(_activeCardAnimation.isCompleted && !_activeCardDragUnderway)
On 2015/07/08 22:21:59, Matt Perry wrote:
> would this be simpler if AnimationPerformance supplied an "animationComplete"
> callback?

I'm not sure. I'd still need to add a callback with 
activeCardAnimation.timeline.onValueChanged.listen(), since dragging a card
updates the progress property (which defines the cards opacity and translation).
Dragging the card can cause the animation to "complete" repeatedly.  I could
write:

activeCardAnimation.timeline.onValueChanged.listen(scheduleBuild);

- and - 

activeCardAnimation.onCompleted = (_) {
  setState(() {                                
    if (!_activeCardDragUnderway)
      _dismissedCardIndices.add(_activeCardIndex);
   })
}

I guess that doesn't seem clearer.