First pass on action animations for sprites

Adds action classes
Refactors clamp function

R=eseidel@chromium.org

Committed: https://chromium.googlesource.com/external/mojo/+/b2b69122e7e6c1b3b7477fb74ea09a703823d6d8

[viktorl, 2015-07-01 22:06:33]

viktorl@google.com changed reviewers:
+ eseidel@chromium.org

[viktorl, 2015-07-01 22:07:11]

Actions are a simple animation system, primarily for use with the sprites
package, but it can be used to animate any type of objects. The API is simple,
but will be even simpler with the new additions coming to Dart in the coming
months. Examples are provided in the upcoming syntax.

The basic building blocks of the action system is the ActionTween. It takes a
property of any object and tweens it to a new value over time. The actions are
controlled by ActionController, an ActionController is automatically created for
any Node. Execute any action by passing it to the run method.

To rotate a sprite from 0 to 360 degrees over 1 second, the following code can
be used:

var rotationAction = new ActionTween(mySprite#rotation=, 0.0, 360.0, 1.0);
mySprite.actions.run(rotationAction);

To move the sprite from the origin to 100, 100 over 1 second, use this code:

var moveAction = new ActionTween(mySprite#position=, Point.origin, new
Point(100.0, 100.0), 1.0)
actions.run(moveAction);

To loop the action in an infinite loop, use the ActionRotateForever:

var rotationAction = new ActionTween(mySprite#rotation=, 0.0, 360.0, 1.0);
var rotateForeverAction = new ActionRotateForever(rotationAction);
mySprite.actions.run(rotateForeverAction);

So far, this is system is at a very basic stage, but will include instant
actions, sequences of actions, and more supported property types.

[kulakowski, 2015-07-01 22:18:43]

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

[kulakowski, 2015-07-01 22:18:44]

https://codereview.chromium.org/1215413002/diff/1/sky/sdk/example/game/lib/ac...
File sky/sdk/example/game/lib/action.dart (right):

https://codereview.chromium.org/1215413002/diff/1/sky/sdk/example/game/lib/ac...
sky/sdk/example/game/lib/action.dart:150: if (action._finished) {
How many actions can be pending? If it's a bunch, maybe calling

actions.removeWhere((a) => a._finished);

is more efficient (the API docs are unclear about the exact allocation strategy
of List).

https://codereview.chromium.org/1215413002/diff/1/sky/sdk/example/game/lib/sp...
File sky/sdk/example/game/lib/sprite_box.dart (right):

https://codereview.chromium.org/1215413002/diff/1/sky/sdk/example/game/lib/sp...
sky/sdk/example/game/lib/sprite_box.dart:299: for (int i = node.children.length
- 1; i >= 0; i--) {
FYI List has a |reversed| property:

for (final Node child in node.children.reversed) {
   _runActions(child, dt);
}

[abarth-chromium, 2015-07-01 22:20:52]

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

[abarth-chromium, 2015-07-01 22:20:53]

https://codereview.chromium.org/1215413002/diff/1/sky/sdk/example/game/lib/ut...
File sky/sdk/example/game/lib/util.dart (right):

https://codereview.chromium.org/1215413002/diff/1/sky/sdk/example/game/lib/ut...
sky/sdk/example/game/lib/util.dart:3: num _clamp(num val, num min, num max) {
https://api.dartlang.org/apidocs/channels/stable/dartdoc-viewer/dart:core.num...

[abarth-chromium, 2015-07-01 22:22:26]

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

[abarth-chromium, 2015-07-01 22:22:26]

Might be worth talking with mpcomplete re: animations and lerps, etc.

[eseidel, 2015-07-01 22:26:43]

I don't have strong opinions.  I expect that you want to share code with
mpcomplete's animation system over time.

rs-lgtm.

[viktorl, 2015-07-01 22:28:26]

On 2015/07/01 at 22:26:43, eseidel wrote:
> I don't have strong opinions.  I expect that you want to share code with
mpcomplete's animation system over time.
> 
> rs-lgtm.

Yeah, sharing code definitely would be the best!

[viktorl, 2015-07-01 22:36:10]

Committed patchset #1 (id:1) manually as
b2b69122e7e6c1b3b7477fb74ea09a703823d6d8 (presubmit successful).

[eseidel, 2015-07-01 22:37:25]

I think another problem here is separation of concerns.  I care about your
resuable "game library" code, but I don't really care about the asteroids
specific code.  I think we should sometime-in-the-near-future separate the two
and can then have more rigorous review of your game library changes and not much
of the game demos.

The sky-based-game-library can even be its own pub package if you so desire, or
can just be part of the Sky framework depending.

[viktorl, 2015-07-01 22:42:40]

On 2015/07/01 at 22:37:25, eseidel wrote:
> I think another problem here is separation of concerns.  I care about your
resuable "game library" code, but I don't really care about the asteroids
specific code.  I think we should sometime-in-the-near-future separate the two
and can then have more rigorous review of your game library changes and not much
of the game demos.
> 
> The sky-based-game-library can even be its own pub package if you so desire,
or can just be part of the Sky framework depending.

Yes, definitely agree with this! It's already separated by the 'game_demo'
library and 'sprites', but they should be more separated, just haven't made it a
priority yet.