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Fix TimingAnimation rounding error issue (Take 2)
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Summary:
This fixes a bug where the frames array can contain a duplicate entry at the end.
For example, suppose the duration is 1000.0 then it would create an array with the following:

```
[ 0,
  0.0010119824303159884,
  0.00391003997863186,
  0.00851330482578147,
  0.01466951184383165,
  0.022249135687575607,
  0.03114100006836614,
  0.041248932923769244,
  0.05248918022066495,
  0.06478838042267626,
  0.07808196049642172,
  0.09231285402599128,
  0.1074304693764467,
  0.12338985513375342,
  0.14015102395653428,
  0.15767840628626964,
  0.17594041329987542,
  0.1949090949486824,
  0.21455988464815853,
  0.23487142789035506,
  0.25582549864491233,
  0.27740701626433145,
  0.2996041891505173,
  0.3224088345090182,
  0.34581696665965683,
  0.36982983491413496,
  0.394455794287552,
  0.4197139228812336,
  0.44564199741037275,
  0.4723190090623474,
  0.5000000572130084,
  0.5276809909376533,
  0.5543580025896278,
  0.5802860771187669,
  0.6055442057124484,
  0.6301701650858652,
  0.6541830333403433,
  0.6775911654909819,
  0.7003958108494828,
  0.7225929837356684,
  0.7441745013550876,
  0.7651285721096447,
  0.785440115351841,
  0.8050909050513173,
  0.8240595867001241,
  0.84232159371373,
  0.8598489760434653,
  0.876610144866246,
  0.8925695306235529,
  0.9076871459740083,
  0.9219180395035779,
  0.9352116195773232,
  0.9475108197793346,
  0.9587510670762303,
  0.9688589999316335,
  0.9777508643124241,
  0.9853304881561681,
  0.9914866951742183,
  0.996089960021368,
  0.9989880175696839,
  1,
  1 ]
```

With this change, it now generates the following array:

```
[ 0,
  0.0010119824303159884,
  0.00391003997863186,
  0.00851330482578147,
  0.01466951184383165,
  0.022249135687575607,
  0.03114100006836614,
  0.041248932923769244,
  0.05248918022066495,
  0.06478838042267626,
  0.07808196049642172,
  0.09231285402599128,
  0.1074304693764467,
  0.12338985513375342,
  0.14015102395653428,
  0.15767840628626964,
  0.17594041329987542,
  0.1949090949486824,
  0.21455988464815853,
  0.23487142789035506,
  0.25582549864491233,
  0.27740701626433145,
  0.2996041891505173,
  0.3224088345090182,
  0.34581696665965683,
  0.36982983491413496,
  0.394455794287552,
  0.4197139228812336,
  0.44564199741037275,
  0.4723190090623474,
  0.5000000572130084,
  0.5276809909376533,
  0.5543580025896278,
  0.5802860771187669,
  0.6055442057124484,
  0.6301701650858652,
  0.6541830333403433,
  0.6775911654909819,
  0.7003958108494828,
  0.7225929837356684,
  0.7441745013550876,
  0.7651285721096447,
  0.785440115351841,
  0.8050909050513173,
  0.8240595867001241,
  0.84232159371373,
  0.8598489760434653,
  0.876610144866246,
  0.8925695306235529,
  0.9076871459740083,
  0.9219180395035779,
  0.9352116195773232,
  0.9475108197793346,
  0.9587510670762303,
  0.9688589999316335,
  0.9777508643124241,
  0.9853304881561681,
  0.9914866951742183,
  0.996089960021368,
  0.9989880175696839,
  1 ]
```

Note that the duplicate 1 at the end is now gone. This is because previously when it accumulated dt for 60 frames. dt wasn't quite exactly 1000, it was instead 999.9999999999999 and so didn't break out of the loop when it should have. This adds a tolerance so that it does break out of the loop.

Reviewed By: dimach1977

Differential Revision: D17828204

fbshipit-source-id: 4483303de852071436cf9a82e50296baf3392329
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Martin Sherburn authored and facebook-github-bot committed Oct 10, 2019
1 parent b658708 commit bfd0155
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Showing 2 changed files with 35 additions and 2 deletions.
32 changes: 32 additions & 0 deletions Libraries/Animated/src/__tests__/TimingAnimation-test.js
Original file line number Diff line number Diff line change
@@ -0,0 +1,32 @@
/**
* Copyright (c) Facebook, Inc. and its affiliates.
*
* This source code is licensed under the MIT license found in the
* LICENSE file in the root directory of this source tree.
*
* @format
* @emails oncall+react_native
*/

'use strict';

const TimingAnimation = require('../animations/TimingAnimation');

describe('Timing Animation', () => {
it('should return array of 61 items', () => {
const timingAnim = new TimingAnimation({duration: 1000});
const config = timingAnim.__getNativeAnimationConfig();

expect(config.frames.length).toBe(61);
expect(config.frames[60]).toBe(1);
expect(config.frames[59]).toBeLessThan(1);
});

it('should cope with zero duration', () => {
const timingAnim = new TimingAnimation({duration: 0});
const config = timingAnim.__getNativeAnimationConfig();

expect(config.frames.length).toBe(1);
expect(config.frames[0]).toBe(1);
});
});
5 changes: 3 additions & 2 deletions Libraries/Animated/src/animations/TimingAnimation.js
Original file line number Diff line number Diff line change
Expand Up @@ -66,8 +66,9 @@ class TimingAnimation extends Animation {
__getNativeAnimationConfig(): any {
const frameDuration = 1000.0 / 60.0;
const frames = [];
for (let dt = 0.0; dt < this._duration; dt += frameDuration) {
frames.push(this._easing(dt / this._duration));
const numFrames = Math.round(this._duration / frameDuration);
for (let frame = 0; frame < numFrames; frame++) {
frames.push(this._easing(frame / numFrames));
}
frames.push(this._easing(1));
return {
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