| // Copyright 2015 The Chromium Authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style license that can be |
| // found in the LICENSE file. |
| |
| double _evaluateCubic(double a, double b, double m) { |
| // TODO(abarth): Would Math.pow be faster? |
| return 3 * a * (1 - m) * (1 - m) * m + 3 * b * (1 - m) * m * m + m * m * m; |
| } |
| |
| const double _kCubicErrorBound = 0.001; |
| |
| abstract class Curve { |
| double transform(double t); |
| } |
| |
| class Linear implements Curve { |
| const Linear(); |
| |
| double transform(double t) { |
| return t; |
| } |
| } |
| |
| class ParabolicFall implements Curve { |
| const ParabolicFall(); |
| |
| double transform(double t) { |
| return -t*t + 1; |
| } |
| } |
| |
| class ParabolicRise implements Curve { |
| const ParabolicRise(); |
| |
| double transform(double t) { |
| return -(t-1)*(t-1) + 1; |
| } |
| } |
| |
| class Cubic implements Curve { |
| final double a; |
| final double b; |
| final double c; |
| final double d; |
| |
| const Cubic(this.a, this.b, this.c, this.d); |
| |
| double transform(double t) { |
| double start = 0.0; |
| double end = 1.0; |
| while (true) { |
| double midpoint = (start + end) / 2; |
| double estimate = _evaluateCubic(a, c, midpoint); |
| |
| if ((t - estimate).abs() < _kCubicErrorBound) |
| return _evaluateCubic(b, d, midpoint); |
| |
| if (estimate < t) |
| start = midpoint; |
| else |
| end = midpoint; |
| } |
| } |
| } |
| |
| const Linear linear = const Linear(); |
| const Cubic ease = const Cubic(0.25, 0.1, 0.25, 1.0); |
| const Cubic easeIn = const Cubic(0.42, 0.0, 1.0, 1.0); |
| const Cubic easeOut = const Cubic(0.0, 0.0, 0.58, 1.0); |
| const Cubic easeInOut = const Cubic(0.42, 0.0, 0.58, 1.0); |
| const ParabolicRise parabolicRise = const ParabolicRise(); |
| const ParabolicFall parabolicFall = const ParabolicFall(); |