| // Copyright 2014 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. |
| |
| #ifndef UI_GFX_GEOMETRY_CUBIC_BEZIER_H_ |
| #define UI_GFX_GEOMETRY_CUBIC_BEZIER_H_ |
| |
| #include "base/macros.h" |
| #include "ui/gfx/geometry/geometry_export.h" |
| |
| namespace gfx { |
| |
| class GEOMETRY_EXPORT CubicBezier { |
| public: |
| CubicBezier(double p1x, double p1y, double p2x, double p2y); |
| CubicBezier(const CubicBezier& other); |
| |
| double SampleCurveX(double t) const { |
| // `ax t^3 + bx t^2 + cx t' expanded using Horner's rule. |
| return ((ax_ * t + bx_) * t + cx_) * t; |
| } |
| |
| double SampleCurveY(double t) const { |
| return ((ay_ * t + by_) * t + cy_) * t; |
| } |
| |
| double SampleCurveDerivativeX(double t) const { |
| return (3.0 * ax_ * t + 2.0 * bx_) * t + cx_; |
| } |
| |
| double SampleCurveDerivativeY(double t) const { |
| return (3.0 * ay_ * t + 2.0 * by_) * t + cy_; |
| } |
| |
| static double GetDefaultEpsilon(); |
| |
| // Given an x value, find a parametric value it came from. |
| // x must be in [0, 1] range. Doesn't use gradients. |
| double SolveCurveX(double x, double epsilon) const; |
| |
| // Evaluates y at the given x with default epsilon. |
| double Solve(double x) const; |
| // Evaluates y at the given x. The epsilon parameter provides a hint as to the |
| // required accuracy and is not guaranteed. Uses gradients if x is |
| // out of [0, 1] range. |
| double SolveWithEpsilon(double x, double epsilon) const { |
| if (x < 0.0) |
| return 0.0 + start_gradient_ * x; |
| if (x > 1.0) |
| return 1.0 + end_gradient_ * (x - 1.0); |
| return SampleCurveY(SolveCurveX(x, epsilon)); |
| } |
| |
| // Returns an approximation of dy/dx at the given x with default epsilon. |
| double Slope(double x) const; |
| // Returns an approximation of dy/dx at the given x. |
| // Clamps x to range [0, 1]. |
| double SlopeWithEpsilon(double x, double epsilon) const; |
| |
| // These getters are used rarely. We reverse compute them from coefficients. |
| // See CubicBezier::InitCoefficients. The speed has been traded for memory. |
| double GetX1() const; |
| double GetY1() const; |
| double GetX2() const; |
| double GetY2() const; |
| |
| // Gets the bezier's minimum y value in the interval [0, 1]. |
| double range_min() const { return range_min_; } |
| // Gets the bezier's maximum y value in the interval [0, 1]. |
| double range_max() const { return range_max_; } |
| |
| private: |
| void InitCoefficients(double p1x, double p1y, double p2x, double p2y); |
| void InitGradients(double p1x, double p1y, double p2x, double p2y); |
| void InitRange(double p1y, double p2y); |
| |
| double ax_; |
| double bx_; |
| double cx_; |
| |
| double ay_; |
| double by_; |
| double cy_; |
| |
| double start_gradient_; |
| double end_gradient_; |
| |
| double range_min_; |
| double range_max_; |
| |
| DISALLOW_ASSIGN(CubicBezier); |
| }; |
| |
| } // namespace gfx |
| |
| #endif // UI_GFX_GEOMETRY_CUBIC_BEZIER_H_ |