SMILKeySpline.h

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#ifndef DOM_SMIL_SMILKEYSPLINE_H_
#define DOM_SMIL_SMILKEYSPLINE_H_

#include "mozilla/ArrayUtils.h"
#include "mozilla/PodOperations.h"

namespace mozilla {

/**
 * Utility class to provide scaling defined in a keySplines element.
 */
class SMILKeySpline {
 public:
  constexpr SMILKeySpline() : mX1(0), mY1(0), mX2(0), mY2(0) {
    /* caller must call Init later */\
  }

    /**
     * Creates a new key spline control point description.
     *
     * aX1, etc. are the x1, y1, x2, y2 cubic Bezier control points as defined
     * by SMILANIM 3.2.3. They must each be in the range 0.0 <= x <= 1.0
     */
    SMILKeySpline(double aX1, double aY1, double aX2, double aY2)
        : mX1(0), mY1(0), mX2(0), mY2(0) {
      Init(aX1, aY1, aX2, aY2);
    }

    double X1() const { return mX1; }
    double Y1() const { return mY1; }
    double X2() const { return mX2; }
    double Y2() const { return mY2; }

    void Init(double aX1, double aY1, double aX2, double aY2);

    /**
     * Gets the output (y) value for an input (x).
     *
     * @param aX  The input x value. A floating-point number between 0 and
     *            1 (inclusive).
     */
    double GetSplineValue(double aX) const;

    void GetSplineDerivativeValues(double aX, double& aDX, double& aDY) const;

    bool operator==(const SMILKeySpline& aOther) const {
      return mX1 == aOther.mX1 && mY1 == aOther.mY1 && mX2 == aOther.mX2 &&
             mY2 == aOther.mY2;
    }
    bool operator!=(const SMILKeySpline& aOther) const {
      return !(*this == aOther);
    }
    int32_t Compare(const SMILKeySpline& aRhs) const {
      if (mX1 != aRhs.mX1) return mX1 < aRhs.mX1 ? -1 : 1;
      if (mY1 != aRhs.mY1) return mY1 < aRhs.mY1 ? -1 : 1;
      if (mX2 != aRhs.mX2) return mX2 < aRhs.mX2 ? -1 : 1;
      if (mY2 != aRhs.mY2) return mY2 < aRhs.mY2 ? -1 : 1;
      return 0;
    }

   private:
    void CalcSampleValues();

    /**
     * Returns x(t) given t, x1, and x2, or y(t) given t, y1, and y2.
     */
    static double CalcBezier(double aT, double aA1, double aA2);

    /**
     * Returns dx/dt given t, x1, and x2, or dy/dt given t, y1, and y2.
     */
    static double GetSlope(double aT, double aA1, double aA2);

    double GetTForX(double aX) const;

    double NewtonRaphsonIterate(double aX, double aGuessT) const;

    double BinarySubdivide(double aX, double aA, double aB) const;

    static double A(double aA1, double aA2) {
      return 1.0 - 3.0 * aA2 + 3.0 * aA1;
    }

    static double B(double aA1, double aA2) { return 3.0 * aA2 - 6.0 * aA1; }

    static double C(double aA1) { return 3.0 * aA1; }

    double mX1;
    double mY1;
    double mX2;
    double mY2;

    enum { kSplineTableSize = 11 };
    double mSampleValues[kSplineTableSize] = {};

    static const double kSampleStepSize;
};

}  // namespace mozilla

#endif  // DOM_SMIL_SMILKEYSPLINE_H_