LCOV - code coverage report
Current view: directory - content/smil - nsSMILKeySpline.cpp (source / functions) Found Hit Coverage
Test: app.info Lines: 58 0 0.0 %
Date: 2012-06-02 Functions: 9 0 0.0 %

       1                 : /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
       2                 : /* ***** BEGIN LICENSE BLOCK *****
       3                 :  * Version: MPL 1.1/GPL 2.0/LGPL 2.1
       4                 :  *
       5                 :  * The contents of this file are subject to the Mozilla Public License Version
       6                 :  * 1.1 (the "License"); you may not use this file except in compliance with
       7                 :  * the License. You may obtain a copy of the License at
       8                 :  * http://www.mozilla.org/MPL/
       9                 :  *
      10                 :  * Software distributed under the License is distributed on an "AS IS" basis,
      11                 :  * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
      12                 :  * for the specific language governing rights and limitations under the
      13                 :  * License.
      14                 :  *
      15                 :  * The Original Code is the Mozilla SMIL module.
      16                 :  *
      17                 :  * The Initial Developer of the Original Code is Brian Birtles.
      18                 :  * Portions created by the Initial Developer are Copyright (C) 2005
      19                 :  * the Initial Developer. All Rights Reserved.
      20                 :  *
      21                 :  * Contributor(s):
      22                 :  *   Brian Birtles <birtles@gmail.com>
      23                 :  *
      24                 :  * Alternatively, the contents of this file may be used under the terms of
      25                 :  * either of the GNU General Public License Version 2 or later (the "GPL"),
      26                 :  * or the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
      27                 :  * in which case the provisions of the GPL or the LGPL are applicable instead
      28                 :  * of those above. If you wish to allow use of your version of this file only
      29                 :  * under the terms of either the GPL or the LGPL, and not to allow others to
      30                 :  * use your version of this file under the terms of the MPL, indicate your
      31                 :  * decision by deleting the provisions above and replace them with the notice
      32                 :  * and other provisions required by the GPL or the LGPL. If you do not delete
      33                 :  * the provisions above, a recipient may use your version of this file under
      34                 :  * the terms of any one of the MPL, the GPL or the LGPL.
      35                 :  *
      36                 :  * ***** END LICENSE BLOCK ***** */
      37                 : 
      38                 : #include "nsSMILKeySpline.h"
      39                 : #include "prtypes.h"
      40                 : #include <math.h>
      41                 : 
      42                 : #define NEWTON_ITERATIONS          4
      43                 : #define NEWTON_MIN_SLOPE           0.02
      44                 : #define SUBDIVISION_PRECISION      0.0000001
      45                 : #define SUBDIVISION_MAX_ITERATIONS 10
      46                 : 
      47                 : const double nsSMILKeySpline::kSampleStepSize =
      48                 :                                         1.0 / double(kSplineTableSize - 1);
      49                 : 
      50                 : void
      51               0 : nsSMILKeySpline::Init(double aX1,
      52                 :                       double aY1,
      53                 :                       double aX2,
      54                 :                       double aY2)
      55                 : {
      56               0 :   mX1 = aX1;
      57               0 :   mY1 = aY1;
      58               0 :   mX2 = aX2;
      59               0 :   mY2 = aY2;
      60                 : 
      61               0 :   if (mX1 != mY1 || mX2 != mY2)
      62               0 :     CalcSampleValues();
      63               0 : }
      64                 : 
      65                 : double
      66               0 : nsSMILKeySpline::GetSplineValue(double aX) const
      67                 : {
      68               0 :   if (mX1 == mY1 && mX2 == mY2)
      69               0 :     return aX;
      70                 : 
      71               0 :   return CalcBezier(GetTForX(aX), mY1, mY2);
      72                 : }
      73                 : 
      74                 : void
      75               0 : nsSMILKeySpline::GetSplineDerivativeValues(double aX, double& aDX, double& aDY) const
      76                 : {
      77               0 :   double t = GetTForX(aX);
      78               0 :   aDX = GetSlope(t, mX1, mX2);
      79               0 :   aDY = GetSlope(t, mY1, mY2);
      80               0 : }
      81                 : 
      82                 : void
      83               0 : nsSMILKeySpline::CalcSampleValues()
      84                 : {
      85               0 :   for (PRUint32 i = 0; i < kSplineTableSize; ++i) {
      86               0 :     mSampleValues[i] = CalcBezier(double(i) * kSampleStepSize, mX1, mX2);
      87                 :   }
      88               0 : }
      89                 : 
      90                 : /*static*/ double
      91               0 : nsSMILKeySpline::CalcBezier(double aT,
      92                 :                             double aA1,
      93                 :                             double aA2)
      94                 : {
      95                 :   // use Horner's scheme to evaluate the Bezier polynomial
      96               0 :   return ((A(aA1, aA2)*aT + B(aA1, aA2))*aT + C(aA1))*aT;
      97                 : }
      98                 : 
      99                 : /*static*/ double
     100               0 : nsSMILKeySpline::GetSlope(double aT,
     101                 :                           double aA1,
     102                 :                           double aA2)
     103                 : {
     104               0 :   return 3.0 * A(aA1, aA2)*aT*aT + 2.0 * B(aA1, aA2) * aT + C(aA1);
     105                 : }
     106                 : 
     107                 : double
     108               0 : nsSMILKeySpline::GetTForX(double aX) const
     109                 : {
     110                 :   // Find interval where t lies
     111               0 :   double intervalStart = 0.0;
     112               0 :   const double* currentSample = &mSampleValues[1];
     113               0 :   const double* const lastSample = &mSampleValues[kSplineTableSize - 1];
     114               0 :   for (; currentSample != lastSample && *currentSample <= aX;
     115                 :         ++currentSample) {
     116               0 :     intervalStart += kSampleStepSize;
     117                 :   }
     118               0 :   --currentSample; // t now lies between *currentSample and *currentSample+1
     119                 : 
     120                 :   // Interpolate to provide an initial guess for t
     121                 :   double dist = (aX - *currentSample) /
     122               0 :                 (*(currentSample+1) - *currentSample);
     123               0 :   double guessForT = intervalStart + dist * kSampleStepSize;
     124                 : 
     125                 :   // Check the slope to see what strategy to use. If the slope is too small
     126                 :   // Newton-Raphson iteration won't converge on a root so we use bisection
     127                 :   // instead.
     128               0 :   double initialSlope = GetSlope(guessForT, mX1, mX2);
     129               0 :   if (initialSlope >= NEWTON_MIN_SLOPE) {
     130               0 :     return NewtonRaphsonIterate(aX, guessForT);
     131               0 :   } else if (initialSlope == 0.0) {
     132               0 :     return guessForT;
     133                 :   } else {
     134               0 :     return BinarySubdivide(aX, intervalStart, intervalStart + kSampleStepSize);
     135                 :   }
     136                 : }
     137                 : 
     138                 : double
     139               0 : nsSMILKeySpline::NewtonRaphsonIterate(double aX, double aGuessT) const
     140                 : {
     141                 :   // Refine guess with Newton-Raphson iteration
     142               0 :   for (PRUint32 i = 0; i < NEWTON_ITERATIONS; ++i) {
     143                 :     // We're trying to find where f(t) = aX,
     144                 :     // so we're actually looking for a root for: CalcBezier(t) - aX
     145               0 :     double currentX = CalcBezier(aGuessT, mX1, mX2) - aX;
     146               0 :     double currentSlope = GetSlope(aGuessT, mX1, mX2);
     147                 : 
     148               0 :     if (currentSlope == 0.0)
     149               0 :       return aGuessT;
     150                 : 
     151               0 :     aGuessT -= currentX / currentSlope;
     152                 :   }
     153                 : 
     154               0 :   return aGuessT;
     155                 : }
     156                 : 
     157                 : double
     158               0 : nsSMILKeySpline::BinarySubdivide(double aX, double aA, double aB) const
     159                 : {
     160                 :   double currentX;
     161                 :   double currentT;
     162               0 :   PRUint32 i = 0;
     163                 : 
     164               0 :   do
     165                 :   {
     166               0 :     currentT = aA + (aB - aA) / 2.0;
     167               0 :     currentX = CalcBezier(currentT, mX1, mX2) - aX;
     168                 : 
     169               0 :     if (currentX > 0.0) {
     170               0 :       aB = currentT;
     171                 :     } else {
     172               0 :       aA = currentT;
     173                 :     }
     174               0 :   } while (fabs(currentX) > SUBDIVISION_PRECISION
     175                 :            && ++i < SUBDIVISION_MAX_ITERATIONS);
     176                 : 
     177               0 :   return currentT;
     178                 : }

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