src/java.desktop/share/classes/sun/java2d/marlin/DDasher.java
changeset 47216 71c04702a3d5
parent 47126 188ef162f019
child 48284 fd7fbc929001
equal deleted inserted replaced
47215:4ebc2e2fb97c 47216:71c04702a3d5
       
     1 /*
       
     2  * Copyright (c) 2007, 2017, Oracle and/or its affiliates. All rights reserved.
       
     3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
       
     4  *
       
     5  * This code is free software; you can redistribute it and/or modify it
       
     6  * under the terms of the GNU General Public License version 2 only, as
       
     7  * published by the Free Software Foundation.  Oracle designates this
       
     8  * particular file as subject to the "Classpath" exception as provided
       
     9  * by Oracle in the LICENSE file that accompanied this code.
       
    10  *
       
    11  * This code is distributed in the hope that it will be useful, but WITHOUT
       
    12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
       
    13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
       
    14  * version 2 for more details (a copy is included in the LICENSE file that
       
    15  * accompanied this code).
       
    16  *
       
    17  * You should have received a copy of the GNU General Public License version
       
    18  * 2 along with this work; if not, write to the Free Software Foundation,
       
    19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
       
    20  *
       
    21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
       
    22  * or visit www.oracle.com if you need additional information or have any
       
    23  * questions.
       
    24  */
       
    25 
       
    26 package sun.java2d.marlin;
       
    27 
       
    28 import java.util.Arrays;
       
    29 
       
    30 /**
       
    31  * The <code>DDasher</code> class takes a series of linear commands
       
    32  * (<code>moveTo</code>, <code>lineTo</code>, <code>close</code> and
       
    33  * <code>end</code>) and breaks them into smaller segments according to a
       
    34  * dash pattern array and a starting dash phase.
       
    35  *
       
    36  * <p> Issues: in J2Se, a zero length dash segment as drawn as a very
       
    37  * short dash, whereas Pisces does not draw anything.  The PostScript
       
    38  * semantics are unclear.
       
    39  *
       
    40  */
       
    41 final class DDasher implements DPathConsumer2D, MarlinConst {
       
    42 
       
    43     static final int REC_LIMIT = 4;
       
    44     static final double ERR = 0.01d;
       
    45     static final double MIN_T_INC = 1.0d / (1 << REC_LIMIT);
       
    46 
       
    47     // More than 24 bits of mantissa means we can no longer accurately
       
    48     // measure the number of times cycled through the dash array so we
       
    49     // punt and override the phase to just be 0 past that point.
       
    50     static final double MAX_CYCLES = 16000000.0d;
       
    51 
       
    52     private DPathConsumer2D out;
       
    53     private double[] dash;
       
    54     private int dashLen;
       
    55     private double startPhase;
       
    56     private boolean startDashOn;
       
    57     private int startIdx;
       
    58 
       
    59     private boolean starting;
       
    60     private boolean needsMoveTo;
       
    61 
       
    62     private int idx;
       
    63     private boolean dashOn;
       
    64     private double phase;
       
    65 
       
    66     private double sx, sy;
       
    67     private double x0, y0;
       
    68 
       
    69     // temporary storage for the current curve
       
    70     private final double[] curCurvepts;
       
    71 
       
    72     // per-thread renderer context
       
    73     final DRendererContext rdrCtx;
       
    74 
       
    75     // flag to recycle dash array copy
       
    76     boolean recycleDashes;
       
    77 
       
    78     // dashes ref (dirty)
       
    79     final DoubleArrayCache.Reference dashes_ref;
       
    80     // firstSegmentsBuffer ref (dirty)
       
    81     final DoubleArrayCache.Reference firstSegmentsBuffer_ref;
       
    82 
       
    83     /**
       
    84      * Constructs a <code>DDasher</code>.
       
    85      * @param rdrCtx per-thread renderer context
       
    86      */
       
    87     DDasher(final DRendererContext rdrCtx) {
       
    88         this.rdrCtx = rdrCtx;
       
    89 
       
    90         dashes_ref = rdrCtx.newDirtyDoubleArrayRef(INITIAL_ARRAY); // 1K
       
    91 
       
    92         firstSegmentsBuffer_ref = rdrCtx.newDirtyDoubleArrayRef(INITIAL_ARRAY); // 1K
       
    93         firstSegmentsBuffer     = firstSegmentsBuffer_ref.initial;
       
    94 
       
    95         // we need curCurvepts to be able to contain 2 curves because when
       
    96         // dashing curves, we need to subdivide it
       
    97         curCurvepts = new double[8 * 2];
       
    98     }
       
    99 
       
   100     /**
       
   101      * Initialize the <code>DDasher</code>.
       
   102      *
       
   103      * @param out an output <code>DPathConsumer2D</code>.
       
   104      * @param dash an array of <code>double</code>s containing the dash pattern
       
   105      * @param dashLen length of the given dash array
       
   106      * @param phase a <code>double</code> containing the dash phase
       
   107      * @param recycleDashes true to indicate to recycle the given dash array
       
   108      * @return this instance
       
   109      */
       
   110     DDasher init(final DPathConsumer2D out, double[] dash, int dashLen,
       
   111                 double phase, boolean recycleDashes)
       
   112     {
       
   113         this.out = out;
       
   114 
       
   115         // Normalize so 0 <= phase < dash[0]
       
   116         int sidx = 0;
       
   117         dashOn = true;
       
   118         double sum = 0.0d;
       
   119         for (double d : dash) {
       
   120             sum += d;
       
   121         }
       
   122         double cycles = phase / sum;
       
   123         if (phase < 0.0d) {
       
   124             if (-cycles >= MAX_CYCLES) {
       
   125                 phase = 0.0d;
       
   126             } else {
       
   127                 int fullcycles = FloatMath.floor_int(-cycles);
       
   128                 if ((fullcycles & dash.length & 1) != 0) {
       
   129                     dashOn = !dashOn;
       
   130                 }
       
   131                 phase += fullcycles * sum;
       
   132                 while (phase < 0.0d) {
       
   133                     if (--sidx < 0) {
       
   134                         sidx = dash.length - 1;
       
   135                     }
       
   136                     phase += dash[sidx];
       
   137                     dashOn = !dashOn;
       
   138                 }
       
   139             }
       
   140         } else if (phase > 0) {
       
   141             if (cycles >= MAX_CYCLES) {
       
   142                 phase = 0.0d;
       
   143             } else {
       
   144                 int fullcycles = FloatMath.floor_int(cycles);
       
   145                 if ((fullcycles & dash.length & 1) != 0) {
       
   146                     dashOn = !dashOn;
       
   147                 }
       
   148                 phase -= fullcycles * sum;
       
   149                 double d;
       
   150                 while (phase >= (d = dash[sidx])) {
       
   151                     phase -= d;
       
   152                     sidx = (sidx + 1) % dash.length;
       
   153                     dashOn = !dashOn;
       
   154                 }
       
   155             }
       
   156         }
       
   157 
       
   158         this.dash = dash;
       
   159         this.dashLen = dashLen;
       
   160         this.startPhase = this.phase = phase;
       
   161         this.startDashOn = dashOn;
       
   162         this.startIdx = sidx;
       
   163         this.starting = true;
       
   164         needsMoveTo = false;
       
   165         firstSegidx = 0;
       
   166 
       
   167         this.recycleDashes = recycleDashes;
       
   168 
       
   169         return this; // fluent API
       
   170     }
       
   171 
       
   172     /**
       
   173      * Disposes this dasher:
       
   174      * clean up before reusing this instance
       
   175      */
       
   176     void dispose() {
       
   177         if (DO_CLEAN_DIRTY) {
       
   178             // Force zero-fill dirty arrays:
       
   179             Arrays.fill(curCurvepts, 0.0d);
       
   180         }
       
   181         // Return arrays:
       
   182         if (recycleDashes) {
       
   183             dash = dashes_ref.putArray(dash);
       
   184         }
       
   185         firstSegmentsBuffer = firstSegmentsBuffer_ref.putArray(firstSegmentsBuffer);
       
   186     }
       
   187 
       
   188     double[] copyDashArray(final float[] dashes) {
       
   189         final int len = dashes.length;
       
   190         final double[] newDashes;
       
   191         if (len <= MarlinConst.INITIAL_ARRAY) {
       
   192             newDashes = dashes_ref.initial;
       
   193         } else {
       
   194             if (DO_STATS) {
       
   195                 rdrCtx.stats.stat_array_dasher_dasher.add(len);
       
   196             }
       
   197             newDashes = dashes_ref.getArray(len);
       
   198         }
       
   199         for (int i = 0; i < len; i++) { newDashes[i] = dashes[i]; }
       
   200         return newDashes;
       
   201     }
       
   202 
       
   203     @Override
       
   204     public void moveTo(double x0, double y0) {
       
   205         if (firstSegidx > 0) {
       
   206             out.moveTo(sx, sy);
       
   207             emitFirstSegments();
       
   208         }
       
   209         needsMoveTo = true;
       
   210         this.idx = startIdx;
       
   211         this.dashOn = this.startDashOn;
       
   212         this.phase = this.startPhase;
       
   213         this.sx = this.x0 = x0;
       
   214         this.sy = this.y0 = y0;
       
   215         this.starting = true;
       
   216     }
       
   217 
       
   218     private void emitSeg(double[] buf, int off, int type) {
       
   219         switch (type) {
       
   220         case 8:
       
   221             out.curveTo(buf[off+0], buf[off+1],
       
   222                         buf[off+2], buf[off+3],
       
   223                         buf[off+4], buf[off+5]);
       
   224             return;
       
   225         case 6:
       
   226             out.quadTo(buf[off+0], buf[off+1],
       
   227                        buf[off+2], buf[off+3]);
       
   228             return;
       
   229         case 4:
       
   230             out.lineTo(buf[off], buf[off+1]);
       
   231             return;
       
   232         default:
       
   233         }
       
   234     }
       
   235 
       
   236     private void emitFirstSegments() {
       
   237         final double[] fSegBuf = firstSegmentsBuffer;
       
   238 
       
   239         for (int i = 0; i < firstSegidx; ) {
       
   240             int type = (int)fSegBuf[i];
       
   241             emitSeg(fSegBuf, i + 1, type);
       
   242             i += (type - 1);
       
   243         }
       
   244         firstSegidx = 0;
       
   245     }
       
   246     // We don't emit the first dash right away. If we did, caps would be
       
   247     // drawn on it, but we need joins to be drawn if there's a closePath()
       
   248     // So, we store the path elements that make up the first dash in the
       
   249     // buffer below.
       
   250     private double[] firstSegmentsBuffer; // dynamic array
       
   251     private int firstSegidx;
       
   252 
       
   253     // precondition: pts must be in relative coordinates (relative to x0,y0)
       
   254     private void goTo(double[] pts, int off, final int type) {
       
   255         double x = pts[off + type - 4];
       
   256         double y = pts[off + type - 3];
       
   257         if (dashOn) {
       
   258             if (starting) {
       
   259                 int len = type - 1; // - 2 + 1
       
   260                 int segIdx = firstSegidx;
       
   261                 double[] buf = firstSegmentsBuffer;
       
   262                 if (segIdx + len  > buf.length) {
       
   263                     if (DO_STATS) {
       
   264                         rdrCtx.stats.stat_array_dasher_firstSegmentsBuffer
       
   265                             .add(segIdx + len);
       
   266                     }
       
   267                     firstSegmentsBuffer = buf
       
   268                         = firstSegmentsBuffer_ref.widenArray(buf, segIdx,
       
   269                                                              segIdx + len);
       
   270                 }
       
   271                 buf[segIdx++] = type;
       
   272                 len--;
       
   273                 // small arraycopy (2, 4 or 6) but with offset:
       
   274                 System.arraycopy(pts, off, buf, segIdx, len);
       
   275                 segIdx += len;
       
   276                 firstSegidx = segIdx;
       
   277             } else {
       
   278                 if (needsMoveTo) {
       
   279                     out.moveTo(x0, y0);
       
   280                     needsMoveTo = false;
       
   281                 }
       
   282                 emitSeg(pts, off, type);
       
   283             }
       
   284         } else {
       
   285             starting = false;
       
   286             needsMoveTo = true;
       
   287         }
       
   288         this.x0 = x;
       
   289         this.y0 = y;
       
   290     }
       
   291 
       
   292     @Override
       
   293     public void lineTo(double x1, double y1) {
       
   294         double dx = x1 - x0;
       
   295         double dy = y1 - y0;
       
   296 
       
   297         double len = dx*dx + dy*dy;
       
   298         if (len == 0.0d) {
       
   299             return;
       
   300         }
       
   301         len = Math.sqrt(len);
       
   302 
       
   303         // The scaling factors needed to get the dx and dy of the
       
   304         // transformed dash segments.
       
   305         final double cx = dx / len;
       
   306         final double cy = dy / len;
       
   307 
       
   308         final double[] _curCurvepts = curCurvepts;
       
   309         final double[] _dash = dash;
       
   310 
       
   311         double leftInThisDashSegment;
       
   312         double dashdx, dashdy, p;
       
   313 
       
   314         while (true) {
       
   315             leftInThisDashSegment = _dash[idx] - phase;
       
   316 
       
   317             if (len <= leftInThisDashSegment) {
       
   318                 _curCurvepts[0] = x1;
       
   319                 _curCurvepts[1] = y1;
       
   320                 goTo(_curCurvepts, 0, 4);
       
   321 
       
   322                 // Advance phase within current dash segment
       
   323                 phase += len;
       
   324                 // TODO: compare double values using epsilon:
       
   325                 if (len == leftInThisDashSegment) {
       
   326                     phase = 0.0d;
       
   327                     idx = (idx + 1) % dashLen;
       
   328                     dashOn = !dashOn;
       
   329                 }
       
   330                 return;
       
   331             }
       
   332 
       
   333             dashdx = _dash[idx] * cx;
       
   334             dashdy = _dash[idx] * cy;
       
   335 
       
   336             if (phase == 0.0d) {
       
   337                 _curCurvepts[0] = x0 + dashdx;
       
   338                 _curCurvepts[1] = y0 + dashdy;
       
   339             } else {
       
   340                 p = leftInThisDashSegment / _dash[idx];
       
   341                 _curCurvepts[0] = x0 + p * dashdx;
       
   342                 _curCurvepts[1] = y0 + p * dashdy;
       
   343             }
       
   344 
       
   345             goTo(_curCurvepts, 0, 4);
       
   346 
       
   347             len -= leftInThisDashSegment;
       
   348             // Advance to next dash segment
       
   349             idx = (idx + 1) % dashLen;
       
   350             dashOn = !dashOn;
       
   351             phase = 0.0d;
       
   352         }
       
   353     }
       
   354 
       
   355     // shared instance in DDasher
       
   356     private final LengthIterator li = new LengthIterator();
       
   357 
       
   358     // preconditions: curCurvepts must be an array of length at least 2 * type,
       
   359     // that contains the curve we want to dash in the first type elements
       
   360     private void somethingTo(int type) {
       
   361         if (pointCurve(curCurvepts, type)) {
       
   362             return;
       
   363         }
       
   364         li.initializeIterationOnCurve(curCurvepts, type);
       
   365 
       
   366         // initially the current curve is at curCurvepts[0...type]
       
   367         int curCurveoff = 0;
       
   368         double lastSplitT = 0.0d;
       
   369         double t;
       
   370         double leftInThisDashSegment = dash[idx] - phase;
       
   371 
       
   372         while ((t = li.next(leftInThisDashSegment)) < 1.0d) {
       
   373             if (t != 0.0d) {
       
   374                 DHelpers.subdivideAt((t - lastSplitT) / (1.0d - lastSplitT),
       
   375                                     curCurvepts, curCurveoff,
       
   376                                     curCurvepts, 0,
       
   377                                     curCurvepts, type, type);
       
   378                 lastSplitT = t;
       
   379                 goTo(curCurvepts, 2, type);
       
   380                 curCurveoff = type;
       
   381             }
       
   382             // Advance to next dash segment
       
   383             idx = (idx + 1) % dashLen;
       
   384             dashOn = !dashOn;
       
   385             phase = 0.0d;
       
   386             leftInThisDashSegment = dash[idx];
       
   387         }
       
   388         goTo(curCurvepts, curCurveoff+2, type);
       
   389         phase += li.lastSegLen();
       
   390         if (phase >= dash[idx]) {
       
   391             phase = 0.0d;
       
   392             idx = (idx + 1) % dashLen;
       
   393             dashOn = !dashOn;
       
   394         }
       
   395         // reset LengthIterator:
       
   396         li.reset();
       
   397     }
       
   398 
       
   399     private static boolean pointCurve(double[] curve, int type) {
       
   400         for (int i = 2; i < type; i++) {
       
   401             if (curve[i] != curve[i-2]) {
       
   402                 return false;
       
   403             }
       
   404         }
       
   405         return true;
       
   406     }
       
   407 
       
   408     // Objects of this class are used to iterate through curves. They return
       
   409     // t values where the left side of the curve has a specified length.
       
   410     // It does this by subdividing the input curve until a certain error
       
   411     // condition has been met. A recursive subdivision procedure would
       
   412     // return as many as 1<<limit curves, but this is an iterator and we
       
   413     // don't need all the curves all at once, so what we carry out a
       
   414     // lazy inorder traversal of the recursion tree (meaning we only move
       
   415     // through the tree when we need the next subdivided curve). This saves
       
   416     // us a lot of memory because at any one time we only need to store
       
   417     // limit+1 curves - one for each level of the tree + 1.
       
   418     // NOTE: the way we do things here is not enough to traverse a general
       
   419     // tree; however, the trees we are interested in have the property that
       
   420     // every non leaf node has exactly 2 children
       
   421     static final class LengthIterator {
       
   422         private enum Side {LEFT, RIGHT};
       
   423         // Holds the curves at various levels of the recursion. The root
       
   424         // (i.e. the original curve) is at recCurveStack[0] (but then it
       
   425         // gets subdivided, the left half is put at 1, so most of the time
       
   426         // only the right half of the original curve is at 0)
       
   427         private final double[][] recCurveStack; // dirty
       
   428         // sides[i] indicates whether the node at level i+1 in the path from
       
   429         // the root to the current leaf is a left or right child of its parent.
       
   430         private final Side[] sides; // dirty
       
   431         private int curveType;
       
   432         // lastT and nextT delimit the current leaf.
       
   433         private double nextT;
       
   434         private double lenAtNextT;
       
   435         private double lastT;
       
   436         private double lenAtLastT;
       
   437         private double lenAtLastSplit;
       
   438         private double lastSegLen;
       
   439         // the current level in the recursion tree. 0 is the root. limit
       
   440         // is the deepest possible leaf.
       
   441         private int recLevel;
       
   442         private boolean done;
       
   443 
       
   444         // the lengths of the lines of the control polygon. Only its first
       
   445         // curveType/2 - 1 elements are valid. This is an optimization. See
       
   446         // next() for more detail.
       
   447         private final double[] curLeafCtrlPolyLengths = new double[3];
       
   448 
       
   449         LengthIterator() {
       
   450             this.recCurveStack = new double[REC_LIMIT + 1][8];
       
   451             this.sides = new Side[REC_LIMIT];
       
   452             // if any methods are called without first initializing this object
       
   453             // on a curve, we want it to fail ASAP.
       
   454             this.nextT = Double.MAX_VALUE;
       
   455             this.lenAtNextT = Double.MAX_VALUE;
       
   456             this.lenAtLastSplit = Double.MIN_VALUE;
       
   457             this.recLevel = Integer.MIN_VALUE;
       
   458             this.lastSegLen = Double.MAX_VALUE;
       
   459             this.done = true;
       
   460         }
       
   461 
       
   462         /**
       
   463          * Reset this LengthIterator.
       
   464          */
       
   465         void reset() {
       
   466             // keep data dirty
       
   467             // as it appears not useful to reset data:
       
   468             if (DO_CLEAN_DIRTY) {
       
   469                 final int recLimit = recCurveStack.length - 1;
       
   470                 for (int i = recLimit; i >= 0; i--) {
       
   471                     Arrays.fill(recCurveStack[i], 0.0d);
       
   472                 }
       
   473                 Arrays.fill(sides, Side.LEFT);
       
   474                 Arrays.fill(curLeafCtrlPolyLengths, 0.0d);
       
   475                 Arrays.fill(nextRoots, 0.0d);
       
   476                 Arrays.fill(flatLeafCoefCache, 0.0d);
       
   477                 flatLeafCoefCache[2] = -1.0d;
       
   478             }
       
   479         }
       
   480 
       
   481         void initializeIterationOnCurve(double[] pts, int type) {
       
   482             // optimize arraycopy (8 values faster than 6 = type):
       
   483             System.arraycopy(pts, 0, recCurveStack[0], 0, 8);
       
   484             this.curveType = type;
       
   485             this.recLevel = 0;
       
   486             this.lastT = 0.0d;
       
   487             this.lenAtLastT = 0.0d;
       
   488             this.nextT = 0.0d;
       
   489             this.lenAtNextT = 0.0d;
       
   490             goLeft(); // initializes nextT and lenAtNextT properly
       
   491             this.lenAtLastSplit = 0.0d;
       
   492             if (recLevel > 0) {
       
   493                 this.sides[0] = Side.LEFT;
       
   494                 this.done = false;
       
   495             } else {
       
   496                 // the root of the tree is a leaf so we're done.
       
   497                 this.sides[0] = Side.RIGHT;
       
   498                 this.done = true;
       
   499             }
       
   500             this.lastSegLen = 0.0d;
       
   501         }
       
   502 
       
   503         // 0 == false, 1 == true, -1 == invalid cached value.
       
   504         private int cachedHaveLowAcceleration = -1;
       
   505 
       
   506         private boolean haveLowAcceleration(double err) {
       
   507             if (cachedHaveLowAcceleration == -1) {
       
   508                 final double len1 = curLeafCtrlPolyLengths[0];
       
   509                 final double len2 = curLeafCtrlPolyLengths[1];
       
   510                 // the test below is equivalent to !within(len1/len2, 1, err).
       
   511                 // It is using a multiplication instead of a division, so it
       
   512                 // should be a bit faster.
       
   513                 if (!DHelpers.within(len1, len2, err * len2)) {
       
   514                     cachedHaveLowAcceleration = 0;
       
   515                     return false;
       
   516                 }
       
   517                 if (curveType == 8) {
       
   518                     final double len3 = curLeafCtrlPolyLengths[2];
       
   519                     // if len1 is close to 2 and 2 is close to 3, that probably
       
   520                     // means 1 is close to 3 so the second part of this test might
       
   521                     // not be needed, but it doesn't hurt to include it.
       
   522                     final double errLen3 = err * len3;
       
   523                     if (!(DHelpers.within(len2, len3, errLen3) &&
       
   524                           DHelpers.within(len1, len3, errLen3))) {
       
   525                         cachedHaveLowAcceleration = 0;
       
   526                         return false;
       
   527                     }
       
   528                 }
       
   529                 cachedHaveLowAcceleration = 1;
       
   530                 return true;
       
   531             }
       
   532 
       
   533             return (cachedHaveLowAcceleration == 1);
       
   534         }
       
   535 
       
   536         // we want to avoid allocations/gc so we keep this array so we
       
   537         // can put roots in it,
       
   538         private final double[] nextRoots = new double[4];
       
   539 
       
   540         // caches the coefficients of the current leaf in its flattened
       
   541         // form (see inside next() for what that means). The cache is
       
   542         // invalid when it's third element is negative, since in any
       
   543         // valid flattened curve, this would be >= 0.
       
   544         private final double[] flatLeafCoefCache = new double[]{0.0d, 0.0d, -1.0d, 0.0d};
       
   545 
       
   546         // returns the t value where the remaining curve should be split in
       
   547         // order for the left subdivided curve to have length len. If len
       
   548         // is >= than the length of the uniterated curve, it returns 1.
       
   549         double next(final double len) {
       
   550             final double targetLength = lenAtLastSplit + len;
       
   551             while (lenAtNextT < targetLength) {
       
   552                 if (done) {
       
   553                     lastSegLen = lenAtNextT - lenAtLastSplit;
       
   554                     return 1.0d;
       
   555                 }
       
   556                 goToNextLeaf();
       
   557             }
       
   558             lenAtLastSplit = targetLength;
       
   559             final double leaflen = lenAtNextT - lenAtLastT;
       
   560             double t = (targetLength - lenAtLastT) / leaflen;
       
   561 
       
   562             // cubicRootsInAB is a fairly expensive call, so we just don't do it
       
   563             // if the acceleration in this section of the curve is small enough.
       
   564             if (!haveLowAcceleration(0.05d)) {
       
   565                 // We flatten the current leaf along the x axis, so that we're
       
   566                 // left with a, b, c which define a 1D Bezier curve. We then
       
   567                 // solve this to get the parameter of the original leaf that
       
   568                 // gives us the desired length.
       
   569                 final double[] _flatLeafCoefCache = flatLeafCoefCache;
       
   570 
       
   571                 if (_flatLeafCoefCache[2] < 0.0d) {
       
   572                     double x =     curLeafCtrlPolyLengths[0],
       
   573                           y = x + curLeafCtrlPolyLengths[1];
       
   574                     if (curveType == 8) {
       
   575                         double z = y + curLeafCtrlPolyLengths[2];
       
   576                         _flatLeafCoefCache[0] = 3.0d * (x - y) + z;
       
   577                         _flatLeafCoefCache[1] = 3.0d * (y - 2.0d * x);
       
   578                         _flatLeafCoefCache[2] = 3.0d * x;
       
   579                         _flatLeafCoefCache[3] = -z;
       
   580                     } else if (curveType == 6) {
       
   581                         _flatLeafCoefCache[0] = 0.0d;
       
   582                         _flatLeafCoefCache[1] = y - 2.0d * x;
       
   583                         _flatLeafCoefCache[2] = 2.0d * x;
       
   584                         _flatLeafCoefCache[3] = -y;
       
   585                     }
       
   586                 }
       
   587                 double a = _flatLeafCoefCache[0];
       
   588                 double b = _flatLeafCoefCache[1];
       
   589                 double c = _flatLeafCoefCache[2];
       
   590                 double d = t * _flatLeafCoefCache[3];
       
   591 
       
   592                 // we use cubicRootsInAB here, because we want only roots in 0, 1,
       
   593                 // and our quadratic root finder doesn't filter, so it's just a
       
   594                 // matter of convenience.
       
   595                 int n = DHelpers.cubicRootsInAB(a, b, c, d, nextRoots, 0, 0.0d, 1.0d);
       
   596                 if (n == 1 && !Double.isNaN(nextRoots[0])) {
       
   597                     t = nextRoots[0];
       
   598                 }
       
   599             }
       
   600             // t is relative to the current leaf, so we must make it a valid parameter
       
   601             // of the original curve.
       
   602             t = t * (nextT - lastT) + lastT;
       
   603             if (t >= 1.0d) {
       
   604                 t = 1.0d;
       
   605                 done = true;
       
   606             }
       
   607             // even if done = true, if we're here, that means targetLength
       
   608             // is equal to, or very, very close to the total length of the
       
   609             // curve, so lastSegLen won't be too high. In cases where len
       
   610             // overshoots the curve, this method will exit in the while
       
   611             // loop, and lastSegLen will still be set to the right value.
       
   612             lastSegLen = len;
       
   613             return t;
       
   614         }
       
   615 
       
   616         double lastSegLen() {
       
   617             return lastSegLen;
       
   618         }
       
   619 
       
   620         // go to the next leaf (in an inorder traversal) in the recursion tree
       
   621         // preconditions: must be on a leaf, and that leaf must not be the root.
       
   622         private void goToNextLeaf() {
       
   623             // We must go to the first ancestor node that has an unvisited
       
   624             // right child.
       
   625             int _recLevel = recLevel;
       
   626             final Side[] _sides = sides;
       
   627 
       
   628             _recLevel--;
       
   629             while(_sides[_recLevel] == Side.RIGHT) {
       
   630                 if (_recLevel == 0) {
       
   631                     recLevel = 0;
       
   632                     done = true;
       
   633                     return;
       
   634                 }
       
   635                 _recLevel--;
       
   636             }
       
   637 
       
   638             _sides[_recLevel] = Side.RIGHT;
       
   639             // optimize arraycopy (8 values faster than 6 = type):
       
   640             System.arraycopy(recCurveStack[_recLevel], 0,
       
   641                              recCurveStack[_recLevel+1], 0, 8);
       
   642             _recLevel++;
       
   643 
       
   644             recLevel = _recLevel;
       
   645             goLeft();
       
   646         }
       
   647 
       
   648         // go to the leftmost node from the current node. Return its length.
       
   649         private void goLeft() {
       
   650             double len = onLeaf();
       
   651             if (len >= 0.0d) {
       
   652                 lastT = nextT;
       
   653                 lenAtLastT = lenAtNextT;
       
   654                 nextT += (1 << (REC_LIMIT - recLevel)) * MIN_T_INC;
       
   655                 lenAtNextT += len;
       
   656                 // invalidate caches
       
   657                 flatLeafCoefCache[2] = -1.0d;
       
   658                 cachedHaveLowAcceleration = -1;
       
   659             } else {
       
   660                 DHelpers.subdivide(recCurveStack[recLevel], 0,
       
   661                                   recCurveStack[recLevel+1], 0,
       
   662                                   recCurveStack[recLevel], 0, curveType);
       
   663                 sides[recLevel] = Side.LEFT;
       
   664                 recLevel++;
       
   665                 goLeft();
       
   666             }
       
   667         }
       
   668 
       
   669         // this is a bit of a hack. It returns -1 if we're not on a leaf, and
       
   670         // the length of the leaf if we are on a leaf.
       
   671         private double onLeaf() {
       
   672             double[] curve = recCurveStack[recLevel];
       
   673             double polyLen = 0.0d;
       
   674 
       
   675             double x0 = curve[0], y0 = curve[1];
       
   676             for (int i = 2; i < curveType; i += 2) {
       
   677                 final double x1 = curve[i], y1 = curve[i+1];
       
   678                 final double len = DHelpers.linelen(x0, y0, x1, y1);
       
   679                 polyLen += len;
       
   680                 curLeafCtrlPolyLengths[i/2 - 1] = len;
       
   681                 x0 = x1;
       
   682                 y0 = y1;
       
   683             }
       
   684 
       
   685             final double lineLen = DHelpers.linelen(curve[0], curve[1],
       
   686                                                   curve[curveType-2],
       
   687                                                   curve[curveType-1]);
       
   688             if ((polyLen - lineLen) < ERR || recLevel == REC_LIMIT) {
       
   689                 return (polyLen + lineLen) / 2.0d;
       
   690             }
       
   691             return -1.0d;
       
   692         }
       
   693     }
       
   694 
       
   695     @Override
       
   696     public void curveTo(double x1, double y1,
       
   697                         double x2, double y2,
       
   698                         double x3, double y3)
       
   699     {
       
   700         final double[] _curCurvepts = curCurvepts;
       
   701         _curCurvepts[0] = x0;        _curCurvepts[1] = y0;
       
   702         _curCurvepts[2] = x1;        _curCurvepts[3] = y1;
       
   703         _curCurvepts[4] = x2;        _curCurvepts[5] = y2;
       
   704         _curCurvepts[6] = x3;        _curCurvepts[7] = y3;
       
   705         somethingTo(8);
       
   706     }
       
   707 
       
   708     @Override
       
   709     public void quadTo(double x1, double y1, double x2, double y2) {
       
   710         final double[] _curCurvepts = curCurvepts;
       
   711         _curCurvepts[0] = x0;        _curCurvepts[1] = y0;
       
   712         _curCurvepts[2] = x1;        _curCurvepts[3] = y1;
       
   713         _curCurvepts[4] = x2;        _curCurvepts[5] = y2;
       
   714         somethingTo(6);
       
   715     }
       
   716 
       
   717     @Override
       
   718     public void closePath() {
       
   719         lineTo(sx, sy);
       
   720         if (firstSegidx > 0) {
       
   721             if (!dashOn || needsMoveTo) {
       
   722                 out.moveTo(sx, sy);
       
   723             }
       
   724             emitFirstSegments();
       
   725         }
       
   726         moveTo(sx, sy);
       
   727     }
       
   728 
       
   729     @Override
       
   730     public void pathDone() {
       
   731         if (firstSegidx > 0) {
       
   732             out.moveTo(sx, sy);
       
   733             emitFirstSegments();
       
   734         }
       
   735         out.pathDone();
       
   736 
       
   737         // Dispose this instance:
       
   738         dispose();
       
   739     }
       
   740 
       
   741     @Override
       
   742     public long getNativeConsumer() {
       
   743         throw new InternalError("DDasher does not use a native consumer");
       
   744     }
       
   745 }
       
   746