Randomize seed for SkDiscretePathEffect::filterPath()

src/effects/SkDiscretePathEffect.cpp

 
 /*
  * Copyright 2006 The Android Open Source Project
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 
 #include "SkDiscretePathEffect.h"
 #include "SkReadBuffer.h"
 #include "SkWriteBuffer.h"
 #include "SkPathMeasure.h"
 #include "SkRandom.h"
+#include "SkTime.h"

[scroggo, 2014/06/05 16:09:30]

Not used. Please remove.

[rs.prinja, 2014/06/07 10:46:05]

Done.

 
 static void Perterb(SkPoint* p, const SkVector& tangent, SkScalar scale) {
     SkVector normal = tangent;
     normal.rotateCCW();
     normal.setLength(scale);
     *p += normal;
 }
 
+uint32_t SkDiscretePathEffect::fObjectIdGenerator = 0;
 
-SkDiscretePathEffect::SkDiscretePathEffect(SkScalar segLength, SkScalar deviation)
-    : fSegLength(segLength), fPerterb(deviation)
+SkDiscretePathEffect::SkDiscretePathEffect(SkScalar segLength, SkScalar deviation, uint32_t seedAssist)

[scroggo, 2014/06/05 16:09:30]

Over 100 chars.

[rs.prinja, 2014/06/07 10:46:05]

Done.

+    : fSegLength(segLength), fPerterb(deviation), fSeedAssist(seedAssist)
 {
+    fObjectId = fObjectIdGenerator++;
 }
 
 bool SkDiscretePathEffect::filterPath(SkPath* dst, const SkPath& src,
                                       SkStrokeRec* rec, const SkRect*) const {
     bool doFill = rec->isFillStyle();
 
     SkPathMeasure   meas(src, doFill);
-    uint32_t        seed = SkScalarRoundToInt(meas.getLength());
+
+    /* We want to have identical seeds for identical paths that share the same effect object
+     * but different seeds for identical paths that use different effect objects */
+    uint32_t seed = fObjectId + SkScalarRoundToInt(meas.getLength());

[scroggo, 2014/06/05 16:09:30]

As stated elsewhere, please just use the length and the seed.

[rs.prinja, 2014/06/07 10:46:05]

Done.

+
+    /* Also, across different runs of the same program, the same path should be seeded differently */
+    seed += SkTime::GetMSecs() / 1000;

[scroggo, 2014/06/05 16:09:30]

Please remove.

[rs.prinja, 2014/06/07 10:46:05]

Done.

+
+    /* Caller may supply their own seed assist, which by default is 1 */
+    seed *= fSeedAssist;
+
     SkLCGRandom     rand(seed ^ ((seed << 16) | (seed >> 16)));
     SkScalar        scale = fPerterb;
     SkPoint         p;
     SkVector        v;
 
     do {
         SkScalar    length = meas.getLength();
 
         if (fSegLength * (2 + doFill) > length) {
             meas.getSegment(0, length, dst, true);  // to short for us to mangle
@@ skipping 29 matching lines @@
 void SkDiscretePathEffect::flatten(SkWriteBuffer& buffer) const {
     this->INHERITED::flatten(buffer);
     buffer.writeScalar(fSegLength);
     buffer.writeScalar(fPerterb);
 }
 
 SkDiscretePathEffect::SkDiscretePathEffect(SkReadBuffer& buffer) {
     fSegLength = buffer.readScalar();
     fPerterb = buffer.readScalar();
 }