Extract most of the mutable state of SkShader into a separate Context object.

src/effects/SkPerlinNoiseShader.cpp

 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkDither.h"
 #include "SkPerlinNoiseShader.h"
 #include "SkColorFilter.h"
@@ skipping 260 matching lines @@
                                          const SkISize* tileSize)
   : fType(type)
   , fBaseFrequencyX(baseFrequencyX)
   , fBaseFrequencyY(baseFrequencyY)
   , fNumOctaves(numOctaves > 255 ? 255 : numOctaves/*[0,255] octaves allowed*/)
   , fSeed(seed)
   , fTileSize(NULL == tileSize ? SkISize::Make(0, 0) : *tileSize)
   , fStitchTiles(!fTileSize.isEmpty())
 {
     SkASSERT(numOctaves >= 0 && numOctaves < 256);
-    fMatrix.reset();
     fPaintingData = SkNEW_ARGS(PaintingData, (fTileSize, fSeed, fBaseFrequencyX, fBaseFrequencyY));
 }
 
 SkPerlinNoiseShader::SkPerlinNoiseShader(SkReadBuffer& buffer)
     : INHERITED(buffer)
 {
     fType           = (SkPerlinNoiseShader::Type) buffer.readInt();
     fBaseFrequencyX = buffer.readScalar();
     fBaseFrequencyY = buffer.readScalar();
     fNumOctaves     = buffer.readInt();
     fSeed           = buffer.readScalar();
     fStitchTiles    = buffer.readBool();
     fTileSize.fWidth  = buffer.readInt();
     fTileSize.fHeight = buffer.readInt();
-    fMatrix.reset();
     fPaintingData = SkNEW_ARGS(PaintingData, (fTileSize, fSeed, fBaseFrequencyX, fBaseFrequencyY));
     buffer.validate(perlin_noise_type_is_valid(fType) &&
                     (fNumOctaves >= 0) && (fNumOctaves <= 255) &&
                     (fStitchTiles != fTileSize.isEmpty()));
 }
 
 SkPerlinNoiseShader::~SkPerlinNoiseShader() {
     // Safety, should have been done in endContext()
     SkDELETE(fPaintingData);
 }
 
 void SkPerlinNoiseShader::flatten(SkWriteBuffer& buffer) const {
     this->INHERITED::flatten(buffer);
     buffer.writeInt((int) fType);
     buffer.writeScalar(fBaseFrequencyX);
     buffer.writeScalar(fBaseFrequencyY);
     buffer.writeInt(fNumOctaves);
     buffer.writeScalar(fSeed);
     buffer.writeBool(fStitchTiles);
     buffer.writeInt(fTileSize.fWidth);
     buffer.writeInt(fTileSize.fHeight);
 }
 
-SkScalar SkPerlinNoiseShader::noise2D(int channel, const PaintingData& paintingData,
-                                      const StitchData& stitchData,
-                                      const SkPoint& noiseVector) const {
+SkScalar SkPerlinNoiseShader::PerlinNoiseShaderContext::noise2D(
+        int channel, const PaintingData& paintingData,
+        const StitchData& stitchData, const SkPoint& noiseVector) const {
     struct Noise {
         int noisePositionIntegerValue;
         SkScalar noisePositionFractionValue;
         Noise(SkScalar component)
         {
             SkScalar position = component + kPerlinNoise;
             noisePositionIntegerValue = SkScalarFloorToInt(position);
             noisePositionFractionValue = position - SkIntToScalar(noisePositionIntegerValue);
         }
     };
     Noise noiseX(noiseVector.x());
     Noise noiseY(noiseVector.y());
     SkScalar u, v;
+    const SkPerlinNoiseShader& perlinNoiseShader = static_cast<const SkPerlinNoiseShader&>(fShader);
     // If stitching, adjust lattice points accordingly.
-    if (fStitchTiles) {
+    if (perlinNoiseShader.fStitchTiles) {
         noiseX.noisePositionIntegerValue =
             checkNoise(noiseX.noisePositionIntegerValue, stitchData.fWrapX, stitchData.fWidth);
         noiseY.noisePositionIntegerValue =
             checkNoise(noiseY.noisePositionIntegerValue, stitchData.fWrapY, stitchData.fHeight);
     }
     noiseX.noisePositionIntegerValue &= kBlockMask;
     noiseY.noisePositionIntegerValue &= kBlockMask;
     int latticeIndex =
         paintingData.fLatticeSelector[noiseX.noisePositionIntegerValue] +
         noiseY.noisePositionIntegerValue;
@@ skipping 10 matching lines @@
     v = paintingData.fGradient[channel][nextLatticeIndex & kBlockMask].dot(fractionValue);
     SkScalar a = SkScalarInterp(u, v, sx);
     fractionValue.fY -= SK_Scalar1; // Offset (-1,-1)
     v = paintingData.fGradient[channel][(nextLatticeIndex + 1) & kBlockMask].dot(fractionValue);
     fractionValue.fX = noiseX.noisePositionFractionValue; // Offset (0,-1)
     u = paintingData.fGradient[channel][(latticeIndex + 1) & kBlockMask].dot(fractionValue);
     SkScalar b = SkScalarInterp(u, v, sx);
     return SkScalarInterp(a, b, sy);
 }
 
-SkScalar SkPerlinNoiseShader::calculateTurbulenceValueForPoint(int channel,
-                                                               const PaintingData& paintingData,
-                                                               StitchData& stitchData,
-                                                               const SkPoint& point) const {
-    if (fStitchTiles) {
+SkScalar SkPerlinNoiseShader::PerlinNoiseShaderContext::calculateTurbulenceValueForPoint(
+        int channel, const PaintingData& paintingData,
+        StitchData& stitchData, const SkPoint& point) const {
+    const SkPerlinNoiseShader& perlinNoiseShader = static_cast<const SkPerlinNoiseShader&>(fShader);
+    if (perlinNoiseShader.fStitchTiles) {
         // Set up TurbulenceInitial stitch values.
         stitchData = paintingData.fStitchDataInit;
     }
     SkScalar turbulenceFunctionResult = 0;
     SkPoint noiseVector(SkPoint::Make(SkScalarMul(point.x(), paintingData.fBaseFrequency.fX),
                                       SkScalarMul(point.y(), paintingData.fBaseFrequency.fY)));
     SkScalar ratio = SK_Scalar1;
-    for (int octave = 0; octave < fNumOctaves; ++octave) {
+    for (int octave = 0; octave < perlinNoiseShader.fNumOctaves; ++octave) {
         SkScalar noise = noise2D(channel, paintingData, stitchData, noiseVector);
         turbulenceFunctionResult += SkScalarDiv(
-            (fType == kFractalNoise_Type) ? noise : SkScalarAbs(noise), ratio);
+            (perlinNoiseShader.fType == kFractalNoise_Type) ? noise : SkScalarAbs(noise), ratio);
         noiseVector.fX *= 2;
         noiseVector.fY *= 2;
         ratio *= 2;
-        if (fStitchTiles) {
+        if (perlinNoiseShader.fStitchTiles) {
             // Update stitch values
             stitchData.fWidth  *= 2;
             stitchData.fWrapX   = stitchData.fWidth + kPerlinNoise;
             stitchData.fHeight *= 2;
             stitchData.fWrapY   = stitchData.fHeight + kPerlinNoise;
         }
     }
 
     // The value of turbulenceFunctionResult comes from ((turbulenceFunctionResult) + 1) / 2
     // by fractalNoise and (turbulenceFunctionResult) by turbulence.
-    if (fType == kFractalNoise_Type) {
+    if (perlinNoiseShader.fType == kFractalNoise_Type) {
         turbulenceFunctionResult =
             SkScalarMul(turbulenceFunctionResult, SK_ScalarHalf) + SK_ScalarHalf;
     }
 
     if (channel == 3) { // Scale alpha by paint value
         turbulenceFunctionResult = SkScalarMul(turbulenceFunctionResult,
             SkScalarDiv(SkIntToScalar(getPaintAlpha()), SkIntToScalar(255)));
     }
 
     // Clamp result
     return SkScalarPin(turbulenceFunctionResult, 0, SK_Scalar1);
 }
 
-SkPMColor SkPerlinNoiseShader::shade(const SkPoint& point, StitchData& stitchData) const {
+SkPMColor SkPerlinNoiseShader::PerlinNoiseShaderContext::shade(
+        const SkPoint& point, StitchData& stitchData) const {
+    const SkPerlinNoiseShader& perlinNoiseShader = static_cast<const SkPerlinNoiseShader&>(fShader);
     SkPoint newPoint;
     fMatrix.mapPoints(&newPoint, &point, 1);
     newPoint.fX = SkScalarRoundToScalar(newPoint.fX);
     newPoint.fY = SkScalarRoundToScalar(newPoint.fY);
 
     U8CPU rgba[4];
     for (int channel = 3; channel >= 0; --channel) {
         rgba[channel] = SkScalarFloorToInt(255 *
-            calculateTurbulenceValueForPoint(channel, *fPaintingData, stitchData, newPoint));
+            calculateTurbulenceValueForPoint(channel, *perlinNoiseShader.fPaintingData,
+                                             stitchData, newPoint));
     }
     return SkPreMultiplyARGB(rgba[3], rgba[0], rgba[1], rgba[2]);
 }
 
-bool SkPerlinNoiseShader::setContext(const SkBitmap& device, const SkPaint& paint,
-                                     const SkMatrix& matrix) {
+SkShader::Context* SkPerlinNoiseShader::createContext(const SkBitmap& device, const SkPaint& paint,
+                                                      const SkMatrix& matrix, void* storage) const {
+    if (!this->validContext(device, paint, matrix)) {
+        return NULL;
+    }
+
+    return SkNEW_PLACEMENT_ARGS(storage, PerlinNoiseShaderContext, (*this, device, paint, matrix));
+}
+
+size_t SkPerlinNoiseShader::contextSize() const {
+    return sizeof(PerlinNoiseShaderContext);
+}
+
+SkPerlinNoiseShader::PerlinNoiseShaderContext::PerlinNoiseShaderContext(
+        const SkPerlinNoiseShader& shader, const SkBitmap& device,
+        const SkPaint& paint, const SkMatrix& matrix)
+    : INHERITED(shader, device, paint, matrix)
+{
     SkMatrix newMatrix = matrix;
-    newMatrix.postConcat(getLocalMatrix());
+    newMatrix.postConcat(shader.getLocalMatrix());
     SkMatrix invMatrix;
     if (!newMatrix.invert(&invMatrix)) {
         invMatrix.reset();
     }
     // This (1,1) translation is due to WebKit's 1 based coordinates for the noise
     // (as opposed to 0 based, usually). The same adjustment is in the setData() function.
     newMatrix.postTranslate(SK_Scalar1, SK_Scalar1);
     newMatrix.postConcat(invMatrix);
     newMatrix.postConcat(invMatrix);
     fMatrix = newMatrix;
-    return INHERITED::setContext(device, paint, matrix);
 }
 
-void SkPerlinNoiseShader::shadeSpan(int x, int y, SkPMColor result[], int count) {
+void SkPerlinNoiseShader::PerlinNoiseShaderContext::shadeSpan(
+        int x, int y, SkPMColor result[], int count) {
     SkPoint point = SkPoint::Make(SkIntToScalar(x), SkIntToScalar(y));
     StitchData stitchData;
     for (int i = 0; i < count; ++i) {
         result[i] = shade(point, stitchData);
         point.fX += SK_Scalar1;
     }
 }
 
-void SkPerlinNoiseShader::shadeSpan16(int x, int y, uint16_t result[], int count) {
+void SkPerlinNoiseShader::PerlinNoiseShaderContext::shadeSpan16(
+        int x, int y, uint16_t result[], int count) {
     SkPoint point = SkPoint::Make(SkIntToScalar(x), SkIntToScalar(y));
     StitchData stitchData;
     DITHER_565_SCAN(y);
     for (int i = 0; i < count; ++i) {
         unsigned dither = DITHER_VALUE(x);
         result[i] = SkDitherRGB32To565(shade(point, stitchData), dither);
         DITHER_INC_X(x);
         point.fX += SK_Scalar1;
     }
 }
@@ skipping 883 matching lines @@
     str->append(" seed: ");
     str->appendScalar(fSeed);
     str->append(" stitch tiles: ");
     str->append(fStitchTiles ? "true " : "false ");
 
     this->INHERITED::toString(str);
 
     str->append(")");
 }
 #endif