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

src/effects/gradients/SkSweepGradient.cpp

 
 /*
  * Copyright 2012 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkSweepGradient.h"
 
@@ skipping 34 matching lines @@
 SkSweepGradient::SkSweepGradient(SkReadBuffer& buffer)
     : INHERITED(buffer),
       fCenter(buffer.readPoint()) {
 }
 
 void SkSweepGradient::flatten(SkWriteBuffer& buffer) const {
     this->INHERITED::flatten(buffer);
     buffer.writePoint(fCenter);
 }
 
+size_t SkSweepGradient::contextSize() const {
+    return sizeof(SweepGradientContext);
+}
+
+SkShader::Context* SkSweepGradient::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, SweepGradientContext, (*this, device, paint, matrix));
+}
+
+SkSweepGradient::SweepGradientContext::SweepGradientContext(
+        const SkSweepGradient& shader, const SkBitmap& device,
+        const SkPaint& paint, const SkMatrix& matrix)
+    : INHERITED(shader, device, paint, matrix) {}
+
 //  returns angle in a circle [0..2PI) -> [0..255]
 static unsigned SkATan2_255(float y, float x) {
     //    static const float g255Over2PI = 255 / (2 * SK_ScalarPI);
     static const float g255Over2PI = 40.584510488433314f;
 
     float result = sk_float_atan2(y, x);
     if (result < 0) {
         result += 2 * SK_ScalarPI;
     }
     SkASSERT(result >= 0);
     // since our value is always >= 0, we can cast to int, which is faster than
     // calling floorf()
     int ir = (int)(result * g255Over2PI);
     SkASSERT(ir >= 0 && ir <= 255);
     return ir;
 }
 
-void SkSweepGradient::shadeSpan(int x, int y, SkPMColor* SK_RESTRICT dstC,
-                               int count) {
+void SkSweepGradient::SweepGradientContext::shadeSpan(int x, int y, SkPMColor* SK_RESTRICT dstC,
+                                                      int count) {
     SkMatrix::MapXYProc proc = fDstToIndexProc;
     const SkMatrix&     matrix = fDstToIndex;
-    const SkPMColor* SK_RESTRICT cache = this->getCache32();
+    const SkPMColor* SK_RESTRICT cache = fCache->getCache32();
     int                 toggle = init_dither_toggle(x, y);
     SkPoint             srcPt;
 
     if (fDstToIndexClass != kPerspective_MatrixClass) {
         proc(matrix, SkIntToScalar(x) + SK_ScalarHalf,
                      SkIntToScalar(y) + SK_ScalarHalf, &srcPt);
         SkScalar dx, fx = srcPt.fX;
         SkScalar dy, fy = srcPt.fY;
 
         if (fDstToIndexClass == kFixedStepInX_MatrixClass) {
@@ skipping 17 matching lines @@
     } else {  // perspective case
         for (int stop = x + count; x < stop; x++) {
             proc(matrix, SkIntToScalar(x) + SK_ScalarHalf,
                          SkIntToScalar(y) + SK_ScalarHalf, &srcPt);
             *dstC++ = cache[toggle + SkATan2_255(srcPt.fY, srcPt.fX)];
             toggle = next_dither_toggle(toggle);
         }
     }
 }
 
-void SkSweepGradient::shadeSpan16(int x, int y, uint16_t* SK_RESTRICT dstC,
-                                 int count) {
+void SkSweepGradient::SweepGradientContext::shadeSpan16(int x, int y, uint16_t* SK_RESTRICT dstC,
+                                                        int count) {
     SkMatrix::MapXYProc proc = fDstToIndexProc;
     const SkMatrix&     matrix = fDstToIndex;
-    const uint16_t* SK_RESTRICT cache = this->getCache16();
+    const uint16_t* SK_RESTRICT cache = fCache->getCache16();
     int                 toggle = init_dither_toggle16(x, y);
     SkPoint             srcPt;
 
     if (fDstToIndexClass != kPerspective_MatrixClass) {
         proc(matrix, SkIntToScalar(x) + SK_ScalarHalf,
                      SkIntToScalar(y) + SK_ScalarHalf, &srcPt);
         SkScalar dx, fx = srcPt.fX;
         SkScalar dy, fy = srcPt.fY;
 
         if (fDstToIndexClass == kFixedStepInX_MatrixClass) {
@@ skipping 164 matching lines @@
     str->appendScalar(fCenter.fX);
     str->append(", ");
     str->appendScalar(fCenter.fY);
     str->append(") ");
 
     this->INHERITED::toString(str);
 
     str->append(")");
 }
 #endif