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

src/effects/SkTransparentShader.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 "SkTransparentShader.h"
 #include "SkColorPriv.h"
 #include "SkString.h"
 
-bool SkTransparentShader::setContext(const SkBitmap& device,
-                                     const SkPaint& paint,
-                                     const SkMatrix& matrix) {
-    fDevice = &device;
-    fAlpha = paint.getAlpha();
+SkShader::Context* SkTransparentShader::createContext(const SkBitmap& device,
+                                                      const SkPaint& paint,
+                                                      const SkMatrix& matrix,
+                                                      void* storage) const {
+    if (!this->validContext(device, paint, matrix)) {
+        return NULL;
+    }
 
-    return this->INHERITED::setContext(device, paint, matrix);
+    return SkNEW_PLACEMENT_ARGS(storage, TransparentShaderContext, (*this, device, paint, matrix));
 }
 
-uint32_t SkTransparentShader::getFlags() {
+size_t SkTransparentShader::contextSize() const {
+    return sizeof(TransparentShaderContext);
+}
+
+SkTransparentShader::TransparentShaderContext::TransparentShaderContext(
+        const SkTransparentShader& shader, const SkBitmap& device,
+        const SkPaint& paint, const SkMatrix& matrix)
+    : INHERITED(shader, device, paint, matrix)
+    , fDevice(&device) {}
+
+SkTransparentShader::TransparentShaderContext::~TransparentShaderContext() {}
+
+uint32_t SkTransparentShader::TransparentShaderContext::getFlags() const {
     uint32_t flags = this->INHERITED::getFlags();
 
     switch (fDevice->colorType()) {
         case kRGB_565_SkColorType:
             flags |= kHasSpan16_Flag;
-            if (fAlpha == 255)
+            if (this->getPaintAlpha() == 255)
                 flags |= kOpaqueAlpha_Flag;
             break;
         case kN32_SkColorType:
-            if (fAlpha == 255 && fDevice->isOpaque())
+            if (this->getPaintAlpha() == 255 && fDevice->isOpaque())
                 flags |= kOpaqueAlpha_Flag;
             break;
         default:
             break;
     }
     return flags;
 }
 
-void SkTransparentShader::shadeSpan(int x, int y, SkPMColor span[], int count) {
-    unsigned scale = SkAlpha255To256(fAlpha);
+void SkTransparentShader::TransparentShaderContext::shadeSpan(int x, int y, SkPMColor span[],
+                                                              int count) {
+    unsigned scale = SkAlpha255To256(this->getPaintAlpha());
 
     switch (fDevice->colorType()) {
         case kN32_SkColorType:
             if (scale == 256) {
                 SkPMColor* src = fDevice->getAddr32(x, y);
                 if (src != span) {
                     memcpy(span, src, count * sizeof(SkPMColor));
                 }
             } else {
                 const SkPMColor* src = fDevice->getAddr32(x, y);
                 for (int i = count - 1; i >= 0; --i) {
                     span[i] = SkAlphaMulQ(src[i], scale);
                 }
             }
             break;
         case kRGB_565_SkColorType: {
             const uint16_t* src = fDevice->getAddr16(x, y);
             if (scale == 256) {
                 for (int i = count - 1; i >= 0; --i) {
                     span[i] = SkPixel16ToPixel32(src[i]);
                 }
             } else {
-                unsigned alpha = fAlpha;
+                unsigned alpha = this->getPaintAlpha();
                 for (int i = count - 1; i >= 0; --i) {
                     uint16_t c = src[i];
                     unsigned r = SkPacked16ToR32(c);
                     unsigned g = SkPacked16ToG32(c);
                     unsigned b = SkPacked16ToB32(c);
 
                     span[i] = SkPackARGB32( alpha,
                                             SkAlphaMul(r, scale),
                                             SkAlphaMul(g, scale),
                                             SkAlphaMul(b, scale));
@@ skipping 13 matching lines @@
                 }
             }
             break;
         }
         default:
             SkDEBUGFAIL("colorType not supported as a destination device");
             break;
     }
 }
 
-void SkTransparentShader::shadeSpan16(int x, int y, uint16_t span[], int count) {
+void SkTransparentShader::TransparentShaderContext::shadeSpan16(int x, int y, uint16_t span[],
+                                                                int count) {
     SkASSERT(fDevice->colorType() == kRGB_565_SkColorType);
 
     uint16_t* src = fDevice->getAddr16(x, y);
     if (src != span) {
         memcpy(span, src, count << 1);
     }
 }
 
 #ifndef SK_IGNORE_TO_STRING
 void SkTransparentShader::toString(SkString* str) const {
     str->append("SkTransparentShader: (");
 
     this->INHERITED::toString(str);
 
     str->append(")");
 }
 #endif