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);
+}
+
+bool SkTransparentShader::validContext(const SkBitmap& device,

[scroggo, 2014/03/24 21:24:46]

Why did you override this if all you do is call inherited?

[Dominik Grewe, 2014/03/26 17:22:22]

Removed it.

+                                       const SkPaint& paint,
+                                       const SkMatrix& matrix) const {
+    return this->INHERITED::validContext(device, paint, matrix);
+}
+
+SkTransparentShader::TransparentShaderContext::TransparentShaderContext(
+    const SkTransparentShader& shader, const SkBitmap& device,

[scroggo, 2014/03/24 21:24:46]

nit: 8 space indent.

[Dominik Grewe, 2014/03/26 17:22:22]

Done.

+    const SkPaint& paint, const SkMatrix& matrix)
+    : INHERITED(shader, device, paint, matrix)
+    , fDevice(&device)
+    , fAlpha(paint.getAlpha()) {}

[scroggo, 2014/03/24 21:24:46]

fAlpha wasn't created by you, but as long as we're modifying this code - isn't
it redundant? Can't you call getPaintAlpha() when you need it?

[Dominik Grewe, 2014/03/26 17:22:22]

Done.

+
+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)
                 flags |= kOpaqueAlpha_Flag;
             break;
         case kPMColor_SkColorType:
             if (fAlpha == 255 && fDevice->isOpaque())
                 flags |= kOpaqueAlpha_Flag;
             break;
         default:
             break;
     }
     return flags;
 }
 
-void SkTransparentShader::shadeSpan(int x, int y, SkPMColor span[], int count) {
+void SkTransparentShader::TransparentShaderContext::shadeSpan(
+        int x, int y, SkPMColor span[], int count) {

[scroggo, 2014/03/24 21:24:46]

nit: The parameters that fit on the same line should remain on the initial line.

     unsigned scale = SkAlpha255To256(fAlpha);
 
     switch (fDevice->colorType()) {
         case kPMColor_SkColorType:
             if (scale == 256) {
                 SkPMColor* src = fDevice->getAddr32(x, y);
                 if (src != span) {
                     memcpy(span, src, count * sizeof(SkPMColor));
                 }
             } else {
@@ skipping 37 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) {

[scroggo, 2014/03/24 21:24:46]

same.

     SkASSERT(fDevice->colorType() == kRGB_565_SkColorType);
 
     uint16_t* src = fDevice->getAddr16(x, y);
     if (src != span) {
         memcpy(span, src, count << 1);
     }
 }
 
 #ifdef SK_DEVELOPER
 void SkTransparentShader::toString(SkString* str) const {
     str->append("SkTransparentShader: (");
 
     this->INHERITED::toString(str);
 
     str->append(")");
 }
 #endif