Work in progress to make SkShader immutable.

src/core/SkComposeShader.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 "SkComposeShader.h"
@@ skipping 51 matching lines @@
 };
 #define SkAutoAlphaRestore(...) SK_REQUIRE_LOCAL_VAR(SkAutoAlphaRestore)
 
 void SkComposeShader::flatten(SkWriteBuffer& buffer) const {
     this->INHERITED::flatten(buffer);
     buffer.writeFlattenable(fShaderA);
     buffer.writeFlattenable(fShaderB);
     buffer.writeFlattenable(fMode);
 }
 
+struct ComposeContext {
+    SkShader::Context* fContextA;
+    SkShader::Context* fContextB;
+};
+
+// Helper function to get the ComposeContext from the Context.
+static ComposeContext* get_compose_context(SkShader::Context* c, const SkShader& shader) {
+    return (ComposeContext*) shader.getMyContext(c);
+}
+
+size_t SkComposeShader::getMySpaceNeededForContext() const {
+    return sizeof(ComposeContext);
+}
+
 /*  We call setContext on our two worker shaders. However, we
     always let them see opaque alpha, and if the paint really
     is translucent, then we apply that after the fact.
 
     We need to keep the calls to setContext/endContext balanced, since if we
     return false, our endContext() will not be called.
  */
-bool SkComposeShader::setContext(const SkBitmap& device,
-                                 const SkPaint& paint,
-                                 const SkMatrix& matrix) {
-    if (!this->INHERITED::setContext(device, paint, matrix)) {
+bool SkComposeShader::onSetContext(Context* c, const SkBitmap& device,
+                                   const SkPaint& paint,
+                                   const SkMatrix& matrix) {
+    if (!this->INHERITED::onSetContext(c, device, paint, matrix)) {
         return false;
     }
 
     // we preconcat our localMatrix (if any) with the device matrix
     // before calling our sub-shaders
 
     SkMatrix tmpM;
 
+    // Will come from the paint.
     tmpM.setConcat(matrix, this->getLocalMatrix());
 
     SkAutoAlphaRestore  restore(const_cast<SkPaint*>(&paint), 0xFF);
 
-    bool setContextA = fShaderA->setContext(device, paint, tmpM);
-    bool setContextB = fShaderB->setContext(device, paint, tmpM);
-    if (!setContextA || !setContextB) {
-        if (setContextB) {
-            fShaderB->endContext();
-        }
-        else if (setContextA) {
-            fShaderA->endContext();
-        }
-        this->INHERITED::endContext();
+    SkShader::Context* contextA = fShaderA->setContext(device, paint, tmpM);
+    if (!contextA) {
         return false;
     }
+
+    SkShader::Context* contextB = fShaderB->setContext(device, paint, tmpM);
+    if (!contextB) {
+        SkDELETE(contextA);
+        return false;
+    }
+
+    ComposeContext* composeContext = get_compose_context(c, *this);
+    composeContext->fContextA = contextA;
+    composeContext->fContextB = contextB;
+
     return true;
 }
 
-void SkComposeShader::endContext() {
-    fShaderB->endContext();
-    fShaderA->endContext();
-    this->INHERITED::endContext();
+void SkComposeShader::endContext(Context* c) {
+    ComposeContext* composeContext = get_compose_context(c, *this);
+
+    fShaderB->endContext(c->fContextA);
+    fShaderA->endContext(c->fContextB);
+    this->INHERITED::endContext(c);
 }
 
 // larger is better (fewer times we have to loop), but we shouldn't
 // take up too much stack-space (each element is 4 bytes)
 #define TMP_COLOR_COUNT     64
 
-void SkComposeShader::shadeSpan(int x, int y, SkPMColor result[], int count) {
+void SkComposeShader::shadeSpan(Context* c, int x, int y, SkPMColor result[], int count) {
     SkShader*   shaderA = fShaderA;
     SkShader*   shaderB = fShaderB;
     SkXfermode* mode = fMode;
-    unsigned    scale = SkAlpha255To256(this->getPaintAlpha());
+    unsigned    scale = SkAlpha255To256(c->getPaintAlpha());
 
     SkPMColor   tmp[TMP_COLOR_COUNT];
 
+    ComposeContext* composeContext = get_compose_context(c, *this);
+
     if (NULL == mode) {   // implied SRC_OVER
         // TODO: when we have a good test-case, should use SkBlitRow::Proc32
         // for these loops
         do {
             int n = count;
             if (n > TMP_COLOR_COUNT) {
                 n = TMP_COLOR_COUNT;
             }
 
-            shaderA->shadeSpan(x, y, result, n);
-            shaderB->shadeSpan(x, y, tmp, n);
+            shaderA->shadeSpan(composeContext->fContextA, x, y, result, n);
+            shaderB->shadeSpan(composeContext->fContextB, x, y, tmp, n);
 
             if (256 == scale) {
                 for (int i = 0; i < n; i++) {
                     result[i] = SkPMSrcOver(tmp[i], result[i]);
                 }
             } else {
                 for (int i = 0; i < n; i++) {
                     result[i] = SkAlphaMulQ(SkPMSrcOver(tmp[i], result[i]),
                                             scale);
                 }
             }
 
             result += n;
             x += n;
             count -= n;
         } while (count > 0);
     } else {    // use mode for the composition
         do {
             int n = count;
             if (n > TMP_COLOR_COUNT) {
                 n = TMP_COLOR_COUNT;
             }
 
-            shaderA->shadeSpan(x, y, result, n);
-            shaderB->shadeSpan(x, y, tmp, n);
+            shaderA->shadeSpan(composeContext->fContextA, x, y, result, n);
+            shaderB->shadeSpan(composeContext->fContextB, x, y, tmp, n);
             mode->xfer32(result, tmp, n, NULL);
 
             if (256 == scale) {
                 for (int i = 0; i < n; i++) {
                     result[i] = SkAlphaMulQ(result[i], scale);
                 }
             }
 
             result += n;
             x += n;
@@ skipping 11 matching lines @@
     str->append(" ShaderB: ");
     fShaderB->toString(str);
     str->append(" Xfermode: ");
     fMode->toString(str);
 
     this->INHERITED::toString(str);
 
     str->append(")");
 }
 #endif