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

src/core/SkBitmapProcShader.cpp

Index: src/core/SkBitmapProcShader.cpp
diff --git a/src/core/SkBitmapProcShader.cpp b/src/core/SkBitmapProcShader.cpp
index 55a772ec10ace94578a4be78cedbd508de1deb97..ecd35cc6eb8d87c988b5a796c32ca0abde5fa370 100644
--- a/src/core/SkBitmapProcShader.cpp
+++ b/src/core/SkBitmapProcShader.cpp
@@ -34,18 +34,16 @@ bool SkBitmapProcShader::CanDo(const SkBitmap& bm, TileMode tx, TileMode ty) {
 SkBitmapProcShader::SkBitmapProcShader(const SkBitmap& src,
                                        TileMode tmx, TileMode tmy) {
     fRawBitmap = src;
-    fState.fTileModeX = (uint8_t)tmx;
-    fState.fTileModeY = (uint8_t)tmy;
-    fFlags = 0; // computed in setContext
+    fTileModeX = (uint8_t)tmx;
+    fTileModeY = (uint8_t)tmy;
 }
 
 SkBitmapProcShader::SkBitmapProcShader(SkReadBuffer& buffer)
         : INHERITED(buffer) {
     buffer.readBitmap(&fRawBitmap);
     fRawBitmap.setImmutable();
-    fState.fTileModeX = buffer.readUInt();
-    fState.fTileModeY = buffer.readUInt();
-    fFlags = 0; // computed in setContext
+    fTileModeX = buffer.readUInt();
+    fTileModeY = buffer.readUInt();
 }
 
 SkShader::BitmapType SkBitmapProcShader::asABitmap(SkBitmap* texture,
@@ -58,8 +56,8 @@ SkShader::BitmapType SkBitmapProcShader::asABitmap(SkBitmap* texture,
         texM->reset();
     }
     if (xy) {
-        xy[0] = (TileMode)fState.fTileModeX;
-        xy[1] = (TileMode)fState.fTileModeY;
+        xy[0] = (TileMode)fTileModeX;
+        xy[1] = (TileMode)fTileModeY;
     }
     return kDefault_BitmapType;
 }
@@ -68,8 +66,8 @@ void SkBitmapProcShader::flatten(SkWriteBuffer& buffer) const {
     this->INHERITED::flatten(buffer);
 
     buffer.writeBitmap(fRawBitmap);
-    buffer.writeUInt(fState.fTileModeX);
-    buffer.writeUInt(fState.fTileModeY);
+    buffer.writeUInt(fTileModeX);
+    buffer.writeUInt(fTileModeY);
 }
 
 static bool only_scale_and_translate(const SkMatrix& matrix) {
@@ -98,24 +96,56 @@ static bool valid_for_drawing(const SkBitmap& bm) {
     return true;
 }
 
-bool SkBitmapProcShader::setContext(const SkBitmap& device,
-                                    const SkPaint& paint,
-                                    const SkMatrix& matrix) {
+bool SkBitmapProcShader::validContext(const SkBitmap& device,
+                                      const SkPaint& paint,
+                                      const SkMatrix& matrix,
+                                      SkMatrix* totalInverse) const {
     if (!fRawBitmap.getTexture() && !valid_for_drawing(fRawBitmap)) {
         return false;
     }
 
-    // do this first, so we have a correct inverse matrix
-    if (!this->INHERITED::setContext(device, paint, matrix)) {
+    // Do this first, so we know the matrix can be inverted.
+    if (!this->INHERITED::validContext(device, paint, matrix, totalInverse)) {
         return false;
     }
 
-    fState.fOrigBitmap = fRawBitmap;
-    if (!fState.chooseProcs(this->getTotalInverse(), paint)) {
-        this->INHERITED::endContext();
+    SkBitmapProcState state;
+    state.fTileModeX = fTileModeX;
+    state.fTileModeY = fTileModeY;
+    state.fOrigBitmap = fRawBitmap;
+    // TODO(dominikg): Could we have a more light-weight method instead of chooseProcs that only
+    //                 validates the inputs?
+    if (!state.chooseProcs(*totalInverse, paint)) {
         return false;
     }
 
+    return true;
+}
+
+SkShader::Context* SkBitmapProcShader::createContext(const SkBitmap& device, const SkPaint& paint,
+                                                     const SkMatrix& matrix, void* storage) const {
+    SkMatrix totalInverse;
+    if (!this->validContext(device, paint, matrix, &totalInverse)) {
+        return NULL;
+    }
+
+    return SkNEW_PLACEMENT_ARGS(storage, BitmapProcShaderContext, (*this, device, paint, matrix));
+}
+
+size_t SkBitmapProcShader::contextSize() const {
+    return sizeof(BitmapProcShaderContext);
+}
+
+SkBitmapProcShader::BitmapProcShaderContext::BitmapProcShaderContext(
+        const SkBitmapProcShader& shader, const SkBitmap& device,
+        const SkPaint& paint, const SkMatrix& matrix) 
+    : INHERITED(shader, device, paint, matrix) {
+
+    fState.fTileModeX = shader.fTileModeX;
+    fState.fTileModeY = shader.fTileModeY;
+    fState.fOrigBitmap = shader.fRawBitmap;
+    SkASSERT(fState.chooseProcs(this->getTotalInverse(), paint));
+
     const SkBitmap& bitmap = *fState.fBitmap;
     bool bitmapIsOpaque = bitmap.isOpaque();
 
@@ -157,12 +187,6 @@ bool SkBitmapProcShader::setContext(const SkBitmap& device,
     }
 
     fFlags = flags;
-    return true;
-}
-
-void SkBitmapProcShader::endContext() {
-    fState.endContext();
-    this->INHERITED::endContext();
 }
 
 #define BUF_MAX     128
@@ -176,7 +200,8 @@ void SkBitmapProcShader::endContext() {
     #define TEST_BUFFER_EXTRA   0
 #endif
 
-void SkBitmapProcShader::shadeSpan(int x, int y, SkPMColor dstC[], int count) {
+void SkBitmapProcShader::BitmapProcShaderContext::shadeSpan(int x, int y, SkPMColor dstC[],
+                                                            int count) {
     const SkBitmapProcState& state = fState;
     if (state.getShaderProc32()) {
         state.getShaderProc32()(state, x, y, dstC, count);
@@ -220,7 +245,7 @@ void SkBitmapProcShader::shadeSpan(int x, int y, SkPMColor dstC[], int count) {
     }
 }
 
-SkShader::ShadeProc SkBitmapProcShader::asAShadeProc(void** ctx) {
+SkShader::Context::ShadeProc SkBitmapProcShader::BitmapProcShaderContext::asAShadeProc(void** ctx) {
     if (fState.getShaderProc32()) {
         *ctx = &fState;
         return (ShadeProc)fState.getShaderProc32();
@@ -228,7 +253,8 @@ SkShader::ShadeProc SkBitmapProcShader::asAShadeProc(void** ctx) {
     return NULL;
 }
 
-void SkBitmapProcShader::shadeSpan16(int x, int y, uint16_t dstC[], int count) {
+void SkBitmapProcShader::BitmapProcShaderContext::shadeSpan16(int x, int y, uint16_t dstC[],
+                                                              int count) {
     const SkBitmapProcState& state = fState;
     if (state.getShaderProc16()) {
         state.getShaderProc16()(state, x, y, dstC, count);
@@ -342,8 +368,8 @@ void SkBitmapProcShader::toString(SkString* str) const {
     str->append("BitmapShader: (");
 
     str->appendf("(%s, %s)",
-                 gTileModeName[fState.fTileModeX],
-                 gTileModeName[fState.fTileModeY]);
+                 gTileModeName[fTileModeX],
+                 gTileModeName[fTileModeY]);
 
     str->append(" ");
     fRawBitmap.toString(str);
@@ -384,8 +410,8 @@ GrEffectRef* SkBitmapProcShader::asNewEffect(GrContext* context, const SkPaint&
     matrix.preConcat(lmInverse);
 
     SkShader::TileMode tm[] = {
-        (TileMode)fState.fTileModeX,
-        (TileMode)fState.fTileModeY,
+        (TileMode)fTileModeX,
+        (TileMode)fTileModeY,
     };
 
     // Must set wrap and filter on the sampler before requesting a texture. In two places below