Add XferProcessor factory in GrPaint and GrDrawState.

src/gpu/effects/GrPorterDuffXferProcessor.cpp

Index: src/gpu/effects/GrPorterDuffXferProcessor.cpp
diff --git a/src/gpu/effects/GrPorterDuffXferProcessor.cpp b/src/gpu/effects/GrPorterDuffXferProcessor.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..b304f6c18876fdff80daa14b05d6ca99cd71c86e
--- /dev/null
+++ b/src/gpu/effects/GrPorterDuffXferProcessor.cpp
@@ -0,0 +1,75 @@
+/*
+ * Copyright 2014 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "GrPorterDuffXferProcessor.h"
+
+#include "GrBackendProcessorFactory.h"
+#include "GrDrawState.h"
+#include "GrInvariantOutput.h"
+#include "GrProcessor.h"
+#include "GrTBackendProcessorFactory.h"
+#include "GrTypes.h"
+#include "GrXferProcessor.h"
+#include "gl/GrGLProcessor.h"
+#include "gl/builders/GrGLFragmentShaderBuilder.h"
+#include "gl/builders/GrGLProgramBuilder.h"
+
+class GrGLPorterDuffXferProcessor : public GrGLXferProcessor {
+public:
+    GrGLPorterDuffXferProcessor(const GrBackendProcessorFactory& factory, const GrProcessor&)
+        : INHERITED(factory) {}
+
+    virtual ~GrGLPorterDuffXferProcessor() {}
+
+    virtual void emitCode(GrGLFPBuilder* builder,
+                          const GrFragmentProcessor& fp,
+                          const char* outputColor,
+                          const char* inputColor,
+                          const TransformedCoordsArray& coords,
+                          const TextureSamplerArray& samplers) SK_OVERRIDE {
+        GrGLFPFragmentBuilder* fsBuilder = builder->getFragmentShaderBuilder();
+        fsBuilder->codeAppendf("%s = %s;", outputColor, inputColor);
+    }
+
+    virtual void setData(const GrGLProgramDataManager&, const GrProcessor&) SK_OVERRIDE {};
+
+    static void GenKey(const GrProcessor&, const GrGLCaps& caps, GrProcessorKeyBuilder* b) {};
+
+private:
+    typedef GrGLXferProcessor INHERITED;
+};
+
+///////////////////////////////////////////////////////////////////////////////
+
+GrPorterDuffXferProcessor::GrPorterDuffXferProcessor(GrBlendCoeff srcBlend, GrBlendCoeff dstBlend)
+    : fSrcBlend(srcBlend), fDstBlend(dstBlend) {}
+
+GrPorterDuffXferProcessor::~GrPorterDuffXferProcessor() {
+}
+
+const GrBackendFragmentProcessorFactory& GrPorterDuffXferProcessor::getFactory() const {
+    return GrTBackendFragmentProcessorFactory<GrPorterDuffXferProcessor>::getInstance();
+}
+
+void GrPorterDuffXferProcessor::onComputeInvariantOutput(GrInvariantOutput* inout) const {
+    inout->setToUnknown(GrInvariantOutput::kWillNot_ReadInput);
+}
+
+///////////////////////////////////////////////////////////////////////////////
+
+const GrXferProcessor* GrPorterDuffXPFactory::createXferProcessor() const {
+    return GrPorterDuffXferProcessor::Create(fSrc, fDst);
+}
+
+bool GrPorterDuffXPFactory::supportsRGBCoverage(const GrDrawState& drawState) const {
+    if (kOne_GrBlendCoeff == fSrc && kISA_GrBlendCoeff == fDst &&
+        0 == drawState.numColorStages() && !drawState.coverageWillBeSingleComponent()) {

[bsalomon, 2014/12/01 19:24:40]

so what if this took something like

class GrXPFactory::InputInfo {
   GrColor  fKnownColorValues;
   uint32_t fKnownColorFlags;
   enum CoverageType {
       kSolid_CoverageType,
       kSingleComponent_CoverageType,
       kRGBA_CoverageType,
   } fCoverageType;
}

But why is it told what the coverage is single channel? It seems like we need to
ask this question before installing a four channel coverage.

[egdaniel, 2014/12/02 15:07:09]

Done partially. The change to actually check before adding the the four channel
coverage will involve a decent amount of changes in the text contexts. So for
now we will function as we previously have and once all the initial XP cl's land
I will go back in a follow up cl to fix up the text stuff.

+        return true;
+    }
+    return false;
+}
+