Add XP to handle the cases where we disable color write.

BUG=skia:

Review URL: https://codereview.chromium.org/787233003

2 files changed, 22 insertions, 16 deletions

diff --git a/include/gpu/GrXferProcessor.h b/include/gpu/GrXferProcessor.h
index 98585c6a53..2c9961fc6b 100644
--- a/include/gpu/GrXferProcessor.h
+++ b/include/gpu/GrXferProcessor.h
@@ -86,18 +86,19 @@ public:
      * A caller who calls this function on a XP is required to honor the returned OptFlags
      * and color values for its draw.
      */
-    // TODO: remove need for colorWriteDisabled once colorWriteDisabled is its own XP.
     virtual OptFlags getOptimizations(const GrProcOptInfo& colorPOI,
                                       const GrProcOptInfo& coveragePOI,
-                                      bool colorWriteDisabled,
                                       bool doesStencilWrite,
                                       GrColor* overrideColor,
                                       const GrDrawTargetCaps& caps) = 0;
 
     struct BlendInfo {
+        BlendInfo() : fWriteColor(true) {}
+
         GrBlendCoeff fSrcBlend;
         GrBlendCoeff fDstBlend;
         GrColor      fBlendConstant;
+        bool         fWriteColor;
     };
 
     virtual void getBlendInfo(BlendInfo* blendInfo) const = 0;
@@ -176,9 +177,8 @@ public:
      * certain state information (colorWriteDisabled) to determine whether
      * coverage can be handled correctly.
      */
-    // TODO: remove need for colorWriteDisabled once colorWriteDisabled is its own XP.
-    virtual bool canApplyCoverage(const GrProcOptInfo& colorPOI, const GrProcOptInfo& coveragePOI,
-                                  bool colorWriteDisabled) const = 0;
+    virtual bool canApplyCoverage(const GrProcOptInfo& colorPOI,
+                                  const GrProcOptInfo& coveragePOI) const = 0;
 
 
     struct InvariantOutput {
@@ -192,9 +192,8 @@ public:
      * this xp factory. The invariant color information returned by this function refers to the
      * final color produced after all blending.
      */
-    // TODO: remove need for colorWriteDisabled once only XP can read dst.
     virtual void getInvariantOutput(const GrProcOptInfo& colorPOI, const GrProcOptInfo& coveragePOI,
-                                    bool colorWriteDisabled, InvariantOutput*) const = 0;
+                                    InvariantOutput*) const = 0;
 
     /**
      * Determines whether multiplying the computed per-pixel color by the pixel's fractional
@@ -203,6 +202,14 @@ public:
      */
     virtual bool canTweakAlphaForCoverage() const = 0;
 
+    /**
+     *  Returns true if the XP generated by this factory will read dst.
+     */
+    // TODO: Currently this function must also check if the color/coverage stages read dst.
+    //       Once only XP's can read dst we can remove the ProcOptInfo's from this function.
+    virtual bool willReadDst(const GrProcOptInfo& colorPOI,
+                             const GrProcOptInfo& coveragePOI) const = 0;
+
     bool isEqual(const GrXPFactory& that) const {
         if (this->classID() != that.classID()) {
             return false;
diff --git a/include/gpu/effects/GrPorterDuffXferProcessor.h b/include/gpu/effects/GrPorterDuffXferProcessor.h
index fab14c732a..6850cb5646 100644
--- a/include/gpu/effects/GrPorterDuffXferProcessor.h
+++ b/include/gpu/effects/GrPorterDuffXferProcessor.h
@@ -12,7 +12,6 @@
 #include "GrXferProcessor.h"
 #include "SkXfermode.h"
 
-class GrInvariantOutput;
 class GrProcOptInfo;
 
 class GrPorterDuffXferProcessor : public GrXferProcessor {
@@ -22,15 +21,15 @@ public:
         return SkNEW_ARGS(GrPorterDuffXferProcessor, (srcBlend, dstBlend, constant));
     }
 
-    virtual ~GrPorterDuffXferProcessor();
+    ~GrPorterDuffXferProcessor() SK_OVERRIDE;
 
-    virtual const char* name() const SK_OVERRIDE { return "Porter Duff"; }
+    const char* name() const SK_OVERRIDE { return "Porter Duff"; }
 
     void getGLProcessorKey(const GrGLCaps& caps, GrProcessorKeyBuilder* b) const SK_OVERRIDE;
 
     GrGLXferProcessor* createGLInstance() const SK_OVERRIDE;
 
-    virtual bool hasSecondaryOutput() const SK_OVERRIDE;
+    bool hasSecondaryOutput() const SK_OVERRIDE;
 
     ///////////////////////////////////////////////////////////////////////////
     /// @name Stage Output Types
@@ -68,7 +67,6 @@ public:
 
     GrXferProcessor::OptFlags getOptimizations(const GrProcOptInfo& colorPOI,
                                                const GrProcOptInfo& coveragePOI,
-                                               bool colorWriteDisabled,
                                                bool doesStencilWrite,
                                                GrColor* overrideColor,
                                                const GrDrawTargetCaps& caps) SK_OVERRIDE;
@@ -96,7 +94,6 @@ private:
 
     GrXferProcessor::OptFlags internalGetOptimizations(const GrProcOptInfo& colorPOI,
                                                        const GrProcOptInfo& coveragePOI,
-                                                       bool colorWriteDisabled,
                                                        bool doesStencilWrite);
 
     void calcOutputTypes(GrXferProcessor::OptFlags blendOpts, const GrDrawTargetCaps& caps,
@@ -130,15 +127,17 @@ public:
 
     bool supportsRGBCoverage(GrColor knownColor, uint32_t knownColorFlags) const SK_OVERRIDE;
 
-    bool canApplyCoverage(const GrProcOptInfo& colorPOI, const GrProcOptInfo& coveragePOI,
-                          bool colorWriteDisabled) const SK_OVERRIDE;
+    bool canApplyCoverage(const GrProcOptInfo& colorPOI,
+                          const GrProcOptInfo& coveragePOI) const SK_OVERRIDE;
 
     bool canTweakAlphaForCoverage() const SK_OVERRIDE;
 
     void getInvariantOutput(const GrProcOptInfo& colorPOI, const GrProcOptInfo& coveragePOI,
-                            bool colorWriteDisabled,
                             GrXPFactory::InvariantOutput*) const SK_OVERRIDE;
 
+    bool willReadDst(const GrProcOptInfo& colorPOI,
+                     const GrProcOptInfo& coveragePOI) const SK_OVERRIDE;
+
 private:
     GrPorterDuffXPFactory(GrBlendCoeff src, GrBlendCoeff dst);