Add mixed samples support to XPs

include/gpu/GrXferProcessor.h

 /*
  * Copyright 2014 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef GrXferProcessor_DEFINED
 #define GrXferProcessor_DEFINED
 
 #include "GrColor.h"
 #include "GrProcessor.h"
 #include "GrTexture.h"
 #include "GrTypes.h"
 #include "SkXfermode.h"
 
+class GrPipelineBuilder;
 class GrShaderCaps;
 class GrGLSLCaps;
 class GrGLXferProcessor;
 class GrProcOptInfo;
 
 /**
  * Equations for alpha-blending.
  */
 enum GrBlendEquation {
     // Basic blend equations.
@@ skipping 194 matching lines @@
 
         SkDEBUGCODE(SkString dump() const;)
 
         GrBlendEquation fEquation;
         GrBlendCoeff    fSrcBlend;
         GrBlendCoeff    fDstBlend;
         GrColor         fBlendConstant;
         bool            fWriteColor;
     };
 
-    void getBlendInfo(BlendInfo* blendInfo) const {
-        blendInfo->reset();
-        this->onGetBlendInfo(blendInfo);
-    }
+    void getBlendInfo(BlendInfo* blendInfo) const;
 
     bool willReadDstColor() const { return fWillReadDstColor; }
 
     /**
      * Returns the texture to be used as the destination when reading the dst in the fragment
      * shader. If the returned texture is NULL then the XP is either not reading the dst or we have
      * extentions that support framebuffer fetching and thus don't need a copy of the dst texture.
      */
     const GrTexture* getDstTexture() const { return fDstTexture.getTexture(); }
 
     /**
      * Returns the offset in device coords to use when accessing the dst texture to get the dst
      * pixel color in the shader. This value is only valid if getDstTexture() != NULL.
      */
     const SkIPoint& dstTextureOffset() const {
         SkASSERT(this->getDstTexture());
         return fDstTextureOffset;
     }
 
     /**
+     * If we are performing a dst read, returns whether this class will use mixed samples to
+     * antialias the shader's final output. (If not doing a dst read, the subclass is responsible to
+     * account for any mixed samples.)
+     */
+    bool dstReadUsesMixedSamples() const { return fDstReadUsesMixedSamples; }
+
+    /**
      * Returns whether or not the XP will look at coverage when doing its blending.
      */
     bool readsCoverage() const { return fReadsCoverage; }
 
-    /** 
+    /**
      * Returns whether or not this xferProcossor will set a secondary output to be used with dual
      * source blending.
      */
-    virtual bool hasSecondaryOutput() const { return false; }
+    bool hasSecondaryOutput() const;
 
     /** Returns true if this and other processor conservatively draw identically. It can only return
         true when the two processor are of the same subclass (i.e. they return the same object from
         from getFactory()).
 
         A return value of true from isEqual() should not be used to test whether the processor would
         generate the same shader code. To test for identical code generation use getGLProcessorKey*/
     
     bool isEqual(const GrXferProcessor& that) const {
         if (this->classID() != that.classID()) {
             return false;
         }
         if (this->fWillReadDstColor != that.fWillReadDstColor) {
             return false;
         }
         if (this->fReadsCoverage != that.fReadsCoverage) {
             return false;
         }
         if (this->fDstTexture.getTexture() != that.fDstTexture.getTexture()) {
             return false;
         }
         if (this->fDstTextureOffset != that.fDstTextureOffset) {
             return false;
         }
+        if (this->fDstReadUsesMixedSamples != that.fDstReadUsesMixedSamples) {
+            return false;
+        }
         return this->onIsEqual(that);
     }
    
 protected:
     GrXferProcessor();
-    GrXferProcessor(const DstTexture*, bool willReadDstColor);
+    GrXferProcessor(const GrPipelineBuilder&, const DstTexture*, bool willReadDstColor);
 
 private:
     virtual OptFlags onGetOptimizations(const GrProcOptInfo& colorPOI,
                                         const GrProcOptInfo& coveragePOI,
                                         bool doesStencilWrite,
                                         GrColor* overrideColor,
                                         const GrCaps& caps) = 0;
 
     /**
      * Sets a unique key on the GrProcessorKeyBuilder that is directly associated with this xfer
      * processor's GL backend implementation.
      */
     virtual void onGetGLProcessorKey(const GrGLSLCaps& caps,
                                      GrProcessorKeyBuilder* b) const = 0;
 
     /**
      * If not using a texture barrier, retrieves whether the subclass will require a different type
      * of barrier.
      */
     virtual bool onWillNeedXferBarrier(const GrRenderTarget*,
                                        const GrCaps&,
                                        GrXferBarrierType* outBarrierType SK_UNUSED) const {
         return false;
     }
 
     /**
-     * Retrieves the hardware blend state required by this Xfer processor. The BlendInfo struct
-     * comes initialized to default values, so the Xfer processor only needs to set the state it
-     * needs. It may not even need to override this method at all.
+     * If we are not performing a dst read, returns whether the subclass will set a secondary
+     * output. If we are doing a dst read, the base class controls the secondary output and this
+     * method will not be called.
+     */
+    virtual bool onHasSecondaryOutput() const { return false; }
+
+    /**
+     * If we are not performing a dst read, retrieves the fixed-function blend state required by the
+     * subclass. If we are doing a dst read, the base class controls the fixed-function blend state
+     * and this method will not be called. The BlendInfo struct comes initialized to "no blending".
      */
     virtual void onGetBlendInfo(BlendInfo*) const {}
 
     virtual bool onIsEqual(const GrXferProcessor&) const = 0;
 
     bool                    fWillReadDstColor;
+    bool                    fDstReadUsesMixedSamples;
     bool                    fReadsCoverage;
     SkIPoint                fDstTextureOffset;
     GrTextureAccess         fDstTexture;
 
     typedef GrFragmentProcessor INHERITED;
 };
 
 GR_MAKE_BITFIELD_OPS(GrXferProcessor::OptFlags);
 
 ///////////////////////////////////////////////////////////////////////////////
 
 /**
  * We install a GrXPFactory (XPF) early on in the pipeline before all the final draw information is
  * known (e.g. whether there is fractional pixel coverage, will coverage be 1 or 4 channel, is the
  * draw opaque, etc.). Once the state of the draw is finalized, we use the XPF along with all the
  * draw information to create a GrXferProcessor (XP) which can implement the desired blending for
  * the draw.
  *
  * Before the XP is created, the XPF is able to answer queries about what functionality the XPs it
  * creates will have. For example, can it create an XP that supports RGB coverage or will the XP
  * blend with the destination color.
  */
 class GrXPFactory : public SkRefCnt {
 public:
     typedef GrXferProcessor::DstTexture DstTexture;
-    GrXferProcessor* createXferProcessor(const GrProcOptInfo& colorPOI,
+    GrXferProcessor* createXferProcessor(const GrPipelineBuilder&,

[Chris Dalton, 2015/06/04 01:19:18]

I thought it might be nicer to just send in a PipelineBuilder rather than a
parameter like 'bool hasMixedSamples'.

(In the future we may also be able to hang the dst texture and/or POIs off the
PipelineBuilder?)

+                                         const GrProcOptInfo& colorPOI,
                                          const GrProcOptInfo& coveragePOI,
                                          const DstTexture*,
                                          const GrCaps& caps) const;
 
     /**
      * This function returns true if the GrXferProcessor generated from this factory will be able to
      * correctly blend when using RGB coverage. The knownColor and knownColorFlags represent the
      * final computed color from the color stages.
      */
     virtual bool supportsRGBCoverage(GrColor knownColor, uint32_t knownColorFlags) const = 0;
 
     /**
      * Known color information after blending, but before accounting for any coverage.
      */
     struct InvariantBlendedColor {
         bool                     fWillBlendWithDst;
         GrColor                  fKnownColor;
         GrColorComponentFlags    fKnownColorFlags;
     };
 
     /** 
      * Returns information about the output color, produced by XPs from this factory, that will be
      * known after blending. Note that we can conflate coverage and color, so the actual values
      * written to pixels with partial coverage may not always seem consistent with the invariant
      * information returned by this function.
      */
     virtual void getInvariantBlendedColor(const GrProcOptInfo& colorPOI,
                                           InvariantBlendedColor*) const = 0;
 
-    bool willNeedDstTexture(const GrCaps& caps, const GrProcOptInfo& colorPOI,
-                            const GrProcOptInfo& coveragePOI) const;
+    bool willNeedDstTexture(const GrCaps& caps, const GrPipelineBuilder&,
+                            const GrProcOptInfo& colorPOI, const GrProcOptInfo& coveragePOI) const;
 
     bool isEqual(const GrXPFactory& that) const {
         if (this->classID() != that.classID()) {
             return false;
         }
         return this->onIsEqual(that);
     }
 
     /**
       * Helper for down-casting to a GrXPFactory subclass
       */
     template <typename T> const T& cast() const { return *static_cast<const T*>(this); }
 
     uint32_t classID() const { SkASSERT(kIllegalXPFClassID != fClassID); return fClassID; }
 
 protected:
     GrXPFactory() : fClassID(kIllegalXPFClassID) {}
 
     template <typename XPF_SUBCLASS> void initClassID() {
          static uint32_t kClassID = GenClassID();
          fClassID = kClassID;
     }
 
     uint32_t fClassID;
 
 private:
     virtual GrXferProcessor* onCreateXferProcessor(const GrCaps& caps,
+                                                   const GrPipelineBuilder&,
                                                    const GrProcOptInfo& colorPOI,
                                                    const GrProcOptInfo& coveragePOI,
                                                    const DstTexture*) const = 0;
     /**
      *  Returns true if the XP generated by this factory will explicitly read dst in the fragment
      *  shader.
      */
     virtual bool willReadDstColor(const GrCaps& caps,
+                                  const GrPipelineBuilder&,
                                   const GrProcOptInfo& colorPOI,
                                   const GrProcOptInfo& coveragePOI) const = 0;
 
     virtual bool onIsEqual(const GrXPFactory&) const = 0;
 
     static uint32_t GenClassID() {
         // fCurrXPFactoryID has been initialized to kIllegalXPFactoryID. The
         // atomic inc returns the old value not the incremented value. So we add
         // 1 to the returned value.
         uint32_t id = static_cast<uint32_t>(sk_atomic_inc(&gCurrXPFClassID)) + 1;
         if (!id) {
             SkFAIL("This should never wrap as it should only be called once for each GrXPFactory "
                    "subclass.");
         }
         return id;
     }
 
     enum {
         kIllegalXPFClassID = 0,
     };
     static int32_t gCurrXPFClassID;
 
     typedef GrProgramElement INHERITED;
 };
 
 #endif