Add gl_SampleMask functionality to fragment builders

src/gpu/glsl/GrGLSLFragmentShaderBuilder.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 GrGLSLFragmentShaderBuilder_DEFINED
 #define GrGLSLFragmentShaderBuilder_DEFINED
 
@@ skipping 49 matching lines @@
 
 /*
  * This class is used by fragment processors to build their fragment code.
  */
 class GrGLSLFPFragmentBuilder : virtual public GrGLSLFragmentBuilder {
 public:
     /** Appease the compiler; the derived class initializes GrGLSLFragmentBuilder. */
     GrGLSLFPFragmentBuilder() : GrGLSLFragmentBuilder(nullptr) {}
 
     /**
+     * Subtracts sample coverage from the fragment. Any sample whose corresponding bit is not found
+     * in the mask will not be written out to the framebuffer.
+     *
+     * @param mask      int that contains the sample mask. Bit N corresponds to the Nth sample.
+     * @param invert    perform a bit-wise NOT on the provided mask before applying it?
+     *
+     * Requires GLSL support for sample variables.
+     */
+    virtual void maskSampleCoverage(const char* mask, bool invert = false) = 0;
+
+    /**
      * Fragment procs with child procs should call these functions before/after calling emitCode
      * on a child proc.
      */
     virtual void onBeforeChildProcEmitCode() = 0;
     virtual void onAfterChildProcEmitCode() = 0;
 
     virtual const SkString& getMangleString() const = 0;
 };
 
 /*
  * This class is used by primitive processors to build their fragment code.
  */
 class GrGLSLPPFragmentBuilder : public GrGLSLFPFragmentBuilder {
 public:
     /** Appease the compiler; the derived class initializes GrGLSLFragmentBuilder. */
     GrGLSLPPFragmentBuilder() : GrGLSLFragmentBuilder(nullptr) {}
+
+    /**
+     * Overrides the fragment's sample coverage. The provided mask determines which samples will now
+     * be written out to the framebuffer. Note that this mask can be reduced by a future call to
+     * maskSampleCoverage.
+     *
+     * If a primitive processor uses this method, it must guarantee that every codepath through the
+     * shader overrides the sample mask at some point.
+     *
+     * @param mask    int that contains the new coverage mask. Bit N corresponds to the Nth sample.
+     *
+     * Requires NV_sample_mask_override_coverage.
+     */
+    virtual void overrideSampleCoverage(const char* mask) = 0;
 };
 
 /*
  * This class is used by Xfer processors to build their fragment code.
  */
 class GrGLSLXPFragmentBuilder : virtual public GrGLSLFragmentBuilder {
 public:
     /** Appease the compiler; the derived class initializes GrGLSLFragmentBuilder. */
     GrGLSLXPFragmentBuilder() : GrGLSLFragmentBuilder(nullptr) {}
 
@@ skipping 24 matching lines @@
 
     GrGLSLFragmentShaderBuilder(GrGLSLProgramBuilder* program, uint8_t fragPosKey);
 
     // Shared GrGLSLFragmentBuilder interface.
     bool enableFeature(GLSLFeature) override;
     virtual SkString ensureFSCoords2D(const GrGLSLTransformedCoordsArray& coords,
                                       int index) override;
     const char* fragmentPosition() override;
 
     // GrGLSLFPFragmentBuilder interface.
+    void maskSampleCoverage(const char* mask, bool invert = false) override;
+    void overrideSampleCoverage(const char* mask) override;
     const SkString& getMangleString() const override { return fMangleString; }
     void onBeforeChildProcEmitCode() override;
     void onAfterChildProcEmitCode() override;
 
     // GrGLSLXPFragmentBuilder interface.
     bool hasCustomColorOutput() const override { return fHasCustomColorOutput; }
     bool hasSecondaryOutput() const override { return fHasSecondaryOutput; }
     const char* dstColor() override;
     void enableAdvancedBlendEquationIfNeeded(GrBlendEquation) override;
 
@@ skipping 50 matching lines @@
      * have "_c3_c1_c2" appended to its name, which can be interpreted as "base proc's 3rd child's
      * 1st child's 2nd child".
      */
     SkString fMangleString;
 
     bool fSetupFragPosition;
     bool fTopLeftFragPosRead;
     bool fHasCustomColorOutput;
     int  fCustomColorOutputIndex;
     bool fHasSecondaryOutput;
+    bool fHasInitializedSampleMask;
 
     // some state to verify shaders and effects are consistent, this is reset between effects by
     // the program creator
     bool fHasReadDstColor;
     bool fHasReadFragmentPosition;
 
     friend class GrGLSLProgramBuilder;
     friend class GrGLProgramBuilder;
 };
 
 #endif