text: /*
   * 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 "src/core/SkPathPriv.h"
  #include "src/gpu/effects/GrConvexPolyEffect.h"
  #include "src/gpu/effects/generated/GrAARectEffect.h"
  #include "src/gpu/effects/generated/GrConstColorProcessor.h"
  #include "src/gpu/glsl/GrGLSLFragmentProcessor.h"
  #include "src/gpu/glsl/GrGLSLFragmentShaderBuilder.h"
  #include "src/gpu/glsl/GrGLSLProgramDataManager.h"
  #include "src/gpu/glsl/GrGLSLUniformHandler.h"
  
  //////////////////////////////////////////////////////////////////////////////
  
  class GrGLConvexPolyEffect : public GrGLSLFragmentProcessor {
  public:
      GrGLConvexPolyEffect() {
          for (size_t i = 0; i < SK_ARRAY_COUNT(fPrevEdges); ++i) {
              fPrevEdges[i] = SK_ScalarNaN;
          }
      }
  
      void emitCode(EmitArgs&) override;
  
      static inline void GenKey(const GrProcessor&, const GrShaderCaps&, GrProcessorKeyBuilder*);
  
  protected:
      void onSetData(const GrGLSLProgramDataManager&, const GrFragmentProcessor&) override;
  
  private:
      GrGLSLProgramDataManager::UniformHandle fEdgeUniform;
      SkScalar                                fPrevEdges[3 * GrConvexPolyEffect::kMaxEdges];
      typedef GrGLSLFragmentProcessor INHERITED;
  };
  
  void GrGLConvexPolyEffect::emitCode(EmitArgs& args) {
      const GrConvexPolyEffect& cpe = args.fFp.cast<GrConvexPolyEffect>();
  
      const char *edgeArrayName;
      fEdgeUniform = args.fUniformHandler->addUniformArray(&cpe,
                                                           kFragment_GrShaderFlag,
                                                           kHalf3_GrSLType,
                                                           "edges",
                                                           cpe.getEdgeCount(),
                                                           &edgeArrayName);
      GrGLSLFPFragmentBuilder* fragBuilder = args.fFragBuilder;
      fragBuilder->codeAppend("\t\thalf alpha = 1.0;\n");
      fragBuilder->codeAppend("\t\thalf edge;\n");
      for (int i = 0; i < cpe.getEdgeCount(); ++i) {
          fragBuilder->codeAppendf("\t\tedge = dot(%s[%d], half3(half(sk_FragCoord.x), "
                                                                "half(sk_FragCoord.y), "
                                                                "1));\n",
                                   edgeArrayName, i);
          if (GrProcessorEdgeTypeIsAA(cpe.getEdgeType())) {
              fragBuilder->codeAppend("\t\tedge = saturate(edge);\n");
          } else {
              fragBuilder->codeAppend("\t\tedge = edge >= 0.5 ? 1.0 : 0.0;\n");
          }
          fragBuilder->codeAppend("\t\talpha *= edge;\n");
      }
  
      if (GrProcessorEdgeTypeIsInverseFill(cpe.getEdgeType())) {
          fragBuilder->codeAppend("\talpha = 1.0 - alpha;\n");
      }
      fragBuilder->codeAppendf("\t%s = %s * alpha;\n", args.fOutputColor, args.fInputColor);
  }
  
  void GrGLConvexPolyEffect::onSetData(const GrGLSLProgramDataManager& pdman,
                                       const GrFragmentProcessor& effect) {
      const GrConvexPolyEffect& cpe = effect.cast<GrConvexPolyEffect>();
      size_t byteSize = 3 * cpe.getEdgeCount() * sizeof(SkScalar);
      if (0 != memcmp(fPrevEdges, cpe.getEdges(), byteSize)) {
          pdman.set3fv(fEdgeUniform, cpe.getEdgeCount(), cpe.getEdges());
          memcpy(fPrevEdges, cpe.getEdges(), byteSize);
      }
  }
  
  void GrGLConvexPolyEffect::GenKey(const GrProcessor& processor, const GrShaderCaps&,
                                    GrProcessorKeyBuilder* b) {
      const GrConvexPolyEffect& cpe = processor.cast<GrConvexPolyEffect>();
      static_assert(kGrClipEdgeTypeCnt <= 8);
      uint32_t key = (cpe.getEdgeCount() << 3) | (int) cpe.getEdgeType();
      b->add32(key);
  }
  
  //////////////////////////////////////////////////////////////////////////////
  
  std::unique_ptr<GrFragmentProcessor> GrConvexPolyEffect::Make(GrClipEdgeType type,
                                                                const SkPath& path) {
      if (GrClipEdgeType::kHairlineAA == type) {
          return nullptr;
      }
      if (path.getSegmentMasks() != SkPath::kLine_SegmentMask ||
          !path.isConvex()) {
          return nullptr;
      }
  
      SkPathPriv::FirstDirection dir;
      // The only way this should fail is if the clip is effectively a infinitely thin line. In that
      // case nothing is inside the clip. It'd be nice to detect this at a higher level and either
      // skip the draw or omit the clip element.
      if (!SkPathPriv::CheapComputeFirstDirection(path, &dir)) {
          if (GrProcessorEdgeTypeIsInverseFill(type)) {
              return GrConstColorProcessor::Make(SK_PMColor4fWHITE,
                                                 GrConstColorProcessor::InputMode::kModulateRGBA);
          }
          // This could use kIgnore instead of kModulateRGBA but it would trigger a debug print
          // about a coverage processor not being compatible with the alpha-as-coverage optimization.
          // We don't really care about this unlikely case so we just use kModulateRGBA to suppress
          // the print.
          return GrConstColorProcessor::Make(SK_PMColor4fTRANSPARENT,
                                             GrConstColorProcessor::InputMode::kModulateRGBA);
      }
  
      SkScalar        edges[3 * kMaxEdges];
      SkPoint         pts[4];
      SkPath::Verb    verb;
      SkPath::Iter    iter(path, true);
  
      // SkPath considers itself convex so long as there is a convex contour within it,
      // regardless of any degenerate contours such as a string of moveTos before it.
      // Iterate here to consume any degenerate contours and only process the points
      // on the actual convex contour.
      int n = 0;
      while ((verb = iter.next(pts)) != SkPath::kDone_Verb) {
          switch (verb) {
              case SkPath::kMove_Verb:
                  SkASSERT(n == 0);
              case SkPath::kClose_Verb:
                  break;
              case SkPath::kLine_Verb: {
                  if (n >= kMaxEdges) {
                      return nullptr;
                  }
                  if (pts[0] != pts[1]) {
                      SkVector v = pts[1] - pts[0];
                      v.normalize();
                      if (SkPathPriv::kCCW_FirstDirection == dir) {
                          edges[3 * n] = v.fY;
                          edges[3 * n + 1] = -v.fX;
                      } else {
                          edges[3 * n] = -v.fY;
                          edges[3 * n + 1] = v.fX;
                      }
                      edges[3 * n + 2] = -(edges[3 * n] * pts[1].fX + edges[3 * n + 1] * pts[1].fY);
                      ++n;
                  }
                  break;
              }
              default:
                  return nullptr;
          }
      }
  
      if (path.isInverseFillType()) {
          type = GrInvertProcessorEdgeType(type);
      }
      return Make(type, n, edges);
  }
  
  std::unique_ptr<GrFragmentProcessor> GrConvexPolyEffect::Make(GrClipEdgeType edgeType,
                                                                const SkRect& rect) {
      if (GrClipEdgeType::kHairlineAA == edgeType){
          return nullptr;
      }
      return GrAARectEffect::Make(edgeType, rect);
  }
  
  GrConvexPolyEffect::~GrConvexPolyEffect() {}
  
  void GrConvexPolyEffect::onGetGLSLProcessorKey(const GrShaderCaps& caps,
                                                 GrProcessorKeyBuilder* b) const {
      GrGLConvexPolyEffect::GenKey(*this, caps, b);
  }
  
  GrGLSLFragmentProcessor* GrConvexPolyEffect::onCreateGLSLInstance() const  {
      return new GrGLConvexPolyEffect;
  }
  
  GrConvexPolyEffect::GrConvexPolyEffect(GrClipEdgeType edgeType, int n, const SkScalar edges[])
          : INHERITED(kGrConvexPolyEffect_ClassID, kCompatibleWithCoverageAsAlpha_OptimizationFlag)
          , fEdgeType(edgeType)
          , fEdgeCount(n) {
      // Factory function should have already ensured this.
      SkASSERT(n <= kMaxEdges);
      memcpy(fEdges, edges, 3 * n * sizeof(SkScalar));
      // Outset the edges by 0.5 so that a pixel with center on an edge is 50% covered in the AA case
      // and 100% covered in the non-AA case.
      for (int i = 0; i < n; ++i) {
          fEdges[3 * i + 2] += SK_ScalarHalf;
      }
  }
  
  GrConvexPolyEffect::GrConvexPolyEffect(const GrConvexPolyEffect& that)
          : INHERITED(kGrConvexPolyEffect_ClassID, kCompatibleWithCoverageAsAlpha_OptimizationFlag)
          , fEdgeType(that.fEdgeType)
          , fEdgeCount(that.fEdgeCount) {
      memcpy(fEdges, that.fEdges, 3 * that.fEdgeCount * sizeof(SkScalar));
  }
  
  std::unique_ptr<GrFragmentProcessor> GrConvexPolyEffect::clone() const {
      return std::unique_ptr<GrFragmentProcessor>(new GrConvexPolyEffect(*this));
  }
  
  bool GrConvexPolyEffect::onIsEqual(const GrFragmentProcessor& other) const {
      const GrConvexPolyEffect& cpe = other.cast<GrConvexPolyEffect>();
      // ignore the fact that 0 == -0 and just use memcmp.
      return (cpe.fEdgeType == fEdgeType && cpe.fEdgeCount == fEdgeCount &&
              0 == memcmp(cpe.fEdges, fEdges, 3 * fEdgeCount * sizeof(SkScalar)));
  }
  
  //////////////////////////////////////////////////////////////////////////////
  
  GR_DEFINE_FRAGMENT_PROCESSOR_TEST(GrConvexPolyEffect);
  
  #if GR_TEST_UTILS
  std::unique_ptr<GrFragmentProcessor> GrConvexPolyEffect::TestCreate(GrProcessorTestData* d) {
      int count = d->fRandom->nextULessThan(kMaxEdges) + 1;
      SkScalar edges[kMaxEdges * 3];
      for (int i = 0; i < 3 * count; ++i) {
          edges[i] = d->fRandom->nextSScalar1();
      }
  
      std::unique_ptr<GrFragmentProcessor> fp;
      do {
          GrClipEdgeType edgeType = static_cast<GrClipEdgeType>(
                  d->fRandom->nextULessThan(kGrClipEdgeTypeCnt));
          fp = GrConvexPolyEffect::Make(edgeType, count, edges);
      } while (nullptr == fp);
      return fp;
  }
  #endif
  