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.
   */
  
  #ifndef GrConvexPolyEffect_DEFINED
  #define GrConvexPolyEffect_DEFINED
  
  #include "GrCaps.h"
  #include "GrFragmentProcessor.h"
  #include "GrProcessor.h"
  #include "GrTypesPriv.h"
  
  class GrInvariantOutput;
  class SkPath;
  
  /**
   * An effect that renders a convex polygon. It is intended to be used as a coverage effect.
   * Bounding geometry is rendered and the effect computes coverage based on the fragment's
   * position relative to the polygon.
   */
  class GrConvexPolyEffect : public GrFragmentProcessor {
  public:
      enum {
          kMaxEdges = 8,
      };
  
      /**
       * edges is a set of n edge equations where n is limited to kMaxEdges. It contains 3*n values.
       * The edges should form a convex polygon. The positive half-plane is considered to be the
       * inside. The equations should be normalized such that the first two coefficients are a unit
       * 2d vector.
       *
       * Currently the edges are specified in device space. In the future we may prefer to specify
       * them in src space. There are a number of ways this could be accomplished but we'd probably
       * have to modify the effect/shaderbuilder interface to make it possible (e.g. give access
       * to the view matrix or untransformed positions in the fragment shader).
       */
      static GrFragmentProcessor* Create(GrPrimitiveEdgeType edgeType, int n,
                                         const SkScalar edges[]) {
          if (n <= 0 || n > kMaxEdges || kHairlineAA_GrProcessorEdgeType == edgeType) {
              return NULL;
          }
          return SkNEW_ARGS(GrConvexPolyEffect, (edgeType, n, edges));
      }
  
      /**
       * Creates an effect that clips against the path. If the path is not a convex polygon, is
       * inverse filled, or has too many edges, this will return NULL. If offset is non-NULL, then
       * the path is translated by the vector.
       */
      static GrFragmentProcessor* Create(GrPrimitiveEdgeType, const SkPath&,
                                         const SkVector* offset = NULL);
  
      /**
       * Creates an effect that fills inside the rect with AA edges..
       */
      static GrFragmentProcessor* Create(GrPrimitiveEdgeType, const SkRect&);
  
      virtual ~GrConvexPolyEffect();
  
      const char* name() const override { return "ConvexPoly"; }
  
      GrPrimitiveEdgeType getEdgeType() const { return fEdgeType; }
  
      int getEdgeCount() const { return fEdgeCount; }
  
      const SkScalar* getEdges() const { return fEdges; }
  
      void getGLProcessorKey(const GrGLSLCaps&, GrProcessorKeyBuilder*) const override;
  
      GrGLFragmentProcessor* createGLInstance() const override;
  
  private:
      GrConvexPolyEffect(GrPrimitiveEdgeType edgeType, int n, const SkScalar edges[]);
  
      bool onIsEqual(const GrFragmentProcessor& other) const override;
  
      void onComputeInvariantOutput(GrInvariantOutput* inout) const override;
  
      GrPrimitiveEdgeType    fEdgeType;
      int                    fEdgeCount;
      SkScalar               fEdges[3 * kMaxEdges];
  
      GR_DECLARE_FRAGMENT_PROCESSOR_TEST;
  
      typedef GrFragmentProcessor INHERITED;
  };
  
  
  #endif
  