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      1 /*
      2  * Copyright 2014 Google Inc.
      3  *
      4  * Use of this source code is governed by a BSD-style license that can be
      5  * found in the LICENSE file.
      6  */
      7 
      8 #ifndef GrConvexPolyEffect_DEFINED
      9 #define GrConvexPolyEffect_DEFINED
     10 
     11 #include "GrDrawTargetCaps.h"
     12 #include "GrProcessor.h"
     13 #include "GrTypesPriv.h"
     14 
     15 class GrGLConvexPolyEffect;
     16 class SkPath;
     17 
     18 /**
     19  * An effect that renders a convex polygon. It is intended to be used as a coverage effect.
     20  * Bounding geometry is rendered and the effect computes coverage based on the fragment's
     21  * position relative to the polygon.
     22  */
     23 class GrConvexPolyEffect : public GrFragmentProcessor {
     24 public:
     25     enum {
     26         kMaxEdges = 8,
     27     };
     28 
     29     /**
     30      * edges is a set of n edge equations where n is limited to kMaxEdges. It contains 3*n values.
     31      * The edges should form a convex polygon. The positive half-plane is considered to be the
     32      * inside. The equations should be normalized such that the first two coefficients are a unit
     33      * 2d vector.
     34      *
     35      * Currently the edges are specified in device space. In the future we may prefer to specify
     36      * them in src space. There are a number of ways this could be accomplished but we'd probably
     37      * have to modify the effect/shaderbuilder interface to make it possible (e.g. give access
     38      * to the view matrix or untransformed positions in the fragment shader).
     39      */
     40     static GrFragmentProcessor* Create(GrPrimitiveEdgeType edgeType, int n,
     41                                        const SkScalar edges[]) {
     42         if (n <= 0 || n > kMaxEdges || kHairlineAA_GrProcessorEdgeType == edgeType) {
     43             return NULL;
     44         }
     45         return SkNEW_ARGS(GrConvexPolyEffect, (edgeType, n, edges));
     46     }
     47 
     48     /**
     49      * Creates an effect that clips against the path. If the path is not a convex polygon, is
     50      * inverse filled, or has too many edges, this will return NULL. If offset is non-NULL, then
     51      * the path is translated by the vector.
     52      */
     53     static GrFragmentProcessor* Create(GrPrimitiveEdgeType, const SkPath&,
     54                                        const SkVector* offset = NULL);
     55 
     56     /**
     57      * Creates an effect that fills inside the rect with AA edges..
     58      */
     59     static GrFragmentProcessor* Create(GrPrimitiveEdgeType, const SkRect&);
     60 
     61     virtual ~GrConvexPolyEffect();
     62 
     63     static const char* Name() { return "ConvexPoly"; }
     64 
     65     GrPrimitiveEdgeType getEdgeType() const { return fEdgeType; }
     66 
     67     int getEdgeCount() const { return fEdgeCount; }
     68 
     69     const SkScalar* getEdges() const { return fEdges; }
     70 
     71     typedef GrGLConvexPolyEffect GLProcessor;
     72 
     73     virtual void getConstantColorComponents(GrColor* color, uint32_t* validFlags) const SK_OVERRIDE;
     74 
     75     virtual const GrBackendFragmentProcessorFactory& getFactory() const SK_OVERRIDE;
     76 
     77 private:
     78     GrConvexPolyEffect(GrPrimitiveEdgeType edgeType, int n, const SkScalar edges[]);
     79 
     80     virtual bool onIsEqual(const GrProcessor& other) const SK_OVERRIDE;
     81 
     82     GrPrimitiveEdgeType    fEdgeType;
     83     int                    fEdgeCount;
     84     SkScalar               fEdges[3 * kMaxEdges];
     85 
     86     GR_DECLARE_FRAGMENT_PROCESSOR_TEST;
     87 
     88     typedef GrFragmentProcessor INHERITED;
     89 };
     90 
     91 
     92 #endif
     93