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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 "GrEffect.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 GrEffect {
     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 GrEffectRef* Create(GrEffectEdgeType edgeType, int n, const SkScalar edges[]) {
     41         if (n <= 0 || n > kMaxEdges || kHairlineAA_GrEffectEdgeType == edgeType) {
     42             return NULL;
     43         }
     44         return CreateEffectRef(AutoEffectUnref(SkNEW_ARGS(GrConvexPolyEffect,
     45                                                           (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 GrEffectRef* Create(GrEffectEdgeType, const SkPath&, const SkVector* offset = NULL);
     54 
     55     /**
     56      * Creates an effect that fills inside the rect with AA edges..
     57      */
     58     static GrEffectRef* Create(GrEffectEdgeType, const SkRect&);
     59 
     60     virtual ~GrConvexPolyEffect();
     61 
     62     static const char* Name() { return "ConvexPoly"; }
     63 
     64     GrEffectEdgeType getEdgeType() const { return fEdgeType; }
     65 
     66     int getEdgeCount() const { return fEdgeCount; }
     67 
     68     const SkScalar* getEdges() const { return fEdges; }
     69 
     70     typedef GrGLConvexPolyEffect GLEffect;
     71 
     72     virtual void getConstantColorComponents(GrColor* color, uint32_t* validFlags) const SK_OVERRIDE;
     73 
     74     virtual const GrBackendEffectFactory& getFactory() const SK_OVERRIDE;
     75 
     76 private:
     77     GrConvexPolyEffect(GrEffectEdgeType edgeType, int n, const SkScalar edges[]);
     78 
     79     virtual bool onIsEqual(const GrEffect& other) const SK_OVERRIDE;
     80 
     81     GrEffectEdgeType    fEdgeType;
     82     int                 fEdgeCount;
     83     SkScalar            fEdges[3 * kMaxEdges];
     84 
     85     GR_DECLARE_EFFECT_TEST;
     86 
     87     typedef GrEffect INHERITED;
     88 };
     89 
     90 
     91 #endif
     92