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 "GrCaps.h"
12 #include "GrFragmentProcessor.h"
13 #include "GrProcessor.h"
14 #include "GrTypesPriv.h"
15 
16 class GrInvariantOutput;
17 class SkPath;
18 
19 /**
20  * An effect that renders a convex polygon. It is intended to be used as a coverage effect.
21  * Bounding geometry is rendered and the effect computes coverage based on the fragment's
22  * position relative to the polygon.
23  */
24 class GrConvexPolyEffect : public GrFragmentProcessor {
25 public:
26     enum {
27         kMaxEdges = 8,
28     };
29 
30     /**
31      * edges is a set of n edge equations where n is limited to kMaxEdges. It contains 3*n values.
32      * The edges should form a convex polygon. The positive half-plane is considered to be the
33      * inside. The equations should be normalized such that the first two coefficients are a unit
34      * 2d vector.
35      *
36      * Currently the edges are specified in device space. In the future we may prefer to specify
37      * them in src space. There are a number of ways this could be accomplished but we'd probably
38      * have to modify the effect/shaderbuilder interface to make it possible (e.g. give access
39      * to the view matrix or untransformed positions in the fragment shader).
40      */
Make(GrPrimitiveEdgeType edgeType,int n,const SkScalar edges[])41     static sk_sp<GrFragmentProcessor> Make(GrPrimitiveEdgeType edgeType, int n,
42                                            const SkScalar edges[]) {
43         if (n <= 0 || n > kMaxEdges || kHairlineAA_GrProcessorEdgeType == edgeType) {
44             return nullptr;
45         }
46         return sk_sp<GrFragmentProcessor>(new GrConvexPolyEffect(edgeType, n, edges));
47     }
48 
49     /**
50      * Creates an effect that clips against the path. If the path is not a convex polygon, is
51      * inverse filled, or has too many edges, this will return nullptr.
52      */
53     static sk_sp<GrFragmentProcessor> Make(GrPrimitiveEdgeType, const SkPath&);
54 
55     /**
56      * Creates an effect that fills inside the rect with AA edges..
57      */
58     static sk_sp<GrFragmentProcessor> Make(GrPrimitiveEdgeType, const SkRect&);
59 
60     ~GrConvexPolyEffect() override;
61 
name()62     const char* name() const override { return "ConvexPoly"; }
63 
getEdgeType()64     GrPrimitiveEdgeType getEdgeType() const { return fEdgeType; }
65 
getEdgeCount()66     int getEdgeCount() const { return fEdgeCount; }
67 
getEdges()68     const SkScalar* getEdges() const { return fEdges; }
69 
70 private:
71     GrConvexPolyEffect(GrPrimitiveEdgeType edgeType, int n, const SkScalar edges[]);
72 
73     GrGLSLFragmentProcessor* onCreateGLSLInstance() const override;
74 
75     void onGetGLSLProcessorKey(const GrShaderCaps&, GrProcessorKeyBuilder*) const override;
76 
77     bool onIsEqual(const GrFragmentProcessor& other) const override;
78 
79     GrPrimitiveEdgeType    fEdgeType;
80     int                    fEdgeCount;
81     SkScalar               fEdges[3 * kMaxEdges];
82 
83     GR_DECLARE_FRAGMENT_PROCESSOR_TEST;
84 
85     typedef GrFragmentProcessor INHERITED;
86 };
87 
88 
89 #endif
90