1 /*
2  * Copyright 2013 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 GrGeometryProcessor_DEFINED
9 #define GrGeometryProcessor_DEFINED
10 
11 #include "GrPrimitiveProcessor.h"
12 
13 /**
14  * A GrGeometryProcessor is a flexible method for rendering a primitive.  The GrGeometryProcessor
15  * has complete control over vertex attributes and uniforms(aside from the render target) but it
16  * must obey the same contract as any GrPrimitiveProcessor, specifically it must emit a color and
17  * coverage into the fragment shader.  Where this color and coverage come from is completely the
18  * responsibility of the GrGeometryProcessor.
19  */
20 class GrGeometryProcessor : public GrPrimitiveProcessor {
21 public:
GrGeometryProcessor()22     GrGeometryProcessor()
23         : fWillUseGeoShader(false)
24         , fLocalCoordsType(kUnused_LocalCoordsType)
25         , fSampleShading(0.0) {}
26 
willUseGeoShader()27     bool willUseGeoShader() const override { return fWillUseGeoShader; }
28 
hasExplicitLocalCoords()29     bool hasExplicitLocalCoords() const override {
30         return kHasExplicit_LocalCoordsType == fLocalCoordsType;
31     }
32 
33     /**
34      * Returns the minimum fraction of samples for which the fragment shader will be run. For
35      * instance, if sampleShading is 0.5 in MSAA16 mode, the fragment shader will run a minimum of
36      * 8 times per pixel. The default value is zero.
37      */
getSampleShading()38     float getSampleShading() const override {
39         return fSampleShading;
40     }
41 
42 protected:
43     /**
44      * Subclasses call this from their constructor to register vertex attributes.  Attributes
45      * will be padded to the nearest 4 bytes for performance reasons.
46      * TODO After deferred geometry, we should do all of this inline in GenerateGeometry alongside
47      * the struct used to actually populate the attributes.  This is all extremely fragile, vertex
48      * attributes have to be added in the order they will appear in the struct which maps memory.
49      * The processor key should reflect the vertex attributes, or there lack thereof in the
50      * GrGeometryProcessor.
51      */
52     const Attribute& addVertexAttrib(const char* name, GrVertexAttribType type,
53                                      GrSLPrecision precision = kDefault_GrSLPrecision) {
54         fAttribs.emplace_back(name, type, precision);
55         fVertexStride += fAttribs.back().fOffset;
56         return fAttribs.back();
57     }
58 
setWillUseGeoShader()59     void setWillUseGeoShader() { fWillUseGeoShader = true; }
60 
61     /**
62      * If a GrFragmentProcessor in the GrPipeline needs localCoods, we will provide them in one of
63      * three ways
64      * 1) LocalCoordTransform * Position - in Shader
65      * 2) LocalCoordTransform * ExplicitLocalCoords- in Shader
66      * 3) A transformation on the CPU uploaded via vertex attribute
67      */
68     enum LocalCoordsType {
69         kUnused_LocalCoordsType,
70         kHasExplicit_LocalCoordsType,
71         kHasTransformed_LocalCoordsType
72     };
73 
setHasExplicitLocalCoords()74     void setHasExplicitLocalCoords() {
75         SkASSERT(kUnused_LocalCoordsType == fLocalCoordsType);
76         fLocalCoordsType = kHasExplicit_LocalCoordsType;
77     }
setHasTransformedLocalCoords()78     void setHasTransformedLocalCoords() {
79         SkASSERT(kUnused_LocalCoordsType == fLocalCoordsType);
80         fLocalCoordsType = kHasTransformed_LocalCoordsType;
81     }
82 
setSampleShading(float sampleShading)83     void setSampleShading(float sampleShading) {
84         fSampleShading = sampleShading;
85     }
86 
87 private:
88     bool fWillUseGeoShader;
89     LocalCoordsType fLocalCoordsType;
90     float fSampleShading;
91 
92     typedef GrPrimitiveProcessor INHERITED;
93 };
94 
95 #endif
96