1 /*
2  * Copyright 2018 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 GrCCConicShader_DEFINED
9 #define GrCCConicShader_DEFINED
10 
11 #include "ccpr/GrCCCoverageProcessor.h"
12 
13 /**
14  * This class renders the coverage of closed conic curves using the techniques outlined in
15  * "Resolution Independent Curve Rendering using Programmable Graphics Hardware" by Charles Loop and
16  * Jim Blinn:
17  *
18  * https://www.microsoft.com/en-us/research/wp-content/uploads/2005/01/p1000-loop.pdf
19  *
20  * The provided curves must be monotonic with respect to the vector of their closing edge [P2 - P0].
21  * (Use GrCCGeometry::conicTo().)
22  */
23 class GrCCConicShader : public GrCCCoverageProcessor::Shader {
24 public:
25     void emitSetupCode(GrGLSLVertexGeoBuilder*, const char* pts, const char* wind,
26                        const char** outHull4) const override;
27 
28     void onEmitVaryings(GrGLSLVaryingHandler*, GrGLSLVarying::Scope, SkString* code,
29                         const char* position, const char* coverage,
30                         const char* cornerCoverage) override;
31 
32     void onEmitFragmentCode(GrGLSLFPFragmentBuilder*, const char* outputCoverage) const override;
33 
34 private:
35     void calcHullCoverage(SkString* code, const char* klm, const char* grad,
36                           const char* outputCoverage) const;
37 
38     const GrShaderVar fKLMMatrix{"klm_matrix", kFloat3x3_GrSLType};
39     const GrShaderVar fControlPoint{"control_point", kFloat2_GrSLType};
40     GrGLSLVarying fKLM_fWind;
41     GrGLSLVarying fGrad_fCorner;
42 };
43 
44 #endif
45