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 "src/gpu/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 */
23class GrCCConicShader : public GrCCCoverageProcessor::Shader {
24public:
25 bool calculatesOwnEdgeCoverage() const override { return true; }
26
27 void emitSetupCode(
28 GrGLSLVertexGeoBuilder*, const char* pts, const char** outHull4) const override;
29
30 void onEmitVaryings(
31 GrGLSLVaryingHandler*, GrGLSLVarying::Scope, SkString* code, const char* position,
32 const char* coverage, const char* cornerCoverage, const char* wind) override;
33
34 void emitFragmentCoverageCode(
35 GrGLSLFPFragmentBuilder*, const char* outputCoverage) const override;
36
37 void emitSampleMaskCode(GrGLSLFPFragmentBuilder*) const override;
38
39private:
40 void calcHullCoverage(SkString* code, const char* klm, const char* grad,
41 const char* outputCoverage) const;
42
43 const GrShaderVar fKLMMatrix{"klm_matrix", kFloat3x3_GrSLType};
44 const GrShaderVar fControlPoint{"control_point", kFloat2_GrSLType};
45 GrGLSLVarying fKLM_fWind;
46 GrGLSLVarying fGrad_fCorner;
47};
48
49#endif
50