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/*
* Copyright 2017 Google Inc.
*
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
*/
#ifndef GrCCCubicShader_DEFINED
#define GrCCCubicShader_DEFINED
#include "ccpr/GrCCCoverageProcessor.h"
/**
* This class renders the coverage of convex closed cubic segments using the techniques outlined in
* "Resolution Independent Curve Rendering using Programmable Graphics Hardware" by Charles Loop and
* Jim Blinn:
*
* https://www.microsoft.com/en-us/research/wp-content/uploads/2005/01/p1000-loop.pdf
*
* The provided curve segments must be convex, monotonic with respect to the vector of their closing
* edge [P3 - P0], and must not contain or be near any inflection points or loop intersections.
* (Use GrCCGeometry::cubicTo().)
*/
class GrCCCubicShader : public GrCCCoverageProcessor::Shader {
public:
void emitSetupCode(GrGLSLVertexGeoBuilder*, const char* pts, const char* wind,
const char** outHull4) const override;
void onEmitVaryings(GrGLSLVaryingHandler*, GrGLSLVarying::Scope, SkString* code,
const char* position, const char* coverage,
const char* cornerCoverage) override;
void onEmitFragmentCode(GrGLSLFPFragmentBuilder*, const char* outputCoverage) const override;
private:
void calcHullCoverage(SkString* code, const char* klmAndEdge, const char* gradMatrix,
const char* outputCoverage) const;
const GrShaderVar fKLMMatrix{"klm_matrix", kFloat3x3_GrSLType};
const GrShaderVar fEdgeDistanceEquation{"edge_distance_equation", kFloat3_GrSLType};
GrGLSLVarying fKLM_fEdge;
GrGLSLVarying fGradMatrix;
GrGLSLVarying fCornerCoverage;
};
#endif
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