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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 GrCCQuadraticShader_DEFINED
#define GrCCQuadraticShader_DEFINED
#include "ccpr/GrCCCoverageProcessor.h"
/**
* This class renders the coverage of closed quadratic curves 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 curves must be monotonic with respect to the vector of their closing edge [P2 - P0].
* (Use GrCCGeometry.)
*/
class GrCCQuadraticShader : public GrCCCoverageProcessor::Shader {
protected:
void emitSetupCode(GrGLSLVertexGeoBuilder*, const char* pts, const char* repetitionID,
const char* wind, GeometryVars*) const final;
virtual void onEmitSetupCode(GrGLSLVertexGeoBuilder*, const char* pts, const char* repetitionID,
GeometryVars*) const = 0;
void onEmitVaryings(GrGLSLVaryingHandler*, GrGLSLVarying::Scope, SkString* code,
const char* position, const char* inputCoverage, const char* wind) final;
virtual void onEmitVaryings(GrGLSLVaryingHandler*, GrGLSLVarying::Scope, SkString* code) {}
void onEmitFragmentCode(GrGLSLFPFragmentBuilder*, const char* outputCoverage) const final;
virtual void emitCoverage(GrGLSLFPFragmentBuilder*, const char* outputCoverage) const = 0;
const GrShaderVar fCanonicalMatrix{"canonical_matrix", kFloat3x3_GrSLType};
const GrShaderVar fEdgeDistanceEquation{"edge_distance_equation", kFloat3_GrSLType};
GrGLSLVarying fXYDW;
};
/**
* This pass draws a conservative raster hull around the quadratic bezier curve, computes the
* curve's coverage using the gradient-based AA technique outlined in the Loop/Blinn paper, and
* uses simple distance-to-edge to subtract out coverage for the flat closing edge [P2 -> P0]. Since
* the provided curves are monotonic, this will get every pixel right except the two corners.
*/
class GrCCQuadraticHullShader : public GrCCQuadraticShader {
void onEmitSetupCode(GrGLSLVertexGeoBuilder*, const char* pts, const char* repetitionID,
GeometryVars*) const override;
void onEmitVaryings(GrGLSLVaryingHandler*, GrGLSLVarying::Scope, SkString* code) override;
void emitCoverage(GrGLSLFPFragmentBuilder*, const char* outputCoverage) const override;
GrGLSLVarying fGrad;
};
/**
* This pass fixes the corners of a closed quadratic segment with soft MSAA.
*/
class GrCCQuadraticCornerShader : public GrCCQuadraticShader {
void onEmitSetupCode(GrGLSLVertexGeoBuilder*, const char* pts, const char* repetitionID,
GeometryVars*) const override;
void onEmitVaryings(GrGLSLVaryingHandler*, GrGLSLVarying::Scope, SkString* code) override;
void emitCoverage(GrGLSLFPFragmentBuilder*, const char* outputCoverage) const override;
GrGLSLVarying fdXYDdx;
GrGLSLVarying fdXYDdy;
};
#endif
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