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/*
* Copyright 2012 Google Inc.
*
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
*/
#ifndef SkTwoPointConicalGradient_DEFINED
#define SkTwoPointConicalGradient_DEFINED
#include "SkColorSpaceXformer.h"
#include "SkGradientShaderPriv.h"
class SkTwoPointConicalGradient final : public SkGradientShaderBase {
public:
// See https://skia.org/dev/design/conical for what focal data means and how our shader works.
// We make it public so the GPU shader can also use it.
struct FocalData {
SkScalar fR1; // r1 after mapping focal point to (0, 0)
SkScalar fFocalX; // f
bool fIsSwapped; // whether we swapped r0, r1
// The input r0, r1 are the radii when we map centers to {(0, 0), (1, 0)}.
// We'll post concat matrix with our transformation matrix that maps focal point to (0, 0).
// Returns true if the set succeeded
bool set(SkScalar r0, SkScalar r1, SkMatrix* matrix);
// Whether the focal point (0, 0) is on the end circle with center (1, 0) and radius r1. If
// this is true, it's as if an aircraft is flying at Mach 1 and all circles (soundwaves)
// will go through the focal point (aircraft). In our previous implementations, this was
// known as the edge case where the inside circle touches the outside circle (on the focal
// point). If we were to solve for t bruteforcely using a quadratic equation, this case
// implies that the quadratic equation degenerates to a linear equation.
bool isFocalOnCircle() const { return SkScalarNearlyZero(1 - fR1); }
bool isSwapped() const { return fIsSwapped; }
bool isWellBehaved() const { return !this->isFocalOnCircle() && fR1 > 1; }
bool isNativelyFocal() const { return SkScalarNearlyZero(fFocalX); }
};
enum class Type {
kRadial,
kStrip,
kFocal
};
static sk_sp<SkShader> Create(const SkPoint& start, SkScalar startRadius,
const SkPoint& end, SkScalar endRadius,
const Descriptor&);
SkShader::GradientType asAGradient(GradientInfo* info) const override;
#if SK_SUPPORT_GPU
std::unique_ptr<GrFragmentProcessor> asFragmentProcessor(const GrFPArgs&) const override;
#endif
bool isOpaque() const override;
SkScalar getCenterX1() const { return SkPoint::Distance(fCenter1, fCenter2); }
SkScalar getStartRadius() const { return fRadius1; }
SkScalar getDiffRadius() const { return fRadius2 - fRadius1; }
const SkPoint& getStartCenter() const { return fCenter1; }
const SkPoint& getEndCenter() const { return fCenter2; }
SkScalar getEndRadius() const { return fRadius2; }
Type getType() const { return fType; }
const SkMatrix& getGradientMatrix() const { return fPtsToUnit; }
const FocalData& getFocalData() const { return fFocalData; }
SK_DECLARE_PUBLIC_FLATTENABLE_DESERIALIZATION_PROCS(SkTwoPointConicalGradient)
protected:
void flatten(SkWriteBuffer& buffer) const override;
sk_sp<SkShader> onMakeColorSpace(SkColorSpaceXformer* xformer) const override;
void appendGradientStages(SkArenaAlloc* alloc, SkRasterPipeline* tPipeline,
SkRasterPipeline* postPipeline) const override;
private:
SkTwoPointConicalGradient(const SkPoint& c0, SkScalar r0,
const SkPoint& c1, SkScalar r1,
const Descriptor&, Type, const SkMatrix&, const FocalData&);
SkPoint fCenter1;
SkPoint fCenter2;
SkScalar fRadius1;
SkScalar fRadius2;
Type fType;
FocalData fFocalData;
friend class SkGradientShader;
typedef SkGradientShaderBase INHERITED;
};
#endif
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