/*
* 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 SkConicalGradient_DEFINED
#define SkConicalGradient_DEFINED
#include "include/core/SkFlattenable.h"
#include "include/core/SkPoint.h"
#include "include/core/SkRefCnt.h"
#include "include/core/SkScalar.h"
#include "src/shaders/gradients/SkGradientBaseShader.h"
class SkArenaAlloc;
class SkMatrix;
class SkRasterPipeline;
class SkReadBuffer;
class SkShader;
class SkWriteBuffer;
// Please see https://skia.org/dev/design/conical for how our shader works.
class SkConicalGradient final :
public SkGradientBaseShader {
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 bool MapToUnitX(
const SkPoint& startCenter,
const SkPoint& endCenter,
SkMatrix* dstMatrix);
static sk_sp<SkShader> Create(
const SkPoint& start,
SkScalar startRadius,
const SkPoint& end,
SkScalar endRadius,
const Descriptor&,
const SkMatrix* localMatrix);
GradientType asGradient(GradientInfo* info, SkMatrix* localMatrix)
const override;
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 FocalData& getFocalData()
const {
return fFocalData; }
SkConicalGradient(
const SkPoint& c0,
SkScalar r0,
const SkPoint& c1,
SkScalar r1,
const Descriptor&,
Type,
const SkMatrix&,
const FocalData&);
protected:
void flatten(SkWriteBuffer& buffer)
const override;
void appendGradientStages(SkArenaAlloc* alloc,
SkRasterPipeline* tPipeline,
SkRasterPipeline* postPipeline)
const override;
private:
friend void ::SkRegisterConicalGradientShaderFlattenable();
SK_FLATTENABLE_HOOKS(SkConicalGradient)
SkPoint fCenter1;
SkPoint fCenter2;
SkScalar fRadius1;
SkScalar fRadius2;
Type fType;
FocalData fFocalData;
};
#endif
