1/*
2 * Copyright 2012 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 SkTwoPointConicalGradient_DEFINED
9#define SkTwoPointConicalGradient_DEFINED
10
11#include "src/shaders/gradients/SkGradientShaderPriv.h"
12
13class SkTwoPointConicalGradient final : public SkGradientShaderBase {
14public:
15 // See https://skia.org/dev/design/conical for what focal data means and how our shader works.
16 // We make it public so the GPU shader can also use it.
17 struct FocalData {
18 SkScalar fR1; // r1 after mapping focal point to (0, 0)
19 SkScalar fFocalX; // f
20 bool fIsSwapped; // whether we swapped r0, r1
21
22 // The input r0, r1 are the radii when we map centers to {(0, 0), (1, 0)}.
23 // We'll post concat matrix with our transformation matrix that maps focal point to (0, 0).
24 // Returns true if the set succeeded
25 bool set(SkScalar r0, SkScalar r1, SkMatrix* matrix);
26
27 // Whether the focal point (0, 0) is on the end circle with center (1, 0) and radius r1. If
28 // this is true, it's as if an aircraft is flying at Mach 1 and all circles (soundwaves)
29 // will go through the focal point (aircraft). In our previous implementations, this was
30 // known as the edge case where the inside circle touches the outside circle (on the focal
31 // point). If we were to solve for t bruteforcely using a quadratic equation, this case
32 // implies that the quadratic equation degenerates to a linear equation.
33 bool isFocalOnCircle() const { return SkScalarNearlyZero(1 - fR1); }
34
35 bool isSwapped() const { return fIsSwapped; }
36 bool isWellBehaved() const { return !this->isFocalOnCircle() && fR1 > 1; }
37 bool isNativelyFocal() const { return SkScalarNearlyZero(fFocalX); }
38 };
39
40 enum class Type {
41 kRadial,
42 kStrip,
43 kFocal
44 };
45
46 static sk_sp<SkShader> Create(const SkPoint& start, SkScalar startRadius,
47 const SkPoint& end, SkScalar endRadius,
48 const Descriptor&);
49
50 SkShader::GradientType asAGradient(GradientInfo* info) const override;
51#if SK_SUPPORT_GPU
52 std::unique_ptr<GrFragmentProcessor> asFragmentProcessor(const GrFPArgs&) const override;
53#endif
54 bool isOpaque() const override;
55
56 SkScalar getCenterX1() const { return SkPoint::Distance(fCenter1, fCenter2); }
57 SkScalar getStartRadius() const { return fRadius1; }
58 SkScalar getDiffRadius() const { return fRadius2 - fRadius1; }
59 const SkPoint& getStartCenter() const { return fCenter1; }
60 const SkPoint& getEndCenter() const { return fCenter2; }
61 SkScalar getEndRadius() const { return fRadius2; }
62
63 Type getType() const { return fType; }
64 const FocalData& getFocalData() const { return fFocalData; }
65
66protected:
67 void flatten(SkWriteBuffer& buffer) const override;
68
69 void appendGradientStages(SkArenaAlloc* alloc, SkRasterPipeline* tPipeline,
70 SkRasterPipeline* postPipeline) const override;
71
72 skvm::F32 transformT(skvm::Builder*, skvm::Uniforms*,
73 skvm::F32 x, skvm::F32 y, skvm::I32* mask) const final;
74
75private:
76 SK_FLATTENABLE_HOOKS(SkTwoPointConicalGradient)
77
78 SkTwoPointConicalGradient(const SkPoint& c0, SkScalar r0,
79 const SkPoint& c1, SkScalar r1,
80 const Descriptor&, Type, const SkMatrix&, const FocalData&);
81
82 SkPoint fCenter1;
83 SkPoint fCenter2;
84 SkScalar fRadius1;
85 SkScalar fRadius2;
86 Type fType;
87
88 FocalData fFocalData;
89
90 friend class SkGradientShader;
91 typedef SkGradientShaderBase INHERITED;
92};
93
94#endif
95