1/*
2 * Copyright 2018 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#include "SkCubicMap.h"
9#include "SkNx.h"
10#include "../../src/pathops/SkPathOpsCubic.h"
11
12void SkCubicMap::setPts(SkPoint p1, SkPoint p2) {
13    Sk2s s1 = Sk2s::Load(&p1) * 3;
14    Sk2s s2 = Sk2s::Load(&p2) * 3;
15
16    s1 = Sk2s::Min(Sk2s::Max(s1, 0), 3);
17    s2 = Sk2s::Min(Sk2s::Max(s2, 0), 3);
18
19    (Sk2s(1) + s1 - s2).store(&fCoeff[0]);
20    (s2 - s1 - s1).store(&fCoeff[1]);
21    s1.store(&fCoeff[2]);
22
23    this->buildXTable();
24}
25
26SkPoint SkCubicMap::computeFromT(float t) const {
27    Sk2s a = Sk2s::Load(&fCoeff[0]);
28    Sk2s b = Sk2s::Load(&fCoeff[1]);
29    Sk2s c = Sk2s::Load(&fCoeff[2]);
30
31    SkPoint result;
32    (((a * t + b) * t + c) * t).store(&result);
33    return result;
34}
35
36float SkCubicMap::computeYFromX(float x) const {
37    x = SkTPin<float>(x, 0, 0.99999f) * kTableCount;
38    float ix = sk_float_floor(x);
39    int index = (int)ix;
40    SkASSERT((unsigned)index < SK_ARRAY_COUNT(fXTable));
41    return this->computeFromT(fXTable[index].fT0 + fXTable[index].fDT * (x - ix)).fY;
42}
43
44float SkCubicMap::hackYFromX(float x) const {
45    x = SkTPin<float>(x, 0, 0.99999f) * kTableCount;
46    float ix = sk_float_floor(x);
47    int index = (int)ix;
48    SkASSERT((unsigned)index < SK_ARRAY_COUNT(fXTable));
49    return fXTable[index].fY0 + fXTable[index].fDY * (x - ix);
50}
51
52static float compute_t_from_x(float A, float B, float C, float x) {
53    double roots[3];
54    SkDEBUGCODE(int count =) SkDCubic::RootsValidT(A, B, C, -x, roots);
55    SkASSERT(count == 1);
56    return (float)roots[0];
57}
58
59void SkCubicMap::buildXTable() {
60    float prevT = 0;
61
62    const float dx = 1.0f / kTableCount;
63    float x = dx;
64
65    fXTable[0].fT0 = 0;
66    fXTable[0].fY0 = 0;
67    for (int i = 1; i < kTableCount; ++i) {
68        float t = compute_t_from_x(fCoeff[0].fX, fCoeff[1].fX, fCoeff[2].fX, x);
69        SkASSERT(t > prevT);
70
71        fXTable[i - 1].fDT = t - prevT;
72        fXTable[i].fT0 = t;
73
74        SkPoint p = this->computeFromT(t);
75        fXTable[i - 1].fDY = p.fY - fXTable[i - 1].fY0;
76        fXTable[i].fY0 = p.fY;
77
78        prevT = t;
79        x += dx;
80    }
81    fXTable[kTableCount - 1].fDT = 1 - prevT;
82    fXTable[kTableCount - 1].fDY = 1 - fXTable[kTableCount - 1].fY0;
83}
84