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 <string>
9#include "include/core/SkCanvas.h"
10#include "include/core/SkFont.h"
11#include "include/core/SkPath.h"
12#include "samplecode/Sample.h"
13#include "src/core/SkGeometry.h"
14#include "tools/timer/TimeUtils.h"
15
16// This draws an animation where every cubic has a cusp, to test drawing a circle
17// at the cusp point. Create a unit square. A cubic with its control points
18// at the four corners crossing over itself has a cusp.
19
20// Project the unit square through a random affine matrix.
21// Chop the cubic in two. One half of the cubic will have a cusp
22// (unless it was chopped exactly at the cusp point).
23
24// Running this looks mostly OK, but will occasionally draw something odd.
25// The odd parts don't appear related to the cusp code, but are old stroking
26// bugs that have not been fixed, yet.
27
28SkMSec start = 0;
29SkMSec curTime;
30bool first = true;
31
32// Create a path with one or two cubics, where one has a cusp.
33static SkPath cusp(const SkPoint P[4], SkPoint PP[7], bool& split, int speed, SkScalar phase) {
34    SkPath path;
35    path.moveTo(P[0]);
36    SkScalar t = (curTime % speed) / SkIntToFloat(speed);
37    t += phase;
38    if (t > 1) {
39        t -= 1;
40    }
41    if (0 <= t || t >= 1) {
42        path.cubicTo(P[1], P[2], P[3]);
43        split = false;
44    } else {
45        SkChopCubicAt(P, PP, t);
46        path.cubicTo(PP[1], PP[2], PP[3]);
47        path.cubicTo(PP[4], PP[5], PP[6]);
48        split = true;
49    }
50    return path;
51}
52
53// Scale the animation counter to a value that oscillates from -scale to +scale.
54static SkScalar linearToLoop(int speed, SkScalar phase, SkScalar scale) {
55    SkScalar loop;
56    SkScalar linear = (curTime % speed) / SkIntToFloat(speed);  // 0 to 1
57    linear += phase;
58    if (linear > 1) {
59        linear -= 1;
60    }
61    if (linear < .25) {
62        loop = linear * 4;     //  0 to .25  ==> 0 to  1
63    } else if (linear < .75) { // .25 to .75 ==> 1 to -1
64        loop = (.5 - linear) * 4;
65    } else  {                  // .75 to 1   ==> -1 to 0
66        loop = (linear - 1) * 4;
67    }
68    return loop * scale;
69}
70
71struct data {
72    SkIPoint pt[4];
73} dat[] = {
74// When the animation looks funny, pause, and paste the last part of the stream in stdout here.
75// Enable the 1st #if to play the recorded stream backwards.
76// Enable the 2nd #if and replace the second 'i = ##' with the value of datCount that shows the bug.
77{{{0x43480000,0x43960000},{0x4318b999,0x4321570b},{0x432f999a,0x435a0a3d},{0x43311fff,0x43734cce},}},
78{{{0x43480000,0x43960000},{0x431d1ddf,0x4321ae13},{0x4331ddde,0x435c147c},{0x43334001,0x43719997},}},
79{{{0x43480000,0x43960000},{0x43218224,0x43220520},{0x43342223,0x435e1eba},{0x43356001,0x436fe666},}},
80{{{0x43480000,0x43960000},{0x4325a445,0x43225708},{0x43364444,0x43600a3c},{0x43376001,0x436e4ccc},}},
81{{{0x43480000,0x43960000},{0x432a0889,0x4322ae16},{0x43388889,0x4362147b},{0x43398000,0x436c999b},}},
82{{{0x43480000,0x43960000},{0x432e6ccd,0x43230523},{0x433acccd,0x43641eba},{0x433ba000,0x436ae66a},}},
83{{{0x43480000,0x43960000},{0x43328eef,0x4323570c},{0x433ceeee,0x43660a3c},{0x433da000,0x43694cd0},}},
84{{{0x43480000,0x43960000},{0x4336f333,0x4323ae13},{0x433f3333,0x4368147a},{0x433fc000,0x43679998},}},
85{{{0x43480000,0x43960000},{0x433b5777,0x43240520},{0x43417777,0x436a1eb9},{0x4341e000,0x4365e668},}},
86{{{0x43480000,0x43960000},{0x433f799a,0x4324570c},{0x4343999a,0x436c0a3e},{0x4343e000,0x43644cce},}},
87{{{0x43480000,0x43960000},{0x4343ddde,0x4324ae13},{0x4345dddf,0x436e147c},{0x43460000,0x43629996},}},
88{{{0x43480000,0x43960000},{0x43484222,0x4325051e},{0x43482222,0x43701eb9},{0x43481fff,0x4360e666},}},
89{{{0x43480000,0x43960000},{0x434c6446,0x43255709},{0x434a4444,0x43720a3e},{0x434a2002,0x435f4ccc},}},
90{{{0x43480000,0x43960000},{0x4350c888,0x4325ae16},{0x434c8889,0x4374147c},{0x434c3fff,0x435d999a},}},
91{{{0x43480000,0x43960000},{0x43552cce,0x43260521},{0x434ecccd,0x43761eb8},{0x434e6001,0x435be669},}},
92{{{0x43480000,0x43960000},{0x43594eee,0x4326570c},{0x4350eeef,0x43780a3d},{0x43505fff,0x435a4ccf},}},
93{{{0x43480000,0x43960000},{0x435db334,0x4326ae19},{0x43533333,0x437a147c},{0x43528001,0x4358999e},}},
94{{{0x43480000,0x43960000},{0x4361d555,0x43270002},{0x43555555,0x437bfffe},{0x43547fff,0x43570004},}},
95{{{0x43480000,0x43960000},{0x4366399a,0x4327570c},{0x4357999a,0x437e0a3f},{0x4356a001,0x43554ccd},}},
96{{{0x43480000,0x43960000},{0x436a9ddc,0x4327ae12},{0x4359ddde,0x43800a3e},{0x4358bffe,0x43539996},}},
97{{{0x43480000,0x43960000},{0x436f0222,0x4328051c},{0x435c2222,0x43810f5c},{0x435ae000,0x4351e664},}},
98};
99
100size_t datCount = SK_ARRAY_COUNT(dat);
101
102class CuspView : public Sample {
103public:
104    CuspView() {}
105protected:
106    SkString name() override { return SkString("Cusp"); }
107
108    void onDrawContent(SkCanvas* canvas) override {
109        SkPaint p;
110        p.setAntiAlias(true);
111        p.setStyle(SkPaint::kStroke_Style);
112        p.setStrokeWidth(20);
113    #if 0   // enable to play through the stream above backwards.
114        SkPath path;
115        int i;
116    #if 0  // disable to draw only one problematic cubic
117        i = --datCount;
118    #else
119        i = 14; // index into dat of  problematic cubic
120    #endif
121        path.moveTo( SkBits2Float(dat[i].pt[0].fX), SkBits2Float(dat[i].pt[0].fY));
122        path.cubicTo(SkBits2Float(dat[i].pt[1].fX), SkBits2Float(dat[i].pt[1].fY),
123                     SkBits2Float(dat[i].pt[2].fX), SkBits2Float(dat[i].pt[2].fY),
124                     SkBits2Float(dat[i].pt[3].fX), SkBits2Float(dat[i].pt[3].fY));
125    #else
126        SkPath path;
127        SkRect rect;
128        rect.setWH(100, 100);
129        SkMatrix matrix;
130        SkScalar vals[9];
131        vals[0] = linearToLoop(3000, 0, 1);
132        vals[1] = linearToLoop(4000, .25, 1.25);
133        vals[2] = 200;
134        vals[3] = linearToLoop(5000, .5, 1.5);
135        vals[4] = linearToLoop(7000, .75, 1.75);
136        vals[5] = 300;
137        vals[6] = 0;
138        vals[7] = 0;
139        vals[8] = 1;
140        matrix.set9(vals);
141        SkPoint pts[4], pp[7];
142        matrix.mapRectToQuad(pts, rect);
143        std::swap(pts[1], pts[2]);
144        bool split;
145        path = cusp(pts, pp, split, 8000, .125);
146        auto debugOutCubic = [](const SkPoint* pts) {
147            return false; // comment out to capture stream of cusp'd cubics in stdout
148            SkDebugf("{{");
149            for (int i = 0; i < 4; ++i) {
150                SkDebugf("{0x%08x,0x%08x},", SkFloat2Bits(pts[i].fX), SkFloat2Bits(pts[i].fY));
151            }
152            SkDebugf("}},\n");
153        };
154        if (split) {
155            debugOutCubic(&pp[0]);
156            debugOutCubic(&pp[4]);
157        } else {
158            debugOutCubic(&pts[0]);
159        }
160    #endif
161        canvas->drawPath(path, p);
162        // draw time to make it easier to guess when the bad cubic was drawn
163        std::string timeStr = std::to_string((float) (curTime - start) / 1000.f);
164        canvas->drawSimpleText(timeStr.c_str(), timeStr.size(), SkTextEncoding::kUTF8, 20, 20, SkFont(), SkPaint());
165    }
166
167    bool onAnimate(double nanos) override {
168        curTime = TimeUtils::NanosToMSec(nanos);
169        if (!start) {
170            start = curTime;
171        }
172        return true;
173    }
174
175private:
176
177    using INHERITED = Sample;
178};
179
180DEF_SAMPLE( return new CuspView(); )
181