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 
28 SkMSec start = 0;
29 SkMSec curTime;
30 bool first = true;
31 
32 // Create a path with one or two cubics, where one has a cusp.
cusp(const SkPoint P[4],SkPoint PP[7],bool & split,int speed,SkScalar phase)33 static 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.
linearToLoop(int speed,SkScalar phase,SkScalar scale)54 static 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 
71 struct 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 
100 size_t datCount = SK_ARRAY_COUNT(dat);
101 
102 class CuspView : public Sample {
103 public:
CuspView()104     CuspView() {}
105 protected:
name()106     SkString name() override { return SkString("Cusp"); }
107 
onDrawContent(SkCanvas * canvas)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         SkDebugf("");
166     }
167 
onAnimate(double nanos)168     bool onAnimate(double nanos) override {
169         curTime = TimeUtils::NanosToMSec(nanos);
170         if (!start) {
171             start = curTime;
172         }
173         return true;
174     }
175 
176 private:
177 
178     typedef Sample INHERITED;
179 };
180 
181 DEF_SAMPLE( return new CuspView(); )
182