1 /*
2  * Copyright 2013 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 "gm.h"
9 #include "sk_tool_utils.h"
10 #include "SkAnimTimer.h"
11 #include "SkCanvas.h"
12 #include "SkPath.h"
13 
14 // Reproduces https://code.google.com/p/chromium/issues/detail?id=279014
15 
16 constexpr int kWidth = 440;
17 constexpr int kHeight = 440;
18 constexpr SkScalar kAngle = 0.305f;
19 constexpr int kMaxNumSteps = 140;
20 
21 // Renders a string art shape.
22 // The particular shape rendered can be controlled by adjusting kAngle, from 0 to 1
23 
24 class StringArtGM : public skiagm::GM {
25 public:
26     StringArtGM() : fNumSteps(kMaxNumSteps) {}
27 
28 protected:
29 
30     SkString onShortName() override {
31         return SkString("stringart");
32     }
33 
34     SkISize onISize() override {
35         return SkISize::Make(kWidth, kHeight);
36     }
37 
38     void onDraw(SkCanvas* canvas) override {
39         SkScalar angle = kAngle*SK_ScalarPI + SkScalarHalf(SK_ScalarPI);
40         SkScalar size = SkIntToScalar(SkMin32(kWidth, kHeight));
41         SkPoint center = SkPoint::Make(SkScalarHalf(kWidth), SkScalarHalf(kHeight));
42         SkScalar length = 5;
43         SkScalar step = angle;
44 
45         SkPath path;
46         path.moveTo(center);
47 
48         for (int i = 0; i < fNumSteps && length < (SkScalarHalf(size) - 10.f); ++i) {
49             SkPoint rp = SkPoint::Make(length*SkScalarCos(step) + center.fX,
50                                        length*SkScalarSin(step) + center.fY);
51             path.lineTo(rp);
52             length += angle / SkScalarHalf(SK_ScalarPI);
53             step += angle;
54         }
55 
56         SkPaint paint;
57         paint.setAntiAlias(true);
58         paint.setStyle(SkPaint::kStroke_Style);
59         paint.setColor(sk_tool_utils::color_to_565(0xFF007700));
60 
61         canvas->drawPath(path, paint);
62     }
63 
64     bool onAnimate(const SkAnimTimer& timer) override {
65         constexpr SkScalar kDesiredDurationSecs = 3.0f;
66 
67         // Make the animation ping-pong back and forth but start in the fully drawn state
68         SkScalar fraction = 1.0f - timer.scaled(2.0f/kDesiredDurationSecs, 2.0f);
69         if (fraction <= 0.0f) {
70             fraction = -fraction;
71         }
72 
73         SkASSERT(fraction >= 0.0f && fraction <= 1.0f);
74 
75         fNumSteps = (int) (fraction * kMaxNumSteps);
76         return true;
77     }
78 
79 private:
80     int fNumSteps;
81 
82     typedef GM INHERITED;
83 };
84 
85 DEF_GM( return new StringArtGM; )
86