SampleDegenerateTwoPtRadials.cpp revision fe17456d5e528078ce69b5f15cf7adf1fab963f9 
1/*
2 * Copyright 2011 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 "SampleCode.h"
9#include "SkAnimTimer.h"
10#include "SkView.h"
11#include "SkCanvas.h"
12#include "SkGradientShader.h"
13#include "SkString.h"
14
15static void draw_gradient2(SkCanvas* canvas, const SkRect& rect, SkScalar delta) {
16    SkColor colors[] = { SK_ColorRED, SK_ColorGREEN, SK_ColorBLUE, SK_ColorMAGENTA };
17    SkScalar pos[] = { 0, 0.25f, 0.75f, SK_Scalar1 };
18
19    SkScalar l = rect.fLeft;
20    SkScalar t = rect.fTop;
21    SkScalar w = rect.width();
22    SkScalar h = rect.height();
23
24    SkASSERT(0 == SkScalarMod(w, SK_Scalar1 * 5));
25
26    SkPoint c0 = { l + 2 * w / 5 + delta, t + h / 2 };
27    SkPoint c1 = { l + 3 * w / 5, t + h / 2 };
28    SkScalar r0 = w / 5;
29    SkScalar r1 = 2 * w / 5;
30    SkPaint paint;
31    paint.setShader(SkGradientShader::MakeTwoPointConical(c0, r0, c1, r1, colors,
32                                                          pos, SK_ARRAY_COUNT(pos),
33                                                          SkShader::kClamp_TileMode));
34    canvas->drawRect(rect, paint);
35}
36
37
38class DegenerateTwoPtRadialsView : public SampleView {
39public:
40    DegenerateTwoPtRadialsView() {
41        fTime = 0;
42        this->setBGColor(0xFFDDDDDD);
43    }
44
45protected:
46    bool onQuery(SkEvent* evt) override {
47        if (SampleCode::TitleQ(*evt)) {
48            SampleCode::TitleR(evt, "DegenerateTwoPtRadials");
49            return true;
50        }
51        return this->INHERITED::onQuery(evt);
52    }
53
54    void onDrawContent(SkCanvas* canvas) override {
55        SkScalar delta = fTime / 15.f;
56        int intPart = SkScalarFloorToInt(delta);
57        delta = delta - SK_Scalar1 * intPart;
58        if (intPart % 2) {
59            delta = SK_Scalar1 - delta;
60        }
61        delta -= SK_ScalarHalf;
62        static const int DELTA_SCALE = 500;
63        delta /= DELTA_SCALE;
64
65        SkScalar w = SK_Scalar1 * 500;
66        SkScalar h = SK_Scalar1 * 500;
67        SkScalar l = SK_Scalar1 * 100;
68        SkScalar t = SK_Scalar1 * 100;
69        draw_gradient2(canvas, SkRect::MakeXYWH(l, t, w, h), delta);
70        SkString txt;
71        txt.appendf("gap at \"tangent\" pt = %f", SkScalarToFloat(delta));
72        SkPaint paint;
73        paint.setAntiAlias(true);
74        paint.setColor(SK_ColorBLACK);
75        canvas->drawString(txt, l + w/2 + w*DELTA_SCALE*delta, t + h + SK_Scalar1 * 10, paint);
76    }
77
78    bool onAnimate(const SkAnimTimer& timer) override {
79        fTime = SkDoubleToScalar(timer.secs() / 15);
80        return true;
81    }
82
83private:
84    SkScalar           fTime;
85    typedef SampleView INHERITED;
86};
87
88//////////////////////////////////////////////////////////////////////////////
89
90static SkView* MyFactory() { return new DegenerateTwoPtRadialsView; }
91static SkViewRegister reg(MyFactory);
92