circulararcs.cpp revision 4c54788e9298dce2b963ce288baf0d1695323e1f 
1/*
2 * Copyright 2016 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 <functional>
9#include "SkCanvas.h"
10#include "gm.h"
11
12static constexpr SkScalar kStarts[] = {0.f, 10.f, 30.f, 45.f, 90.f, 165.f, 180.f, 270.f};
13static constexpr SkScalar kSweeps[] = {45.f, 90.f, 165.f, 180.f, 220.f, 270.f, 300.f, 315.f};
14static constexpr SkScalar kDiameter = 40.f;
15static constexpr SkRect kRect = {0.f, 0.f, kDiameter, kDiameter};
16static constexpr int kW = 1000;
17static constexpr int kH = 1000;
18static constexpr SkScalar kPad = 20.f;
19
20void draw_arcs(SkCanvas* canvas, std::function<void(SkPaint*)> configureStyle) {
21    // Draws grid of arcs with different start/sweep angles in red and their complement arcs in
22    // blue.
23    auto drawGrid = [canvas, &configureStyle] (SkScalar x, SkScalar y, bool useCenter, bool aa) {
24        SkPaint p0;
25        p0.setColor(SK_ColorRED);
26        p0.setAntiAlias(aa);
27        // Set a reasonable stroke width that configureStyle can override.
28        p0.setStrokeWidth(15.f);
29        SkPaint p1 = p0;
30        p1.setColor(SK_ColorBLUE);
31        // Use alpha so we see magenta on overlap between arc and its complement.
32        p0.setAlpha(100);
33        p1.setAlpha(100);
34        configureStyle(&p0);
35        configureStyle(&p1);
36
37        canvas->save();
38        canvas->translate(kPad + x, kPad + y);
39        for (auto start : kStarts) {
40            canvas->save();
41            for (auto sweep : kSweeps) {
42                canvas->drawArc(kRect, start, sweep, useCenter, p0);
43                canvas->drawArc(kRect, start, -(360.f - sweep), useCenter, p1);
44                canvas->translate(kRect.width() + kPad, 0.f);
45            }
46            canvas->restore();
47            canvas->translate(0, kRect.height() + kPad);
48        }
49        canvas->restore();
50    };
51    // Draw a grids for combo of enabling/disabling aa and using center.
52    static constexpr SkScalar kGridW = kW / 2.f;
53    static constexpr SkScalar kGridH = kH / 2.f;
54    drawGrid(0.f   , 0.f   , false, false);
55    drawGrid(kGridW, 0.f   , true , false);
56    drawGrid(0.f   , kGridH, false, true );
57    drawGrid(kGridW, kGridH, true , true );
58    // Draw separators between the grids.
59    SkPaint linePaint;
60    linePaint.setAntiAlias(true);
61    linePaint.setColor(SK_ColorBLACK);
62    canvas->drawLine(kGridW, 0.f   , kGridW,            SkIntToScalar(kH), linePaint);
63    canvas->drawLine(0.f   , kGridH, SkIntToScalar(kW), kGridH,            linePaint);
64}
65
66#define DEF_ARC_GM(name) DEF_SIMPLE_GM(circular_arcs_##name, canvas, kW, kH)
67
68DEF_ARC_GM(fill) {
69    auto setFill = [] (SkPaint*p) { p->setStyle(SkPaint::kFill_Style); };
70    draw_arcs(canvas, setFill);
71}
72
73DEF_ARC_GM(hairline) {
74    auto setHairline = [] (SkPaint* p) {
75        p->setStyle(SkPaint::kStroke_Style);
76        p->setStrokeWidth(0.f);
77    };
78    draw_arcs(canvas, setHairline);
79}
80
81DEF_ARC_GM(stroke_butt) {
82    auto setStroke = [](SkPaint* p) {
83        p->setStyle(SkPaint::kStroke_Style);
84        p->setStrokeCap(SkPaint::kButt_Cap);
85    };
86    draw_arcs(canvas, setStroke);
87}
88
89DEF_ARC_GM(stroke_square) {
90    auto setStroke = [] (SkPaint* p) {
91        p->setStyle(SkPaint::kStroke_Style);
92        p->setStrokeCap(SkPaint::kSquare_Cap);
93    };
94    draw_arcs(canvas, setStroke);
95}
96
97DEF_ARC_GM(stroke_round) {
98    auto setStroke = [] (SkPaint* p) {
99        p->setStyle(SkPaint::kStroke_Style);
100        p->setStrokeCap(SkPaint::kRound_Cap);
101    };
102    draw_arcs(canvas, setStroke);
103}
104