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50
51#include "circlewidget.h"
52
53#include <QPainter>
54
55#include <stdlib.h>
56
57//! [0]
58CircleWidget::CircleWidget(QWidget *parent)
59 : QWidget(parent)
60{
61 floatBased = false;
62 antialiased = false;
63 frameNo = 0;
64
65 setBackgroundRole(QPalette::Base);
66 setSizePolicy(hor: QSizePolicy::Expanding, ver: QSizePolicy::Expanding);
67}
68//! [0]
69
70//! [1]
71void CircleWidget::setFloatBased(bool floatBased)
72{
73 this->floatBased = floatBased;
74 update();
75}
76//! [1]
77
78//! [2]
79void CircleWidget::setAntialiased(bool antialiased)
80{
81 this->antialiased = antialiased;
82 update();
83}
84//! [2]
85
86//! [3]
87QSize CircleWidget::minimumSizeHint() const
88{
89 return QSize(50, 50);
90}
91//! [3]
92
93//! [4]
94QSize CircleWidget::sizeHint() const
95{
96 return QSize(180, 180);
97}
98//! [4]
99
100//! [5]
101void CircleWidget::nextAnimationFrame()
102{
103 ++frameNo;
104 update();
105}
106//! [5]
107
108//! [6]
109void CircleWidget::paintEvent(QPaintEvent *)
110{
111 QPainter painter(this);
112 painter.setRenderHint(hint: QPainter::Antialiasing, on: antialiased);
113 painter.translate(dx: width() / 2, dy: height() / 2);
114//! [6]
115
116//! [7]
117 for (int diameter = 0; diameter < 256; diameter += 9) {
118 int delta = abs(x: (frameNo % 128) - diameter / 2);
119 int alpha = 255 - (delta * delta) / 4 - diameter;
120//! [7] //! [8]
121 if (alpha > 0) {
122 painter.setPen(QPen(QColor(0, diameter / 2, 127, alpha), 3));
123
124 if (floatBased)
125 painter.drawEllipse(r: QRectF(-diameter / 2.0, -diameter / 2.0, diameter, diameter));
126 else
127 painter.drawEllipse(r: QRect(-diameter / 2, -diameter / 2, diameter, diameter));
128 }
129 }
130}
131//! [8]
132

source code of qtbase/examples/widgets/painting/concentriccircles/circlewidget.cpp