Отражение шара от стенок коробки - C++ - Ответ 1175130

#ifndef MYWIDGET_H
#define MYWIDGET_H
 
#include <QtGui>
 
class MyWidget : public QWidget {
    Q_OBJECT
    int dx;
    int dy;
    QRect circleBounds;
public:
    MyWidget(QWidget * parent) : QWidget(parent) {
        dx = 10;
        dy = 10;
        circleBounds.setLeft(34);
        circleBounds.setTop(21);
        circleBounds.setWidth(50);
        circleBounds.setHeight(50);
 
        QTimer * timer = new QTimer();
        connect(timer, SIGNAL(timeout()), this, SLOT(repaint()));
        timer->start(100);
    }
 
    void paintEvent(QPaintEvent *){
        QPainter painter(this);
        painter.setPen(Qt::NoPen);
        painter.setBrush(Qt::white);
        painter.drawRect(this->rect());
 
        if ( ( circleBounds.left() + dx ) < 0 || ( circleBounds.right() + dx ) > this->rect().width() )
            dx = -dx;
        if ( ( circleBounds.top() + dy ) < 0 || ( circleBounds.bottom() + dy ) > this->rect().height() )
            dy = -dy;
        circleBounds.setLeft(circleBounds.left() + dx);
        circleBounds.setTop(circleBounds.top() + dy);
        circleBounds.setWidth(50);
        circleBounds.setHeight(50);
        painter.setBrush(Qt::red);
        painter.drawEllipse(circleBounds);
    }
 
};
 
#endif // MYWIDGET_H

#include <QtGui>
#include "MyWidget.h"
 
 
int main(int argc, char ** argv){
    QApplication app(argc, argv);
    MyWidget mw(0);
 
    mw.resize(500, 500);
    mw.show();
 
    return app.exec();
}