- Qt 5.5
- Qt Widgets
- Colliding Mice Example
- mouse.cpp Example File
- Qt 5.5.1 Reference Documentation

# mouse.cpp Example File

graphicsview/collidingmice/mouse.cpp

    /****************************************************************************
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    ** This file is part of the examples of the Qt Toolkit.
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    #include "mouse.h"

    #include <QGraphicsScene>
    #include <QPainter>
    #include <QStyleOption>

    #include <math.h>

    static const double Pi = 3.14159265358979323846264338327950288419717;
    static double TwoPi = 2.0 * Pi;

    static qreal normalizeAngle(qreal angle)
    {
        while (angle < 0)
            angle += TwoPi;
        while (angle > TwoPi)
            angle -= TwoPi;
        return angle;
    }

    Mouse::Mouse()
        : angle(0), speed(0), mouseEyeDirection(0),
          color(qrand() % 256, qrand() % 256, qrand() % 256)
    {
        setRotation(qrand() % (360 * 16));
    }

    QRectF Mouse::boundingRect() const
    {
        qreal adjust = 0.5;
        return QRectF(-18 - adjust, -22 - adjust,
                      36 + adjust, 60 + adjust);
    }

    QPainterPath Mouse::shape() const
    {
        QPainterPath path;
        path.addRect(-10, -20, 20, 40);
        return path;
    }

    void Mouse::paint(QPainter *painter, const QStyleOptionGraphicsItem *, QWidget *)
    {
        // Body
        painter->setBrush(color);
        painter->drawEllipse(-10, -20, 20, 40);

        // Eyes
        painter->setBrush(Qt::white);
        painter->drawEllipse(-10, -17, 8, 8);
        painter->drawEllipse(2, -17, 8, 8);

        // Nose
        painter->setBrush(Qt::black);
        painter->drawEllipse(QRectF(-2, -22, 4, 4));

        // Pupils
        painter->drawEllipse(QRectF(-8.0 + mouseEyeDirection, -17, 4, 4));
        painter->drawEllipse(QRectF(4.0 + mouseEyeDirection, -17, 4, 4));

        // Ears
        painter->setBrush(scene()->collidingItems(this).isEmpty() ? Qt::darkYellow : Qt::red);
        painter->drawEllipse(-17, -12, 16, 16);
        painter->drawEllipse(1, -12, 16, 16);

        // Tail
        QPainterPath path(QPointF(0, 20));
        path.cubicTo(-5, 22, -5, 22, 0, 25);
        path.cubicTo(5, 27, 5, 32, 0, 30);
        path.cubicTo(-5, 32, -5, 42, 0, 35);
        painter->setBrush(Qt::NoBrush);
        painter->drawPath(path);
    }

    void Mouse::advance(int step)
    {
        if (!step)
            return;
        // Don't move too far away
        QLineF lineToCenter(QPointF(0, 0), mapFromScene(0, 0));
        if (lineToCenter.length() > 150) {
            qreal angleToCenter = ::acos(lineToCenter.dx() / lineToCenter.length());
            if (lineToCenter.dy() < 0)
                angleToCenter = TwoPi - angleToCenter;
            angleToCenter = normalizeAngle((Pi - angleToCenter) + Pi / 2);

            if (angleToCenter < Pi && angleToCenter > Pi / 4) {
                // Rotate left
                angle += (angle < -Pi / 2) ? 0.25 : -0.25;
            } else if (angleToCenter >= Pi && angleToCenter < (Pi + Pi / 2 + Pi / 4)) {
                // Rotate right
                angle += (angle < Pi / 2) ? 0.25 : -0.25;
            }
        } else if (::sin(angle) < 0) {
            angle += 0.25;
        } else if (::sin(angle) > 0) {
            angle -= 0.25;
        }

        // Try not to crash with any other mice
        QList<QGraphicsItem *> dangerMice = scene()->items(QPolygonF()
                                                           << mapToScene(0, 0)
                                                           << mapToScene(-30, -50)
                                                           << mapToScene(30, -50));
        foreach (QGraphicsItem *item, dangerMice) {
            if (item == this)
                continue;

            QLineF lineToMouse(QPointF(0, 0), mapFromItem(item, 0, 0));
            qreal angleToMouse = ::acos(lineToMouse.dx() / lineToMouse.length());
            if (lineToMouse.dy() < 0)
                angleToMouse = TwoPi - angleToMouse;
            angleToMouse = normalizeAngle((Pi - angleToMouse) + Pi / 2);

            if (angleToMouse >= 0 && angleToMouse < Pi / 2) {
                // Rotate right
                angle += 0.5;
            } else if (angleToMouse <= TwoPi && angleToMouse > (TwoPi - Pi / 2)) {
                // Rotate left
                angle -= 0.5;
            }
        }

        // Add some random movement
        if (dangerMice.size() > 1 && (qrand() % 10) == 0) {
            if (qrand() % 1)
                angle += (qrand() % 100) / 500.0;
            else
                angle -= (qrand() % 100) / 500.0;
        }

        speed += (-50 + qrand() % 100) / 100.0;

        qreal dx = ::sin(angle) * 10;
        mouseEyeDirection = (qAbs(dx / 5) < 1) ? 0 : dx / 5;

        setRotation(rotation() + dx);
        setPos(mapToParent(0, -(3 + sin(speed) * 3)));
    }