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bubble.cpp Example File
^{opengl/overpainting/bubble.cpp}

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    **
    ** This file is part of the documentation of the Qt Toolkit.
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    ** and appearing in the file LICENSE.GPL included in the packaging of
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    #include <QtGui>

    #include "bubble.h"

    Bubble::Bubble(const QPointF &position, qreal radius, const QPointF &velocity)
        : position(position), vel(velocity), radius(radius)
    {
        innerColor = randomColor();
        outerColor = randomColor();
        updateBrush();
    }

    void Bubble::updateBrush()
    {
        QRadialGradient gradient(QPointF(radius, radius), radius,
                                 QPointF(radius*0.5, radius*0.5));

        gradient.setColorAt(0, QColor(255, 255, 255, 255));
        gradient.setColorAt(0.25, innerColor);
        gradient.setColorAt(1, outerColor);
        brush = QBrush(gradient);
    }

    void Bubble::drawBubble(QPainter *painter)
    {
        painter->save();
        painter->translate(position.x() - radius, position.y() - radius);
        painter->setBrush(brush);
        painter->drawEllipse(0, 0, int(2*radius), int(2*radius));
        painter->restore();
    }

    QColor Bubble::randomColor()
    {
        int red = int(205 + 50.0*rand()/(RAND_MAX+1.0));
        int green = int(205 + 50.0*rand()/(RAND_MAX+1.0));
        int blue = int(205 + 50.0*rand()/(RAND_MAX+1.0));
        int alpha = int(91 + 100.0*rand()/(RAND_MAX+1.0));

        return QColor(red, green, blue, alpha);
    }

    void Bubble::move(const QRect &bbox)
    {
        position += vel;
        qreal leftOverflow = position.x() - radius - bbox.left();
        qreal rightOverflow = position.x() + radius - bbox.right();
        qreal topOverflow = position.y() - radius - bbox.top();
        qreal bottomOverflow = position.y() + radius - bbox.bottom();

        if (leftOverflow < 0.0) {
            position.setX(position.x() - 2 * leftOverflow);
            vel.setX(-vel.x());
        } else if (rightOverflow > 0.0) {
            position.setX(position.x() - 2 * rightOverflow);
            vel.setX(-vel.x());
        }

        if (topOverflow < 0.0) {
            position.setY(position.y() - 2 * topOverflow);
            vel.setY(-vel.y());
        } else if (bottomOverflow > 0.0) {
            position.setY(position.y() - 2 * bottomOverflow);
            vel.setY(-vel.y());
        }
    }

    QRectF Bubble::rect()
    {
        return QRectF(position.x() - radius, position.y() - radius,
                      2 * radius, 2 * radius);
    }