cannonfield.cpp Example File
^{tutorial/t10/cannonfield.cpp}

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    **
    ** This file is part of the documentation of the Qt Toolkit.
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    #include <QPaintEvent>
    #include <QPainter>

    #include "cannonfield.h"

    CannonField::CannonField(QWidget *parent)
        : QWidget(parent)
    {
        currentAngle = 45;
        currentForce = 0;
        setPalette(QPalette(QColor(250, 250, 200)));
        setAutoFillBackground(true);
    }

    void CannonField::setAngle(int angle)
    {
        if (angle < 5)
            angle = 5;
        if (angle > 70)
            angle = 70;
        if (currentAngle == angle)
            return;
        currentAngle = angle;
        update(cannonRect());
        emit angleChanged(currentAngle);
    }

    void CannonField::setForce(int force)
    {
        if (force < 0)
            force = 0;
        if (currentForce == force)
            return;
        currentForce = force;
        emit forceChanged(currentForce);
    }

    void CannonField::paintEvent(QPaintEvent * /* event */)
    {
        QPainter painter(this);

        painter.setPen(Qt::NoPen);
        painter.setBrush(Qt::blue);

        painter.translate(0, height());
        painter.drawPie(QRect(-35, -35, 70, 70), 0, 90 * 16);
        painter.rotate(-currentAngle);
        painter.drawRect(QRect(30, -5, 20, 10));
    }

    QRect CannonField::cannonRect() const
    {
        QRect result(0, 0, 50, 50);
        result.moveBottomLeft(rect().bottomLeft());
        return result;
    }