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cannonfield.cpp

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

//! [0]
#include <math.h>
//! [0]

#include "cannonfield.h"

//! [1]
CannonField::CannonField(QWidget *parent)
    : QWidget(parent)
{
    currentAngle = 45;
    currentForce = 0;
    timerCount = 0;
    autoShootTimer = new QTimer(this);
    connect(autoShootTimer, SIGNAL(timeout()), this, SLOT(moveShot()));
    shootAngle = 0;
    shootForce = 0;
    setPalette(QPalette(QColor(250, 250, 200)));
    setAutoFillBackground(true);
}
//! [1]

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);
}

//! [2]
00094 void CannonField::shoot()
{
    if (autoShootTimer->isActive())
        return;
    timerCount = 0;
    shootAngle = currentAngle;
    shootForce = currentForce;
    autoShootTimer->start(5);
//! [2] //! [3]
}
//! [3]

//! [4]
00107 void CannonField::moveShot()
{
    QRegion region = shotRect();
    ++timerCount;

    QRect shotR = shotRect();

    if (shotR.x() > width() || shotR.y() > height()) {
        autoShootTimer->stop();
    } else {
        region = region.unite(shotR);
    }
    update(region);
//! [4] //! [5]
}
//! [5]

//! [6]
void CannonField::paintEvent(QPaintEvent * /* event */)
{
    QPainter painter(this);

    paintCannon(painter);
    if (autoShootTimer->isActive())
        paintShot(painter);
}
//! [6]

//! [7]
00136 void CannonField::paintShot(QPainter &painter)
{
    painter.setPen(Qt::NoPen);
    painter.setBrush(Qt::black);
    painter.drawRect(shotRect());
//! [7] //! [8]
}
//! [8]

const QRect barrelRect(30, -5, 20, 10);

00147 void CannonField::paintCannon(QPainter &painter)
{
    painter.setPen(Qt::NoPen);
    painter.setBrush(Qt::blue);

    painter.save();
    painter.translate(0, height());
    painter.drawPie(QRect(-35, -35, 70, 70), 0, 90 * 16);
    painter.rotate(-currentAngle);
    painter.drawRect(barrelRect);
    painter.restore();
}

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

//! [9]
00168 QRect CannonField::shotRect() const
{
    const double gravity = 4;

    double time = timerCount / 20.0;
    double velocity = shootForce;
    double radians = shootAngle * 3.14159265 / 180;

    double velx = velocity * cos(radians);
    double vely = velocity * sin(radians);
    double x0 = (barrelRect.right() + 5) * cos(radians);
    double y0 = (barrelRect.right() + 5) * sin(radians);
    double x = x0 + velx * time;
    double y = y0 + vely * time - 0.5 * gravity * time * time;

    QRect result(0, 0, 6, 6);
    result.moveCenter(QPoint(qRound(x), height() - 1 - qRound(y)));
    return result;
//! [9] //! [10]
}
//! [10]

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