- Qt 5.5
- Qt D-Bus
- D-Bus Remote Controlled Car Example
- car.cpp Example File
- Qt 5.5.1 Reference Documentation

# car.cpp Example File

remotecontrolledcar/car/car.cpp

    /****************************************************************************
    **
    ** Copyright (C) 2015 The Qt Company Ltd.
    ** Contact: http://www.qt.io/licensing/
    **
    ** This file is part of the examples of the Qt Toolkit.
    **
    ** $QT_BEGIN_LICENSE:BSD$
    ** You may use this file under the terms of the BSD license as follows:
    **
    ** "Redistribution and use in source and binary forms, with or without
    ** modification, are permitted provided that the following conditions are
    ** met:
    **   * Redistributions of source code must retain the above copyright
    **     notice, this list of conditions and the following disclaimer.
    **   * Redistributions in binary form must reproduce the above copyright
    **     notice, this list of conditions and the following disclaimer in
    **     the documentation and/or other materials provided with the
    **     distribution.
    **   * Neither the name of The Qt Company Ltd nor the names of its
    **     contributors may be used to endorse or promote products derived
    **     from this software without specific prior written permission.
    **
    **
    ** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
    ** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
    ** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
    ** A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
    ** OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
    ** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
    ** LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
    ** DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
    ** THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
    ** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
    ** OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE."
    **
    ** $QT_END_LICENSE$
    **
    ****************************************************************************/

    #include "car.h"
    #include <QtWidgets/QtWidgets>
    #include <math.h>

    static const double Pi = 3.14159265358979323846264338327950288419717;

    QRectF Car::boundingRect() const
    {
        return QRectF(-35, -81, 70, 115);
    }

    Car::Car() : color(Qt::green), wheelsAngle(0), speed(0)
    {
        startTimer(1000 / 33);
        setFlag(QGraphicsItem::ItemIsMovable, true);
        setFlag(QGraphicsItem::ItemIsFocusable, true);
    }

    void Car::accelerate()
    {
        if (speed < 10)
            ++speed;
    }

    void Car::decelerate()
    {
        if (speed > -10)
            --speed;
    }

    void Car::turnLeft()
    {
        if (wheelsAngle > -30)
            wheelsAngle -= 5;
    }

    void Car::turnRight()
    {
        if (wheelsAngle < 30)
           wheelsAngle += 5;
    }

    void Car::paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget)
    {
        Q_UNUSED(option);
        Q_UNUSED(widget);

        painter->setBrush(Qt::gray);
        painter->drawRect(-20, -58, 40, 2); // front axel
        painter->drawRect(-20, 7, 40, 2); // rear axel

        painter->setBrush(color);
        painter->drawRect(-25, -79, 50, 10); // front wing

        painter->drawEllipse(-25, -48, 50, 20); // side pods
        painter->drawRect(-25, -38, 50, 35); // side pods
        painter->drawRect(-5, 9, 10, 10); // back pod

        painter->drawEllipse(-10, -81, 20, 100); // main body

        painter->drawRect(-17, 19, 34, 15); // rear wing

        painter->setBrush(Qt::black);
        painter->drawPie(-5, -51, 10, 15, 0, 180 * 16);
        painter->drawRect(-5, -44, 10, 10); // cocpit

        painter->save();
        painter->translate(-20, -58);
        painter->rotate(wheelsAngle);
        painter->drawRect(-10, -7, 10, 15); // front left
        painter->restore();

        painter->save();
        painter->translate(20, -58);
        painter->rotate(wheelsAngle);
        painter->drawRect(0, -7, 10, 15); // front left
        painter->restore();

        painter->drawRect(-30, 0, 12, 17); // rear left
        painter->drawRect(19, 0, 12, 17);  // rear right
    }

    void Car::timerEvent(QTimerEvent *event)
    {
        Q_UNUSED(event);

        const qreal axelDistance = 54;
        qreal wheelsAngleRads = (wheelsAngle * Pi) / 180;
        qreal turnDistance = ::cos(wheelsAngleRads) * axelDistance * 2;
        qreal turnRateRads = wheelsAngleRads / turnDistance;  // rough estimate
        qreal turnRate = (turnRateRads * 180) / Pi;
        qreal rotation = speed * turnRate;

        setTransform(QTransform().rotate(rotation), true);
        setTransform(QTransform::fromTranslate(0, -speed), true);
        update();
    }