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# car.cpp Example File

dbus/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:
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     ** "Redistribution and use in source and binary forms, with or without
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     **   * Redistributions of source code must retain the above copyright
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     **     contributors may be used to endorse or promote products derived
     **     from this software without specific prior written permission.
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     #include "car.h"
     #include <QtGui/QtGui>
     #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;

         rotate(rotation);
         translate(0, -speed);
         update();
     }