Qt 5.11 | Qt D-Bus | D-Bus Remote Controlled Car Example | car.cpp Example File

Qt 5.11.3 Reference Documentation

# car.cpp Example File

remotecontrolledcar/car/car.cpp

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

      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 = qDegreesToRadians(wheelsAngle);
          qreal turnDistance = ::cos(wheelsAngleRads) * axelDistance * 2;
          qreal turnRateRads = wheelsAngleRads / turnDistance;  // rough estimate
          qreal turnRate = qRadiansToDegrees(turnRateRads);
          qreal rotation = speed * turnRate;

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