mouse.cpp Example File

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  #include "mouse.h"

  #include <QGraphicsScene>
  #include <QPainter>
  #include <QStyleOption>

  #include <math.h>

  static const double Pi = 3.14159265358979323846264338327950288419717;
  static double TwoPi = 2.0 * Pi;

  static qreal normalizeAngle(qreal angle)
  {
      while (angle < 0)
          angle += TwoPi;
      while (angle > TwoPi)
          angle -= TwoPi;
      return angle;
  }

  Mouse::Mouse()
      : angle(0), speed(0), mouseEyeDirection(0),
        color(qrand() % 256, qrand() % 256, qrand() % 256)
  {
      setRotation(qrand() % (360 * 16));
  }

  QRectF Mouse::boundingRect() const
  {
      qreal adjust = 0.5;
      return QRectF(-18 - adjust, -22 - adjust,
                    36 + adjust, 60 + adjust);
  }

  QPainterPath Mouse::shape() const
  {
      QPainterPath path;
      path.addRect(-10, -20, 20, 40);
      return path;
  }

  void Mouse::paint(QPainter *painter, const QStyleOptionGraphicsItem *, QWidget *)
  {
      // Body
      painter->setBrush(color);
      painter->drawEllipse(-10, -20, 20, 40);

      // Eyes
      painter->setBrush(Qt::white);
      painter->drawEllipse(-10, -17, 8, 8);
      painter->drawEllipse(2, -17, 8, 8);

      // Nose
      painter->setBrush(Qt::black);
      painter->drawEllipse(QRectF(-2, -22, 4, 4));

      // Pupils
      painter->drawEllipse(QRectF(-8.0 + mouseEyeDirection, -17, 4, 4));
      painter->drawEllipse(QRectF(4.0 + mouseEyeDirection, -17, 4, 4));

      // Ears
      painter->setBrush(scene()->collidingItems(this).isEmpty() ? Qt::darkYellow : Qt::red);
      painter->drawEllipse(-17, -12, 16, 16);
      painter->drawEllipse(1, -12, 16, 16);

      // Tail
      QPainterPath path(QPointF(0, 20));
      path.cubicTo(-5, 22, -5, 22, 0, 25);
      path.cubicTo(5, 27, 5, 32, 0, 30);
      path.cubicTo(-5, 32, -5, 42, 0, 35);
      painter->setBrush(Qt::NoBrush);
      painter->drawPath(path);
  }

  void Mouse::advance(int step)
  {
      if (!step)
          return;
      // Don't move too far away
      QLineF lineToCenter(QPointF(0, 0), mapFromScene(0, 0));
      if (lineToCenter.length() > 150) {
          qreal angleToCenter = ::acos(lineToCenter.dx() / lineToCenter.length());
          if (lineToCenter.dy() < 0)
              angleToCenter = TwoPi - angleToCenter;
          angleToCenter = normalizeAngle((Pi - angleToCenter) + Pi / 2);

          if (angleToCenter < Pi && angleToCenter > Pi / 4) {
              // Rotate left
              angle += (angle < -Pi / 2) ? 0.25 : -0.25;
          } else if (angleToCenter >= Pi && angleToCenter < (Pi + Pi / 2 + Pi / 4)) {
              // Rotate right
              angle += (angle < Pi / 2) ? 0.25 : -0.25;
          }
      } else if (::sin(angle) < 0) {
          angle += 0.25;
      } else if (::sin(angle) > 0) {
          angle -= 0.25;
      }

      // Try not to crash with any other mice
      QList<QGraphicsItem *> dangerMice = scene()->items(QPolygonF()
                                                         << mapToScene(0, 0)
                                                         << mapToScene(-30, -50)
                                                         << mapToScene(30, -50));
      foreach (QGraphicsItem *item, dangerMice) {
          if (item == this)
              continue;

          QLineF lineToMouse(QPointF(0, 0), mapFromItem(item, 0, 0));
          qreal angleToMouse = ::acos(lineToMouse.dx() / lineToMouse.length());
          if (lineToMouse.dy() < 0)
              angleToMouse = TwoPi - angleToMouse;
          angleToMouse = normalizeAngle((Pi - angleToMouse) + Pi / 2);

          if (angleToMouse >= 0 && angleToMouse < Pi / 2) {
              // Rotate right
              angle += 0.5;
          } else if (angleToMouse <= TwoPi && angleToMouse > (TwoPi - Pi / 2)) {
              // Rotate left
              angle -= 0.5;
          }
      }

      // Add some random movement
      if (dangerMice.size() > 1 && (qrand() % 10) == 0) {
          if (qrand() % 1)
              angle += (qrand() % 100) / 500.0;
          else
              angle -= (qrand() % 100) / 500.0;
      }

      speed += (-50 + qrand() % 100) / 100.0;

      qreal dx = ::sin(angle) * 10;
      mouseEyeDirection = (qAbs(dx / 5) < 1) ? 0 : dx / 5;

      setRotation(rotation() + dx);
      setPos(mapToParent(0, -(3 + sin(speed) * 3)));
  }