coloritem.cpp Example File

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  #include <QtWidgets>

  #include "coloritem.h"

  ColorItem::ColorItem()
      : color(qrand() % 256, qrand() % 256, qrand() % 256)
  {
      setToolTip(QString("QColor(%1, %2, %3)\n%4")
                .arg(color.red()).arg(color.green()).arg(color.blue())
                .arg("Click and drag this color onto the robot!"));
      setCursor(Qt::OpenHandCursor);
      setAcceptedMouseButtons(Qt::LeftButton);
  }

  QRectF ColorItem::boundingRect() const
  {
      return QRectF(-15.5, -15.5, 34, 34);
  }

  void ColorItem::paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget)
  {
      Q_UNUSED(option);
      Q_UNUSED(widget);
      painter->setPen(Qt::NoPen);
      painter->setBrush(Qt::darkGray);
      painter->drawEllipse(-12, -12, 30, 30);
      painter->setPen(QPen(Qt::black, 1));
      painter->setBrush(QBrush(color));
      painter->drawEllipse(-15, -15, 30, 30);
  }

  void ColorItem::mousePressEvent(QGraphicsSceneMouseEvent *)
  {
      setCursor(Qt::ClosedHandCursor);
  }

  void ColorItem::mouseMoveEvent(QGraphicsSceneMouseEvent *event)
  {
      if (QLineF(event->screenPos(), event->buttonDownScreenPos(Qt::LeftButton))
          .length() < QApplication::startDragDistance()) {
          return;
      }

      QDrag *drag = new QDrag(event->widget());
      QMimeData *mime = new QMimeData;
      drag->setMimeData(mime);

      static int n = 0;
      if (n++ > 2 && (qrand() % 3) == 0) {
          QImage image(":/images/head.png");
          mime->setImageData(image);

          drag->setPixmap(QPixmap::fromImage(image).scaled(30, 40));
          drag->setHotSpot(QPoint(15, 30));
      } else {
          mime->setColorData(color);
          mime->setText(QString("#%1%2%3")
                        .arg(color.red(), 2, 16, QLatin1Char('0'))
                        .arg(color.green(), 2, 16, QLatin1Char('0'))
                        .arg(color.blue(), 2, 16, QLatin1Char('0')));

          QPixmap pixmap(34, 34);
          pixmap.fill(Qt::white);

          QPainter painter(&pixmap);
          painter.translate(15, 15);
          painter.setRenderHint(QPainter::Antialiasing);
          paint(&painter, 0, 0);
          painter.end();

          pixmap.setMask(pixmap.createHeuristicMask());

          drag->setPixmap(pixmap);
          drag->setHotSpot(QPoint(15, 20));
      }

      drag->exec();
      setCursor(Qt::OpenHandCursor);
  }

  void ColorItem::mouseReleaseEvent(QGraphicsSceneMouseEvent *)
  {
      setCursor(Qt::OpenHandCursor);
  }