Qt 4.3: coloritem.cpp Example File (graphicsview/dragdroprobot/coloritem.cpp)

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# coloritem.cpp Example File
graphicsview/dragdroprobot/coloritem.cpp

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     #include <QtGui>

     #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);
     }

     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 *event)
     {
         if (event->button() != Qt::LeftButton) {
             event->ignore();
             return;
         }

         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);
     }