<code c++>
#include "mainwindow.h"
#include "ui_mainwindow.h"

#include <QGraphicsRectItem>
#include <QGraphicsSceneWheelEvent>
#include <QGraphicsSceneDragDropEvent>

#include <QDrag>
#include <QMimeData>

MainWindow * win = 0;

class MyItem : public QGraphicsRectItem
{
private:
    QColor clr;
    int cnt;
public:
    void setClr ()
    {
        clr = QColor::fromHsl(abs (cnt) % 360, 250, 150);
        setBrush (clr);
        setToolTip (QString::number(cnt));
        // setRotation(abs (cnt) % 360);
    }

    MyItem (int p = 0) :
       cnt (p)
    {
        setClr ();
        setPen (QColor ("red"));
        setOpacity (0.5);
        setFlag (QGraphicsItem::ItemIsMovable);
        setAcceptDrops (true);
    }
protected:
    virtual void wheelEvent ( QGraphicsSceneWheelEvent * event )
    {
        cnt += event->delta() / 8;
        setClr ();
        // setBrush (Qt::green);
    }
    virtual void mousePressEvent ( QGraphicsSceneMouseEvent * event )
    {
        // #include <QDrag>
        // #include <QMimeData>
        QDrag * d = new QDrag (win);
        QMimeData * m = new QMimeData;
        m->setText ("abc");
        m->setColorData (clr);
        d->setMimeData (m);
        d->exec ();
    }
    virtual void dropEvent ( QGraphicsSceneDragDropEvent * event )
    {
        setBrush (Qt::green);
        const QMimeData * m = event->mimeData();
        if (m->hasText())
            setToolTip(m->text());
        if (m->hasColor())
            setBrush (qvariant_cast<QColor>(m->colorData()));
    }

};

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);
    win = this;

    QGraphicsScene * scene = new QGraphicsScene;
    scene->setSceneRect (0, 0, 300, 200);
    ui->graphicsView->setScene (scene);

    for (int i = 1; i <= 5; i++)
    {

        MyItem * item = new MyItem (45*i);
        item->setRect (80*i, 40*i, 100, 200);
        scene->addItem (item);
    }

    /*
    scene->addText ("Hello");
    scene->addLine (0, 0, 100, 100, QColor ("red"));
    scene->addRect (100, 10, 40, 40, QColor ("blue"), QColor ("yellow"));

    QGraphicsRectItem * item = new QGraphicsRectItem;
    item->setPen (QPen (QColor ("blue"), 3));
    item->setBrush (QBrush(QColor ("cornflowerblue"), Qt::FDiagPattern));
    item->setRect (40, 40, 100, 200);
    item->setToolTip ("abc");
    item->setFlags(QGraphicsItem::ItemIsMovable);
    // item->setFlags(QGraphicsItem::ItemIsSelectable);
    scene->addItem (item);
    */
}

MainWindow::~MainWindow()
{
    delete ui;
}

</code>