- Qt 5.5
- Qt Widgets
- Drag and Drop Robot Example
- coloritem.cpp Example File
- Qt 5.5.1 Reference Documentation

# coloritem.cpp Example File

graphicsview/dragdroprobot/coloritem.cpp

    /****************************************************************************
    **
    ** Copyright (C) 2015 The Qt Company Ltd.
    ** Contact: http://www.qt.io/licensing/
    **
    ** This file is part of the examples of the Qt Toolkit.
    **
    ** $QT_BEGIN_LICENSE:BSD$
    ** You may use this file under the terms of the BSD license as follows:
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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);
    }