Qt 4.0: dragwidget.cpp Example File (draganddrop/draggableicons/dragwidget.cpp)

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# dragwidget.cpp Example File
draganddrop/draggableicons/dragwidget.cpp

        /****************************************************************************
        **
        ** Copyright (C) 2005-2005 Trolltech AS. All rights reserved.
        **
        ** This file is part of the documentation of the Qt Toolkit.
        **
        ** This file may be used under the terms of the GNU General Public
    ** License version 2.0 as published by the Free Software Foundation
    ** and appearing in the file LICENSE.GPL included in the packaging of
    ** this file.  Please review the following information to ensure GNU
    ** General Public Licensing requirements will be met:
    ** http://www.trolltech.com/products/qt/opensource.html
    **
    ** If you are unsure which license is appropriate for your use, please
    ** review the following information:
    ** http://www.trolltech.com/products/qt/licensing.html or contact the
    ** sales department at sales@trolltech.com.
        **
        ** This file is provided AS IS with NO WARRANTY OF ANY KIND, INCLUDING THE
        ** WARRANTY OF DESIGN, MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
        **
        ****************************************************************************/

        #include <QtGui>

        #include "dragwidget.h"

        DragWidget::DragWidget(QWidget *parent)
            : QFrame(parent)
        {
            setMinimumSize(200, 200);
            setFrameStyle(QFrame::Sunken | QFrame::StyledPanel);
            setAcceptDrops(true);

            QLabel *boatIcon = new QLabel(this);
            boatIcon->setPixmap(QPixmap(":/images/boat.png"));
            boatIcon->move(20, 20);
            boatIcon->show();
            boatIcon->setAttribute(Qt::WA_DeleteOnClose);

            QLabel *carIcon = new QLabel(this);
            carIcon->setPixmap(QPixmap(":/images/car.png"));
            carIcon->move(120, 20);
            carIcon->show();
            carIcon->setAttribute(Qt::WA_DeleteOnClose);

            QLabel *houseIcon = new QLabel(this);
            houseIcon->setPixmap(QPixmap(":/images/house.png"));
            houseIcon->move(20, 120);
            houseIcon->show();
            houseIcon->setAttribute(Qt::WA_DeleteOnClose);
        }

        void DragWidget::dragEnterEvent(QDragEnterEvent *event)
        {
            if (event->mimeData()->hasFormat("application/x-dnditemdata")) {
                if (event->source() == this) {
                    event->setDropAction(Qt::MoveAction);
                    event->accept();
                } else {
                    event->acceptProposedAction();
                }
            } else {
                event->ignore();
            }
        }

        void DragWidget::dropEvent(QDropEvent *event)
        {
            if (event->mimeData()->hasFormat("application/x-dnditemdata")) {
                QByteArray itemData = event->mimeData()->data("application/x-dnditemdata");
                QDataStream dataStream(&itemData, QIODevice::ReadOnly);

                QPixmap pixmap;
                QPoint offset;
                dataStream >> pixmap >> offset;

                QLabel *newIcon = new QLabel(this);
                newIcon->setPixmap(pixmap);
                newIcon->move(event->pos() - offset);
                newIcon->show();
                newIcon->setAttribute(Qt::WA_DeleteOnClose);

                if (event->source() == this) {
                    event->setDropAction(Qt::MoveAction);
                    event->accept();
                } else {
                    event->acceptProposedAction();
                }
            } else {
                event->ignore();
            }
        }

        void DragWidget::mousePressEvent(QMouseEvent *event)
        {
            QLabel *child = static_cast<QLabel*>(childAt(event->pos()));
            if (!child)
                return;

            QPixmap pixmap = *child->pixmap();

            QByteArray itemData;
            QDataStream dataStream(&itemData, QIODevice::WriteOnly);
            dataStream << pixmap << QPoint(event->pos() - child->pos());

            QMimeData *mimeData = new QMimeData;
            mimeData->setData("application/x-dnditemdata", itemData);

            QDrag *drag = new QDrag(this);
            drag->setMimeData(mimeData);
            drag->setPixmap(pixmap);
            drag->setHotSpot(event->pos() - child->pos());

            QPixmap tempPixmap = pixmap;
            QPainter painter;
            painter.begin(&tempPixmap);
            painter.fillRect(pixmap.rect(), QColor(127, 127, 127, 127));
            painter.end();

            child->setPixmap(tempPixmap);

            if (drag->start(Qt::CopyAction | Qt::MoveAction) == Qt::MoveAction)
                child->close();
            else {
                child->show();
                child->setPixmap(pixmap);
            }
        }