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# pieceslist.cpp Example File
draganddrop/puzzle/pieceslist.cpp

        /****************************************************************************
        **
        ** Copyright (C) 2005-2006 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 "pieceslist.h"

        PiecesList::PiecesList(QWidget *parent)
            : QListWidget(parent)
        {
            setDragEnabled(true);
            setViewMode(QListView::IconMode);
            setIconSize(QSize(60, 60));
            setSpacing(10);
            setAcceptDrops(true);
            setDropIndicatorShown(true);
        }

        void PiecesList::dragEnterEvent(QDragEnterEvent *event)
        {
            if (event->mimeData()->hasFormat("image/x-puzzle-piece"))
                event->accept();
            else
                event->ignore();
        }

        void PiecesList::dragMoveEvent(QDragMoveEvent *event)
        {
            if (event->mimeData()->hasFormat("image/x-puzzle-piece")) {
                event->setDropAction(Qt::MoveAction);
                event->accept();
            } else
                event->ignore();
        }

        void PiecesList::dropEvent(QDropEvent *event)
        {
            if (event->mimeData()->hasFormat("image/x-puzzle-piece")) {
                QByteArray pieceData = event->mimeData()->data("image/x-puzzle-piece");
                QDataStream dataStream(&pieceData, QIODevice::ReadOnly);
                QPixmap pixmap;
                QPoint location;
                dataStream >> pixmap >> location;

                addPiece(pixmap, location);

                event->setDropAction(Qt::MoveAction);
                event->accept();
            } else
                event->ignore();
        }

        void PiecesList::addPiece(QPixmap pixmap, QPoint location)
        {
            QListWidgetItem *pieceItem = new QListWidgetItem(this);
            pieceItem->setIcon(QIcon(pixmap));
            pieceItem->setData(Qt::UserRole, QVariant(pixmap));
            pieceItem->setData(Qt::UserRole+1, location);
            pieceItem->setFlags(Qt::ItemIsEnabled | Qt::ItemIsSelectable
                                | Qt::ItemIsDragEnabled);
        }

        void PiecesList::startDrag(Qt::DropActions supportedActions)
        {
            QListWidgetItem *item = currentItem();

            QByteArray itemData;
            QDataStream dataStream(&itemData, QIODevice::WriteOnly);
            QPixmap pixmap = qVariantValue<QPixmap>(item->data(Qt::UserRole));
            QPoint location = item->data(Qt::UserRole+1).toPoint();

            dataStream << pixmap << location;

            QMimeData *mimeData = new QMimeData;
            mimeData->setData("image/x-puzzle-piece", itemData);

            QDrag *drag = new QDrag(this);
            drag->setMimeData(mimeData);
            drag->setHotSpot(QPoint(pixmap.width()/2, pixmap.height()/2));
            drag->setPixmap(pixmap);

            if (drag->start(Qt::MoveAction) == Qt::MoveAction)
                delete takeItem(row(item));
        }