pieceslist.cpp Example File
^{draganddrop/puzzle/pieceslist.cpp}

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    **
    ** Copyright (C) 2005-2006 Trolltech ASA. 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
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    ** http://www.trolltech.com/products/qt/opensource.html
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    ** review the following information:
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    #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));
    }