Qt 4.8: pieceslist.cpp Example File (draganddrop/puzzle/pieceslist.cpp)

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# pieceslist.cpp Example File

draganddrop/puzzle/pieceslist.cpp

     /****************************************************************************
     **
     ** Copyright (C) 2012 Digia Plc and/or its subsidiary(-ies).
     ** Contact: http://www.qt-project.org/legal
     **
     ** 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:
     **
     ** "Redistribution and use in source and binary forms, with or without
     ** modification, are permitted provided that the following conditions are
     ** met:
     **   * Redistributions of source code must retain the above copyright
     **     notice, this list of conditions and the following disclaimer.
     **   * Redistributions in binary form must reproduce the above copyright
     **     notice, this list of conditions and the following disclaimer in
     **     the documentation and/or other materials provided with the
     **     distribution.
     **   * Neither the name of Digia Plc and its Subsidiary(-ies) nor the names
     **     of its contributors may be used to endorse or promote products derived
     **     from this software without specific prior written permission.
     **
     **
     ** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
     ** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
     ** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
     ** A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
     ** OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
     ** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
     ** LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
     ** DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
     ** THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
     ** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
     ** OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE."
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     ** $QT_END_LICENSE$
     **
     ****************************************************************************/

     #include <QtGui>

     #include "pieceslist.h"

     PiecesList::PiecesList(int pieceSize, QWidget *parent)
         : QListWidget(parent), m_PieceSize(pieceSize)
     {
         setDragEnabled(true);
         setViewMode(QListView::IconMode);
         setIconSize(QSize(m_PieceSize, m_PieceSize));
         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 = qvariant_cast<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->exec(Qt::MoveAction) == Qt::MoveAction)
             delete takeItem(row(item));
     }