Qt 4.3: pieceslist.cpp Example File (draganddrop/puzzle/pieceslist.cpp)

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

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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->exec(Qt::MoveAction) == Qt::MoveAction)
             delete takeItem(row(item));
     }