- Qt 5.5
- Qt Widgets
- Drag and Drop Puzzle Example
- pieceslist.cpp Example File
- Qt 5.5.1 Reference Documentation

# pieceslist.cpp Example File

draganddrop/puzzle/pieceslist.cpp

    /****************************************************************************
    **
    ** Copyright (C) 2015 The Qt Company Ltd.
    ** Contact: http://www.qt.io/licensing/
    **
    ** This file is part of the examples of the Qt Toolkit.
    **
    ** $QT_BEGIN_LICENSE:BSD$
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    #include "pieceslist.h"

    #include <QDrag>
    #include <QDragEnterEvent>
    #include <QMimeData>

    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));
    }