puzzlewidget.cpp Example File
^{draganddrop/puzzle/puzzlewidget.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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    ** review the following information:
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    ** WARRANTY OF DESIGN, MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
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    ****************************************************************************/

    #include <QtGui>

    #include "puzzlewidget.h"

    PuzzleWidget::PuzzleWidget(QWidget *parent)
        : QWidget(parent)
    {
        setAcceptDrops(true);
        setMinimumSize(400, 400);
        setMaximumSize(400, 400);
    }

    void PuzzleWidget::clear()
    {
        pieceLocations.clear();
        piecePixmaps.clear();
        pieceRects.clear();
        highlightedRect = QRect();
        inPlace = 0;
        update();
    }

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

    void PuzzleWidget::dragLeaveEvent(QDragLeaveEvent *event)
    {
        QRect updateRect = highlightedRect;
        highlightedRect = QRect();
        update(updateRect);
        event->accept();
    }

    void PuzzleWidget::dragMoveEvent(QDragMoveEvent *event)
    {
        QRect updateRect = highlightedRect.unite(targetSquare(event->pos()));

        if (event->mimeData()->hasFormat("image/x-puzzle-piece")
            && findPiece(targetSquare(event->pos())) == -1) {

            highlightedRect = targetSquare(event->pos());
            event->setDropAction(Qt::MoveAction);
            event->accept();
        } else {
            highlightedRect = QRect();
            event->ignore();
        }

        update(updateRect);
    }

    void PuzzleWidget::dropEvent(QDropEvent *event)
    {
        if (event->mimeData()->hasFormat("image/x-puzzle-piece")
            && findPiece(targetSquare(event->pos())) == -1) {

            QByteArray pieceData = event->mimeData()->data("image/x-puzzle-piece");
            QDataStream dataStream(&pieceData, QIODevice::ReadOnly);
            QRect square = targetSquare(event->pos());
            QPixmap pixmap;
            QPoint location;
            dataStream >> pixmap >> location;

            pieceLocations.append(location);
            piecePixmaps.append(pixmap);
            pieceRects.append(square);

            highlightedRect = QRect();
            update(square);

            event->setDropAction(Qt::MoveAction);
            event->accept();

            if (location == QPoint(square.x()/80, square.y()/80)) {
                inPlace++;
                if (inPlace == 25)
                    emit puzzleCompleted();
            }
        } else {
            highlightedRect = QRect();
            event->ignore();
        }
    }

    int PuzzleWidget::findPiece(const QRect &pieceRect) const
    {
        for (int i = 0; i < pieceRects.size(); ++i) {
            if (pieceRect == pieceRects[i]) {
                return i;
            }
        }
        return -1;
    }

    void PuzzleWidget::mousePressEvent(QMouseEvent *event)
    {
        QRect square = targetSquare(event->pos());
        int found = findPiece(square);

        if (found == -1)
            return;

        QPoint location = pieceLocations[found];
        QPixmap pixmap = piecePixmaps[found];
        pieceLocations.removeAt(found);
        piecePixmaps.removeAt(found);
        pieceRects.removeAt(found);

        if (location == QPoint(square.x()/80, square.y()/80))
            inPlace--;

        update(square);

        QByteArray itemData;
        QDataStream dataStream(&itemData, QIODevice::WriteOnly);

        dataStream << pixmap << location;

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

        QDrag *drag = new QDrag(this);
        drag->setMimeData(mimeData);
        drag->setHotSpot(event->pos() - square.topLeft());
        drag->setPixmap(pixmap);

        if (!(drag->start(Qt::MoveAction) == Qt::MoveAction)) {
            pieceLocations.insert(found, location);
            piecePixmaps.insert(found, pixmap);
            pieceRects.insert(found, square);
            update(targetSquare(event->pos()));

            if (location == QPoint(square.x()/80, square.y()/80))
                inPlace++;
        }
    }

    void PuzzleWidget::paintEvent(QPaintEvent *event)
    {
        QPainter painter;
        painter.begin(this);
        painter.fillRect(event->rect(), Qt::white);

        if (highlightedRect.isValid()) {
            painter.setBrush(QColor("#ffcccc"));
            painter.setPen(Qt::NoPen);
            painter.drawRect(highlightedRect.adjusted(0, 0, -1, -1));
        }

        for (int i = 0; i < pieceRects.size(); ++i) {
            painter.drawPixmap(pieceRects[i], piecePixmaps[i]);
        }
        painter.end();
    }

    const QRect PuzzleWidget::targetSquare(const QPoint &position) const
    {
        return QRect(position.x()/80 * 80, position.y()/80 * 80, 80, 80);
    }