dragwidget.cpp Example File
^{draganddrop/fridgemagnets/dragwidget.cpp}

    /****************************************************************************
    **
    ** 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
    ** General Public Licensing requirements will be met:
    ** http://www.trolltech.com/products/qt/opensource.html
    **
    ** If you are unsure which license is appropriate for your use, please
    ** review the following information:
    ** http://www.trolltech.com/products/qt/licensing.html or contact the
    ** sales department at sales@trolltech.com.
    **
    ** This file is provided AS IS with NO WARRANTY OF ANY KIND, INCLUDING THE
    ** WARRANTY OF DESIGN, MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
    **
    ****************************************************************************/

    #include <QtGui>

    #include "draglabel.h"
    #include "dragwidget.h"

    DragWidget::DragWidget(QWidget *parent)
        : QWidget(parent)
    {
        QFile dictionaryFile(":/dictionary/words.txt");
        dictionaryFile.open(QFile::ReadOnly);
        QTextStream inputStream(&dictionaryFile);

        int x = 5;
        int y = 5;

        while (!inputStream.atEnd()) {
            QString word;
            inputStream >> word;
            if (!word.isEmpty()) {
                DragLabel *wordLabel = new DragLabel(word, this);
                wordLabel->move(x, y);
                wordLabel->show();
                x += wordLabel->width() + 2;
                if (x >= 245) {
                    x = 5;
                    y += wordLabel->height() + 2;
                }
            }
        }

        QPalette newPalette = palette();
        newPalette.setColor(QPalette::Background, Qt::white);
        setPalette(newPalette);

        setAcceptDrops(true);
        setMinimumSize(400, qMax(200, y));
        setWindowTitle(tr("Fridge Magnets"));
    }

    void DragWidget::dragEnterEvent(QDragEnterEvent *event)
    {
        if (event->mimeData()->hasFormat("application/x-fridgemagnet")) {
            if (children().contains(event->source())) {
                event->setDropAction(Qt::MoveAction);
                event->accept();
            } else {
                event->acceptProposedAction();
            }
        } else if (event->mimeData()->hasText()) {
            event->acceptProposedAction();
        } else {
            event->ignore();
        }
    }

    void DragWidget::dragMoveEvent(QDragMoveEvent *event)
    {
        if (event->mimeData()->hasFormat("application/x-fridgemagnet")) {
            if (children().contains(event->source())) {
                event->setDropAction(Qt::MoveAction);
                event->accept();
            } else {
                event->acceptProposedAction();
            }
        } else if (event->mimeData()->hasText()) {
            event->acceptProposedAction();
        } else {
            event->ignore();
        }
    }

    void DragWidget::dropEvent(QDropEvent *event)
    {
        if (event->mimeData()->hasFormat("application/x-fridgemagnet")) {
            QByteArray itemData = event->mimeData()->data("application/x-fridgemagnet");
            QDataStream dataStream(&itemData, QIODevice::ReadOnly);

            QString text;
            QPoint offset;
            dataStream >> text >> offset;

            DragLabel *newLabel = new DragLabel(text, this);
            newLabel->move(event->pos() - offset);
            newLabel->show();

            if (children().contains(event->source())) {
                event->setDropAction(Qt::MoveAction);
                event->accept();
            } else {
                event->acceptProposedAction();
            }
        } else if (event->mimeData()->hasText()) {
            QStringList pieces = event->mimeData()->text().split(QRegExp("\\s+"),
                                 QString::SkipEmptyParts);
            QPoint position = event->pos();

            foreach (QString piece, pieces) {
                DragLabel *newLabel = new DragLabel(piece, this);
                newLabel->move(position);
                newLabel->show();

                position += QPoint(newLabel->width(), 0);
            }

            event->acceptProposedAction();
        } else {
            event->ignore();
        }
    }