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dropsitewidget.cpp Example File
^{draganddrop/dropsite/dropsitewidget.cpp}

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    **
    ** Copyright (C) 2005-2006 Trolltech AS. 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:
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    **
    ** This file is provided AS IS with NO WARRANTY OF ANY KIND, INCLUDING THE
    ** WARRANTY OF DESIGN, MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
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    #include <QtGui>

    #include "dropsitewidget.h"
    #include "dropsitewindow.h"

    DropSiteWidget::DropSiteWidget(QWidget *parent)
        : QLabel(parent)
    {
        setMinimumSize(200, 200);
        setFrameStyle(QFrame::Sunken | QFrame::StyledPanel);
        setAcceptDrops(true);
        setAutoFillBackground(true);
        setBackgroundRole(QPalette::Dark);

        setText(tr("<drop content>"));
        setAlignment(Qt::AlignCenter);
    }

    void DropSiteWidget::dragEnterEvent(QDragEnterEvent *event)
    {
        setText(tr("<drop content>"));
        setBackgroundRole(QPalette::Light);

        event->acceptProposedAction();
        emit changed(event->mimeData());
    }

    void DropSiteWidget::dropEvent(QDropEvent *event)
    {
        const QMimeData *mimeData = event->mimeData();
        QStringList formats = mimeData->formats();

        foreach (QString format, formats)
        {
            if (format.startsWith("image/")) {
                QPixmap pixmap = createPixmap(mimeData->data(format), format);
                if (!pixmap.isNull()) {
                    setPixmap(pixmap);
                    break;
                }
            }
            QString text = createPlainText(mimeData->data(format), format);
            if (!text.isEmpty()) {
                setText(text);
                break;
            } else {
                setText(tr("No supported format"));
            }
        }

        setBackgroundRole(QPalette::Dark);
        event->acceptProposedAction();
    }

    void DropSiteWidget::dragLeaveEvent(QDragLeaveEvent *event)
    {
        clear();
        event->accept();
    }

    void DropSiteWidget::clear()
    {
        setText(tr("<drop content>"));
        setBackgroundRole(QPalette::Dark);

        emit changed();
    }

    QPixmap DropSiteWidget::createPixmap(QByteArray data, QString format)
    {
        QList<QByteArray> imageFormats = QImageReader::supportedImageFormats();
        QPixmap pixmap;

        foreach (QByteArray imageFormat, imageFormats) {
            if (format.mid(6) == QString(imageFormat)) {
                pixmap.loadFromData(data, imageFormat);
                break;
            }
        }
        return pixmap;
    }

    QString DropSiteWidget::createPlainText(QByteArray data, QString format)
    {
        QString text = "";

        if (format.startsWith("text/plain")) {
            text.append(QString(data));
        } else if (format.startsWith("text/plain;")) {
            int index = format.indexOf('=');
            if (index > 0) {
                QTextCodec *codec = QTextCodec::codecForName(format.mid(index + 1).toAscii());
                text.append(QString(codec->toUnicode(data)));
            }
        }
        return text;
    }