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dragwidget.cpp Example File
draganddrop/draggabletext/dragwidget.cpp

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 ** Alternatively, this file may be used under the terms of the GNU
 ** General Public License version 3.0 as published by the Free Software
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 #include <QtGui>

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

 DragWidget::DragWidget(QWidget *parent)
     : QWidget(parent)
 {
     QFile dictionaryFile(":/dictionary/words.txt");
     dictionaryFile.open(QIODevice::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();
             wordLabel->setAttribute(Qt::WA_DeleteOnClose);
             x += wordLabel->width() + 2;
             if (x >= 195) {
                 x = 5;
                 y += wordLabel->height() + 2;
             }
         }
     }

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

     setAcceptDrops(true);
     setMinimumSize(400, qMax(200, y));
     setWindowTitle(tr("Draggable Text"));
 }

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

 void DragWidget::dropEvent(QDropEvent *event)
 {
     if (event->mimeData()->hasText()) {
         const QMimeData *mime = event->mimeData();
         QStringList pieces = mime->text().split(QRegExp("\\s+"),
                              QString::SkipEmptyParts);
         QPoint position = event->pos();
         QPoint hotSpot;

         QList<QByteArray> hotSpotPos = mime->data("application/x-hotspot").split(' ');
         if (hotSpotPos.size() == 2) {
             hotSpot.setX(hotSpotPos.first().toInt());
             hotSpot.setY(hotSpotPos.last().toInt());
         }

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

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

         if (event->source() == this) {
             event->setDropAction(Qt::MoveAction);
             event->accept();
         } else {
             event->acceptProposedAction();
         }
     } else {
         event->ignore();
     }
     foreach (QObject *child, children()) {
         if (child->inherits("QWidget")) {
             QWidget *widget = static_cast<QWidget *>(child);
             if (!widget->isVisible())
                 widget->deleteLater();
         }
     }
 }

 void DragWidget::mousePressEvent(QMouseEvent *event)
 {
     QLabel *child = static_cast<QLabel*>(childAt(event->pos()));
     if (!child)
         return;

     QPoint hotSpot = event->pos() - child->pos();

     QMimeData *mimeData = new QMimeData;
     mimeData->setText(child->text());
     mimeData->setData("application/x-hotspot",
                       QByteArray::number(hotSpot.x())
                       + " " + QByteArray::number(hotSpot.y()));

     QPixmap pixmap(child->size());
     child->render(&pixmap);

     QDrag *drag = new QDrag(this);
     drag->setMimeData(mimeData);
     drag->setPixmap(pixmap);
     drag->setHotSpot(hotSpot);

     Qt::DropAction dropAction = drag->exec(Qt::CopyAction | Qt::MoveAction, Qt::CopyAction);

     if (dropAction == Qt::MoveAction)
         child->close();
 }