dragwidget.cpp Example File
draganddrop/fridgemagnets/dragwidget.cpp

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 ** This file is part of the example classes of the Qt Toolkit.
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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(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::Window, Qt::white);
     setPalette(newPalette);

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

 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")) {
         const QMimeData *mime = event->mimeData();
         QByteArray itemData = mime->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();
     }
 }