Qt 4.8: dragwidget.cpp Example File (draganddrop/fridgemagnets/dragwidget.cpp)

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# dragwidget.cpp Example File

draganddrop/fridgemagnets/dragwidget.cpp

     /****************************************************************************
     **
     ** Copyright (C) 2015 The Qt Company Ltd.
     ** Contact: http://www.qt.io/licensing/
     **
     ** This file is part of the examples of the Qt Toolkit.
     **
     ** $QT_BEGIN_LICENSE:BSD$
     ** You may use this file under the terms of the BSD license as follows:
     **
     ** "Redistribution and use in source and binary forms, with or without
     ** modification, are permitted provided that the following conditions are
     ** met:
     **   * Redistributions of source code must retain the above copyright
     **     notice, this list of conditions and the following disclaimer.
     **   * Redistributions in binary form must reproduce the above copyright
     **     notice, this list of conditions and the following disclaimer in
     **     the documentation and/or other materials provided with the
     **     distribution.
     **   * Neither the name of The Qt Company Ltd nor the names of its
     **     contributors may be used to endorse or promote products derived
     **     from this software without specific prior written permission.
     **
     **
     ** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
     ** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
     ** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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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;
             word = inputStream.readLine();
             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 defined(Q_WS_MAEMO_5) || defined(Q_WS_SIMULATOR)
                 if (x >= 345) {
     #else
                 if (x >= 245) {
     #endif
                     x = 5;
                     y += wordLabel->height() + 2;
                 }
             }
         }

         #ifndef Q_WS_S60
         //Fridge magnets is used for demoing Qt on S60 and themed backgrounds look better than white
         QPalette newPalette = palette();
         newPalette.setColor(QPalette::Window, Qt::white);
         setPalette(newPalette);
         #endif

         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();
             newLabel->setAttribute(Qt::WA_DeleteOnClose);

             if (event->source() == this) {
                 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();
                 newLabel->setAttribute(Qt::WA_DeleteOnClose);

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

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

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

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

         QByteArray itemData;
         QDataStream dataStream(&itemData, QIODevice::WriteOnly);
         dataStream << child->labelText() << QPoint(hotSpot);

         QMimeData *mimeData = new QMimeData;
         mimeData->setData("application/x-fridgemagnet", itemData);
         mimeData->setText(child->labelText());

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

         child->hide();

         if (drag->exec(Qt::MoveAction | Qt::CopyAction, Qt::CopyAction) == Qt::MoveAction)
             child->close();
         else
             child->show();
     }