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

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# dragwidget.cpp Example File

draganddrop/draggabletext/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.
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     **
     ** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
     ** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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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 >= 245) {
                     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 (event->source() == this) {
                 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();
     }