dragwidget.cpp Example File

 /****************************************************************************
 **
 ** Copyright (C) 2013 Digia Plc and/or its subsidiary(-ies).
 ** Contact: http://www.qt-project.org/legal
 **
 ** 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 Digia Plc and its Subsidiary(-ies) 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
 ** A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 ** OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 ** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 ** LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 ** DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 ** THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 ** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 ** OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE."
 **
 ** $QT_END_LICENSE$
 **
 ****************************************************************************/

 #include <QtGui>

 #include "dragwidget.h"

 DragWidget::DragWidget(QWidget *parent)
     : QFrame(parent)
 {
 #if defined(Q_OS_SYMBIAN) || defined(Q_WS_MAEMO_5) || defined(Q_WS_SIMULATOR)
 #else
     setMinimumSize(200, 200);
 #endif
     setFrameStyle(QFrame::Sunken | QFrame::StyledPanel);
     setAcceptDrops(true);

     QLabel *boatIcon = new QLabel(this);
     boatIcon->setPixmap(QPixmap(":/images/boat.png"));
     boatIcon->move(10, 10);
     boatIcon->show();
     boatIcon->setAttribute(Qt::WA_DeleteOnClose);

     QLabel *carIcon = new QLabel(this);
     carIcon->setPixmap(QPixmap(":/images/car.png"));
     carIcon->move(100, 10);
     carIcon->show();
     carIcon->setAttribute(Qt::WA_DeleteOnClose);

     QLabel *houseIcon = new QLabel(this);
     houseIcon->setPixmap(QPixmap(":/images/house.png"));
     houseIcon->move(10, 80);
     houseIcon->show();
     houseIcon->setAttribute(Qt::WA_DeleteOnClose);
 }

 void DragWidget::dragEnterEvent(QDragEnterEvent *event)
 {
     if (event->mimeData()->hasFormat("application/x-dnditemdata")) {
         if (event->source() == this) {
             event->setDropAction(Qt::MoveAction);
             event->accept();
         } else {
             event->acceptProposedAction();
         }
     } else {
         event->ignore();
     }
 }

 void DragWidget::dragMoveEvent(QDragMoveEvent *event)
 {
     if (event->mimeData()->hasFormat("application/x-dnditemdata")) {
         if (event->source() == this) {
             event->setDropAction(Qt::MoveAction);
             event->accept();
         } else {
             event->acceptProposedAction();
         }
     } else {
         event->ignore();
     }
 }

 void DragWidget::dropEvent(QDropEvent *event)
 {
     if (event->mimeData()->hasFormat("application/x-dnditemdata")) {
         QByteArray itemData = event->mimeData()->data("application/x-dnditemdata");
         QDataStream dataStream(&itemData, QIODevice::ReadOnly);

         QPixmap pixmap;
         QPoint offset;
         dataStream >> pixmap >> offset;

         QLabel *newIcon = new QLabel(this);
         newIcon->setPixmap(pixmap);
         newIcon->move(event->pos() - offset);
         newIcon->show();
         newIcon->setAttribute(Qt::WA_DeleteOnClose);

         if (event->source() == this) {
             event->setDropAction(Qt::MoveAction);
             event->accept();
         } else {
             event->acceptProposedAction();
         }
     } else {
         event->ignore();
     }
 }

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

     QPixmap pixmap = *child->pixmap();

     QByteArray itemData;
     QDataStream dataStream(&itemData, QIODevice::WriteOnly);
     dataStream << pixmap << QPoint(event->pos() - child->pos());

     QMimeData *mimeData = new QMimeData;
     mimeData->setData("application/x-dnditemdata", itemData);

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

     QPixmap tempPixmap = pixmap;
     QPainter painter;
     painter.begin(&tempPixmap);
     painter.fillRect(pixmap.rect(), QColor(127, 127, 127, 127));
     painter.end();

     child->setPixmap(tempPixmap);

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