Qt 5.6 | Qt Widgets | Fridge Magnets Example | dragwidget.cpp Example File

Qt 5.6.3 Reference Documentation

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

      #include <QtWidgets>

      static inline QString fridgetMagnetsMimeType() { return QStringLiteral("application/x-fridgemagnet"); }

      DragWidget::DragWidget(QWidget *parent)
          : QWidget(parent)
      {
          QFile dictionaryFile(QStringLiteral(":/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();
                  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);

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

      void DragWidget::dragEnterEvent(QDragEnterEvent *event)
      {
          if (event->mimeData()->hasFormat(fridgetMagnetsMimeType())) {
              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(fridgetMagnetsMimeType())) {
              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(fridgetMagnetsMimeType())) {
              const QMimeData *mime = event->mimeData();
              QByteArray itemData = mime->data(fridgetMagnetsMimeType());
              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(QRegularExpression(QStringLiteral("\\s+")),
                                   QString::SkipEmptyParts);
              QPoint position = event->pos();

              foreach (const 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(fridgetMagnetsMimeType(), 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();
      }