dragwidget.cpp Example File

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  #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();
  }