dragwidget.cpp Example File

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  #include <QtWidgets>

  #include "dragwidget.h"

  static QLabel *createDragLabel(const QString &text, QWidget *parent)
  {
      QLabel *label = new QLabel(text, parent);
      label->setAutoFillBackground(true);
      label->setFrameShape(QFrame::Panel);
      label->setFrameShadow(QFrame::Raised);
      return label;
  }

  static QString hotSpotMimeDataKey() { return QStringLiteral("application/x-hotspot"); }

  DragWidget::DragWidget(QWidget *parent)
      : QWidget(parent)
  {
      QFile dictionaryFile(QStringLiteral(":/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()) {
              QLabel *wordLabel = createDragLabel(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;
              }
          }
      }

      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(QRegularExpression(QStringLiteral("\\s+")),
                               QString::SkipEmptyParts);
          QPoint position = event->pos();
          QPoint hotSpot;

          QByteArrayList hotSpotPos = mime->data(hotSpotMimeDataKey()).split(' ');
          if (hotSpotPos.size() == 2) {
              hotSpot.setX(hotSpotPos.first().toInt());
              hotSpot.setY(hotSpotPos.last().toInt());
          }

          foreach (const QString &piece, pieces) {
              QLabel *newLabel = createDragLabel(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 (QWidget *widget, findChildren<QWidget *>()) {
          if (!widget->isVisible())
              widget->deleteLater();
      }
  }

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

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

      QMimeData *mimeData = new QMimeData;
      mimeData->setText(child->text());
      mimeData->setData(hotSpotMimeDataKey(),
                        QByteArray::number(hotSpot.x()) + ' ' + QByteArray::number(hotSpot.y()));

      qreal dpr = window()->windowHandle()->devicePixelRatio();
      QPixmap pixmap(child->size() * dpr);
      pixmap.setDevicePixelRatio(dpr);
      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();
  }