Qt 5.8 | Qt Widgets | Draggable Text Example | dragwidget.cpp Example File

Qt 5.8.0 Reference Documentation

# dragwidget.cpp Example File

draganddrop/draggabletext/dragwidget.cpp

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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();
      }