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

Qt 5.6.2 Reference Documentation

# dragwidget.cpp Example File

draganddrop/fridgemagnets/dragwidget.cpp

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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();
      }