Qt 5.11 | Qt Widgets | Drag and Drop Puzzle Example | pieceslist.cpp Example File

Qt 5.11.3 Reference Documentation

# pieceslist.cpp Example File

draganddrop/puzzle/pieceslist.cpp

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      #include "pieceslist.h"

      #include <QDrag>
      #include <QDragEnterEvent>
      #include <QMimeData>

      PiecesList::PiecesList(int pieceSize, QWidget *parent)
          : QListWidget(parent), m_PieceSize(pieceSize)
      {
          setDragEnabled(true);
          setViewMode(QListView::IconMode);
          setIconSize(QSize(m_PieceSize, m_PieceSize));
          setSpacing(10);
          setAcceptDrops(true);
          setDropIndicatorShown(true);
      }

      void PiecesList::dragEnterEvent(QDragEnterEvent *event)
      {
          if (event->mimeData()->hasFormat(PiecesList::puzzleMimeType()))
              event->accept();
          else
              event->ignore();
      }

      void PiecesList::dragMoveEvent(QDragMoveEvent *event)
      {
          if (event->mimeData()->hasFormat(PiecesList::puzzleMimeType())) {
              event->setDropAction(Qt::MoveAction);
              event->accept();
          } else {
              event->ignore();
          }
      }

      void PiecesList::dropEvent(QDropEvent *event)
      {
          if (event->mimeData()->hasFormat(PiecesList::puzzleMimeType())) {
              QByteArray pieceData = event->mimeData()->data(PiecesList::puzzleMimeType());
              QDataStream dataStream(&pieceData, QIODevice::ReadOnly);
              QPixmap pixmap;
              QPoint location;
              dataStream >> pixmap >> location;

              addPiece(pixmap, location);

              event->setDropAction(Qt::MoveAction);
              event->accept();
          } else {
              event->ignore();
          }
      }

      void PiecesList::addPiece(const QPixmap &pixmap, const QPoint &location)
      {
          QListWidgetItem *pieceItem = new QListWidgetItem(this);
          pieceItem->setIcon(QIcon(pixmap));
          pieceItem->setData(Qt::UserRole, QVariant(pixmap));
          pieceItem->setData(Qt::UserRole+1, location);
          pieceItem->setFlags(Qt::ItemIsEnabled | Qt::ItemIsSelectable | Qt::ItemIsDragEnabled);
      }

      void PiecesList::startDrag(Qt::DropActions /*supportedActions*/)
      {
          QListWidgetItem *item = currentItem();

          QByteArray itemData;
          QDataStream dataStream(&itemData, QIODevice::WriteOnly);
          QPixmap pixmap = qvariant_cast<QPixmap>(item->data(Qt::UserRole));
          QPoint location = item->data(Qt::UserRole+1).toPoint();

          dataStream << pixmap << location;

          QMimeData *mimeData = new QMimeData;
          mimeData->setData(PiecesList::puzzleMimeType(), itemData);

          QDrag *drag = new QDrag(this);
          drag->setMimeData(mimeData);
          drag->setHotSpot(QPoint(pixmap.width()/2, pixmap.height()/2));
          drag->setPixmap(pixmap);

          if (drag->exec(Qt::MoveAction) == Qt::MoveAction)
              delete takeItem(row(item));
      }