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

Qt 5.11.3 Reference Documentation

# puzzlewidget.cpp Example File

draganddrop/puzzle/puzzlewidget.cpp

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      #include "puzzlewidget.h"
      #include "pieceslist.h"

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

      PuzzleWidget::PuzzleWidget(int imageSize, QWidget *parent)
          : QWidget(parent), m_ImageSize(imageSize)
      {
          setAcceptDrops(true);
          setMinimumSize(m_ImageSize, m_ImageSize);
          setMaximumSize(m_ImageSize, m_ImageSize);
      }

      void PuzzleWidget::clear()
      {
          pieces.clear();
          highlightedRect = QRect();
          inPlace = 0;
          update();
      }

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

      void PuzzleWidget::dragLeaveEvent(QDragLeaveEvent *event)
      {
          QRect updateRect = highlightedRect;
          highlightedRect = QRect();
          update(updateRect);
          event->accept();
      }

      void PuzzleWidget::dragMoveEvent(QDragMoveEvent *event)
      {
          QRect updateRect = highlightedRect.united(targetSquare(event->pos()));

          if (event->mimeData()->hasFormat(PiecesList::puzzleMimeType())
              && findPiece(targetSquare(event->pos())) == -1) {

              highlightedRect = targetSquare(event->pos());
              event->setDropAction(Qt::MoveAction);
              event->accept();
          } else {
              highlightedRect = QRect();
              event->ignore();
          }

          update(updateRect);
      }

      void PuzzleWidget::dropEvent(QDropEvent *event)
      {
          if (event->mimeData()->hasFormat(PiecesList::puzzleMimeType())
              && findPiece(targetSquare(event->pos())) == -1) {

              QByteArray pieceData = event->mimeData()->data(PiecesList::puzzleMimeType());
              QDataStream dataStream(&pieceData, QIODevice::ReadOnly);
              Piece piece;
              piece.rect = targetSquare(event->pos());
              dataStream >> piece.pixmap >> piece.location;

              pieces.append(piece);

              highlightedRect = QRect();
              update(piece.rect);

              event->setDropAction(Qt::MoveAction);
              event->accept();

              if (piece.location == piece.rect.topLeft() / pieceSize()) {
                  inPlace++;
                  if (inPlace == 25)
                      emit puzzleCompleted();
              }
          } else {
              highlightedRect = QRect();
              event->ignore();
          }
      }

      int PuzzleWidget::findPiece(const QRect &pieceRect) const
      {
          for (int i = 0, size = pieces.size(); i < size; ++i) {
              if (pieces.at(i).rect == pieceRect)
                  return i;
          }
          return -1;
      }

      void PuzzleWidget::mousePressEvent(QMouseEvent *event)
      {
          QRect square = targetSquare(event->pos());
          const int found = findPiece(square);

          if (found == -1)
              return;

          Piece piece = pieces.takeAt(found);

          if (piece.location == square.topLeft() / pieceSize())
              inPlace--;

          update(square);

          QByteArray itemData;
          QDataStream dataStream(&itemData, QIODevice::WriteOnly);

          dataStream << piece.pixmap << piece.location;

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

          QDrag *drag = new QDrag(this);
          drag->setMimeData(mimeData);
          drag->setHotSpot(event->pos() - square.topLeft());
          drag->setPixmap(piece.pixmap);

          if (drag->exec(Qt::MoveAction) != Qt::MoveAction) {
              pieces.insert(found, piece);
              update(targetSquare(event->pos()));

              if (piece.location == square.topLeft() / pieceSize())
                  inPlace++;
          }
      }

      void PuzzleWidget::paintEvent(QPaintEvent *event)
      {
          QPainter painter(this);
          painter.fillRect(event->rect(), Qt::white);

          if (highlightedRect.isValid()) {
              painter.setBrush(QColor("#ffcccc"));
              painter.setPen(Qt::NoPen);
              painter.drawRect(highlightedRect.adjusted(0, 0, -1, -1));
          }

          for (const Piece &piece : pieces)
              painter.drawPixmap(piece.rect, piece.pixmap);
      }

      const QRect PuzzleWidget::targetSquare(const QPoint &position) const
      {
          return QRect(position / pieceSize() * pieceSize(),
                       QSize(pieceSize(), pieceSize()));
      }

      int PuzzleWidget::pieceSize() const
      {
          return m_ImageSize / 5;
      }

      int PuzzleWidget::imageSize() const
      {
          return m_ImageSize;
      }