puzzlewidget.cpp Example File

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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;
 }