Revamp QtWidgets/DragAndDrop examples to C++11

Introduce nullptr and replace foreach with new C++11 range based for
loops. Minor fixups of signals, file dialog usage.

Apply the same changes to the ItemViews/puzzle example since it
shares parts of the code with DragAndDrop/puzzle. Make some
changes to both examples to that the diff of the two becomes
small for easier comparison.

Task-number: QTBUG-60635
Change-Id: I8af824229ebac24d6ec151eae92176d227695490
Reviewed-by: Venugopal Shivashankar <Venugopal.Shivashankar@qt.io>
Reviewed-by: Gatis Paeglis <gatis.paeglis@qt.io>

examples/widgets/draganddrop/draggableicons/dragwidget.h

@@ -62,7 +62,7 @@ QT_END_NAMESPACE
 class DragWidget : public QFrame
 {
 public:
-    DragWidget(QWidget *parent = 0);
+    explicit DragWidget(QWidget *parent = nullptr);
 
 protected:
     void dragEnterEvent(QDragEnterEvent *event) override;

examples/widgets/draganddrop/draggabletext/dragwidget.cpp

@@ -123,7 +123,7 @@ void DragWidget::dropEvent(QDropEvent *event)
             hotSpot.setY(hotSpotPos.last().toInt());
         }
 
-        foreach (const QString &piece, pieces) {
+        for (const QString &piece : pieces) {
             QLabel *newLabel = createDragLabel(piece, this);
             newLabel->move(position - hotSpot);
             newLabel->show();
@@ -141,7 +141,7 @@ void DragWidget::dropEvent(QDropEvent *event)
     } else {
         event->ignore();
     }
-    foreach (QWidget *widget, findChildren<QWidget *>()) {
+    for (QWidget *widget : findChildren<QWidget *>()) {
         if (!widget->isVisible())
             widget->deleteLater();
     }

examples/widgets/draganddrop/draggabletext/dragwidget.h

@@ -61,7 +61,7 @@ QT_END_NAMESPACE
 class DragWidget : public QWidget
 {
 public:
-    DragWidget(QWidget *parent = 0);
+    explicit DragWidget(QWidget *parent = nullptr);
 
 protected:
     void dragEnterEvent(QDragEnterEvent *event) override;

examples/widgets/draganddrop/dropsite/droparea.h

@@ -63,13 +63,13 @@ class DropArea : public QLabel
     Q_OBJECT
 
 public:
-    DropArea(QWidget *parent = 0);
+    explicit DropArea(QWidget *parent = nullptr);
 
 public slots:
     void clear();
 
 signals:
-    void changed(const QMimeData *mimeData = 0);
+    void changed(const QMimeData *mimeData = nullptr);
 //! [DropArea header part1]
 
 //! [DropArea header part2]

examples/widgets/draganddrop/dropsite/dropsitewindow.cpp

@@ -88,8 +88,8 @@ DropSiteWindow::DropSiteWindow()
     buttonBox->addButton(clearButton, QDialogButtonBox::ActionRole);
     buttonBox->addButton(quitButton, QDialogButtonBox::RejectRole);
 
-    connect(quitButton, &QAbstractButton::pressed, this, &QWidget::close);
+    connect(quitButton, &QAbstractButton::clicked, this, &QWidget::close);
-    connect(clearButton, &QAbstractButton::pressed, dropArea, &DropArea::clear);
+    connect(clearButton, &QAbstractButton::clicked, dropArea, &DropArea::clear);
 //! [constructor part4]
 
 //! [constructor part5]
@@ -113,7 +113,7 @@ void DropSiteWindow::updateFormatsTable(const QMimeData *mimeData)
 //! [updateFormatsTable() part1]
 
 //! [updateFormatsTable() part2]
-    foreach (QString format, mimeData->formats()) {
+    for (const QString &format : mimeData->formats()) {
         QTableWidgetItem *formatItem = new QTableWidgetItem(format);
         formatItem->setFlags(Qt::ItemIsEnabled);
         formatItem->setTextAlignment(Qt::AlignTop | Qt::AlignLeft);

examples/widgets/draganddrop/fridgemagnets/dragwidget.cpp

@@ -167,7 +167,7 @@ void DragWidget::dropEvent(QDropEvent *event)
                              QString::SkipEmptyParts);
         QPoint position = event->pos();
 
-        foreach (const QString &piece, pieces) {
+        for (const QString &piece : pieces) {
             DragLabel *newLabel = new DragLabel(piece, this);
             newLabel->move(position);
             newLabel->show();

examples/widgets/draganddrop/fridgemagnets/dragwidget.h

@@ -62,7 +62,7 @@ QT_END_NAMESPACE
 class DragWidget : public QWidget
 {
 public:
-    DragWidget(QWidget *parent = 0);
+    explicit DragWidget(QWidget *parent = nullptr);
 
 protected:
     void dragEnterEvent(QDragEnterEvent *event) override;

examples/widgets/draganddrop/puzzle/main.cpp

@@ -48,10 +48,10 @@
 **
 ****************************************************************************/
 
-#include <QApplication>
-
 #include "mainwindow.h"
 
+#include <QApplication>
+
 int main(int argc, char *argv[])
 {
     Q_INIT_RESOURCE(puzzle);

examples/widgets/draganddrop/puzzle/mainwindow.cpp

@@ -67,12 +67,19 @@ MainWindow::MainWindow(QWidget *parent)
 
 void MainWindow::openImage()
 {
-    const QString fileName =
+    const QString directory =
-        QFileDialog::getOpenFileName(this, tr("Open Image"), QString(),
+        QStandardPaths::standardLocations(QStandardPaths::PicturesLocation).value(0, QDir::homePath());
-                                     tr("Image Files (*.png *.jpg *.bmp)"));
+    QFileDialog dialog(this, tr("Open Image"), directory);
-
+    dialog.setAcceptMode(QFileDialog::AcceptOpen);
-    if (!fileName.isEmpty())
+    dialog.setFileMode(QFileDialog::ExistingFile);
-        loadImage(fileName);
+    QStringList mimeTypeFilters;
+    for (const QByteArray &mimeTypeName : QImageReader::supportedMimeTypes())
+        mimeTypeFilters.append(mimeTypeName);
+    mimeTypeFilters.sort();
+    dialog.setMimeTypeFilters(mimeTypeFilters);
+    dialog.selectMimeTypeFilter("image/jpeg");
+    if (dialog.exec() == QDialog::Accepted)
+        loadImage(dialog.selectedFiles().constFirst());
 }
 
 void MainWindow::loadImage(const QString &fileName)
@@ -101,8 +108,8 @@ void MainWindow::setCompleted()
 void MainWindow::setupPuzzle()
 {
     int size = qMin(puzzleImage.width(), puzzleImage.height());
-    puzzleImage = puzzleImage.copy((puzzleImage.width() - size)/2,
+    puzzleImage = puzzleImage.copy((puzzleImage.width() - size) / 2,
-        (puzzleImage.height() - size)/2, size, size).scaled(puzzleWidget->width(),
+        (puzzleImage.height() - size) / 2, size, size).scaled(puzzleWidget->width(),
             puzzleWidget->height(), Qt::IgnoreAspectRatio, Qt::SmoothTransformation);
 
     piecesList->clear();

examples/widgets/draganddrop/puzzle/mainwindow.h

@@ -51,8 +51,8 @@
 #ifndef MAINWINDOW_H
 #define MAINWINDOW_H
 
-#include <QPixmap>
 #include <QMainWindow>
+#include <QPixmap>
 
 class PiecesList;
 class PuzzleWidget;
@@ -65,7 +65,7 @@ class MainWindow : public QMainWindow
     Q_OBJECT
 
 public:
-    MainWindow(QWidget *parent = 0);
+    explicit MainWindow(QWidget *parent = nullptr);
     void loadImage(const QString &path);
 
 public slots:

examples/widgets/draganddrop/puzzle/pieceslist.cpp

@@ -101,7 +101,7 @@ void PiecesList::dropEvent(QDropEvent *event)
     }
 }
 
-void PiecesList::addPiece(QPixmap pixmap, QPoint location)
+void PiecesList::addPiece(const QPixmap &pixmap, const QPoint &location)
 {
     QListWidgetItem *pieceItem = new QListWidgetItem(this);
     pieceItem->setIcon(QIcon(pixmap));

examples/widgets/draganddrop/puzzle/pieceslist.h

@@ -58,8 +58,8 @@ class PiecesList : public QListWidget
     Q_OBJECT
 
 public:
-    explicit PiecesList(int pieceSize, QWidget *parent = 0);
+    explicit PiecesList(int pieceSize, QWidget *parent = nullptr);
-    void addPiece(QPixmap pixmap, QPoint location);
+    void addPiece(const QPixmap &pixmap, const QPoint &location);
 
     static QString puzzleMimeType() { return QStringLiteral("image/x-puzzle-piece"); }
 

examples/widgets/draganddrop/puzzle/puzzlewidget.cpp

@@ -66,9 +66,7 @@ PuzzleWidget::PuzzleWidget(int imageSize, QWidget *parent)
 
 void PuzzleWidget::clear()
 {
-    pieceLocations.clear();
+    pieces.clear();
-    piecePixmaps.clear();
-    pieceRects.clear();
     highlightedRect = QRect();
     inPlace = 0;
     update();
@@ -95,7 +93,7 @@ void PuzzleWidget::dragMoveEvent(QDragMoveEvent *event)
     QRect updateRect = highlightedRect.united(targetSquare(event->pos()));
 
     if (event->mimeData()->hasFormat(PiecesList::puzzleMimeType())
-        && pieceRects.indexOf(targetSquare(event->pos())) == -1) {
+        && findPiece(targetSquare(event->pos())) == -1) {
 
         highlightedRect = targetSquare(event->pos());
         event->setDropAction(Qt::MoveAction);
@@ -111,26 +109,23 @@ void PuzzleWidget::dragMoveEvent(QDragMoveEvent *event)
 void PuzzleWidget::dropEvent(QDropEvent *event)
 {
     if (event->mimeData()->hasFormat(PiecesList::puzzleMimeType())
-        && pieceRects.indexOf(targetSquare(event->pos())) == -1) {
+        && findPiece(targetSquare(event->pos())) == -1) {
 
         QByteArray pieceData = event->mimeData()->data(PiecesList::puzzleMimeType());
         QDataStream dataStream(&pieceData, QIODevice::ReadOnly);
-        QRect square = targetSquare(event->pos());
+        Piece piece;
-        QPixmap pixmap;
+        piece.rect = targetSquare(event->pos());
-        QPoint location;
+        dataStream >> piece.pixmap >> piece.location;
-        dataStream >> pixmap >> location;
 
-        pieceLocations.append(location);
+        pieces.append(piece);
-        piecePixmaps.append(pixmap);
-        pieceRects.append(square);
 
         highlightedRect = QRect();
-        update(square);
+        update(piece.rect);
 
         event->setDropAction(Qt::MoveAction);
         event->accept();
 
-        if (location == QPoint(square.x()/pieceSize(), square.y()/pieceSize())) {
+        if (piece.location == piece.rect.topLeft() / pieceSize()) {
             inPlace++;
             if (inPlace == 25)
                 emit puzzleCompleted();
@@ -141,21 +136,26 @@ void PuzzleWidget::dropEvent(QDropEvent *event)
     }
 }
 
+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());
-    int found = pieceRects.indexOf(square);
+    const int found = findPiece(square);
 
     if (found == -1)
         return;
 
-    QPoint location = pieceLocations[found];
+    Piece piece = pieces.takeAt(found);
-    QPixmap pixmap = piecePixmaps[found];
-    pieceLocations.removeAt(found);
-    piecePixmaps.removeAt(found);
-    pieceRects.removeAt(found);
 
-    if (location == QPoint(square.x()/pieceSize(), square.y()/pieceSize()))
+    if (piece.location == square.topLeft() / pieceSize())
         inPlace--;
 
     update(square);
@@ -163,7 +163,7 @@ void PuzzleWidget::mousePressEvent(QMouseEvent *event)
     QByteArray itemData;
     QDataStream dataStream(&itemData, QIODevice::WriteOnly);
 
-    dataStream << pixmap << location;
+    dataStream << piece.pixmap << piece.location;
 
     QMimeData *mimeData = new QMimeData;
     mimeData->setData(PiecesList::puzzleMimeType(), itemData);
@@ -171,23 +171,20 @@ void PuzzleWidget::mousePressEvent(QMouseEvent *event)
     QDrag *drag = new QDrag(this);
     drag->setMimeData(mimeData);
     drag->setHotSpot(event->pos() - square.topLeft());
-    drag->setPixmap(pixmap);
+    drag->setPixmap(piece.pixmap);
 
-    if (!(drag->exec(Qt::MoveAction) == Qt::MoveAction)) {
+    if (drag->exec(Qt::MoveAction) != Qt::MoveAction) {
-        pieceLocations.insert(found, location);
+        pieces.insert(found, piece);
-        piecePixmaps.insert(found, pixmap);
-        pieceRects.insert(found, square);
         update(targetSquare(event->pos()));
 
-        if (location == QPoint(square.x()/pieceSize(), square.y()/pieceSize()))
+        if (piece.location == square.topLeft() / pieceSize())
             inPlace++;
     }
 }
 
 void PuzzleWidget::paintEvent(QPaintEvent *event)
 {
-    QPainter painter;
+    QPainter painter(this);
-    painter.begin(this);
     painter.fillRect(event->rect(), Qt::white);
 
     if (highlightedRect.isValid()) {
@@ -196,14 +193,14 @@ void PuzzleWidget::paintEvent(QPaintEvent *event)
         painter.drawRect(highlightedRect.adjusted(0, 0, -1, -1));
     }
 
-    for (int i = 0; i < pieceRects.size(); ++i)
+    for (const Piece &piece : pieces)
-        painter.drawPixmap(pieceRects[i], piecePixmaps[i]);
+        painter.drawPixmap(piece.rect, piece.pixmap);
-    painter.end();
 }
 
 const QRect PuzzleWidget::targetSquare(const QPoint &position) const
 {
-    return QRect(position.x()/pieceSize() * pieceSize(), position.y()/pieceSize() * pieceSize(), pieceSize(), pieceSize());
+    return QRect(position / pieceSize() * pieceSize(),
+                 QSize(pieceSize(), pieceSize()));
 }
 
 int PuzzleWidget::pieceSize() const

examples/widgets/draganddrop/puzzle/puzzlewidget.h

@@ -51,9 +51,9 @@
 #ifndef PUZZLEWIDGET_H
 #define PUZZLEWIDGET_H
 
-#include <QList>
 #include <QPoint>
 #include <QPixmap>
+#include <QVector>
 #include <QWidget>
 
 QT_BEGIN_NAMESPACE
@@ -67,7 +67,7 @@ class PuzzleWidget : public QWidget
     Q_OBJECT
 
 public:
-    explicit PuzzleWidget(int imageSize, QWidget *parent = 0);
+    explicit PuzzleWidget(int imageSize, QWidget *parent = nullptr);
     void clear();
 
     int pieceSize() const;
@@ -85,11 +85,16 @@ protected:
     void paintEvent(QPaintEvent *event) override;
 
 private:
+    struct Piece {
+        QPixmap pixmap;
+        QRect rect;
+        QPoint location;
+    };
+
+    int findPiece(const QRect &pieceRect) const;
     const QRect targetSquare(const QPoint &position) const;
 
-    QList<QPixmap> piecePixmaps;
+    QVector<Piece> pieces;
-    QList<QRect> pieceRects;
-    QList<QPoint> pieceLocations;
     QRect highlightedRect;
     int inPlace;
     int m_ImageSize;

examples/widgets/itemviews/puzzle/main.cpp

@@ -58,7 +58,7 @@ int main(int argc, char *argv[])
 
     QApplication app(argc, argv);
     MainWindow window;
-    window.loadImage(":/images/example.jpg");
+    window.loadImage(QStringLiteral(":/images/example.jpg"));
     window.show();
     return app.exec();
 }

examples/widgets/itemviews/puzzle/mainwindow.cpp

@@ -69,12 +69,19 @@ MainWindow::MainWindow(QWidget *parent)
 
 void MainWindow::openImage()
 {
-    const QString fileName =
+    const QString directory =
-        QFileDialog::getOpenFileName(this,
+        QStandardPaths::standardLocations(QStandardPaths::PicturesLocation).value(0, QDir::homePath());
-                                     tr("Open Image"), QString(),
+    QFileDialog dialog(this, tr("Open Image"), directory);
-                                     tr("Image Files (*.png *.jpg *.bmp)"));
+    dialog.setAcceptMode(QFileDialog::AcceptOpen);
-    if (!fileName.isEmpty())
+    dialog.setFileMode(QFileDialog::ExistingFile);
-        loadImage(fileName);
+    QStringList mimeTypeFilters;
+    for (const QByteArray &mimeTypeName : QImageReader::supportedMimeTypes())
+        mimeTypeFilters.append(mimeTypeName);
+    mimeTypeFilters.sort();
+    dialog.setMimeTypeFilters(mimeTypeFilters);
+    dialog.selectMimeTypeFilter("image/jpeg");
+    if (dialog.exec() == QDialog::Accepted)
+        loadImage(dialog.selectedFiles().constFirst());
 }
 
 void MainWindow::loadImage(const QString &fileName)
@@ -83,7 +90,7 @@ void MainWindow::loadImage(const QString &fileName)
     if (!newImage.load(fileName)) {
         QMessageBox::warning(this, tr("Open Image"),
                              tr("The image file could not be loaded."),
-                             QMessageBox::Cancel);
+                             QMessageBox::Close);
         return;
     }
     puzzleImage = newImage;
@@ -117,19 +124,15 @@ void MainWindow::setupMenus()
 {
     QMenu *fileMenu = menuBar()->addMenu(tr("&File"));
 
-    QAction *openAction = fileMenu->addAction(tr("&Open..."));
+    QAction *openAction = fileMenu->addAction(tr("&Open..."), this, &MainWindow::openImage);
     openAction->setShortcuts(QKeySequence::Open);
 
-    QAction *exitAction = fileMenu->addAction(tr("E&xit"));
+    QAction *exitAction = fileMenu->addAction(tr("E&xit"), qApp, &QCoreApplication::quit);
     exitAction->setShortcuts(QKeySequence::Quit);
 
     QMenu *gameMenu = menuBar()->addMenu(tr("&Game"));
 
-    QAction *restartAction = gameMenu->addAction(tr("&Restart"));
+    gameMenu->addAction(tr("&Restart"), this, &MainWindow::setupPuzzle);
-
-    connect(openAction, &QAction::triggered, this, &MainWindow::openImage);
-    connect(exitAction, &QAction::triggered, qApp, &QCoreApplication::quit);
-    connect(restartAction, &QAction::triggered, this, &MainWindow::setupPuzzle);
 }
 
 void MainWindow::setupWidgets()

examples/widgets/itemviews/puzzle/mainwindow.h

@@ -65,7 +65,7 @@ class MainWindow : public QMainWindow
     Q_OBJECT
 
 public:
-    MainWindow(QWidget *parent = 0);
+    explicit MainWindow(QWidget *parent = nullptr);
 
 public slots:
     void openImage();

examples/widgets/itemviews/puzzle/puzzlewidget.cpp

@@ -62,9 +62,7 @@ PuzzleWidget::PuzzleWidget(int imageSize, QWidget *parent)
 
 void PuzzleWidget::clear()
 {
-    pieceLocations.clear();
+    pieces.clear();
-    piecePixmaps.clear();
-    pieceRects.clear();
     highlightedRect = QRect();
     inPlace = 0;
     update();
@@ -110,23 +108,20 @@ void PuzzleWidget::dropEvent(QDropEvent *event)
         && findPiece(targetSquare(event->pos())) == -1) {
 
         QByteArray pieceData = event->mimeData()->data("image/x-puzzle-piece");
-        QDataStream stream(&pieceData, QIODevice::ReadOnly);
+        QDataStream dataStream(&pieceData, QIODevice::ReadOnly);
-        QRect square = targetSquare(event->pos());
+        Piece piece;
-        QPixmap pixmap;
+        piece.rect = targetSquare(event->pos());
-        QPoint location;
+        dataStream >> piece.pixmap >> piece.location;
-        stream >> pixmap >> location;
 
-        pieceLocations.append(location);
+        pieces.append(piece);
-        piecePixmaps.append(pixmap);
-        pieceRects.append(square);
 
         highlightedRect = QRect();
-        update(square);
+        update(piece.rect);
 
         event->setDropAction(Qt::MoveAction);
         event->accept();
 
-        if (location == QPoint(square.x()/pieceSize(), square.y()/pieceSize())) {
+        if (piece.location == piece.rect.topLeft() / pieceSize()) {
             inPlace++;
             if (inPlace == 25)
                 emit puzzleCompleted();
@@ -139,8 +134,8 @@ void PuzzleWidget::dropEvent(QDropEvent *event)
 
 int PuzzleWidget::findPiece(const QRect &pieceRect) const
 {
-    for (int i = 0; i < pieceRects.size(); ++i) {
+    for (int i = 0, size = pieces.size(); i < size; ++i) {
-        if (pieceRect == pieceRects[i])
+        if (pieces.at(i).rect == pieceRect)
             return i;
     }
     return -1;
@@ -154,13 +149,9 @@ void PuzzleWidget::mousePressEvent(QMouseEvent *event)
     if (found == -1)
         return;
 
-    QPoint location = pieceLocations[found];
+    Piece piece = pieces.takeAt(found);
-    QPixmap pixmap = piecePixmaps[found];
-    pieceLocations.removeAt(found);
-    piecePixmaps.removeAt(found);
-    pieceRects.removeAt(found);
 
-    if (location == QPoint(square.x()/pieceSize(), square.y()/pieceSize()))
+    if (piece.location == square.topLeft() / pieceSize())
         inPlace--;
 
     update(square);
@@ -168,7 +159,7 @@ void PuzzleWidget::mousePressEvent(QMouseEvent *event)
     QByteArray itemData;
     QDataStream dataStream(&itemData, QIODevice::WriteOnly);
 
-    dataStream << pixmap << location;
+    dataStream << piece.pixmap << piece.location;
 
     QMimeData *mimeData = new QMimeData;
     mimeData->setData("image/x-puzzle-piece", itemData);
@@ -176,23 +167,20 @@ void PuzzleWidget::mousePressEvent(QMouseEvent *event)
     QDrag *drag = new QDrag(this);
     drag->setMimeData(mimeData);
     drag->setHotSpot(event->pos() - square.topLeft());
-    drag->setPixmap(pixmap);
+    drag->setPixmap(piece.pixmap);
 
-    if (drag->start(Qt::MoveAction) == 0) {
+    if (drag->start(Qt::MoveAction) == Qt::IgnoreAction) {
-        pieceLocations.insert(found, location);
+        pieces.insert(found, piece);
-        piecePixmaps.insert(found, pixmap);
-        pieceRects.insert(found, square);
         update(targetSquare(event->pos()));
 
-        if (location == QPoint(square.x()/pieceSize(), square.y()/pieceSize()))
+        if (piece.location == QPoint(square.x() / pieceSize(), square.y() / pieceSize()))
             inPlace++;
     }
 }
 
 void PuzzleWidget::paintEvent(QPaintEvent *event)
 {
-    QPainter painter;
+    QPainter painter(this);
-    painter.begin(this);
     painter.fillRect(event->rect(), Qt::white);
 
     if (highlightedRect.isValid()) {
@@ -201,15 +189,14 @@ void PuzzleWidget::paintEvent(QPaintEvent *event)
         painter.drawRect(highlightedRect.adjusted(0, 0, -1, -1));
     }
 
-    for (int i = 0; i < pieceRects.size(); ++i) {
+    for (const Piece &piece : pieces)
-        painter.drawPixmap(pieceRects[i], piecePixmaps[i]);
+        painter.drawPixmap(piece.rect, piece.pixmap);
-    }
-    painter.end();
 }
 
 const QRect PuzzleWidget::targetSquare(const QPoint &position) const
 {
-    return QRect(position.x()/pieceSize() * pieceSize(), position.y()/pieceSize() * pieceSize(), pieceSize(), pieceSize());
+    return QRect(position / pieceSize() * pieceSize(),
+                 QSize(pieceSize(), pieceSize()));
 }
 
 int PuzzleWidget::pieceSize() const

examples/widgets/itemviews/puzzle/puzzlewidget.h

@@ -51,9 +51,9 @@
 #ifndef PUZZLEWIDGET_H
 #define PUZZLEWIDGET_H
 
-#include <QList>
-#include <QPixmap>
 #include <QPoint>
+#include <QPixmap>
+#include <QVector>
 #include <QWidget>
 
 QT_BEGIN_NAMESPACE
@@ -67,7 +67,7 @@ class PuzzleWidget : public QWidget
     Q_OBJECT
 
 public:
-    explicit PuzzleWidget(int imageSize, QWidget *parent = 0);
+    explicit PuzzleWidget(int imageSize, QWidget *parent = nullptr);
     void clear();
 
     int pieceSize() const;
@@ -85,12 +85,16 @@ protected:
     void paintEvent(QPaintEvent *event) override;
 
 private:
+    struct Piece {
+        QPixmap pixmap;
+        QRect rect;
+        QPoint location;
+    };
+
     int findPiece(const QRect &pieceRect) const;
     const QRect targetSquare(const QPoint &position) const;
 
-    QList<QPixmap> piecePixmaps;
+    QVector<Piece> pieces;
-    QList<QRect> pieceRects;
-    QList<QPoint> pieceLocations;
     QRect highlightedRect;
     int inPlace;
     int m_ImageSize;