QtWidgets: replace some index-based for loops with C++11 range-for

This needs to be handled a bit carefully, because Qt containers
will detach upon being iteratoed over using range-for.

In the cases of this patch, that cannot happen, because all
containers are marked as const (either by this patch or before).

Separate patches will deal with other situations.

Apart from being more readable, range-for loops are also the
most efficient for loop.

This patch shaves almost 2K of text size off an optimized Linux
AMD64 GCC 4.9 build.

Change-Id: I53810c7b25420b4fd449d20c90c07503c5e76a66
Reviewed-by: Edward Welbourne <edward.welbourne@theqtcompany.com>
Reviewed-by: Lars Knoll <lars.knoll@theqtcompany.com>

src/widgets/accessible/qaccessiblewidget.cpp

@@ -53,10 +53,9 @@ QT_BEGIN_NAMESPACE
 
 static QList<QWidget*> childWidgets(const QWidget *widget)
 {
-    QList<QObject*> list = widget->children();
     QList<QWidget*> widgets;
-    for (int i = 0; i < list.size(); ++i) {
+    for (QObject *o : widget->children()) {
-        QWidget *w = qobject_cast<QWidget *>(list.at(i));
+        QWidget *w = qobject_cast<QWidget *>(o);
         if (w && !w->isWindow()
             && !qobject_cast<QFocusFrame*>(w)
 #if !defined(QT_NO_MENU)
@@ -77,9 +76,8 @@ static QString buddyString(const QWidget *widget)
     if (!parent)
         return QString();
 #ifndef QT_NO_SHORTCUT
-    QObjectList ol = parent->children();
+    for (QObject *o : parent->children()) {
-    for (int i = 0; i < ol.size(); ++i) {
+        QLabel *label = qobject_cast<QLabel*>(o);
-        QLabel *label = qobject_cast<QLabel*>(ol.at(i));
         if (label && label->buddy() == widget)
             return label->text();
     }
@@ -302,8 +300,8 @@ QAccessibleWidget::relations(QAccessible::Relation match /*= QAccessible::AllRel
             // ideally we would go through all objects and check, but that
             // will be too expensive
             const QList<QWidget*> kids = childWidgets(parent);
-            for (int i = 0; i < kids.count(); ++i) {
+            for (QWidget *kid : kids) {
-                if (QLabel *labelSibling = qobject_cast<QLabel*>(kids.at(i))) {
+                if (QLabel *labelSibling = qobject_cast<QLabel*>(kid)) {
                     if (labelSibling->buddy() == widget()) {
                         QAccessibleInterface *iface = QAccessible::queryAccessibleInterface(labelSibling);
                         rels.append(qMakePair(iface, rel));

src/widgets/accessible/qaccessiblewidgets.cpp

@@ -71,10 +71,9 @@ QList<QWidget*> childWidgets(const QWidget *widget)
 {
     if (widget == 0)
         return QList<QWidget*>();
-    QList<QObject*> list = widget->children();
     QList<QWidget*> widgets;
-    for (int i = 0; i < list.size(); ++i) {
+    for (QObject *o : widget->children()) {
-        QWidget *w = qobject_cast<QWidget *>(list.at(i));
+        QWidget *w = qobject_cast<QWidget *>(o);
         if (!w)
             continue;
         QString objectName = w->objectName();
@@ -1056,10 +1055,9 @@ QAccessibleInterface *QAccessibleMainWindow::childAt(int x, int y) const
     if (!QRect(gp.x(), gp.y(), w->width(), w->height()).contains(x, y))
         return 0;
 
-    QWidgetList kids = childWidgets(mainWindow());
+    const QWidgetList kids = childWidgets(mainWindow());
     QPoint rp = mainWindow()->mapFromGlobal(QPoint(x, y));
-    for (int i = 0; i < kids.size(); ++i) {
+    for (QWidget *child : kids) {
-        QWidget *child = kids.at(i);
         if (!child->isWindow() && !child->isHidden() && child->geometry().contains(rp)) {
             return QAccessible::queryAccessibleInterface(child);
         }

src/widgets/accessible/simplewidgets.cpp

@@ -570,8 +570,8 @@ QAccessibleGroupBox::relations(QAccessible::Relation match /* = QAccessible::All
 
     if ((match & QAccessible::Labelled) && (!groupBox()->title().isEmpty())) {
         const QList<QWidget*> kids = childWidgets(widget());
-        for (int i = 0; i < kids.count(); ++i) {
+        for (QWidget *kid : kids) {
-            QAccessibleInterface *iface = QAccessible::queryAccessibleInterface(kids.at(i));
+            QAccessibleInterface *iface = QAccessible::queryAccessibleInterface(kid);
             if (iface)
                 rels.append(qMakePair(iface, QAccessible::Relation(QAccessible::Labelled)));
         }

src/widgets/dialogs/qfiledialog.cpp

@@ -2587,7 +2587,7 @@ void QFileDialog::accept()
         return;
     }
 
-    QStringList files = selectedFiles();
+    const QStringList files = selectedFiles();
     if (files.isEmpty())
         return;
     QString lineEditText = d->lineEdit()->text();
@@ -2657,10 +2657,10 @@ void QFileDialog::accept()
 
     case ExistingFile:
     case ExistingFiles:
-        for (int i = 0; i < files.count(); ++i) {
+        for (const auto &file : files) {
-            QFileInfo info(files.at(i));
+            QFileInfo info(file);
             if (!info.exists())
-                info = QFileInfo(d->getEnvironmentVariable(files.at(i)));
+                info = QFileInfo(d->getEnvironmentVariable(file));
             if (!info.exists()) {
 #ifndef QT_NO_MESSAGEBOX
                 QString message = tr("%1\nFile not found.\nPlease verify the "
@@ -3444,15 +3444,13 @@ void QFileDialogPrivate::_q_autoCompleteFileName(const QString &text)
         return;
     }
 
-    QStringList multipleFiles = typedFiles();
+    const QStringList multipleFiles = typedFiles();
     if (multipleFiles.count() > 0) {
         QModelIndexList oldFiles = qFileDialogUi->listView->selectionModel()->selectedRows();
         QModelIndexList newFiles;
-        for (int i = 0; i < multipleFiles.count(); ++i) {
+        for (const auto &file : multipleFiles) {
-            QModelIndex idx = model->index(multipleFiles.at(i));
+            QModelIndex idx = model->index(file);
-            if (oldFiles.contains(idx))
+            if (oldFiles.removeAll(idx) == 0)
-                oldFiles.removeAll(idx);
-            else
                 newFiles.append(idx);
         }
         for (int i = 0; i < newFiles.count(); ++i)
@@ -3479,7 +3477,7 @@ void QFileDialogPrivate::_q_updateOkButton()
     bool enableButton = true;
     bool isOpenDirectory = false;
 
-    QStringList files = q->selectedFiles();
+    const QStringList files = q->selectedFiles();
     QString lineEditText = lineEdit()->text();
 
     if (lineEditText.startsWith(QLatin1String("//")) || lineEditText.startsWith(QLatin1Char('\\'))) {
@@ -3538,10 +3536,10 @@ void QFileDialogPrivate::_q_updateOkButton()
         }
         case QFileDialog::ExistingFile:
         case QFileDialog::ExistingFiles:
-            for (int i = 0; i < files.count(); ++i) {
+            for (const auto &file : files) {
-                QModelIndex idx = model->index(files.at(i));
+                QModelIndex idx = model->index(file);
                 if (!idx.isValid())
-                    idx = model->index(getEnvironmentVariable(files.at(i)));
+                    idx = model->index(getEnvironmentVariable(file));
                 if (!idx.isValid()) {
                     enableButton = false;
                     break;
@@ -3682,14 +3680,14 @@ void QFileDialogPrivate::_q_useNameFilter(int index)
 void QFileDialogPrivate::_q_selectionChanged()
 {
     const QFileDialog::FileMode fileMode = q_func()->fileMode();
-    QModelIndexList indexes = qFileDialogUi->listView->selectionModel()->selectedRows();
+    const QModelIndexList indexes = qFileDialogUi->listView->selectionModel()->selectedRows();
     bool stripDirs = (fileMode != QFileDialog::DirectoryOnly && fileMode != QFileDialog::Directory);
 
     QStringList allFiles;
-    for (int i = 0; i < indexes.count(); ++i) {
+    for (const auto &index : indexes) {
-        if (stripDirs && model->isDir(mapToSource(indexes.at(i))))
+        if (stripDirs && model->isDir(mapToSource(index)))
             continue;
-        allFiles.append(indexes.at(i).data().toString());
+        allFiles.append(index.data().toString());
     }
     if (allFiles.count() > 1)
         for (int i = 0; i < allFiles.count(); ++i) {

src/widgets/dialogs/qfileinfogatherer.cpp

@@ -282,8 +282,8 @@ void QFileInfoGatherer::getFileInfos(const QString &path, const QStringList &fil
             infoList = QDir::drives();
         } else {
             infoList.reserve(files.count());
-            for (int i = 0; i < files.count(); ++i)
+            for (const auto &file : files)
-                infoList << QFileInfo(files.at(i));
+                infoList << QFileInfo(file);
         }
         for (int i = infoList.count() - 1; i >= 0; --i) {
             QString driveName = translateDriveName(infoList.at(i));

src/widgets/dialogs/qfilesystemmodel.cpp

@@ -1562,10 +1562,9 @@ void QFileSystemModel::setNameFilters(const QStringList &filters)
         d->bypassFilters.clear();
         // We guarantee that rootPath will stick around
         QPersistentModelIndex root(index(rootPath()));
-        QModelIndexList persistantList = persistentIndexList();
+        const QModelIndexList persistentList = persistentIndexList();
-        for (int i = 0; i < persistantList.count(); ++i) {
+        for (const auto &persistentIndex : persistentList) {
-            QFileSystemModelPrivate::QFileSystemNode *node;
+            QFileSystemModelPrivate::QFileSystemNode *node = d->node(persistentIndex);
-            node = d->node(persistantList.at(i));
             while (node) {
                 if (d->bypassFilters.contains(node))
                     break;
@@ -1579,9 +1578,8 @@ void QFileSystemModel::setNameFilters(const QStringList &filters)
     d->nameFilters.clear();
     const Qt::CaseSensitivity caseSensitive =
         (filter() & QDir::CaseSensitive) ? Qt::CaseSensitive : Qt::CaseInsensitive;
-    for (int i = 0; i < filters.size(); ++i) {
+    for (const auto &filter : filters)
-        d->nameFilters << QRegExp(filters.at(i), caseSensitive, QRegExp::Wildcard);
+        d->nameFilters << QRegExp(filter, caseSensitive, QRegExp::Wildcard);
-    }
     d->forceSort = true;
     d->delayedSort();
 #endif
@@ -1734,9 +1732,9 @@ void QFileSystemModelPrivate::addVisibleFiles(QFileSystemNode *parentNode, const
     if (parentNode->dirtyChildrenIndex == -1)
         parentNode->dirtyChildrenIndex = parentNode->visibleChildren.count();
 
-    for (int i = 0; i < newFiles.count(); ++i) {
+    for (const auto &newFile : newFiles) {
-        parentNode->visibleChildren.append(newFiles.at(i));
+        parentNode->visibleChildren.append(newFile);
-        parentNode->children.value(newFiles.at(i))->isVisible = true;
+        parentNode->children.value(newFile)->isVisible = true;
     }
     if (!indexHidden)
       q->endInsertRows();
@@ -1779,10 +1777,10 @@ void QFileSystemModelPrivate::_q_fileSystemChanged(const QString &path, const QV
     QStringList newFiles;
     QFileSystemModelPrivate::QFileSystemNode *parentNode = node(path, false);
     QModelIndex parentIndex = index(parentNode);
-    for (int i = 0; i < updates.count(); ++i) {
+    for (const auto &update : updates) {
-        QString fileName = updates.at(i).first;
+        QString fileName = update.first;
         Q_ASSERT(!fileName.isEmpty());
-        QExtendedInformation info = fileInfoGatherer.getInfo(updates.at(i).second);
+        QExtendedInformation info = fileInfoGatherer.getInfo(update.second);
         bool previouslyHere = parentNode->children.contains(fileName);
         if (!previouslyHere) {
             addNode(parentNode, fileName, info.fileInfo());
@@ -1971,8 +1969,8 @@ bool QFileSystemModelPrivate::passNameFilters(const QFileSystemNode *node) const
 
     // Check the name regularexpression filters
     if (!(node->isDir() && (filters & QDir::AllDirs))) {
-        for (int i = 0; i < nameFilters.size(); ++i) {
+        for (const auto &nameFilter : nameFilters) {
-            QRegExp copy = nameFilters.at(i);
+            QRegExp copy = nameFilter;
             if (copy.exactMatch(node->fileName))
                 return true;
         }

src/widgets/dialogs/qmessagebox.cpp

@@ -1047,26 +1047,26 @@ void QMessageBoxPrivate::detectEscapeButton()
     }
 
     // if the message box has one RejectRole button, make it the escape button
-    for (int i = 0; i < buttons.count(); i++) {
+    for (auto *button : buttons) {
-        if (buttonBox->buttonRole(buttons.at(i)) == QDialogButtonBox::RejectRole) {
+        if (buttonBox->buttonRole(button) == QDialogButtonBox::RejectRole) {
             if (detectedEscapeButton) { // already detected!
                 detectedEscapeButton = 0;
                 break;
             }
-            detectedEscapeButton = buttons.at(i);
+            detectedEscapeButton = button;
         }
     }
     if (detectedEscapeButton)
         return;
 
     // if the message box has one NoRole button, make it the escape button
-    for (int i = 0; i < buttons.count(); i++) {
+    for (auto *button : buttons) {
-        if (buttonBox->buttonRole(buttons.at(i)) == QDialogButtonBox::NoRole) {
+        if (buttonBox->buttonRole(button) == QDialogButtonBox::NoRole) {
             if (detectedEscapeButton) { // already detected!
                 detectedEscapeButton = 0;
                 break;
             }
-            detectedEscapeButton = buttons.at(i);
+            detectedEscapeButton = button;
         }
     }
 }
@@ -1506,8 +1506,7 @@ void QMessageBox::keyPressEvent(QKeyEvent *e)
         int key = e->key() & ~Qt::MODIFIER_MASK;
         if (key) {
             const QList<QAbstractButton *> buttons = d->buttonBox->buttons();
-            for (int i = 0; i < buttons.count(); ++i) {
+            for (auto *pb : buttons) {
-                QAbstractButton *pb = buttons.at(i);
                 QKeySequence shortcut = pb->shortcut();
                 if (!shortcut.isEmpty() && key == int(shortcut[0] & ~Qt::MODIFIER_MASK)) {
                     pb->animateClick();

src/widgets/dialogs/qsidebar.cpp

@@ -103,9 +103,9 @@ Qt::ItemFlags QUrlModel::flags(const QModelIndex &index) const
 QMimeData *QUrlModel::mimeData(const QModelIndexList &indexes) const
 {
     QList<QUrl> list;
-    for (int i = 0; i < indexes.count(); ++i) {
+    for (const auto &index : indexes) {
-        if (indexes.at(i).column() == 0)
+        if (index.column() == 0)
-           list.append(indexes.at(i).data(UrlRole).toUrl());
+           list.append(index.data(UrlRole).toUrl());
     }
     QMimeData *data = new QMimeData();
     data->setUrls(list);
@@ -125,8 +125,8 @@ bool QUrlModel::canDrop(QDragEnterEvent *event)
         return false;
 
     const QList<QUrl> list = event->mimeData()->urls();
-    for (int i = 0; i < list.count(); ++i) {
+    for (const auto &url : list) {
-        QModelIndex idx = fileSystemModel->index(list.at(0).toLocalFile());
+        const QModelIndex idx = fileSystemModel->index(url.toLocalFile());
         if (!fileSystemModel->isDir(idx))
             return false;
     }

src/widgets/dialogs/qwizard.cpp

@@ -3622,9 +3622,8 @@ void QWizardPage::cleanupPage()
 {
     Q_D(QWizardPage);
     if (d->wizard) {
-        QVector<QWizardField> &fields = d->wizard->d_func()->fields;
+        const QVector<QWizardField> &fields = d->wizard->d_func()->fields;
-        for (int i = 0; i < fields.count(); ++i) {
+        for (const auto &field : fields) {
-            const QWizardField &field = fields.at(i);
             if (field.page == this)
                 field.object->setProperty(field.property, field.initialValue);
         }

src/widgets/graphicsview/qgraph_p.h

@@ -222,9 +222,8 @@ public:
         QSet<Vertex *> setOfVertices = vertices();
         for (typename QSet<Vertex*>::const_iterator it = setOfVertices.begin(); it != setOfVertices.end(); ++it) {
             Vertex *v = *it;
-            QList<Vertex*> adjacents = adjacentVertices(v);
+            const QList<Vertex*> adjacents = adjacentVertices(v);
-            for (int i = 0; i < adjacents.count(); ++i) {
+            for (auto *v1 : adjacents) {
-                Vertex *v1 = adjacents.at(i);
                 EdgeData *data = edgeData(v, v1);
                 bool forward = data->from == v;
                 if (forward) {

src/widgets/itemviews/qabstractitemview.cpp

@@ -4351,8 +4351,7 @@ QItemViewPaintPairs QAbstractItemViewPrivate::draggablePaintPairs(const QModelIn
     QRect &rect = *r;
     const QRect viewportRect = viewport->rect();
     QItemViewPaintPairs ret;
-    for (int i = 0; i < indexes.count(); ++i) {
+    for (const auto &index : indexes) {
-        const QModelIndex &index = indexes.at(i);
         const QRect current = q->visualRect(index);
         if (current.intersects(viewportRect)) {
             QItemViewPaintPair p = { current, index };

src/widgets/itemviews/qabstractitemview_p.h

@@ -177,9 +177,10 @@ public:
         // Whether the data can actually be dropped will be checked in drag move.
         if (event->type() == QEvent::DragEnter && (event->dropAction() & model->supportedDropActions())) {
             const QStringList modelTypes = model->mimeTypes();
-            for (int i = 0; i < modelTypes.count(); ++i)
+            for (const auto &modelType : modelTypes) {
-                if (mime->hasFormat(modelTypes.at(i)))
+                if (mime->hasFormat(modelType))
                     return true;
+            }
         }
 
         QModelIndex index;

src/widgets/itemviews/qdirmodel.cpp

@@ -169,8 +169,8 @@ void QDirModelPrivate::invalidate()
         const QDirNode *current = nodes.pop();
         current->stat = false;
         const QVector<QDirNode> &children = current->children;
-        for (int i = 0; i < children.count(); ++i)
+        for (const auto &child : children)
-            nodes.push(&children.at(i));
+            nodes.push(&child);
     }
 }
 

src/widgets/itemviews/qheaderview.cpp

@@ -2958,8 +2958,7 @@ QRegion QHeaderView::visualRegionForSelection(const QItemSelection &selection) c
         int right = 0;
         int rangeLeft, rangeRight;
 
-        for (int i = 0; i < selection.count(); ++i) {
+        for (const auto &r : selection) {
-            QItemSelectionRange r = selection.at(i);
             if (r.parent().isValid() || !r.isValid())
                 continue; // we only know about toplevel items and we don't want invalid ranges
             // FIXME an item inside the range may be the leftmost or rightmost
@@ -2992,8 +2991,7 @@ QRegion QHeaderView::visualRegionForSelection(const QItemSelection &selection) c
     int bottom = 0;
     int rangeTop, rangeBottom;
 
-    for (int i = 0; i < selection.count(); ++i) {
+    for (const auto &r : selection) {
-        QItemSelectionRange r = selection.at(i);
         if (r.parent().isValid() || !r.isValid())
             continue; // we only know about toplevel items
         // FIXME an item inside the range may be the leftmost or rightmost

src/widgets/itemviews/qheaderview_p.h

@@ -327,8 +327,8 @@ public:
 
     inline int headerLength() const { // for debugging
         int len = 0;
-        for (int i = 0; i < sectionItems.count(); ++i)
+        for (const auto &section : sectionItems)
-            len += sectionItems.at(i).size;
+            len += section.size;
         return len;
     }
 

src/widgets/itemviews/qlistview.cpp

@@ -651,8 +651,7 @@ QItemViewPaintPairs QListViewPrivate::draggablePaintPairs(const QModelIndexList
     const QRect viewportRect = viewport->rect();
     QItemViewPaintPairs ret;
     const QSet<QModelIndex> visibleIndexes = intersectingSet(viewportRect.translated(q->horizontalOffset(), q->verticalOffset())).toList().toSet();
-    for (int i = 0; i < indexes.count(); ++i) {
+    for (const auto &index : indexes) {
-        const QModelIndex &index = indexes.at(i);
         if (visibleIndexes.contains(index)) {
             const QRect current = q->visualRect(index);
             QItemViewPaintPair p = { current, index };
@@ -1398,16 +1397,16 @@ QRegion QListView::visualRegionForSelection(const QItemSelection &selection) con
     int c = d->column;
     QRegion selectionRegion;
     const QRect &viewportRect = d->viewport->rect();
-    for (int i = 0; i < selection.count(); ++i) {
+    for (const auto &elem : selection) {
-        if (!selection.at(i).isValid())
+        if (!elem.isValid())
             continue;
-        QModelIndex parent = selection.at(i).topLeft().parent();
+        QModelIndex parent = elem.topLeft().parent();
         //we only display the children of the root in a listview
         //we're not interested in the other model indexes
         if (parent != d->root)
             continue;
-        int t = selection.at(i).topLeft().row();
+        int t = elem.topLeft().row();
-        int b = selection.at(i).bottomRight().row();
+        int b = elem.bottomRight().row();
         if (d->viewMode == IconMode || d->isWrapping()) { // in non-static mode, we have to go through all selected items
             for (int r = t; r <= b; ++r) {
                 const QRect &rect = visualRect(d->model->index(r, c, parent));
@@ -2771,9 +2770,8 @@ bool QIconModeViewBase::filterDropEvent(QDropEvent *e)
     }
     QPoint start = dd->pressedPosition;
     QPoint delta = (dd->movement == QListView::Snap ? snapToGrid(end) - snapToGrid(start) : end - start);
-    QList<QModelIndex> indexes = dd->selectionModel->selectedIndexes();
+    const QList<QModelIndex> indexes = dd->selectionModel->selectedIndexes();
-    for (int i = 0; i < indexes.count(); ++i) {
+    for (const auto &index : indexes) {
-        QModelIndex index = indexes.at(i);
         QRect rect = dd->rectForIndex(index);
         viewport()->update(dd->mapToViewport(rect, false));
         QPoint dest = rect.topLeft() + delta;

src/widgets/itemviews/qtableview.cpp

@@ -1370,9 +1370,6 @@ void QTableView::paintEvent(QPaintEvent *event)
     uint x = horizontalHeader->length() - horizontalHeader->offset() - (rightToLeft ? 0 : 1);
     uint y = verticalHeader->length() - verticalHeader->offset() - 1;
 
-    const QRegion region = event->region().translated(offset);
-    const QVector<QRect> rects = region.rects();
-
     //firstVisualRow is the visual index of the first visible row.  lastVisualRow is the visual index of the last visible Row.
     //same goes for ...VisualColumn
     int firstVisualRow = qMax(verticalHeader->visualIndexAt(0),0);
@@ -1391,13 +1388,15 @@ void QTableView::paintEvent(QPaintEvent *event)
 
     QBitArray drawn((lastVisualRow - firstVisualRow + 1) * (lastVisualColumn - firstVisualColumn + 1));
 
+    const QRegion region = event->region().translated(offset);
+
     if (d->hasSpans()) {
         d->drawAndClipSpans(region, &painter, option, &drawn,
                              firstVisualRow, lastVisualRow, firstVisualColumn, lastVisualColumn);
     }
 
-    for (int i = 0; i < rects.size(); ++i) {
+    const QVector<QRect> rects = region.rects();
-        QRect dirtyArea = rects.at(i);
+    for (auto dirtyArea : rects) {
         dirtyArea.setBottom(qMin(dirtyArea.bottom(), int(y)));
         if (rightToLeft) {
             dirtyArea.setLeft(qMax(dirtyArea.left(), d->viewport->width() - int(x)));
@@ -1952,8 +1951,7 @@ QRegion QTableView::visualRegionForSelection(const QItemSelection &selection) co
     bool horizontalMoved = horizontalHeader()->sectionsMoved();
 
     if ((verticalMoved && horizontalMoved) || (d->hasSpans() && (verticalMoved || horizontalMoved))) {
-        for (int i = 0; i < selection.count(); ++i) {
+        for (const auto &range : selection) {
-            QItemSelectionRange range = selection.at(i);
             if (range.parent() != d->root || !range.isValid())
                 continue;
             for (int r = range.top(); r <= range.bottom(); ++r)
@@ -1964,8 +1962,7 @@ QRegion QTableView::visualRegionForSelection(const QItemSelection &selection) co
                 }
         }
     } else if (horizontalMoved) {
-        for (int i = 0; i < selection.count(); ++i) {
+        for (const auto &range : selection) {
-            QItemSelectionRange range = selection.at(i);
             if (range.parent() != d->root || !range.isValid())
                 continue;
             int top = rowViewportPosition(range.top());
@@ -1980,8 +1977,7 @@ QRegion QTableView::visualRegionForSelection(const QItemSelection &selection) co
             }
         }
     } else if (verticalMoved) {
-        for (int i = 0; i < selection.count(); ++i) {
+        for (const auto &range : selection) {
-            QItemSelectionRange range = selection.at(i);
             if (range.parent() != d->root || !range.isValid())
                 continue;
             int left = columnViewportPosition(range.left());
@@ -1997,8 +1993,7 @@ QRegion QTableView::visualRegionForSelection(const QItemSelection &selection) co
         }
     } else { // nothing moved
         const int gridAdjust = showGrid() ? 1 : 0;
-        for (int i = 0; i < selection.count(); ++i) {
+        for (auto range : selection) {
-            QItemSelectionRange range = selection.at(i);
             if (range.parent() != d->root || !range.isValid())
                 continue;
             d->trimHiddenSelections(&range);

src/widgets/itemviews/qtablewidget.cpp

@@ -1388,9 +1388,10 @@ void QTableWidgetItem::setData(int role, const QVariant &value)
 QVariant QTableWidgetItem::data(int role) const
 {
     role = (role == Qt::EditRole ? Qt::DisplayRole : role);
-    for (int i = 0; i < values.count(); ++i)
+    for (const auto &value : values) {
-        if (values.at(i).role == role)
+        if (value.role == role)
-            return values.at(i).value;
+            return value.value;
+    }
     return QVariant();
 }
 
@@ -2359,10 +2360,9 @@ QList<QTableWidgetSelectionRange> QTableWidget::selectedRanges() const
 QList<QTableWidgetItem*> QTableWidget::selectedItems() const
 {
     Q_D(const QTableWidget);
-    QModelIndexList indexes = selectionModel()->selectedIndexes();
+    const QModelIndexList indexes = selectionModel()->selectedIndexes();
     QList<QTableWidgetItem*> items;
-    for (int i = 0; i < indexes.count(); ++i) {
+    for (const auto &index : indexes) {
-        QModelIndex index = indexes.at(i);
         if (isIndexHidden(index))
             continue;
         QTableWidgetItem *item = d->tableModel()->item(index);
@@ -2682,22 +2682,21 @@ void QTableWidget::dropEvent(QDropEvent *event) {
         int col = -1;
         int row = -1;
         if (d->dropOn(event, &row, &col, &topIndex)) {
-            QModelIndexList indexes = selectedIndexes();
+            const QModelIndexList indexes = selectedIndexes();
             int top = INT_MAX;
             int left = INT_MAX;
-            for (int i = 0; i < indexes.count(); ++i) {
+            for (const auto &index : indexes) {
-                top = qMin(indexes.at(i).row(), top);
+                top = qMin(index.row(), top);
-                left = qMin(indexes.at(i).column(), left);
+                left = qMin(index.column(), left);
             }
 
             QList<QTableWidgetItem *> taken;
             const int indexesCount = indexes.count();
             taken.reserve(indexesCount);
-            for (int i = 0; i < indexesCount; ++i)
+            for (const auto &index : indexes)
-                taken.append(takeItem(indexes.at(i).row(), indexes.at(i).column()));
+                taken.append(takeItem(index.row(), index.column()));
 
-            for (int i = 0; i < indexes.count(); ++i) {
+            for (const auto &index : indexes) {
-                QModelIndex index = indexes.at(i);
                 int r = index.row() - top + topIndex.row();
                 int c = index.column() - left + topIndex.column();
                 setItem(r, c, taken.takeFirst());

src/widgets/itemviews/qtreeview.cpp

@@ -2393,8 +2393,7 @@ QRegion QTreeView::visualRegionForSelection(const QItemSelection &selection) con
 
     QRegion selectionRegion;
     const QRect &viewportRect = d->viewport->rect();
-    for (int i = 0; i < selection.count(); ++i) {
+    for (const auto &range : selection) {
-        QItemSelectionRange range = selection.at(i);
         if (!range.isValid())
             continue;
         QModelIndex parent = range.parent();

src/widgets/itemviews/qtreewidget.cpp

@@ -725,9 +725,9 @@ QMimeData *QTreeModel::internalMimeData()  const
 QMimeData *QTreeModel::mimeData(const QModelIndexList &indexes) const
 {
     QList<QTreeWidgetItem*> items;
-    for (int i = 0; i < indexes.count(); ++i) {
+    for (const auto &index : indexes) {
-        if (indexes.at(i).column() == 0) // only one item per row
+        if (index.column() == 0) // only one item per row
-            items << item(indexes.at(i));
+            items << item(index);
     }
 
     // cachedIndexes is a little hack to avoid copying from QModelIndexList to
@@ -1735,7 +1735,7 @@ void QTreeWidgetItem::setData(int column, int role, const QVariant &value)
     default:
         if (column < values.count()) {
             bool found = false;
-            QVector<QWidgetItemData> column_values = values.at(column);
+            const QVector<QWidgetItemData> column_values = values.at(column);
             for (int i = 0; i < column_values.count(); ++i) {
                 if (column_values.at(i).role == role) {
                     if (column_values.at(i).value == value)
@@ -1785,9 +1785,10 @@ QVariant QTreeWidgetItem::data(int column, int role) const
    default:
         if (column >= 0 && column < values.size()) {
             const QVector<QWidgetItemData> &column_values = values.at(column);
-            for (int i = 0; i < column_values.count(); ++i)
+            for (const auto &column_value : column_values) {
-                if (column_values.at(i).role == role)
+                if (column_value.role == role)
-                    return column_values.at(i).value;
+                    return column_value.value;
+            }
         }
     }
     return QVariant();
@@ -2136,8 +2137,8 @@ QVariant QTreeWidgetItem::childrenCheckState(int column) const
         return QVariant();
     bool checkedChildren = false;
     bool uncheckedChildren = false;
-    for (int i = 0; i < children.count(); ++i) {
+    for (const auto *child : children) {
-        QVariant value = children.at(i)->data(column, Qt::CheckStateRole);
+        QVariant value = child->data(column, Qt::CheckStateRole);
         if (!value.isValid())
             return QVariant();
 
@@ -3018,13 +3019,13 @@ void QTreeWidget::setItemSelected(const QTreeWidgetItem *item, bool select)
 QList<QTreeWidgetItem*> QTreeWidget::selectedItems() const
 {
     Q_D(const QTreeWidget);
-    QModelIndexList indexes = selectionModel()->selectedIndexes();
+    const QModelIndexList indexes = selectionModel()->selectedIndexes();
     QList<QTreeWidgetItem*> items;
     items.reserve(indexes.count());
     QSet<QTreeWidgetItem *> seen;
     seen.reserve(indexes.count());
-    for (int i = 0; i < indexes.count(); ++i) {
+    for (const auto &index : indexes) {
-        QTreeWidgetItem *item = d->item(indexes.at(i));
+        QTreeWidgetItem *item = d->item(index);
         if (isItemHidden(item) || seen.contains(item))
             continue;
         seen.insert(item);
@@ -3278,8 +3279,7 @@ QMimeData *QTreeWidget::mimeData(const QList<QTreeWidgetItem*> items) const
     Q_D(const QTreeWidget);
     if (d->treeModel()->cachedIndexes.isEmpty()) {
         QList<QModelIndex> indexes;
-        for (int i = 0; i < items.count(); ++i) {
+        for (const auto *item : items) {
-            QTreeWidgetItem *item = items.at(i);
             if (Q_UNLIKELY(!item)) {
                 qWarning("QTreeWidget::mimeData: Null-item passed");
                 return 0;
@@ -3382,12 +3382,12 @@ void QTreeWidget::dropEvent(QDropEvent *event) {
         int col = -1;
         int row = -1;
         if (d->dropOn(event, &row, &col, &topIndex)) {
-            QList<QModelIndex> idxs = selectedIndexes();
+            const QList<QModelIndex> idxs = selectedIndexes();
             QList<QPersistentModelIndex> indexes;
             const int indexesCount = idxs.count();
             indexes.reserve(indexesCount);
-            for (int i = 0; i < indexesCount; i++)
+            for (const auto &idx : idxs)
-                indexes.append(idxs.at(i));
+                indexes.append(idx);
 
             if (indexes.contains(topIndex))
                 return;
@@ -3397,12 +3397,12 @@ void QTreeWidget::dropEvent(QDropEvent *event) {
 
             // Remove the items
             QList<QTreeWidgetItem *> taken;
-            for (int i = 0; i < indexes.count(); ++i) {
+            for (const auto &index : indexes) {
-                QTreeWidgetItem *parent = itemFromIndex(indexes.at(i));
+                QTreeWidgetItem *parent = itemFromIndex(index);
                 if (!parent || !parent->parent()) {
-                    taken.append(takeTopLevelItem(indexes.at(i).row()));
+                    taken.append(takeTopLevelItem(index.row()));
                 } else {
-                    taken.append(parent->parent()->takeChild(indexes.at(i).row()));
+                    taken.append(parent->parent()->takeChild(index.row()));
                 }
             }
 

src/widgets/kernel/qapplication.cpp

@@ -1125,9 +1125,9 @@ QStyle *QApplication::style()
         QStyle *&app_style = QApplicationPrivate::app_style;
         app_style = QStyleFactory::create(style);
         if (!app_style) {
-            QStringList styles = QStyleFactory::keys();
+            const QStringList styles = QStyleFactory::keys();
-            for (int i = 0; i < styles.size(); ++i) {
+            for (const auto &style : styles) {
-                if ((app_style = QStyleFactory::create(styles.at(i))))
+                if ((app_style = QStyleFactory::create(style)))
                     break;
             }
         }
@@ -1742,8 +1742,7 @@ void QApplicationPrivate::notifyWindowIconChanged()
     QWindowList windowList = QGuiApplication::topLevelWindows();
 
     // send to all top-level QWidgets
-    for (int i = 0; i < list.size(); ++i) {
+    for (auto *w : list) {
-        QWidget *w = list.at(i);
         windowList.removeOne(w->windowHandle());
         QCoreApplication::sendEvent(w, &ev);
     }
@@ -1906,9 +1905,8 @@ bool QApplicationPrivate::tryCloseAllWidgetWindows(QWindowList *processedWindows
     }
 
 retry:
-    QWidgetList list = QApplication::topLevelWidgets();
+    const QWidgetList list = QApplication::topLevelWidgets();
-    for (int i = 0; i < list.size(); ++i) {
+    for (auto *w : list) {
-        QWidget *w = list.at(i);
         if (w->isVisible() && w->windowType() != Qt::Desktop &&
                 !w->testAttribute(Qt::WA_DontShowOnScreen) && !w->data->is_closing) {
             QWindow *window = w->windowHandle();
@@ -1995,9 +1993,8 @@ bool QApplication::event(QEvent *e)
         ce->accept();
         closeAllWindows();
 
-        QWidgetList list = topLevelWidgets();
+        const QWidgetList list = topLevelWidgets();
-        for (int i = 0; i < list.size(); ++i) {
+        for (auto *w : list) {
-            QWidget *w = list.at(i);
             if (w->isVisible() && !(w->windowType() == Qt::Desktop) && !(w->windowType() == Qt::Popup) &&
                  (!(w->windowType() == Qt::Dialog) || !w->parentWidget())) {
                 ce->ignore();
@@ -2011,9 +2008,8 @@ bool QApplication::event(QEvent *e)
     } else if (e->type() == QEvent::LocaleChange) {
         // on Windows the event propagation is taken care by the
         // WM_SETTINGCHANGE event handler.
-        QWidgetList list = topLevelWidgets();
+        const QWidgetList list = topLevelWidgets();
-        for (int i = 0; i < list.size(); ++i) {
+        for (auto *w : list) {
-            QWidget *w = list.at(i);
             if (!(w->windowType() == Qt::Desktop)) {
                 if (!w->testAttribute(Qt::WA_SetLocale))
                     w->d_func()->setLocale_helper(QLocale(), true);
@@ -2057,9 +2053,8 @@ bool QApplication::event(QEvent *e)
     }
 
     if(e->type() == QEvent::LanguageChange) {
-        QWidgetList list = topLevelWidgets();
+        const QWidgetList list = topLevelWidgets();
-        for (int i = 0; i < list.size(); ++i) {
+        for (auto *w : list) {
-            QWidget *w = list.at(i);
             if (!(w->windowType() == Qt::Desktop))
                 postEvent(w, new QEvent(QEvent::LanguageChange));
         }
@@ -2085,8 +2080,7 @@ void QApplicationPrivate::notifyLayoutDirectionChange()
     QWindowList windowList = QGuiApplication::topLevelWindows();
 
     // send to all top-level QWidgets
-    for (int i = 0; i < list.size(); ++i) {
+    for (auto *w : list) {
-        QWidget *w = list.at(i);
         windowList.removeAll(w->windowHandle());
         QEvent ev(QEvent::ApplicationLayoutDirectionChange);
         QCoreApplication::sendEvent(w, &ev);
@@ -2137,9 +2131,8 @@ void QApplication::setActiveWindow(QWidget* act)
 
     if (QApplicationPrivate::active_window) {
         if (style()->styleHint(QStyle::SH_Widget_ShareActivation, 0, QApplicationPrivate::active_window)) {
-            QWidgetList list = topLevelWidgets();
+            const QWidgetList list = topLevelWidgets();
-            for (int i = 0; i < list.size(); ++i) {
+            for (auto *w : list) {
-                QWidget *w = list.at(i);
                 if (w->isVisible() && w->isActiveWindow())
                     toBeDeactivated.append(w);
             }
@@ -2160,9 +2153,8 @@ void QApplication::setActiveWindow(QWidget* act)
 
     if (QApplicationPrivate::active_window) {
         if (style()->styleHint(QStyle::SH_Widget_ShareActivation, 0, QApplicationPrivate::active_window)) {
-            QWidgetList list = topLevelWidgets();
+            const QWidgetList list = topLevelWidgets();
-            for (int i = 0; i < list.size(); ++i) {
+            for (auto *w : list) {
-                QWidget *w = list.at(i);
                 if (w->isVisible() && w->isActiveWindow())
                     toBeActivated.append(w);
             }

src/widgets/widgets/qgroupbox.cpp

@@ -653,9 +653,7 @@ void QGroupBox::setChecked(bool b)
 void QGroupBoxPrivate::_q_setChildrenEnabled(bool b)
 {
     Q_Q(QGroupBox);
-    QObjectList childList = q->children();
+    for (QObject *o : q->children()) {
-    for (int i = 0; i < childList.size(); ++i) {
-        QObject *o = childList.at(i);
         if (o->isWidgetType()) {
             QWidget *w = static_cast<QWidget *>(o);
             if (b) {