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>

22 files changed, 138 insertions, 170 deletions

diff --git a/src/widgets/accessible/qaccessiblewidget.cpp b/src/widgets/accessible/qaccessiblewidget.cpp
index ed5b6f86fd..e540980a14 100644
--- a/src/widgets/accessible/qaccessiblewidget.cpp
+++ b/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) {
-        QWidget *w = qobject_cast<QWidget *>(list.at(i));
+    for (QObject *o : widget->children()) {
+        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 (int i = 0; i < ol.size(); ++i) {
-        QLabel *label = qobject_cast<QLabel*>(ol.at(i));
+    for (QObject *o : parent->children()) {
+        QLabel *label = qobject_cast<QLabel*>(o);
         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) {
-                if (QLabel *labelSibling = qobject_cast<QLabel*>(kids.at(i))) {
+            for (QWidget *kid : kids) {
+                if (QLabel *labelSibling = qobject_cast<QLabel*>(kid)) {
                     if (labelSibling->buddy() == widget()) {
                         QAccessibleInterface *iface = QAccessible::queryAccessibleInterface(labelSibling);
                         rels.append(qMakePair(iface, rel));
diff --git a/src/widgets/accessible/qaccessiblewidgets.cpp b/src/widgets/accessible/qaccessiblewidgets.cpp
index a4f433e65a..9bbc01b5cc 100644
--- a/src/widgets/accessible/qaccessiblewidgets.cpp
+++ b/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) {
-        QWidget *w = qobject_cast<QWidget *>(list.at(i));
+    for (QObject *o : widget->children()) {
+        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) {
-        QWidget *child = kids.at(i);
+    for (QWidget *child : kids) {
         if (!child->isWindow() && !child->isHidden() && child->geometry().contains(rp)) {
             return QAccessible::queryAccessibleInterface(child);
         }
diff --git a/src/widgets/accessible/simplewidgets.cpp b/src/widgets/accessible/simplewidgets.cpp
index 065c618cf7..e77839cc12 100644
--- a/src/widgets/accessible/simplewidgets.cpp
+++ b/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) {
-            QAccessibleInterface *iface = QAccessible::queryAccessibleInterface(kids.at(i));
+        for (QWidget *kid : kids) {
+            QAccessibleInterface *iface = QAccessible::queryAccessibleInterface(kid);
             if (iface)
                 rels.append(qMakePair(iface, QAccessible::Relation(QAccessible::Labelled)));
         }
diff --git a/src/widgets/dialogs/qfiledialog.cpp b/src/widgets/dialogs/qfiledialog.cpp
index 1f832abf78..1bf5691837 100644
--- a/src/widgets/dialogs/qfiledialog.cpp
+++ b/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) {
-            QFileInfo info(files.at(i));
+        for (const auto &file : files) {
+            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) {
-            QModelIndex idx = model->index(multipleFiles.at(i));
-            if (oldFiles.contains(idx))
-                oldFiles.removeAll(idx);
-            else
+        for (const auto &file : multipleFiles) {
+            QModelIndex idx = model->index(file);
+            if (oldFiles.removeAll(idx) == 0)
                 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) {
-                QModelIndex idx = model->index(files.at(i));
+            for (const auto &file : files) {
+                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) {
-        if (stripDirs && model->isDir(mapToSource(indexes.at(i))))
+    for (const auto &index : indexes) {
+        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) {
diff --git a/src/widgets/dialogs/qfileinfogatherer.cpp b/src/widgets/dialogs/qfileinfogatherer.cpp
index 92d6b8f3be..d99e3df802 100644
--- a/src/widgets/dialogs/qfileinfogatherer.cpp
+++ b/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)
-                infoList << QFileInfo(files.at(i));
+            for (const auto &file : files)
+                infoList << QFileInfo(file);
         }
         for (int i = infoList.count() - 1; i >= 0; --i) {
             QString driveName = translateDriveName(infoList.at(i));
diff --git a/src/widgets/dialogs/qfilesystemmodel.cpp b/src/widgets/dialogs/qfilesystemmodel.cpp
index 3c154c3dbb..c1d0ecf33b 100644
--- a/src/widgets/dialogs/qfilesystemmodel.cpp
+++ b/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();
-        for (int i = 0; i < persistantList.count(); ++i) {
-            QFileSystemModelPrivate::QFileSystemNode *node;
-            node = d->node(persistantList.at(i));
+        const QModelIndexList persistentList = persistentIndexList();
+        for (const auto &persistentIndex : persistentList) {
+            QFileSystemModelPrivate::QFileSystemNode *node = d->node(persistentIndex);
             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) {
-        d->nameFilters << QRegExp(filters.at(i), caseSensitive, QRegExp::Wildcard);
-    }
+    for (const auto &filter : filters)
+        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) {
-        parentNode->visibleChildren.append(newFiles.at(i));
-        parentNode->children.value(newFiles.at(i))->isVisible = true;
+    for (const auto &newFile : newFiles) {
+        parentNode->visibleChildren.append(newFile);
+        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) {
-        QString fileName = updates.at(i).first;
+    for (const auto &update : updates) {
+        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) {
-            QRegExp copy = nameFilters.at(i);
+        for (const auto &nameFilter : nameFilters) {
+            QRegExp copy = nameFilter;
             if (copy.exactMatch(node->fileName))
                 return true;
         }
diff --git a/src/widgets/dialogs/qmessagebox.cpp b/src/widgets/dialogs/qmessagebox.cpp
index 76a9de0f1c..704883b5c6 100644
--- a/src/widgets/dialogs/qmessagebox.cpp
+++ b/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++) {
-        if (buttonBox->buttonRole(buttons.at(i)) == QDialogButtonBox::RejectRole) {
+    for (auto *button : buttons) {
+        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++) {
-        if (buttonBox->buttonRole(buttons.at(i)) == QDialogButtonBox::NoRole) {
+    for (auto *button : buttons) {
+        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) {
-                QAbstractButton *pb = buttons.at(i);
+            for (auto *pb : buttons) {
                 QKeySequence shortcut = pb->shortcut();
                 if (!shortcut.isEmpty() && key == int(shortcut[0] & ~Qt::MODIFIER_MASK)) {
                     pb->animateClick();
diff --git a/src/widgets/dialogs/qsidebar.cpp b/src/widgets/dialogs/qsidebar.cpp
index f883705cc3..58a92800f4 100644
--- a/src/widgets/dialogs/qsidebar.cpp
+++ b/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) {
-        if (indexes.at(i).column() == 0)
-           list.append(indexes.at(i).data(UrlRole).toUrl());
+    for (const auto &index : indexes) {
+        if (index.column() == 0)
+           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) {
-        QModelIndex idx = fileSystemModel->index(list.at(0).toLocalFile());
+    for (const auto &url : list) {
+        const QModelIndex idx = fileSystemModel->index(url.toLocalFile());
         if (!fileSystemModel->isDir(idx))
             return false;
     }
diff --git a/src/widgets/dialogs/qwizard.cpp b/src/widgets/dialogs/qwizard.cpp
index c050b5b097..6add83e135 100644
--- a/src/widgets/dialogs/qwizard.cpp
+++ b/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;
-        for (int i = 0; i < fields.count(); ++i) {
-            const QWizardField &field = fields.at(i);
+        const QVector<QWizardField> &fields = d->wizard->d_func()->fields;
+        for (const auto &field : fields) {
             if (field.page == this)
                 field.object->setProperty(field.property, field.initialValue);
         }
diff --git a/src/widgets/graphicsview/qgraph_p.h b/src/widgets/graphicsview/qgraph_p.h
index c63c2c6f8e..2c9c58eb4c 100644
--- a/src/widgets/graphicsview/qgraph_p.h
+++ b/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);
-            for (int i = 0; i < adjacents.count(); ++i) {
-                Vertex *v1 = adjacents.at(i);
+            const QList<Vertex*> adjacents = adjacentVertices(v);
+            for (auto *v1 : adjacents) {
                 EdgeData *data = edgeData(v, v1);
                 bool forward = data->from == v;
                 if (forward) {
diff --git a/src/widgets/itemviews/qabstractitemview.cpp b/src/widgets/itemviews/qabstractitemview.cpp
index fe98fae17a..cbf734203a 100644
--- a/src/widgets/itemviews/qabstractitemview.cpp
+++ b/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) {
-        const QModelIndex &index = indexes.at(i);
+    for (const auto &index : indexes) {
         const QRect current = q->visualRect(index);
         if (current.intersects(viewportRect)) {
             QItemViewPaintPair p = { current, index };
diff --git a/src/widgets/itemviews/qabstractitemview_p.h b/src/widgets/itemviews/qabstractitemview_p.h
index cb74586fab..2b28d8db84 100644
--- a/src/widgets/itemviews/qabstractitemview_p.h
+++ b/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)
-                if (mime->hasFormat(modelTypes.at(i)))
+            for (const auto &modelType : modelTypes) {
+                if (mime->hasFormat(modelType))
                     return true;
+            }
         }
 
         QModelIndex index;
diff --git a/src/widgets/itemviews/qdirmodel.cpp b/src/widgets/itemviews/qdirmodel.cpp
index daf00e9362..f18233b64c 100644
--- a/src/widgets/itemviews/qdirmodel.cpp
+++ b/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)
-            nodes.push(&children.at(i));
+        for (const auto &child : children)
+            nodes.push(&child);
     }
 }
 
diff --git a/src/widgets/itemviews/qheaderview.cpp b/src/widgets/itemviews/qheaderview.cpp
index 4cb28d0804..496d36015e 100644
--- a/src/widgets/itemviews/qheaderview.cpp
+++ b/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) {
-            QItemSelectionRange r = selection.at(i);
+        for (const auto &r : selection) {
             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) {
-        QItemSelectionRange r = selection.at(i);
+    for (const auto &r : selection) {
         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
diff --git a/src/widgets/itemviews/qheaderview_p.h b/src/widgets/itemviews/qheaderview_p.h
index 7f92d2a81b..60542e297a 100644
--- a/src/widgets/itemviews/qheaderview_p.h
+++ b/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)
-            len += sectionItems.at(i).size;
+        for (const auto &section : sectionItems)
+            len += section.size;
         return len;
     }
 
diff --git a/src/widgets/itemviews/qlistview.cpp b/src/widgets/itemviews/qlistview.cpp
index 2dbbd211c0..7cd8e890db 100644
--- a/src/widgets/itemviews/qlistview.cpp
+++ b/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) {
-        const QModelIndex &index = indexes.at(i);
+    for (const auto &index : indexes) {
         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) {
-        if (!selection.at(i).isValid())
+    for (const auto &elem : selection) {
+        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 b = selection.at(i).bottomRight().row();
+        int t = elem.topLeft().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();
-    for (int i = 0; i < indexes.count(); ++i) {
-        QModelIndex index = indexes.at(i);
+    const QList<QModelIndex> indexes = dd->selectionModel->selectedIndexes();
+    for (const auto &index : indexes) {
         QRect rect = dd->rectForIndex(index);
         viewport()->update(dd->mapToViewport(rect, false));
         QPoint dest = rect.topLeft() + delta;
diff --git a/src/widgets/itemviews/qtableview.cpp b/src/widgets/itemviews/qtableview.cpp
index 2e88310b2f..88090f1e45 100644
--- a/src/widgets/itemviews/qtableview.cpp
+++ b/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) {
-        QRect dirtyArea = rects.at(i);
+    const QVector<QRect> rects = region.rects();
+    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) {
-            QItemSelectionRange range = selection.at(i);
+        for (const auto &range : selection) {
             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) {
-            QItemSelectionRange range = selection.at(i);
+        for (const auto &range : selection) {
             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) {
-            QItemSelectionRange range = selection.at(i);
+        for (const auto &range : selection) {
             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) {
-            QItemSelectionRange range = selection.at(i);
+        for (auto range : selection) {
             if (range.parent() != d->root || !range.isValid())
                 continue;
             d->trimHiddenSelections(&range);
diff --git a/src/widgets/itemviews/qtablewidget.cpp b/src/widgets/itemviews/qtablewidget.cpp
index 568b52f901..6238835f04 100644
--- a/src/widgets/itemviews/qtablewidget.cpp
+++ b/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)
-        if (values.at(i).role == role)
-            return values.at(i).value;
+    for (const auto &value : values) {
+        if (value.role == role)
+            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) {
-        QModelIndex index = indexes.at(i);
+    for (const auto &index : indexes) {
         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) {
-                top = qMin(indexes.at(i).row(), top);
-                left = qMin(indexes.at(i).column(), left);
+            for (const auto &index : indexes) {
+                top = qMin(index.row(), top);
+                left = qMin(index.column(), left);
             }
 
             QList<QTableWidgetItem *> taken;
             const int indexesCount = indexes.count();
             taken.reserve(indexesCount);
-            for (int i = 0; i < indexesCount; ++i)
-                taken.append(takeItem(indexes.at(i).row(), indexes.at(i).column()));
+            for (const auto &index : indexes)
+                taken.append(takeItem(index.row(), index.column()));
 
-            for (int i = 0; i < indexes.count(); ++i) {
-                QModelIndex index = indexes.at(i);
+            for (const auto &index : indexes) {
                 int r = index.row() - top + topIndex.row();
                 int c = index.column() - left + topIndex.column();
                 setItem(r, c, taken.takeFirst());
diff --git a/src/widgets/itemviews/qtreeview.cpp b/src/widgets/itemviews/qtreeview.cpp
index 41f1ca7502..b11c54ffb8 100644
--- a/src/widgets/itemviews/qtreeview.cpp
+++ b/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) {
-        QItemSelectionRange range = selection.at(i);
+    for (const auto &range : selection) {
         if (!range.isValid())
             continue;
         QModelIndex parent = range.parent();
diff --git a/src/widgets/itemviews/qtreewidget.cpp b/src/widgets/itemviews/qtreewidget.cpp
index 6d3162d387..9dbf7df5fb 100644
--- a/src/widgets/itemviews/qtreewidget.cpp
+++ b/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) {
-        if (indexes.at(i).column() == 0) // only one item per row
-            items << item(indexes.at(i));
+    for (const auto &index : indexes) {
+        if (index.column() == 0) // only one item per row
+            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)
-                if (column_values.at(i).role == role)
-                    return column_values.at(i).value;
+            for (const auto &column_value : column_values) {
+                if (column_value.role == role)
+                    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) {
-        QVariant value = children.at(i)->data(column, Qt::CheckStateRole);
+    for (const auto *child : children) {
+        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) {
-        QTreeWidgetItem *item = d->item(indexes.at(i));
+    for (const auto &index : indexes) {
+        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) {
-            QTreeWidgetItem *item = items.at(i);
+        for (const auto *item : items) {
             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++)
-                indexes.append(idxs.at(i));
+            for (const auto &idx : idxs)
+                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) {
-                QTreeWidgetItem *parent = itemFromIndex(indexes.at(i));
+            for (const auto &index : indexes) {
+                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()));
                 }
             }
 
diff --git a/src/widgets/kernel/qapplication.cpp b/src/widgets/kernel/qapplication.cpp
index 4510fc85b6..ab8c251f50 100644
--- a/src/widgets/kernel/qapplication.cpp
+++ b/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();
-            for (int i = 0; i < styles.size(); ++i) {
-                if ((app_style = QStyleFactory::create(styles.at(i))))
+            const QStringList styles = QStyleFactory::keys();
+            for (const auto &style : styles) {
+                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) {
-        QWidget *w = list.at(i);
+    for (auto *w : list) {
         windowList.removeOne(w->windowHandle());
         QCoreApplication::sendEvent(w, &ev);
     }
@@ -1906,9 +1905,8 @@ bool QApplicationPrivate::tryCloseAllWidgetWindows(QWindowList *processedWindows
     }
 
 retry:
-    QWidgetList list = QApplication::topLevelWidgets();
-    for (int i = 0; i < list.size(); ++i) {
-        QWidget *w = list.at(i);
+    const QWidgetList list = QApplication::topLevelWidgets();
+    for (auto *w : list) {
         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();
-        for (int i = 0; i < list.size(); ++i) {
-            QWidget *w = list.at(i);
+        const QWidgetList list = topLevelWidgets();
+        for (auto *w : list) {
             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();
-        for (int i = 0; i < list.size(); ++i) {
-            QWidget *w = list.at(i);
+        const QWidgetList list = topLevelWidgets();
+        for (auto *w : list) {
             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();
-        for (int i = 0; i < list.size(); ++i) {
-            QWidget *w = list.at(i);
+        const QWidgetList list = topLevelWidgets();
+        for (auto *w : list) {
             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) {
-        QWidget *w = list.at(i);
+    for (auto *w : list) {
         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();
-            for (int i = 0; i < list.size(); ++i) {
-                QWidget *w = list.at(i);
+            const QWidgetList list = topLevelWidgets();
+            for (auto *w : list) {
                 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();
-            for (int i = 0; i < list.size(); ++i) {
-                QWidget *w = list.at(i);
+            const QWidgetList list = topLevelWidgets();
+            for (auto *w : list) {
                 if (w->isVisible() && w->isActiveWindow())
                     toBeActivated.append(w);
             }
diff --git a/src/widgets/widgets/qgroupbox.cpp b/src/widgets/widgets/qgroupbox.cpp
index f1ebf91ad7..559c8bbd33 100644
--- a/src/widgets/widgets/qgroupbox.cpp
+++ b/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 (int i = 0; i < childList.size(); ++i) {
-        QObject *o = childList.at(i);
+    for (QObject *o : q->children()) {
         if (o->isWidgetType()) {
             QWidget *w = static_cast<QWidget *>(o);
             if (b) {