QGraphicsView: replace some Q_FOREACH loops over rvalues with C++11 range-for

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

In the cases of this patch, that trivially cannot happen, because
all containers are marked as const when being assigned the rvalues
previously found on the rhs of the Q_FOREACH. The new code thus
does exactly what the old code did: take a const copy, then iterate
over it.

Separate patches will deal with other situations.

Range-for loops are much more efficient than foreach loops.

This patch shaves almost 4K of text size off an optimized Linux
AMD64 GCC 4.9 build.

Change-Id: Ida868b77d078cbfa0516d17e98e6f0a86fcdb7a3
Reviewed-by: Olivier Goffart (Woboq GmbH) <ogoffart@woboq.com>

6 files changed, 78 insertions, 45 deletions

diff --git a/src/widgets/graphicsview/qgraphicsanchorlayout_p.cpp b/src/widgets/graphicsview/qgraphicsanchorlayout_p.cpp
index e16b427448..adc77ded47 100644
--- a/src/widgets/graphicsview/qgraphicsanchorlayout_p.cpp
+++ b/src/widgets/graphicsview/qgraphicsanchorlayout_p.cpp
@@ -2318,9 +2318,9 @@ void QGraphicsAnchorLayoutPrivate::findPaths(Orientation orientation)
 
     graphPaths[orientation].insert(root, GraphPath());
 
-    foreach (AnchorVertex *v, graph[orientation].adjacentVertices(root)) {
+    const auto adjacentVertices = graph[orientation].adjacentVertices(root);
+    for (AnchorVertex *v : adjacentVertices)
         queue.enqueue(qMakePair(root, v));
-    }
 
     while(!queue.isEmpty()) {
         QPair<AnchorVertex *, AnchorVertex *>  pair = queue.dequeue();
@@ -2339,10 +2339,9 @@ void QGraphicsAnchorLayoutPrivate::findPaths(Orientation orientation)
 
         graphPaths[orientation].insert(pair.second, current);
 
-        foreach (AnchorVertex *v,
-                graph[orientation].adjacentVertices(pair.second)) {
+        const auto adjacentVertices = graph[orientation].adjacentVertices(pair.second);
+        for (AnchorVertex *v : adjacentVertices)
             queue.enqueue(qMakePair(pair.second, v));
-        }
     }
 
     // We will walk through every reachable items (non-float) store them in a temporary set.
@@ -2703,9 +2702,9 @@ void QGraphicsAnchorLayoutPrivate::calculateVertexPositions(
     visited.insert(root);
 
     // Add initial edges to the queue
-    foreach (AnchorVertex *v, graph[orientation].adjacentVertices(root)) {
+    const auto adjacentVertices = graph[orientation].adjacentVertices(root);
+    for (AnchorVertex *v : adjacentVertices)
         queue.enqueue(qMakePair(root, v));
-    }
 
     // Do initial calculation required by "interpolateEdge()"
     setupEdgesInterpolation(orientation);
diff --git a/src/widgets/graphicsview/qgraphicsitem.cpp b/src/widgets/graphicsview/qgraphicsitem.cpp
index 3197a5bf6c..31b2778251 100644
--- a/src/widgets/graphicsview/qgraphicsitem.cpp
+++ b/src/widgets/graphicsview/qgraphicsitem.cpp
@@ -1519,7 +1519,8 @@ QGraphicsItem::~QGraphicsItem()
     if (d_ptr->isObject && !d_ptr->gestureContext.isEmpty()) {
         QGraphicsObject *o = static_cast<QGraphicsObject *>(this);
         if (QGestureManager *manager = QGestureManager::instance()) {
-            foreach (Qt::GestureType type, d_ptr->gestureContext.keys())
+            const auto types  = d_ptr->gestureContext.keys(); // FIXME: iterate over the map directly?
+            for (Qt::GestureType type : types)
                 manager->cleanupCachedGestures(o, type);
         }
     }
@@ -2243,11 +2244,13 @@ void QGraphicsItem::setCursor(const QCursor &cursor)
     d_ptr->hasCursor = 1;
     if (d_ptr->scene) {
         d_ptr->scene->d_func()->allItemsUseDefaultCursor = false;
-        foreach (QGraphicsView *view, d_ptr->scene->views()) {
+        const auto views = d_ptr->scene->views();
+        for (QGraphicsView *view : views) {
             view->viewport()->setMouseTracking(true);
             // Note: Some of this logic is duplicated in QGraphicsView's mouse events.
             if (view->underMouse()) {
-                foreach (QGraphicsItem *itemUnderCursor, view->items(view->mapFromGlobal(QCursor::pos()))) {
+                const auto itemsUnderCursor = view->items(view->mapFromGlobal(QCursor::pos()));
+                for (QGraphicsItem *itemUnderCursor : itemsUnderCursor) {
                     if (itemUnderCursor->hasCursor()) {
                         QMetaObject::invokeMethod(view, "_q_setViewportCursor",
                                                   Q_ARG(QCursor, itemUnderCursor->cursor()));
@@ -2286,7 +2289,8 @@ void QGraphicsItem::unsetCursor()
     d_ptr->unsetExtra(QGraphicsItemPrivate::ExtraCursor);
     d_ptr->hasCursor = 0;
     if (d_ptr->scene) {
-        foreach (QGraphicsView *view, d_ptr->scene->views()) {
+        const auto views = d_ptr->scene->views();
+        for (QGraphicsView *view : views) {
             if (view->underMouse() && view->itemAt(view->mapFromGlobal(QCursor::pos())) == this) {
                 QMetaObject::invokeMethod(view, "_q_unsetViewportCursor");
                 break;
@@ -2922,7 +2926,8 @@ QRectF QGraphicsItemPrivate::effectiveBoundingRect(const QRectF &rect) const
             return effect->boundingRectFor(rect);
         QRectF sceneRect = q->mapRectToScene(rect);
         QRectF sceneEffectRect;
-        foreach (QGraphicsView *view, scene->views()) {
+        const auto views = scene->views();
+        for (QGraphicsView *view : views) {
             QRectF deviceRect = view->d_func()->mapRectFromScene(sceneRect);
             QRect deviceEffectRect = effect->boundingRectFor(deviceRect).toAlignedRect();
             sceneEffectRect |= view->d_func()->mapRectToScene(deviceEffectRect);
@@ -5216,7 +5221,8 @@ bool QGraphicsItem::isObscured(const QRectF &rect) const
     QRectF br = boundingRect();
     QRectF testRect = rect.isNull() ? br : rect;
 
-    foreach (QGraphicsItem *item, d->scene->items(mapToScene(br), Qt::IntersectsItemBoundingRect)) {
+    const auto items = d->scene->items(mapToScene(br), Qt::IntersectsItemBoundingRect);
+    for (QGraphicsItem *item : items) {
         if (item == this)
             break;
         if (qt_QGraphicsItem_isObscured(this, item, testRect))
@@ -5338,7 +5344,8 @@ QRegion QGraphicsItem::boundingRegion(const QTransform &itemToDeviceTransform) c
     QTransform unscale = QTransform::fromScale(1 / granularity, 1 / granularity);
     QRegion r;
     QBitmap colorMask = QBitmap::fromImage(mask.createMaskFromColor(0));
-    foreach (const QRect &rect, QRegion( colorMask ).rects()) {
+    const auto rects = QRegion(colorMask).rects();
+    for (const QRect &rect : rects) {
         QRect xrect = unscale.mapRect(rect).translated(deviceRect.topLeft() - QPoint(pad, pad));
         r += xrect.adjusted(-1, -1, 1, 1) & deviceRect;
     }
@@ -6599,7 +6606,8 @@ bool QGraphicsItem::isUnderMouse() const
         return false;
 
     QPoint cursorPos = QCursor::pos();
-    foreach (QGraphicsView *view, d->scene->views()) {
+    const auto views = d->scene->views();
+    for (QGraphicsView *view : views) {
         if (contains(mapFromScene(view->mapToScene(view->mapFromGlobal(cursorPos)))))
             return true;
     }
diff --git a/src/widgets/graphicsview/qgraphicsproxywidget.cpp b/src/widgets/graphicsview/qgraphicsproxywidget.cpp
index 3ea04efc6b..ea9fc0a0d5 100644
--- a/src/widgets/graphicsview/qgraphicsproxywidget.cpp
+++ b/src/widgets/graphicsview/qgraphicsproxywidget.cpp
@@ -595,7 +595,8 @@ void QGraphicsProxyWidgetPrivate::setWidget_helper(QWidget *newWidget, bool auto
         resolvePalette(inheritedPaletteResolveMask);
         widget->update();
 
-        foreach (QGraphicsItem *child, q->childItems()) {
+        const auto childItems = q->childItems();
+        for (QGraphicsItem *child : childItems) {
             if (child->d_ptr->isProxyWidget()) {
                 QGraphicsProxyWidget *childProxy = static_cast<QGraphicsProxyWidget *>(child);
                 QWidget * parent = childProxy->widget();
diff --git a/src/widgets/graphicsview/qgraphicsscene.cpp b/src/widgets/graphicsview/qgraphicsscene.cpp
index 2dc48a8065..3993138f3f 100644
--- a/src/widgets/graphicsview/qgraphicsscene.cpp
+++ b/src/widgets/graphicsview/qgraphicsscene.cpp
@@ -756,8 +756,9 @@ void QGraphicsScenePrivate::setActivePanelHelper(QGraphicsItem *item, bool durin
         q->sendEvent(activePanel, &event);
     } else if (panel && !duringActivationEvent) {
         // Deactivate the scene if changing activation to a panel.
+        const auto items = q->items();
         QEvent event(QEvent::WindowDeactivate);
-        foreach (QGraphicsItem *item, q->items()) {
+        for (QGraphicsItem *item : items) {
             if (item->isVisible() && !item->isPanel() && !item->parentItem())
                 q->sendEvent(item, &event);
         }
@@ -791,9 +792,10 @@ void QGraphicsScenePrivate::setActivePanelHelper(QGraphicsItem *item, bool durin
             } while (fw != panel);
         }
     } else if (q->isActive()) {
+        const auto items = q->items();
         // Activate the scene
         QEvent event(QEvent::WindowActivate);
-        foreach (QGraphicsItem *item, q->items()) {
+        for (QGraphicsItem *item : items) {
             if (item->isVisible() && !item->isPanel() && !item->parentItem())
                 q->sendEvent(item, &event);
         }
@@ -1545,7 +1547,8 @@ void QGraphicsScenePrivate::updateFont(const QFont &font)
 
     // Resolve the fonts of all top-level widget items, or widget items
     // whose parent is not a widget.
-    foreach (QGraphicsItem *item, q->items()) {
+    const auto items = q->items();
+    for (QGraphicsItem *item : items) {
         if (!item->parentItem()) {
             // Resolvefont for an item is a noop operation, but
             // every item can be a widget, or can have a widget
@@ -1601,7 +1604,8 @@ void QGraphicsScenePrivate::updatePalette(const QPalette &palette)
 
     // Resolve the palettes of all top-level widget items, or widget items
     // whose parent is not a widget.
-    foreach (QGraphicsItem *item, q->items()) {
+    const auto items = q->items();
+    for (QGraphicsItem *item : items) {
         if (!item->parentItem()) {
             // ResolvePalette for an item is a noop operation, but
             // every item can be a widget, or can have a widget
@@ -1947,7 +1951,8 @@ QRectF QGraphicsScene::itemsBoundingRect() const
 {
     // Does not take untransformable items into account.
     QRectF boundingRect;
-    foreach (QGraphicsItem *item, items())
+    const auto items_ = items();
+    for (QGraphicsItem *item : items_)
         boundingRect |= item->sceneBoundingRect();
     return boundingRect;
 }
@@ -2116,7 +2121,8 @@ QList<QGraphicsItem *> QGraphicsScene::collidingItems(const QGraphicsItem *item,
 
     // Does not support ItemIgnoresTransformations.
     QList<QGraphicsItem *> tmp;
-    foreach (QGraphicsItem *itemInVicinity, d->index->estimateItems(item->sceneBoundingRect(), Qt::DescendingOrder)) {
+    const auto itemsInVicinity = d->index->estimateItems(item->sceneBoundingRect(), Qt::DescendingOrder);
+    for (QGraphicsItem *itemInVicinity : itemsInVicinity) {
         if (item != itemInVicinity && item->collidesWithItem(itemInVicinity, mode))
             tmp << itemInVicinity;
     }
@@ -2303,7 +2309,8 @@ void QGraphicsScene::setSelectionArea(const QPainterPath &path,
     bool changed = false;
 
     // Set all items in path to selected.
-    foreach (QGraphicsItem *item, items(path, mode, Qt::DescendingOrder, deviceTransform)) {
+    const auto items = this->items(path, mode, Qt::DescendingOrder, deviceTransform);
+    for (QGraphicsItem *item : items) {
         if (item->flags() & QGraphicsItem::ItemIsSelectable) {
             if (!item->isSelected())
                 changed = true;
@@ -2444,7 +2451,8 @@ QGraphicsItemGroup *QGraphicsScene::createItemGroup(const QList<QGraphicsItem *>
 */
 void QGraphicsScene::destroyItemGroup(QGraphicsItemGroup *group)
 {
-    foreach (QGraphicsItem *item, group->childItems())
+    const auto items = group->childItems();
+    for (QGraphicsItem *item : items)
         group->removeFromGroup(item);
     removeItem(group);
     delete group;
@@ -2559,7 +2567,8 @@ void QGraphicsScene::addItem(QGraphicsItem *item)
     }
 
 #ifndef QT_NO_GESTURES
-    foreach (Qt::GestureType gesture, item->d_ptr->gestureContext.keys())
+    const auto gestures = item->d_ptr->gestureContext.keys(); // FIXME: iterate over hash directly?
+    for (Qt::GestureType gesture : gestures)
         d->grabGesture(item, gesture);
 #endif
 
@@ -3130,7 +3139,8 @@ void QGraphicsScene::setForegroundBrush(const QBrush &brush)
 {
     Q_D(QGraphicsScene);
     d->foregroundBrush = brush;
-    foreach (QGraphicsView *view, views())
+    const auto views_ = views();
+    for (QGraphicsView *view : views_)
         view->viewport()->update();
     update();
 }
@@ -3238,7 +3248,8 @@ void QGraphicsScene::update(const QRectF &rect)
 */
 void QGraphicsScene::invalidate(const QRectF &rect, SceneLayers layers)
 {
-    foreach (QGraphicsView *view, views())
+    const auto views_ = views();
+    for (QGraphicsView *view : views_)
         view->invalidateScene(rect, layers);
     update(rect);
 }
@@ -3279,7 +3290,8 @@ QList <QGraphicsView *> QGraphicsScene::views() const
 void QGraphicsScene::advance()
 {
     for (int i = 0; i < 2; ++i) {
-        foreach (QGraphicsItem *item, items())
+        const auto items_ = items();
+        for (QGraphicsItem *item : items_)
             item->advance(i);
     }
 }
@@ -3434,7 +3446,8 @@ bool QGraphicsScene::event(QEvent *event)
             } else {
                 // Activate all toplevel items.
                 QEvent event(QEvent::WindowActivate);
-                foreach (QGraphicsItem *item, items()) {
+                const auto items_ = items();
+                for (QGraphicsItem *item : items_) {
                     if (item->isVisible() && !item->isPanel() && !item->parentItem())
                         sendEvent(item, &event);
                 }
@@ -3452,7 +3465,8 @@ bool QGraphicsScene::event(QEvent *event)
             } else {
                 // Activate all toplevel items.
                 QEvent event(QEvent::WindowDeactivate);
-                foreach (QGraphicsItem *item, items()) {
+                const auto items_ = items();
+                for (QGraphicsItem *item : items_) {
                     if (item->isVisible() && !item->isPanel() && !item->parentItem())
                         sendEvent(item, &event);
                 }
@@ -3547,9 +3561,10 @@ void QGraphicsScene::contextMenuEvent(QGraphicsSceneContextMenuEvent *contextMen
 
     // Send the event to all items at this position until one item accepts the
     // event.
-    foreach (QGraphicsItem *item, d->itemsAtPosition(contextMenuEvent->screenPos(),
-                                                     contextMenuEvent->scenePos(),
-                                                     contextMenuEvent->widget())) {
+    const auto items = d->itemsAtPosition(contextMenuEvent->screenPos(),
+                                          contextMenuEvent->scenePos(),
+                                          contextMenuEvent->widget());
+    for (QGraphicsItem *item : items) {
         contextMenuEvent->setPos(item->d_ptr->genericMapFromScene(contextMenuEvent->scenePos(),
                                                                   contextMenuEvent->widget()));
         contextMenuEvent->accept();
@@ -3605,9 +3620,10 @@ void QGraphicsScene::dragMoveEvent(QGraphicsSceneDragDropEvent *event)
 
     // Find the topmost enabled items under the cursor. They are all
     // candidates for accepting drag & drop events.
-    foreach (QGraphicsItem *item, d->itemsAtPosition(event->screenPos(),
-                                                     event->scenePos(),
-                                                     event->widget())) {
+    const auto items = d->itemsAtPosition(event->screenPos(),
+                                          event->scenePos(),
+                                          event->widget());
+    for (QGraphicsItem *item : items) {
         if (!item->isEnabled() || !item->acceptDrops())
             continue;
 
@@ -4635,7 +4651,8 @@ void QGraphicsScenePrivate::drawItemHelper(QGraphicsItem *item, QPainter *painte
                 for (int i = 0; i < exposed.size(); ++i)
                     br |= exposed.at(i);
                 QTransform pixmapToItem = itemToPixmap.inverted();
-                foreach (const QRect &r, scrollExposure.rects())
+                const auto rects = scrollExposure.rects();
+                for (const QRect &r : rects)
                     br |= pixmapToItem.mapRect(r);
             }
             styleOptionTmp = *option;
@@ -5564,7 +5581,8 @@ void QGraphicsScene::setStyle(QStyle *style)
     QApplication::sendEvent(this, &event);
 
     // Notify all widgets that don't have a style explicitly set.
-    foreach (QGraphicsItem *item, items()) {
+    const auto items_ = items();
+    for (QGraphicsItem *item : items_) {
         if (item->isWidget()) {
             QGraphicsWidget *widget = static_cast<QGraphicsWidget *>(item);
             if (!widget->testAttribute(Qt::WA_SetStyle))
@@ -5733,7 +5751,8 @@ void QGraphicsScene::setActiveWindow(QGraphicsWidget *widget)
 
         // Find the highest z value.
         qreal z = panel->zValue();
-        foreach (QGraphicsItem *sibling, parent ? parent->childItems() : items()) {
+        const auto siblings = parent ? parent->childItems() : items();
+        for (QGraphicsItem *sibling : siblings) {
             if (sibling != panel && sibling->isWindow())
                 z = qMax(z, sibling->zValue());
         }
@@ -5819,7 +5838,8 @@ void QGraphicsScenePrivate::addView(QGraphicsView *view)
 {
     views << view;
 #ifndef QT_NO_GESTURES
-    foreach (Qt::GestureType gesture, grabbedGestures.keys())
+    const auto gestures = grabbedGestures.keys();
+    for (Qt::GestureType gesture : gestures)
         view->viewport()->grabGesture(gesture);
 #endif
 }
@@ -6304,7 +6324,8 @@ void QGraphicsScenePrivate::gestureEventHandler(QGestureEvent *event)
                 QGraphicsObject *item = cachedTargetItems.at(i);
 
                 // get gestures to deliver to the current item
-                foreach (QGesture *g, cachedItemGestures.value(item)) {
+                const auto gestures = cachedItemGestures.value(item);
+                for (QGesture *g : gestures) {
                     if (!gestureTargets.contains(g)) {
                         gestureTargets.insert(g, item);
                         normalGestures.remove(g);
diff --git a/src/widgets/graphicsview/qgraphicsview.cpp b/src/widgets/graphicsview/qgraphicsview.cpp
index ac8cd45f9e..928d826323 100644
--- a/src/widgets/graphicsview/qgraphicsview.cpp
+++ b/src/widgets/graphicsview/qgraphicsview.cpp
@@ -799,7 +799,8 @@ void QGraphicsViewPrivate::_q_setViewportCursor(const QCursor &cursor)
 void QGraphicsViewPrivate::_q_unsetViewportCursor()
 {
     Q_Q(QGraphicsView);
-    foreach (QGraphicsItem *item, q->items(lastMouseEvent.pos())) {
+    const auto items = q->items(lastMouseEvent.pos());
+    for (QGraphicsItem *item : items) {
         if (item->hasCursor()) {
             _q_setViewportCursor(item->cursor());
             return;
@@ -1139,7 +1140,8 @@ QList<QGraphicsItem *> QGraphicsViewPrivate::findItems(const QRegion &exposedReg
     // the expose region, convert it to a path, and then search for items
     // using QGraphicsScene::items(QPainterPath);
     QRegion adjustedRegion;
-    foreach (const QRect &r, exposedRegion.rects())
+    const auto rects = exposedRegion.rects();
+    for (const QRect &r : rects)
         adjustedRegion += r.adjusted(-1, -1, 1, 1);
 
     const QPainterPath exposedScenePath(q->mapToScene(qt_regionToPath(adjustedRegion)));
@@ -2791,7 +2793,8 @@ void QGraphicsView::setupViewport(QWidget *widget)
 
 #ifndef QT_NO_GESTURES
     if (d->scene) {
-        foreach (Qt::GestureType gesture, d->scene->d_func()->grabbedGestures.keys())
+        const auto gestures = d->scene->d_func()->grabbedGestures.keys();
+        for (Qt::GestureType gesture : gestures)
             widget->grabGesture(gesture);
     }
 #endif
diff --git a/src/widgets/graphicsview/qgraphicswidget.cpp b/src/widgets/graphicsview/qgraphicswidget.cpp
index ef086aeab0..db1cdd42ab 100644
--- a/src/widgets/graphicsview/qgraphicswidget.cpp
+++ b/src/widgets/graphicsview/qgraphicswidget.cpp
@@ -251,7 +251,8 @@ QGraphicsWidget::~QGraphicsWidget()
     //we check if we have a layout previously
     if (d->layout) {
         QGraphicsLayout *temp = d->layout;
-        foreach (QGraphicsItem * item, childItems()) {
+        const auto items = childItems();
+        for (QGraphicsItem *item : items) {
             // In case of a custom layout which doesn't remove and delete items, we ensure that
             // the parent layout item does not point to the deleted layout. This code is here to
             // avoid regression from 4.4 to 4.5, because according to 4.5 docs it is not really needed.