Optimizations for Repeater::clear() and ~QQmlItem()

QQmlRepeater::clear() had quadratic complexity in the number
of items, because the items where removed from the back.

Fix this by searching the cache from the back as well
as searching for child items to remove from the back.

Change-Id: I92e491a8abf47cee9d382ef15cd2471f722fa6dd
Reviewed-by: Simon Hausmann <simon.hausmann@qt.io>

2 files changed, 4 insertions, 4 deletions

diff --git a/src/qml/types/qqmldelegatemodel.cpp b/src/qml/types/qqmldelegatemodel.cpp
index 2f8a70d63b..f1b5759a7d 100644
--- a/src/qml/types/qqmldelegatemodel.cpp
+++ b/src/qml/types/qqmldelegatemodel.cpp
@@ -864,7 +864,7 @@ void QQmlDelegateModelPrivate::releaseIncubator(QQDMIncubationTask *incubationTa
 
 void QQmlDelegateModelPrivate::removeCacheItem(QQmlDelegateModelItem *cacheItem)
 {
-    int cidx = m_cache.indexOf(cacheItem);
+    int cidx = m_cache.lastIndexOf(cacheItem);
     if (cidx >= 0) {
         m_compositor.clearFlags(Compositor::Cache, cidx, 1, Compositor::CacheFlag);
         m_cache.removeAt(cidx);
diff --git a/src/quick/items/qquickitem.cpp b/src/quick/items/qquickitem.cpp
index af60ab879b..54cb8be5da 100644
--- a/src/quick/items/qquickitem.cpp
+++ b/src/quick/items/qquickitem.cpp
@@ -2375,9 +2375,8 @@ QQuickItem::~QQuickItem()
     else if (d->window)
         d->derefWindow();
 
-    // XXX todo - optimize
     while (!d->childItems.isEmpty())
-        d->childItems.constFirst()->setParentItem(0);
+        d->childItems.constLast()->setParentItem(0);
 
     if (!d->changeListeners.isEmpty()) {
         const auto listeners = d->changeListeners; // NOTE: intentional copy (QTBUG-54732)
@@ -2953,7 +2952,8 @@ void QQuickItemPrivate::removeChild(QQuickItem *child)
 
     Q_ASSERT(child);
     Q_ASSERT(childItems.contains(child));
-    childItems.removeOne(child);
+    int idx = childItems.lastIndexOf(child);
+    childItems.removeAt(idx);
     Q_ASSERT(!childItems.contains(child));
 
     QQuickItemPrivate *childPrivate = QQuickItemPrivate::get(child);