1 files changed, 65 insertions, 11 deletions

diff --git a/src/kitemviews/private/kitemlistsizehintresolver.cpp b/src/kitemviews/private/kitemlistsizehintresolver.cpp
index e075b46d0..5db87f34d 100644
--- a/src/kitemviews/private/kitemlistsizehintresolver.cpp
+++ b/src/kitemviews/private/kitemlistsizehintresolver.cpp
@@ -20,7 +20,6 @@
 #include "kitemlistsizehintresolver.h"
 
 #include <kitemviews/kitemlistview.h>
-#include <KDebug>
 
 KItemListSizeHintResolver::KItemListSizeHintResolver(const KItemListView* itemListView) :
     m_itemListView(itemListView),
@@ -42,22 +41,77 @@ QSizeF KItemListSizeHintResolver::sizeHint(int index) const
     return size;
 }
 
-void KItemListSizeHintResolver::itemsInserted(int index, int count)
+void KItemListSizeHintResolver::itemsInserted(const KItemRangeList& itemRanges)
 {
+    int insertedCount = 0;
+    foreach (const KItemRange& range, itemRanges) {
+        insertedCount += range.count;
+    }
+
     const int currentCount = m_sizeHintCache.count();
-    m_sizeHintCache.reserve(currentCount + count);
-    while (count > 0) {
-        m_sizeHintCache.insert(index, QSizeF());
-        ++index;
-        --count;
+    m_sizeHintCache.reserve(currentCount + insertedCount);
+
+    // We build the new list from the end to the beginning to mimize the
+    // number of moves.
+    m_sizeHintCache.insert(m_sizeHintCache.end(), insertedCount, QSizeF());
+
+    int sourceIndex = currentCount - 1;
+    int targetIndex = m_sizeHintCache.count() - 1;
+    int itemsToInsertBeforeCurrentRange = insertedCount;
+
+    for (int rangeIndex = itemRanges.count() - 1; rangeIndex >= 0; --rangeIndex) {
+        const KItemRange& range = itemRanges.at(rangeIndex);
+        itemsToInsertBeforeCurrentRange -= range.count;
+
+        // First: move all existing items that must be put behind 'range'.
+        while (targetIndex >= itemsToInsertBeforeCurrentRange + range.index + range.count) {
+            m_sizeHintCache[targetIndex] = m_sizeHintCache[sourceIndex];
+            --sourceIndex;
+            --targetIndex;
+        }
+
+        // Then: insert QSizeF() for the items which are inserted into 'range'.
+        while (targetIndex >= itemsToInsertBeforeCurrentRange + range.index) {
+            m_sizeHintCache[targetIndex] = QSizeF();
+            --targetIndex;
+        }
     }
+
+    Q_ASSERT(m_sizeHintCache.count() == m_itemListView->model()->count());
 }
 
-void KItemListSizeHintResolver::itemsRemoved(int index, int count)
+void KItemListSizeHintResolver::itemsRemoved(const KItemRangeList& itemRanges)
 {
-    const QVector<QSizeF>::iterator begin = m_sizeHintCache.begin() + index;
-    const QVector<QSizeF>::iterator end = begin + count;
-    m_sizeHintCache.erase(begin, end);
+    const QVector<QSizeF>::iterator begin = m_sizeHintCache.begin();
+    const QVector<QSizeF>::iterator end = m_sizeHintCache.end();
+
+    KItemRangeList::const_iterator rangeIt = itemRanges.constBegin();
+    const KItemRangeList::const_iterator rangeEnd = itemRanges.constEnd();
+
+    QVector<QSizeF>::iterator destIt = begin + rangeIt->index;
+    QVector<QSizeF>::iterator srcIt = destIt + rangeIt->count;
+
+    ++rangeIt;
+
+    while (srcIt != end) {
+        *destIt = *srcIt;
+        ++destIt;
+        ++srcIt;
+
+        if (rangeIt != rangeEnd && srcIt == begin + rangeIt->index) {
+            // Skip the items in the next removed range.
+            srcIt += rangeIt->count;
+            ++rangeIt;
+        }
+    }
+
+    m_sizeHintCache.erase(destIt, end);
+
+    // Note that the cache size might temporarily not match the model size if
+    // this function is called from KItemListView::setModel() to empty the cache.
+    if (!m_sizeHintCache.isEmpty() && m_itemListView->model()) {
+        Q_ASSERT(m_sizeHintCache.count() == m_itemListView->model()->count());
+    }
 }
 
 void KItemListSizeHintResolver::itemsMoved(int index, int count)