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Fix O(N^2) complexity issue in KItemListView::slotItemsRemoved()

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If many item ranges are removed, KItemListView::slotItemsRemoved()
could take very long because it looped over all items after the first
removed one for every removed range, even if most of these items are
not visible at all.

This commit improves this by just looping over the visible items (whose
number is limited by the window size) for each range.

Test case (for very large N):

touch {1..N}.png
touch {1..N}.jpg

(wait until all files are shown in the view)

rm *.jpg

REVIEW: 111398
This commit is contained in:
Frank Reininghaus 2013-07-05 19:47:44 +02:00
parent 654d64d3b8
commit 6c157fcbb8
1 changed files with 22 additions and 20 deletions
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42
dolphin/src/kitemviews/kitemlistview.cpp
View file

@ -44,6 +44,8 @@
#include <QStyleOptionRubberBand>
#include <QTimer>
#include <algorithm>
#include "kitemlistviewaccessible.h"
namespace {
@ -1063,11 +1065,6 @@ void KItemListView::slotItemsRemoved(const KItemRangeList& itemRanges)
m_layouter->markAsDirty();
int removedItemsCount = 0;
for (int i = 0; i < itemRanges.count(); ++i) {
removedItemsCount += itemRanges[i].count;
}
m_sizeHintResolver->itemsRemoved(itemRanges);
for (int i = itemRanges.count() - 1; i >= 0; --i) {
@ -1081,13 +1078,17 @@ void KItemListView::slotItemsRemoved(const KItemRangeList& itemRanges)
const int firstRemovedIndex = index;
const int lastRemovedIndex = index + count - 1;
const int lastIndex = m_model->count() - 1 + removedItemsCount;
removedItemsCount -= count;
// Remeber which items have to be moved because they are behind the removed range.
QVector<int> itemsToMove;
// Remove all KItemListWidget instances that got deleted
for (int i = firstRemovedIndex; i <= lastRemovedIndex; ++i) {
KItemListWidget* widget = m_visibleItems.value(i);
if (!widget) {
foreach (KItemListWidget* widget, m_visibleItems) {
const int i = widget->index();
if (i < firstRemovedIndex) {
continue;
} else if (i > lastRemovedIndex) {
itemsToMove.append(i);
continue;
}
@ -1115,17 +1116,18 @@ void KItemListView::slotItemsRemoved(const KItemRangeList& itemRanges)
}
// Update the indexes of all KItemListWidget instances that are located
// after the deleted items
for (int i = lastRemovedIndex + 1; i <= lastIndex; ++i) {
// after the deleted items. It is important to update them in ascending
// order to prevent overlaps when setting the new index.
std::sort(itemsToMove.begin(), itemsToMove.end());
foreach (int i, itemsToMove) {
KItemListWidget* widget = m_visibleItems.value(i);
if (widget) {
const int newIndex = i - count;
if (hasMultipleRanges) {
setWidgetIndex(widget, newIndex);
} else {
// Try to animate the moving of the item
moveWidgetToIndex(widget, newIndex);
}
Q_ASSERT(widget);
const int newIndex = i - count;
if (hasMultipleRanges) {
setWidgetIndex(widget, newIndex);
} else {
// Try to animate the moving of the item
moveWidgetToIndex(widget, newIndex);
}
}