Store the selected items in a more efficient way

Since Dolphin 2.0, we have stored the selected items in a QSet<int>,
which is neither space-efficient nor particularly fast when inserting
many items which are in a consecutive range.

This commit replaces the QSet<int> by a new class "KItemSet", which
stores the items in a sorted list of ranges. For each range, we only
store the first index and the length of the range, so we need a lot
less memory for most common selection patterns, and we also save quite
a few CPU cycles in many situations, because adding an item to the
KItemSet will in many cases not need a memory allocation at all, and
it's particularly easy when inserting sorted items into the KItemSet in
a row.

KItemSet contains a minimal subset of QSet's API which makes it
suitable as a drop-in replacement for our needs. It also has iterators,
such that the items can be iterated through easily, also with foreach.
One advantage of KItemSet compared to QSet<int> is that the items are
always iterated through in ascending order.

REVIEW: 113488

1 files changed, 2 insertions, 4 deletions

diff --git a/src/kitemviews/kfileitemlistview.cpp b/src/kitemviews/kfileitemlistview.cpp
index 8950c9a1e..fd01f2c4c 100644
--- a/src/kitemviews/kfileitemlistview.cpp
+++ b/src/kitemviews/kfileitemlistview.cpp
@@ -119,7 +119,7 @@ QStringList KFileItemListView::enabledPlugins() const
     return m_modelRolesUpdater ? m_modelRolesUpdater->enabledPlugins() : QStringList();
 }
 
-QPixmap KFileItemListView::createDragPixmap(const QSet<int>& indexes) const
+QPixmap KFileItemListView::createDragPixmap(const KItemSet& indexes) const
 {
     if (!model()) {
         return QPixmap();
@@ -165,10 +165,8 @@ QPixmap KFileItemListView::createDragPixmap(const QSet<int>& indexes) const
     QPainter painter(&dragPixmap);
     int x = 0;
     int y = 0;
-    QSetIterator<int> it(indexes);
-    while (it.hasNext()) {
-        const int index = it.next();
 
+    foreach (int index, indexes) {
         QPixmap pixmap = model()->data(index).value("iconPixmap").value<QPixmap>();
         if (pixmap.isNull()) {
             KIcon icon(model()->data(index).value("iconName").toString());