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, 2 deletions

diff --git a/src/kitemviews/kitemlistview.h b/src/kitemviews/kitemlistview.h
index 14360b02b..dbe923086 100644
--- a/src/kitemviews/kitemlistview.h
+++ b/src/kitemviews/kitemlistview.h
@@ -271,7 +271,7 @@ public:
      * @return Pixmap that is used for a drag operation based on the
      *         items given by \a indexes.
      */
-    virtual QPixmap createDragPixmap(const QSet<int>& indexes) const;
+    virtual QPixmap createDragPixmap(const KItemSet& indexes) const;
 
     /**
      * Lets the user edit the role \a role for item with the index \a index.
@@ -400,7 +400,7 @@ protected slots:
     virtual void slotSortOrderChanged(Qt::SortOrder current, Qt::SortOrder previous);
     virtual void slotSortRoleChanged(const QByteArray& current, const QByteArray& previous);
     virtual void slotCurrentChanged(int current, int previous);
-    virtual void slotSelectionChanged(const QSet<int>& current, const QSet<int>& previous);
+    virtual void slotSelectionChanged(const KItemSet& current, const KItemSet& previous);
 
 private slots:
     void slotAnimationFinished(QGraphicsWidget* widget,