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, 5 insertions, 5 deletions

diff --git a/src/kitemviews/kitemlistselectionmanager.h b/src/kitemviews/kitemlistselectionmanager.h
index c89b8a4b8..c4decd39e 100644
--- a/src/kitemviews/kitemlistselectionmanager.h
+++ b/src/kitemviews/kitemlistselectionmanager.h
@@ -26,9 +26,9 @@
 #include <libdolphin_export.h>
 
 #include <kitemviews/kitemmodelbase.h>
+#include <kitemviews/kitemset.h>
 
 #include <QObject>
-#include <QSet>
 
 class KItemModelBase;
 
@@ -57,8 +57,8 @@ public:
     void setCurrentItem(int current);
     int currentItem() const;
 
-    void setSelectedItems(const QSet<int>& items);
-    QSet<int> selectedItems() const;
+    void setSelectedItems(const KItemSet& items);
+    KItemSet selectedItems() const;
     bool isSelected(int index) const;
     bool hasSelection() const;
 
@@ -73,7 +73,7 @@ public:
 
 signals:
     void currentChanged(int current, int previous);
-    void selectionChanged(const QSet<int>& current, const QSet<int>& previous);
+    void selectionChanged(const KItemSet& current, const KItemSet& previous);
 
 private:
     void setModel(KItemModelBase* model);
@@ -91,7 +91,7 @@ private:
 private:
     int m_currentItem;
     int m_anchorItem;
-    QSet<int> m_selectedItems;
+    KItemSet m_selectedItems;
     bool m_isAnchoredSelectionActive;
 
     KItemModelBase* m_model;