QGraphicsSceneIndex: replace polymorphism with a function pointer

QGraphicsSceneIndexIntersector was used as a kind of polymorpic predicate in
items_helper(). But it had only one function and the instances of it, which
were kept around in QGraphicsSceneIndexPrivate, were re-initialised on every
call to items_helper(), which means that one can just as well pass that
miniscule amount of data to the function itself.

Replaced the polymorphism with a function pointer and the comparison state
(which is conceptually const if it wasn't for the requirement to assign
to it all the time) with a const void * argument.

Effects on Linux AMD64 GCC 4.9-trunk release stripped:
  text:   -1584B
  data:    -376B
  relocs:   -26

I've wrapped the functions in a namespace. The only reason for this is
to keep the functions, previously defined in class bodies, at the same
indentation level so as not to destroy the git-blame history for them.

Change-Id: I8e1f48030047a3c54e881de7c77a3325b3e1f509
Reviewed-by: Alexis Menard <alexis@webkit.org>
Reviewed-by: Andreas Aardal Hanssen <andreas@hanssen.name>

1 files changed, 10 insertions, 23 deletions

diff --git a/src/widgets/graphicsview/qgraphicssceneindex_p.h b/src/widgets/graphicsview/qgraphicssceneindex_p.h
index 29b321fb1d..215fefe9b7 100644
--- a/src/widgets/graphicsview/qgraphicssceneindex_p.h
+++ b/src/widgets/graphicsview/qgraphicssceneindex_p.h
@@ -66,15 +66,14 @@ QT_BEGIN_NAMESPACE
 
 #if !defined(QT_NO_GRAPHICSVIEW)
 
-class QGraphicsSceneIndexIntersector;
-class QGraphicsSceneIndexPointIntersector;
-class QGraphicsSceneIndexRectIntersector;
-class QGraphicsSceneIndexPathIntersector;
 class QGraphicsSceneIndexPrivate;
 class QPointF;
 class QRectF;
 template<typename T> class QList;
 
+typedef bool (*QGraphicsSceneIndexIntersector)(const QGraphicsItem *item, const QRectF &exposeRect, Qt::ItemSelectionMode mode,
+                                               const QTransform &deviceTransform, const void *data);
+
 class Q_AUTOTEST_EXPORT QGraphicsSceneIndex : public QObject
 {
     Q_OBJECT
@@ -133,27 +132,24 @@ public:
     static bool itemCollidesWithPath(const QGraphicsItem *item, const QPainterPath &path, Qt::ItemSelectionMode mode);
 
     void recursive_items_helper(QGraphicsItem *item, QRectF exposeRect,
-                                QGraphicsSceneIndexIntersector *intersector, QList<QGraphicsItem *> *items,
+                                QGraphicsSceneIndexIntersector intersect, QList<QGraphicsItem *> *items,
                                 const QTransform &viewTransform,
-                                Qt::ItemSelectionMode mode, qreal parentOpacity = 1.0) const;
-    inline void items_helper(const QRectF &rect, QGraphicsSceneIndexIntersector *intersector,
+                                Qt::ItemSelectionMode mode, qreal parentOpacity, const void *intersectData) const;
+    inline void items_helper(const QRectF &rect, QGraphicsSceneIndexIntersector intersect,
                              QList<QGraphicsItem *> *items, const QTransform &viewTransform,
-                             Qt::ItemSelectionMode mode, Qt::SortOrder order) const;
+                             Qt::ItemSelectionMode mode, Qt::SortOrder order, const void *intersectData) const;
 
     QGraphicsScene *scene;
-    QGraphicsSceneIndexPointIntersector *pointIntersector;
-    QGraphicsSceneIndexRectIntersector *rectIntersector;
-    QGraphicsSceneIndexPathIntersector *pathIntersector;
 };
 
-inline void QGraphicsSceneIndexPrivate::items_helper(const QRectF &rect, QGraphicsSceneIndexIntersector *intersector,
+inline void QGraphicsSceneIndexPrivate::items_helper(const QRectF &rect, QGraphicsSceneIndexIntersector intersect,
                                                      QList<QGraphicsItem *> *items, const QTransform &viewTransform,
-                                                     Qt::ItemSelectionMode mode, Qt::SortOrder order) const
+                                                     Qt::ItemSelectionMode mode, Qt::SortOrder order, const void *intersectData) const
 {
     Q_Q(const QGraphicsSceneIndex);
     const QList<QGraphicsItem *> tli = q->estimateTopLevelItems(rect, Qt::AscendingOrder);
     for (int i = 0; i < tli.size(); ++i)
-        recursive_items_helper(tli.at(i), rect, intersector, items, viewTransform, mode);
+        recursive_items_helper(tli.at(i), rect, intersect, items, viewTransform, mode, 1.0, intersectData);
     if (order == Qt::DescendingOrder) {
         const int n = items->size();
         for (int i = 0; i < n / 2; ++i)
@@ -161,15 +157,6 @@ inline void QGraphicsSceneIndexPrivate::items_helper(const QRectF &rect, QGraphi
     }
 }
 
-class QGraphicsSceneIndexIntersector
-{
-public:
-    QGraphicsSceneIndexIntersector() { }
-    virtual ~QGraphicsSceneIndexIntersector() { }
-    virtual bool intersect(const QGraphicsItem *item, const QRectF &exposeRect, Qt::ItemSelectionMode mode,
-                           const QTransform &deviceTransform) const = 0;
-};
-
 #endif // QT_NO_GRAPHICSVIEW
 
 QT_END_NAMESPACE