From a85f708449a5fb61740ec12abd4cb9df3a5265ad Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Samuel=20R=C3=B8dal?= <sroedal@trolltech.com>
Date: Mon, 25 Jan 2010 11:52:14 +0100
Subject: Added optimization flag to QGraphicsItemPrivate.
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Avoid traversing the whole child hierarchy when opacity changes unless
there are children with graphics effects.

Reviewed-by: Bjørn Erik Nilsen
---
 src/gui/graphicsview/qgraphicsitem.cpp | 22 ++++++++++++++++++++++
 src/gui/graphicsview/qgraphicsitem_p.h |  3 +++
 2 files changed, 25 insertions(+)

diff --git a/src/gui/graphicsview/qgraphicsitem.cpp b/src/gui/graphicsview/qgraphicsitem.cpp
index b8d392d..66493b7 100644
--- a/src/gui/graphicsview/qgraphicsitem.cpp
+++ b/src/gui/graphicsview/qgraphicsitem.cpp
@@ -1075,6 +1075,10 @@ void QGraphicsItemPrivate::setParentItemHelper(QGraphicsItem *newParent, const Q
         p = p->d_ptr->parent;
     }
 
+    // Update graphics effect optimization flag
+    if (newParent && (graphicsEffect || mayHaveChildWithGraphicsEffect))
+        newParent->d_ptr->updateChildWithGraphicsEffectFlagRecursively();
+
     // Update focus scope item ptr in new scope.
     QGraphicsItem *newFocusScopeItem = subFocusItem ? subFocusItem : parentFocusScopeItem;
     if (newFocusScopeItem && newParent) {
@@ -2612,6 +2616,8 @@ void QGraphicsItem::setGraphicsEffect(QGraphicsEffect *effect)
     if (d_ptr->graphicsEffect) {
         delete d_ptr->graphicsEffect;
         d_ptr->graphicsEffect = 0;
+    } else if (d_ptr->parent) {
+        d_ptr->parent->d_ptr->updateChildWithGraphicsEffectFlagRecursively();
     }
 
     if (effect) {
@@ -2625,6 +2631,19 @@ void QGraphicsItem::setGraphicsEffect(QGraphicsEffect *effect)
 }
 #endif //QT_NO_GRAPHICSEFFECT
 
+void QGraphicsItemPrivate::updateChildWithGraphicsEffectFlagRecursively()
+{
+#ifndef QT_NO_GRAPHICSEFFECT
+    QGraphicsItemPrivate *itemPrivate = this;
+    do {
+        // parent chain already notified?
+        if (itemPrivate->mayHaveChildWithGraphicsEffect)
+            return;
+        itemPrivate->mayHaveChildWithGraphicsEffect = 1;
+    } while ((itemPrivate = itemPrivate->parent ? itemPrivate->parent->d_ptr.data() : 0));
+#endif
+}
+
 /*!
     \internal
     \since 4.6
@@ -5092,6 +5111,9 @@ void QGraphicsItemPrivate::invalidateParentGraphicsEffectsRecursively()
 
 void QGraphicsItemPrivate::invalidateChildGraphicsEffectsRecursively(QGraphicsItemPrivate::InvalidateReason reason)
 {
+    if (!mayHaveChildWithGraphicsEffect)
+        return;
+
     for (int i = 0; i < children.size(); ++i) {
         QGraphicsItemPrivate *childPrivate = children.at(i)->d_ptr.data();
         if (reason == OpacityChanged && (childPrivate->flags & QGraphicsItem::ItemIgnoresParentOpacity))
diff --git a/src/gui/graphicsview/qgraphicsitem_p.h b/src/gui/graphicsview/qgraphicsitem_p.h
index ff6e8bd..986a977 100644
--- a/src/gui/graphicsview/qgraphicsitem_p.h
+++ b/src/gui/graphicsview/qgraphicsitem_p.h
@@ -179,6 +179,7 @@ public:
         updateDueToGraphicsEffect(0),
         scenePosDescendants(0),
         pendingPolish(0),
+        mayHaveChildWithGraphicsEffect(0),
         globalStackingOrder(-1),
         q_ptr(0)
     {
@@ -196,6 +197,7 @@ public:
         return item->d_ptr.data();
     }
 
+    void updateChildWithGraphicsEffectFlagRecursively();
     void updateAncestorFlag(QGraphicsItem::GraphicsItemFlag childFlag,
                             AncestorFlag flag = NoFlag, bool enabled = false, bool root = true);
     void updateAncestorFlags();
@@ -492,6 +494,7 @@ public:
     quint32 updateDueToGraphicsEffect : 1;
     quint32 scenePosDescendants : 1;
     quint32 pendingPolish : 1;
+    quint32 mayHaveChildWithGraphicsEffect : 1;
 
     // Optional stacking order
     int globalStackingOrder;
-- 
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