Fixed a bottleneck in itemviews that would ask for an update outside

of the boundaries of the viewport.

Now we catch this and don't call update. This was a performance
regression against 4.4.

Task-number: 256183
Reviewed-by: alexis

1 files changed, 8 insertions, 2 deletions

diff --git a/src/gui/itemviews/qabstractitemview.cpp b/src/gui/itemviews/qabstractitemview.cpp
index 5673019..c3d1bf7 100644
--- a/src/gui/itemviews/qabstractitemview.cpp
+++ b/src/gui/itemviews/qabstractitemview.cpp
@@ -2901,8 +2901,14 @@ void QAbstractItemView::scrollToBottom()
 void QAbstractItemView::update(const QModelIndex &index)
 {
     Q_D(QAbstractItemView);
-    if (index.isValid())
-        d->viewport->update(visualRect(index));
+    if (index.isValid()) {
+        const QRect rect = visualRect(index);
+        //this test is important for peformance reason
+        //For example in dataChanged we simply update all the cells without checking
+        //it can be a major bottleneck to update rects that aren't even part of the viewport
+        if (d->viewport->geometry().intersects(rect))
+            d->viewport->update(rect);
+    }
 }
 
 /*!