QAbstractItemView::dataChanged(): optimize call to QWidget::update()

When topLeft and bottomRight are different in QAIV::dataChanged(), the
current implementation simply calls QWidget::update() without checking
if the affected cells are visible. This results in a big performance hit
when cells are updated frequently.
Now try to compute the exact update rect by iterating through the
modified indexes.

Fixes: QTBUG-58580
Change-Id: I97de567d494e40ed8cdb1ea1f5b3cf3a2f60455e
Reviewed-by: Samuel Gaist <samuel.gaist@idiap.ch>

1 files changed, 1 insertions, 0 deletions

diff --git a/src/widgets/itemviews/qabstractitemview_p.h b/src/widgets/itemviews/qabstractitemview_p.h
index fe1c00248f..4b29b68b66 100644
--- a/src/widgets/itemviews/qabstractitemview_p.h
+++ b/src/widgets/itemviews/qabstractitemview_p.h
@@ -108,6 +108,7 @@ public:
     virtual void _q_layoutChanged();
     virtual void _q_rowsMoved(const QModelIndex &source, int sourceStart, int sourceEnd, const QModelIndex &destination, int destinationStart);
     virtual void _q_columnsMoved(const QModelIndex &source, int sourceStart, int sourceEnd, const QModelIndex &destination, int destinationStart);
+    virtual QRect intersectedRect(const QRect rect, const QModelIndex &topLeft, const QModelIndex &bottomRight) const;
 
     void _q_headerDataChanged() { doDelayedItemsLayout(); }
     void _q_scrollerStateChanged();