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QGraphicsPathItem: Slow when scaling with children

Subject: QGraphicsPathItem: Slow when scaling with children
From: Markus
Date: Fri, 9 Mar 2007 23:14:24 +0100

I've been programming a GraphicsView application that contains a 
QGraphicsPathItem instance with ~9000 children in a horizontal row. Each such 
child contains two QPainterPath instances which are rendered in the child's 
paint() method. The parent of those 9000 items does not do any drawing by 
itself and is only responsible for vertical scaling.
The items are of such size that only ~20 are visible at a time in the 

The issue I am having is that when scaling, the framerate is very low, 
approximately around 2fps. If I reduce the number of children, the framerate 
increases, even though the same number of items is visible on screen as in 
the previous case.
It thus seems to me that the scaling is propagated to all children, even 
though they are not visible on screen. Is there any way to turn this off or 
otherwise improve performance?


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