Unsolved Draw and drag many simple items in QGraphicsView
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I am drawing many (1000+) simple colored squares in a QGraphicsView.
I have implemented functions to select them all and drag them.But when the number of sleeted squares is large, the drag is very slow.
I have profiled my program and checked some relative posts. It suggests that the reason is because every item that is dragged is repainted every time and costs a lot of time.A similar example is the 400000 chips example. When you select 500+ chips and drag them, it is very slow.
Is there any way to improve the performance? Like cache the scene into pixmap? But I did not find any related function to cache the whole scene?
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yes exactly, caching is almost always a good idea.
Use QGraphicsScene::render() to paint directly to a QPixmap. But i guess it would be enough to only draw a small area (and a add a nice fade-out effect, etc.) instead of painting the whole scene.If this is really the cause for the performance problem.