Hm, another strange thing that showed up: when I add 250 000 small (5x5pix) rectangles on the GraphicsScene and then want to show it using GraphicsView, the cpu 'user' load rises to ~90%. Not just during plotting, but for all the time after the rectangles are drawn. That's looks quite strange to me... (If I draw ~50 000 rectangles, the cpu usage is about 50%)

Does anybody know, what is GraphicsView doing in the background? Still updating the view?
I'm quite disappointed, because they say in Qt docs:
Graphics View uses a BSP (Binary Space Partitioning) tree to provide very fast item discovery, and as a result of this, it can visualize large scenes in real-time, even with millions of items.
But how can one use it, if the cpu load is 90% :/

Well, maybe I've made a mistake somewhere, but I just tried to edit one of the examples (portedcanvas in examples/graphicsview) and instead of adding one rectangle I added many of them, so I don't know what's wrong...

Any advice appreciated, thanks...