QGraphicsScene performance (200000 static items and 1 moving)

**Obey-Kun** · 27th January 2011, 16:27

Hello. I'm making cad-like software. It is for temperature field modeling and visulization. User will work with MANY blocks here. It can be 10000, it can be 10000 or more.

I obviously use Graphics Scene engine for it. Each block is QGraphicsItem.

Also I have 1 item there â€” Anchor. It follows cursor. It is done by signal (from view)l/slot (in Anchor). Slot makes setPos().

The problem is that setPos() sometimes results in scene reindexing. It is slow, when there is many items.

I'm thinking about moving that moving item to view (make it as widget there). Any better solution?

Screenshot discribing why I need many blocks (not so many blocks here): http://obey.su/upload/11-01-23_LOR_QFrost/qfrost2.png

**Lykurg** · 27th January 2011, 21:09

There are several options coming in my mind: disable indexing or "play around" with the various performance tunings the view and scene offers: level of detail, update mode...

Further (please attach images to the forum, that the post stays valid) it seems that you are composing a grid out of items, and your anchor "frames" one item. If so, skip the anchor, and alter the paint method of your items to draw the focus frame itself. To move the anchor, unset the "highlight frame" from the current one and set it to the other.