Lots of pointer casts in QGraphicsView framework and performance?

The performance overhead is mostly prepaid; it's the result of the overhead of having the type() member. It might be efficient to retrieve the item->type() once. You know it doesn't change, but chances are the compiler doesn't.

The performance overhead is mostly prepaid; it's the result of the overhead of having the .type() member. It might be efficient to retrieve the item->type() once. You know it doesn't change, but chances are the compiler doesn't.

Edit Also, if you really have a lot of types, it could be worthwhile to introduce some intermediate types. Eg. If (dynamic_cast(item)) {/* check those types */} else {/* other types */}.

That is a good point. – kleimola Jun 10 '10 at 8:41 Yup. Now you're fetching it for every comparison.

I think it's a virtual call, and while cheap those are not free. Multiply that by every object in every scene, and you have a lot of cheap calls - no longer so cheap, then. – MSalters Jun 10 '10 at 12:21.

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