Rubberband relative to QGraphicsScene

**pherthyl** · 13th December 2007, 00:27

Originally Posted by pherthyl

So now I just have to figure out the strange selection bug...

Aha! Now I've isolated the problem.

Can someone please try out the attached code and select the items as shown in the screenshot? The ellipse is correctly selected, while the rectangle is not. Not sure where this is coming from yet. Something to do with that the rect item has a default shape implementation?

**pherthyl** · 13th December 2007, 03:36

Originally Posted by pherthyl

I'll have to rethink that function.

CacheBackground fixed this problem.

**pherthyl** · 14th December 2007, 07:21

Well I fixed the selection bug by implementing my own version of setSelectionArea and reporting the bug to Trolltech. Now everything works.

**Gopala Krishna** · 14th December 2007, 12:27

Nice, but what bug was there in qt's setSelectionArea function ?

**pherthyl** · 14th December 2007, 15:48

Originally Posted by Gopala Krishna

Nice, but what bug was there in qt's setSelectionArea function ?

No idea. I just gave them the compileable example and let them figure it out

But I wrote my own that just iterates through all the items and uses either shape().intersects() (for line items) and sceneBoundingRect().intersects() for my boxes. Maybe not so great for large numbers of items (haven't checked how qt does it), but I don't anticipate having more than about 100 on the scene at once.

**pherthyl** · 20th December 2007, 19:30

Got a response from Trolltech support:

This does indeed look like a bug in Qt. The problem is most likely the
same as the one reported here

http://trolltech.com/developer/task-...ntry&id=191706

as QGraphicsScene uses QPainterPath for calculating whether the
rectangle intersects with the selection rectangle.

We'll verify that fixing this also solves your problem.

Thanks for reporting.