QGraphicsItem is not drawn again?

[zgulser]

Hi all,

I have the following problem;

I have a scene and items in it. Once I zoom in the scene, some of the items go off the scene normally. But when I zoom out, I don't the items that are there before I zoomed in.

What could be the possible problem?

[high_flyer]

What happens if you zoom so, that for example an item is only half out site the view area, and then zoom back, will you see the whole object item again, or only the part that was not zoomed "out"?

[zgulser]

If only a part of an item is seen after zooming in, then no problem after zooming out. If the item is completely off the scene after zooming in, then nothing appears about the item.

Is it more clear now?

[high_flyer]

can you show your zooming code?

[zgulser]

I'm afraid I can't.

But you see the problem is not about zooming. I guess I failed in updating of the relevant items issue or the scene itself.

[high_flyer]

But you see the problem is not about zooming. I guess I failed in updating of the relevant items issue or the scene itself.

Probably, but that should be visible in the zooming code, since then we can see what happens when you zoom out again...

But without code it very hard to help...

[zgulser]

Batu olm bi gavra hele ya felaket sıkıldım. batu olmazsa seyhun o da olmazsa bu işin ordinasyüsü levent.

[zgulser]

The problem here is basicly because of item's removal from the scene bounding rect. So how can I put the item back into the scene rectangle when it's gone out of it by zooming in action , if I zoom out in the scene again?

[scascio]

Why are you managing yourself the items viewed in your scene?

Since Qt do the job for you and compute the visible items based on QGraphicsItem::boundingRect, you will get in QGraphicsView::drawItems the list of visible items.
So no need to remove or add items.

Are you computing the zoom yourself in the scene, in your custom items or elsewhere?

[zgulser]

I guess you misunderstood me. I didn't remove or add items when I zoom in or zoom out. This is what I think as a possible reason that the items are no longer visible once they are off the scene's bounding rectangle. It is also strange that the program still enters item's paint method although it's not drawn.

I deal zooming stuff in the view by the way.

[scascio]

So that means that the item are seen by Qt, according to its bounding rect.

Can you post a simplified version of your zoom function?

There is probably a coordinates conversion error of your items position, so they are drawn out of the viewed rect.

Another questions :
* Why not using Qt built-in QGraphicsView::scale?
* Do you manage derived QGraphicsItem with overloaded paint?

[zgulser]

Hi,

sorry but I can't because I'm using different library for such operations(zooming, rotating etc.) and the functions are hidden which means not available. I just called setRange(+/- rangeAmount) and it does. Sorry fot that.

By the way, don't you think that items would have drawn wrongly at the begining or at the situations in which the items are in still scene's rectangle if there is a coordinate error?

Anyway regarding your last questions,

I didn't prefer to use it because I deal with geographic coordinates( latitudes and longitudes) so that's why we use different library as I mentioned.

And I don't think my paint functions are overloaded. They're just dealing with paint issues.