canFetchMore is getiing called 3 times ??

[ChrisW67]

Thanks but, I did not mentioned anywhere that I am fetching data in canfectMore().

Not directly but you say the view calls canFetchMore() three times and...

My prob : lets say I wanted to get top 100 items & form tree out of it, because of above behavior I am ending up with 3*100 (buffer size) items.

That is, calling canFetchMore() three times results in 3 times the number of rows fetched in the model. You did not say that the view calls fetchMore() 3 times. If you had done that, then you would have been describing correct and expected operation. I assumed that you were describing unexpected behaviour. One obvious way that unexpected row fetching might happen is if canFetchMore() actually fetched rows.

Problem is that canFetchMore() is calling 3 times when it supposed to call 1 time.

No, you would like it to only call canFetchMore() once but that is not a requirement on the view, just an assumption on your part.
If canFetchMore() returns true then the view can call fetchMore() if it wants, and the correct behaviour of the model is to fetch more rows. The view will fetch rows as it requires and probably in some convenient quantity for its internal buffering/performance/rendering purposes (i would guess 256 rows if the sql model is anything to go by). If you do not like this behaviour then you are free to implement your own view.

[prasad_N]

If canFetchMore() returns true then the view can call fetchMore() if it wants, and the correct behaviour of the model is to fetch more rows. The view will fetch rows as it requires and probably in some convenient quantity for its internal buffering/performance/rendering purposes (i would guess 256 rows if the sql model is anything to go by).

- I understand that because of view internal calls, canFetchMore() is getting called more than once (3 times in my case even if I return false from canfetch() or even if view is full with Items)
- After some experiments I came to know that header data is one which causes canFetchMore() to be called (When we change headerData dynamically its calling canFetchMore() ),
so I decided to have customized model & View for my header & It worked out Now when ever I expand an item (or when canFetchMore() supposed be called by view) instead of 3 times its getting called 2 times.
- now its getting called twice as follows when I expand a item

canFectMore Called with parent = QModelIndex(0,0,0xd00870,DebugTreeModel(0xcf4ec0) ) //one for the expanded Item as parent
canFectMore Called with parent = = QModelIndex(-1,-1,0x0,QObject(0x0) ) //One for root item

this might be of other reason like header data.

If you do not like this behaviour then you are free to implement your own view.

could let me know which functions I have to re implement for this in view ??