[Qt-qml] ListView crashes with more than 256 delegate elements.

[martin.jones at nokia.com]

It is a bug.  The fix for QTBUG-16039 may well have fixed it, but I'd like to test with your case.

Br,
Martin.

> -----Original Message-----
> From: ext Yuvraaj Kelkar [mailto:yuvraaj at gmail.com]
> Sent: Wednesday, 5 January 2011 2:14 AM
> To: QT QML List
> Cc: Jones Martin (Nokia-MS-Qt/Brisbane)
> Subject: Re: [Qt-qml] ListView crashes with more than 256 delegate elements.
> 
> I found a workaround - so I'm not sure if it is still a bug.
> The work around was:
> while (model->canFetchMore()) { model->fetchMore(); }
> 
> The problem (at least what I could figure out) was that the QML list
> view expected the data to be cached and attempted to access it even
> when it wasn't. The fetchmore loop makes sure that the data is cached.
> 
> Now it might very well be that this is still a bug in that I had to
> force fill the entire cache whereas the reason for the fetchmore
> methods is incremental fillups.
> 
> If you think that is a bug then I'll file it.
> 
> On Mon, Jan 3, 2011 at 11:47 PM,  <martin.jones at nokia.com> wrote:
> > This is related to http://bugreports.qt.nokia.com/browse/QTBUG-16039, but it
> would be good if you could create a new bug report with an example which
> reproduces your use case.
> >
> > Br,
> > Martin.
> >
> >> -----Original Message-----
> >> From: qt-qml-bounces+martin.jones=nokia.com at qt.nokia.com [mailto:qt-qml-
> >> bounces+martin.jones=nokia.com at qt.nokia.com] On Behalf Of ext Yuvraaj
> Kelkar
> >> Sent: Tuesday, 4 January 2011 2:36 AM
> >> To: qt-qml at qt.nokia.com
> >> Subject: Re: [Qt-qml] ListView crashes with more than 256 delegate elements.
> >>
> >> Posting the solution to fix this problem:
> >>
> >> > I have a QML List View here:
> >> >
> >>
> http://code.google.com/p/qgvdial/source/browse/branches/contactsui/qml/Contacts
> >> List.qml?r=285
> >> > This list shows contacts from a model which I derive from QSqlQueryModel.
> >> > There are about 800 contacts in the table.
> >> >
> >> > When I scroll down the contacts list, at the point where QML is
> >> > loading the 256th delegate, it spews the output:
> >> > "
> >> > QDeclarativeComponent: Cannot create new component instance before
> >> > completing the previous
> >> > <Unknown File>: QML VisualDataModel: Error creating delgate
> >> > qrc:/ContactsList.qml:105:13: QML Text: Binding loop detected for
> >> > property "text"
> >> > qrc:/ContactsList.qml:95:32767: QML Component: Delegate component must
> >> > be Item type.
> >> > "
> >> >
> >> > And then it segfaults.
> >> >
> >> > If I use qmlviewer with a test ListModel with >1000 contacts, it
> >> > works, but my code does not.
> >> > I think this may be a QML bug, but I am not sure.
> >> > Any help is appreciated.
> >>
> >> The solution is to add
> >> while (model->canFetchMore()) { model->fetchMore(); }
> >> after telling the QML view about the model.
> >>
> >> The QML ListView was attempting to access the next cached model index.
> >> Since only the first 256 entries had been indexed, the 257th attempt
> >> consistently segfaulted.
> >> With the canFetch,fetchMore loop, the cache is entirely populated and
> >> all is well.
> >> _______________________________________________
> >> Qt-qml mailing list
> >> Qt-qml at qt.nokia.com
> >> http://lists.qt.nokia.com/mailman/listinfo/qt-qml
> >