Is it actually possible to use a C++ QList as a model for a QML PathView?

tedmiddleton

I've already asked this question on stack overflow, but I thought I'd ask here where the real Qt experts are.

"http://stackoverflow.com/questions/15753419/qt-qml-data-model-doesnt-seem-to-work-with-c":http://stackoverflow.com/questions/15753419/qt-qml-data-model-doesnt-seem-to-work-with-c

The executive summary is that if I have a QML ListModel, I can set that as the model for either a QML ListView or a QML PathView. If I have C++ objects in a QList<>, which is what some of the QML data model examples do, I can create a working model for QML ListViews, but not QML PathViews. There seems to be something that ListView has that QList<MyClass> doesn't - some glue that gets PathView working but is missing when I make my QList.

I'm using Qt 4.8.4 on Windows. Any ideas? Does anyone know of a sample or an example that does this? Something that populates a PathView with a C++ model? Any C++ model, QList-based or QAbstractListModel-based, would be fine.

tedmiddleton

So I tried out a horrible hack - here it is:

main.cpp:
@
...
dataList.append( new DataObject( "c++ entry6 (purple)", "purple" ) );

QmlApplicationViewer viewer;
QDeclarativeContext * context = viewer.rootContext();
context->setContextProperty( "cppModel", QVariant::fromValue(dataList) );
context->setContextProperty( "cppModelCount", QVariant::fromValue(dataList.count()) );
viewer.setOrientation(QmlApplicationViewer::ScreenOrientationAuto);
...

@

cpptest.qml:

@
...
interactive: true
//model: qmlModel
model: cppModel

    delegate: Rectangle {
        width: 100
        height: 100
        color: colour
        Text {
            anchors.centerIn: parent
            text: name
        }
    }


    path: Path {
        startX: - my_path_view.width * cppModelCount / 2 + my_path_view.width / 2
        startY: my_path_view.height / 2
        PathLine {
            x: my_path_view.width * cppModelCount / 2 + my_path_view.width / 2
            y: my_path_view.height / 2
        }
    }
...

@

This actually produced the expected result. But its a terrible hack. Why is this not working properly? I can't believe that this is as-designed - it really does seem to be a Qt bug in the Path object, or the C++ bindings. cppModel.count, according to my debug printouts in the qml, is never available - in fact, the object that cppModel is bound to has no members at all.

I've build Qt before and I have the source - is there any place that anyone could point me to where I could start debugging this?

tedmiddleton

I got some help from a couple of experts on IRC (#qt-qml) last night and my example is working now. I've answered the StackOverflow question that I linked to above if anyone is interested.