Created attachment 456 [details]
Demo python file

So, it is my understanding that it is reasonable to add to a QML tree by
creating a QDeclarativeItem from a QDeclarativeComponent within Python, as per
the docs*, and then setting that item to have a parent which is an item from
the QML tree.

If the desired parent is the root of the tree, acquired from a QDeclarativeView
object with QDeclarativeView.rootObject(), then the following error is
encountered:
TypeError: 'PySide.QtDeclarative.QDeclarativeItem.setParentItem' called with
wrong argument types:
 
PySide.QtDeclarative.QDeclarativeItem.setParentItem(PySide.QtGui.QGraphicsObject)
Supported signatures:
 
PySide.QtDeclarative.QDeclarativeItem.setParentItem(PySide.QtDeclarative.QDeclarativeItem)

This bug manifested itself after bug 925 was fixed. If one reverts commit
3a4369cf80199d5ab0dd1b5bf80a81abe10902e7, then everthing works as expected.

I have attached 3 files: 

1) A basic QML file (with the root just being a container for a red rectangle
for the purposes of this demo).
2) The python file that defines a ScrollArea object (I used a scroll area to
show something actually happening or not).
3) The ScrollArea QML file.

The bug is demonstrated by commenting out either lines 34 or 37.

In the case of line 34 being uncommented, we attempt to make the ScrollArea a
child of root object and so the error occurs.

In the case of line 37 being uncommented, we make the ScrollArea a child of the
red rectangle, which works just fine.

* http://doc.qt.nokia.com/4.7-snapshot/qdeclarativecomponent.htm and
http://www.pyside.org/docs/pyside/PySide/QtDeclarative/QDeclarativeComponent.html