wxpython DataViewCtrl - correctly identify drop target

Question

I would like to use a DataViewCtrl with a PyDataViewModel as tree-like control with drag-and-drop support. I am almost there but I cannot figure out how to distinguish between dropping an item between the lines or on top of the parent item. The two screenshots illustrate the issue. In both cases the item identified as the drop target is the parent item.

This is the code:

import wx
import wx.dataview as dv

print(wx.__version__)

class Container(list):
    def __init__(self, name):
        self.name = name

    def __str__(self):
        return 'Container {}'.format(self.name)

class Element(object):
    def __init__(self, name):
        self.name = name

    def __str__(self):
        return 'Element {}'.format(self.name)

    @property
    def len(self):
        return str(len(self.name))

class MyTreeListModel(dv.PyDataViewModel):
    def __init__(self, data):
        dv.PyDataViewModel.__init__(self)
        self.data = data

    def GetColumnCount(self):
        return 2

    def GetColumnType(self, col):
        mapper = { 0 : 'string',
                   1 : 'string'
                   }
        return mapper[col]


    def GetChildren(self, parent, children):
        if not parent:
            for cont in self.data:
                children.append(self.ObjectToItem(cont))
            return len(self.data)

        node = self.ItemToObject(parent)
        if isinstance(node, Container):
            for ds in node:
                children.append(self.ObjectToItem(ds))
            return len(node)
        return 0

    def IsContainer(self, item):
        if not item:
            return True
        node = self.ItemToObject(item)
        if isinstance(node, Container):
            return True
        return False

    def GetParent(self, item):
        if not item:
            return dv.NullDataViewItem

        node = self.ItemToObject(item)
        if isinstance(node, Container):
            return dv.NullDataViewItem
        elif isinstance(node, Element):
            for g in self.data:
                try:
                    g.index(node)
                except ValueError:
                    continue
                else:
                    return self.ObjectToItem(g)

    def GetValue(self, item, col):
        node = self.ItemToObject(item)

        if isinstance(node, Container):
            mapper = { 0 : node.name,
                       1 : '',
                       }
            return mapper[col]

        elif isinstance(node, Element):
            mapper = { 0 : node.name,
                       1 : node.len
                       }
            return mapper[col]

        else:
            raise RuntimeError("unknown node type")

class MyFrame(wx.Frame):
    def __init__(self, parent):
        wx.Frame.__init__(self, parent, -1, "Table")

        panel = wx.Panel(self)

        dvcTree = dv.DataViewCtrl(panel,style=wx.BORDER_THEME|dv.DV_MULTIPLE)
        self.model = MyTreeListModel(data)
        dvcTree.AssociateModel(self.model)

        dvcTree.AppendTextColumn("Container",   0, width=80)
        dvcTree.AppendTextColumn("Element",   1, width=80)

        dvcTree.Bind(dv.EVT_DATAVIEW_ITEM_BEGIN_DRAG, self._onDrag)
        dvcTree.Bind(dv.EVT_DATAVIEW_ITEM_DROP, self._onEndDrag)
        dvcTree.Bind(dv.EVT_DATAVIEW_ITEM_DROP_POSSIBLE, self._onDropPossible)

        self.dvcTree = dvcTree
        dvcTree.EnableDragSource(wx.DataFormat(wx.DF_UNICODETEXT))
        dvcTree.EnableDropTarget(wx.DataFormat(wx.DF_UNICODETEXT))

        box = wx.BoxSizer(wx.VERTICAL)
        box.Add(dvcTree, 1, wx.EXPAND)
        panel.SetSizer(box)
        self.Layout()

    def _onDropPossible(self, evt):
        item = evt.GetItem()
        mod = evt.GetModel()

        if not evt.GetItem().IsOk():
            return

    def _onEndDrag(self, evt):
        if not evt.GetItem().IsOk():
            evt.Veto()
            return

        mod = evt.GetModel()
        print('dropped at', mod.ItemToObject(evt.GetItem()))
        try:
            print('parent:',mod.ItemToObject(mod.GetParent(evt.GetItem())))
        except TypeError:
            print('parent: None')

    def _onDrag(self, evt):
        evt.Allow()
        mod = evt.GetModel()
        print('from', mod.GetValue(evt.GetItem(),0))
        evt.SetDataObject(wx.TextDataObject('don\'t know how to retrieve that information in the drop handler'))
        evt.SetDragFlags(wx.Drag_AllowMove)      

data = [Container('eins'),Container('zwei'),Container('drei')]
for d in data:
    d[:] = [Element('element {}'.format('X'*q)) for q in range(5)]

if __name__ == "__main__":
    app = wx.App()
    f = MyFrame(None)
    f.Show()
    app.MainLoop()

EDIT:

This is mostly a problem on OSX since the MSW implementation does not offer to drop between lines. I was not able to test it on linux though.