def _on_tree_begin_drag(self, event):

        # Get the element, its id and the point where the event occurred.
        data, wxid, flags, point = self._unpack_event(event)

        if point == (0,0):
            # Apply workaround.
            point = self._point_left_clicked
            wxid, flags = self.control.HitTest(point)
            data = self.control.GetPyData(wxid)

        if data is not None:
            populated, element = data

            # Trait notification.
            self.element_begin_drag = element

        return
Populates all the main bug tracker fields in the form.
dataset/ETHPy150Open enthought/pyface/pyface/viewer/tree_viewer.py/TreeViewer._on_tree_begin_drag--crossover with--dataset/ETHPy150Open reviewboard/reviewboard/reviewboard/scmtools/forms.py/RepositoryForm._populate_bug_tracker_fields