Gtk.TreeDragSource::drag_data_get

function vfunc_drag_data_get(path:Gtk.TreePath, selection_data:Gtk.SelectionData):Boolean {
}

Asks the Gtk.TreeDragSource to fill in selection_data with a representation of the row at path. selection_data->target gives the required type of the data. Should robustly handle a path no longer found in the model!