⚠️ Deprecated ⚠️

This is deprecated since version 4.10.

Use class@Gtk.ListView or class@Gtk.ColumnView instead

Sets a user function for determining where a column may be dropped when dragged. This function is called on every column pair in turn at the beginning of a column drag to determine where a drop can take place. The arguments passed to @func are: the @tree_view, the GtkTreeViewColumn being dragged, the two GtkTreeViewColumns determining the drop spot, and

Parameters