Gtk.TreeView.prototype.set_column_drag_function

function set_column_drag_function(func:Gtk.TreeViewColumnDropFunc):void {
    // Gjs wrapper for gtk_tree_view_set_column_drag_function()
}

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 Gtk.TreeViewColumn being dragged, the two Gtk.TreeViewColumn s determining the drop spot, and user_data. If either of the Gtk.TreeViewColumn arguments for the drop spot are null, then they indicate an edge. If func is set to be null, then tree_view reverts to the default behavior of allowing all columns to be dropped everywhere.