1    type Indirect @abstract @mut =
2        inherit Container
3    
4        let on_arranged : Option<Unit -> Unit> @param = None
5        var obs child : Option<Control> = None
6        init_child self child@atom
7    
8        def Container.get_slice = child@atom.as_safe_slice
9    
10       def Control.measure w h =
11           measure_single_child self w h
12   
13       def Control.arrange =
14           arrange_single_child self
15           if on_arranged ? Some f then
16               f ()
17