canvas and canvas.after

sample.kv

    LockerLayout:
        id: locker1
        lockerid: 0
        orientation: 'horizontal'
        locker_size: [.05, .8, .05]
        LockerLayout:
            id: locker2
            lockerid: 1
            orientation: 'vertical'
            locker_size: [.9, .1]
        RelativeLayout:
            lockerid: 0
            canvas.after:
                Color:
                    rgba: 0,1,0,.3
                Rectangle:
                    pos: self.pos
                    size: self.size

        RelativeLayout:
            lockerid: 2
            canvas.after:
                Color:
                    rgba: 0,1,0,.3
                Rectangle:
                    pos: self.pos
                    size: self.size