sc.py

from kivy.app import App
from kivy.lang import Builder
from kivy.factory import Factory


KV = '''
FloatLayout:
    Scatter:
        id: scatter
        size_hint: None, None
        auto_bring_to_front: False
        Widget:
            id: widget
            point: 20, 20
            canvas:
                Color:
                Line:
                    rectangle: [0, 0] + self.size
                Rectangle:
                    pos: self.point
                    size: 10, 10

    Widget:
        canvas:
            Color:
                rgba: 1, 0, 0, 1
            Line:
                width: 2
                rectangle:
                    (
                    scatter.pos,
                    scatter.size,
                    scatter.scale,
                    ) and (
                    self.to_widget(*widget.to_window(*widget.point))
                    + (10, 10)
                    )
'''


class Application(App):
    def build(self):
        return Builder.load_string(KV)


if __name__ == "__main__":
    Application().run()