Could someone kindly explain to me this coordinate conversion situation here? I don't get it..

[Philipp Hellmann]

I am trying to understand the coordinates of widgets and their relations to each other.

This is how it looks like

Here is my sample code:

import kivy

kivy.require('1.10.1')

from kivy.app import App

from kivy.base import Builder

from kivy.uix.relativelayout import RelativeLayout

from kivy.graphics import Line

from kivy.uix.label import Label

from kivy.graphics import Color

Builder.load_string("""

#:import random random

<TestScreen>:

   size_hint:.5,.5

   pos_hint: {'right': 0.8,'center_y':0.75}

   canvas:

       Color:

           rgba: [random.random() for x in range(3)] + [0.5]

       Rectangle:

           size:self.size

   Button:

       canvas:

           Color:

               rgba: [random.random() for x in range(3)] + [0.5]

           Rectangle:

               pos: _button.pos

               size:self.size

       id: _button

       text:'PrintPos'

       size_hint: .3,.3

       pos: 200,200

       on_press:root.showPos(*args)

""")

class TestScreen(RelativeLayout):

    def showPos(self, sender):

       print("Pos: {}".format(sender.pos))

       print("Local Pos: {}".format(sender.to_local(*sender.pos)))

       print("Parent Pos: {}".format(sender.to_parent(*sender.pos)))

       print("Parent Local Pos: {}".format(sender.parent.to_local(*sender.pos)))

       print("relative Parent Local Pos: {}".format(sender.parent.to_local(*sender.pos, relative=True)))

       print("Parent Parent Pos: {}".format(sender.parent.to_parent(*sender.pos)))

       print("relative Parent Parent Pos: {}".format(sender.parent.to_parent(*sender.pos, relative=True)))

       print("Widget Pos: {}".format(sender.to_widget(*sender.pos)))

   

class RelativeCoordinatesApp(App):

   def build(self):

       return TestScreen()

if __name__ == '__main__':

   RelativeCoordinatesApp().run()

This is the output:

Pos: [200, 200]

Local Pos: (200, 200)

Parent Pos: (200, 200)

Parent Local Pos: (-40.0, -100.0)

relative Parent Local Pos: (-40.0, -100.0)

Parent Parent Pos: (440.0, 500.0)

relative Parent Parent Pos: (440.0, 500.0)

Widget Pos: (-40.0, -100.0)

How is the Parent Local Pos value calculated?

I cant wrap my head around this.