Kivy scatter on desktop with size=Window.size - kivy

Question

I am developing an application for Linux desktop using Kivy framework. I am trying to set Scatter size the same as the size of the window.
from kivy.app import App
from kivy.core.window import Window
from kivy.uix.scatter import Scatter
from kivy.graphics import Color, Rectangle
class MyScatter(Scatter):
def __init__(self, *args, **kwargs):
super(MyScatter, self).__init__(*args, **kwargs)
self.size_hint=(None, None)
self.size=(Window.width, Window.height)
with self.canvas:
Color(1, 0, 0)
Rectangle(pos=self.pos, size=(100, 200))
class ScatterApp(App):
def build(self):
return MyScatter()
ScatterApp().run()
When I run the code the scatter immediately reflects my mouse motion and moves rectangle.
When I maximize window it reacts agter I press the button only but also scales and rotates itself as if I used two fingers.
When I use a fixed size (i.e. self.size=(100, 200)) the behavior is identical in both cases and scatter moves after I press the button.
Passing the size as a parameter doesn't change anything.
I don't use kv language.
"Mouse" is touchpad.

Answer 1

Not sure about your mouse problems, but the MyScatter widget will fill the window by default. Your code doesn't reflect the correct size. Try this version:
from kivy.app import App
from kivy.core.window import Window
from kivy.uix.scatter import Scatter
from kivy.graphics import Color, Rectangle
from kivy.clock import Clock
class MyScatter(Scatter):
def __init__(self, *args, **kwargs):
super(MyScatter, self).__init__(*args, **kwargs)
Clock.schedule_once(self.show_size, 0.1)
def show_size(self, *args):
with self.canvas:
Color(1, 0, 0)
Rectangle(pos=self.pos, size=self.size)
class ScatterApp(App):
def build(self):
return MyScatter()
if __name__=="__main__":
ScatterApp().run()