kivy: how to create a widget that represents a circled letter?

[Coricoco_fr]

solved:

from kivy.app import App
from kivy.uix.widget import Widget
from kivy.graphics import Color, Ellipse
from kivy.uix.label import Label
from kivy.metrics import dp
from kivy.lang import Builder
from kivy.core.window import Window
from kivy.properties import NumericProperty, ReferenceListProperty, ObjectProperty

Builder.load_string('''

<MyCircleWithLetter>:
    letter: "A"
    
    canvas:
        Color:
            rgba: 1, 1, 0, 1
        Ellipse:
            pos: self.center_x - dp(100), self.center_y - dp(100)
            size: dp(200), dp(200)
    Label:
        text: root.letter
        font_size: dp(100)
        pos: root.center_x - dp(50), root.center_y - dp(50)

<Widgetroot>:
    position: position
    MyCircleWithLetter:
        id: position
        pos: root.pos
       
''')

class MyCircleWithLetter(Widget):
    def __init__(self, **kwargs):
        super().__init__(**kwargs)
        pass
    
class WidgetRoot(Widget):
    position: ObjectProperty()
    def __init__(self, **kwargs):
        self.pos = (Window.width//2, Window.height//2)
        super().__init__(**kwargs)
        
        
class MyPaintApp(App):
    def build(self):
        fl = WidgetRoot()
            
        return fl
if __name__ == "__main__":
    MyPaintApp().run()