Hi Mathieu
    I hope this is better? https://github.com/kivy/kivy/commit/181cdc29caee4db7d72f666b3cb3409a48a778e5\
    It's rather difficult to explain, and I wanted to avoid reference
    the "matrix" (lol) to avoid unnecessary complication?
    ps. Thanks for keeping your eye out. Vigilance is the sign on a
    Ninja! ;-)Mathieu Virbel wrote:
    
      In kivy/graphics/__init__.py:
      > @@ -26,7 +28,15 @@
>          Rectangle(pos=(10, 10), size=(500, 500))
>  
>  The instructions :class:`Color` and :class:`Rectangle` are automaticly added to
> -the canvas object, and will be used when the window drawing will happen.
> +the canvas object and will be used when the window is drawn.
> +
> +.. note::
> +
> +    Drawing instructions are rendered directly by the OpenGL layer,

      This note is not accurate. OpenGL or not, this is not the cause
        of possbile errors here.
        The widget matrix is the window matrix: absolute. Unlike others
        toolking where the canvas start at the same position of the
        widget, this is not the case for us.
        What ever the widget position and size are, the graphics need to
        use them, not forget about it. Or use a relative layout.
      There is no OpenGL involved in it.
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