kivy editable multicolumn list

[Paulo da Silva]

Hi all.
Not sure if this is the place to ask about kivy ...
I apologize if not.

I am playing with the example here
https://gist.github.com/geojeff/4442405

Now I would like to change the background color the editable field.

So I added
	def __init__(self,**kwargs):
		super(EditableLabel,self).__init__(**kwargs)
		with self.canvas.before:
			Color(0,1,0)
			Rectangle(pos=self.pos,size=self.size)
			print(self.pos,self.size)

to class EditableLabel.

But when entering __init__ self.pos and self.size do not have the
correct pos/size for the EditableLabel.

How can I fix this? Please no kv solutions. I need dynamic change it in
a real example.

Thanks for any help.