I'm trying to add a border to Kivy Buttons but it doesn't work as expected. For labels my implementation seems to be OK but for buttons it overrides/clears the standard look of the button.
How can I draw the border above the button with-out changing normal behavior? I'd like to implement it like the ButtonBehavior so I can add a border to every Kivy object with a canvas. I've called it BorderBehavior.
Styling dashed, dotted works only for line width of 1 because there is a bug in Kivy (see https://github.com/kivy/kivy/issues/2037) (Need to figure out what's wrong here later.)
I know that drawing a border is possible with a BorderImage but I'd like to add simple borders with-out an image.
Here is how it looks at the moment:
You can find my source code here (the labels can be dragged just for testing purposes to see that the border is always correctly positioned):