How to add a thin border to a frame?

[Zax]

Hello,

Is there a simple way to draw/add a thin border to a frame, without any .tga file?
Something like CSS attribute border: 1px solid #00ff00

I tried with Backdrop's edgeFile with some built-in texture files but the result is not accurate (the border is not well drawn), at least with small frames like buttons.

My final goal is to write a function like .addBorder(frame, borderWidth, borderColor)