the style of focus ring

["zhenghe zhang" <zhenghe zhang gmail com>]

Hi all
Now I am learning GTK+ , and I have two problems, I hope you help me, thank
you!
As followed:
1).when a button obtains the focus , there is a focus ring. 
Now I want to change the style of "focus ring", Through code how to achieve,
but not "rc document".
2).if the button has a style , and I want to change the style. (e.g.
focus-line-width )
Thank you very much
zh