gtk:render-focus (context cr x y width height)

context -- a gtk:style-context object
cr -- a cairo:context-t context
x -- a number coerced to a double float for the x origin of the rectangle
y -- a number coerced to a double float for the y origin of the rectangle
width -- a number coerced to a double float for the rectangle width
height -- a number coerced to a double float for the rectangle height

Renders a focus indicator on the rectangle determined by x, y, width, height.