Function render_focus 

pub fn render_focus(
    context: &impl IsA<StyleContext>,
    cr: &Context,
    x: f64,
    y: f64,
    width: f64,
    height: f64,
)

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

Typical focus rendering:

context

a StyleContext

cr

a cairo::Context

x

X origin of the rectangle

y

Y origin of the rectangle

width

rectangle width

height

rectangle height