Function circle_outline_runs 

pub fn circle_outline_runs(
    center: (i32, i32),
    radius: u16,
    clip: PxRect,
    f: impl FnMut(i32, i32, i32),
)

Calls f(y, x0, x1) for the runs of the outline of the circle of radius round center inside clip (the module’s rule): one pixel a run.