Function nearest_anchor_target 

pub(crate) fn nearest_anchor_target(
    data: &Drawing<'_>,
    pointer: Pos2,
    exclude: Option<PinId>,
) -> Option<(PinId, Pos2)>

The nearest pin/anchor to pointer within NEW_PIN_ACTIVATION_RANGE, paired with its stub-end point. exclude skips one anchor (a route’s start, which can’t also be its end).