Function draw_selection_frame 

pub fn draw_selection_frame(
    bbox: Rect,
    mode: Option<ResizeMode>,
    painter: &mut Style<'_, impl Renderer>,
)

Draw the four corner resize handles for bbox. Each handle rests as a small dot and grows into the full handle as the pointer approaches, exactly like the route/new-pin anchor targets. When mode is set, that corner is being resized and draws armed (an inverted filled disk) as click-success feedback.

Growing needs a pointer and a clock, which only a live canvas has (Renderer::animator); offline backends (the SVG exporter) draw the handles statically at full size. The growths are read before anything is drawn, since the animator is borrowed from the same backend the draws go to.