Function display_bounds_for_source 

pub fn display_bounds_for_source(
    source_id: Option<&str>,
) -> (f64, f64, f64, f64)

Bounds (CG points) of the captured display, from the recording’s screen-source id (ISS-17). "display-<id>" → that display’s main_display_bounds-style rect; primary / window / malformed → the main display (window-source framing is a further refinement). Non-macOS: the 1080p placeholder.