Function objects_json 

pub fn objects_json(d: &Drawing) -> String

Build the JSON per-object geometry array: one entry per emitted <g id="sN"> group, with the shape kind, its bbox in SVG user units (null for invisible shapes), and — when known — the source span of the statement that produced it (file follows the same convention as diagnostics: absent = user input, "circuits" = the -c library, else the copy include name).