Function build_font_registry

pub fn build_font_registry() -> Option<FontRegistry>

Build a live FontRegistry from the active document’s fonts block, loading each declared source from disk. Sources that fail to read or parse are skipped with a warning on stderr — the registry degrades gracefully so one missing TTF does not take down the rest of the family.

Returns None when the active document declares no families at all (in which case the caller keeps the canvas’ system-font fallback). Callers should hand the returned registry to the canvas via Canvas::set_font_registry; the draw loop already does this at canvas creation time.