catching layout-content

[Thomas Morley]

Hi all,
how can I see from inside a procedure that there is indeed an
\override in \layout ?
Below returns a long list, but nothing like the \override

\layout { \override NoteHead.color = #red }

#(pretty-print
  (sort
    (ly:module->alist (ly:output-def-scope $defaultlayout))
      (lambda (p q)
        (symbol<? (car p) (car q)))))

I'm aware using
\layout { \context { \Voice \override NoteHead.color = #red } }
will return a different result, indicating the layout is indeed changed.

Ideally I would love to catch both cases.


Thanks,
  Harm