Doing the impossible: magic font-lock-keywords-only changes

[Lennart Borgman]

Todays question:
Can You when You execute this

      (message "YY:before: font-lock-keywords-only =%s in buffer %s,
def=%s" font-lock-keywords-only (current-buffer) (default-value
font-lock-keywords-only))
      (if (nth 1 defaults)
          (set (make-local-variable 'font-lock-keywords-only) t)
        (kill-local-variable 'font-lock-keywords-only))
      (message "YY:after : font-lock-keywords-only =%s in buffer %s,
def=%s" font-lock-keywords-only (current-buffer) (default-value
font-lock-keywords-only))

and gett this output? :

    YY:before: font-lock-keywords-only =nil in buffer only-html.html, def=nil
    YY:after : font-lock-keywords-only =t in buffer only-html.html, def=t

I can. Unfortunately.

However I can only do this magic with MuMaMo. But I do not understand
how it does it. Anyone?

Hint: This is in a call from fontification-functions. And the function
where I added the trace above is font-lock-set-defaults.

I am taking a pause now. Some fresh air.