font-lock and text mode

[Oliver Scholz <alkibiades@gmx.de>]

I noticed that `hi-lock-mode' doesn't work properly in text mode (CVS
Emacs): after I have added a regexp with `C-x w h', matches already
in the buffer are highlighted, but matching text that I insert after
that is not.

Also it seems to be impossible to add highlighting via
font-lock-keywords to text mode.

(font-lock-add-keywords nil 
                        '(("\\<lirum larum\\>" . font-lock-warning-face)))

I tried a lot to find the reason for this.  Finally I tested whether
font-locking works with a derived mode of text-mode.

(defvar test-mode-font-lock-keywords
  '(("lirum-larum" . font-lock-warning-face)))

(define-derived-mode test-mode text-mode
  "FIXME"
  (set (make-local-variable 'font-lock-defaults)
       '(test-mode-font-lock-keywords t)))

This is fine. My guess was that this has something to do with the
implementation of `global-font-lock-mode', so I tried to call
`global-font-lock-mode-cmmh' manually, but to no avail. Looking at the
expansion of `define-derived-mode' above and experimenting with it, I
found that `kill-all-local-variables' is critical here. This is enough
to enable font-locking:

(progn (kill-all-local-variables)
       (set (make-local-variable 'font-lock-defaults)
	    '((("\\<lirum-larum\\>" . font-lock-warning-face))
	      t)))

So I looked at the code of `kill-all-local-variables'. But I can't
find anything there relating to `font-lock' (except the hook
`change-major-modes', but calling `global-font-lock-mode-cmmh' should
amount to the same).

I am puzzled. What am I missing?

    Oliver
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