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bug#635: Adding font-lock keywords results in no font-lock at all
From: |
martin rudalics |
Subject: |
bug#635: Adding font-lock keywords results in no font-lock at all |
Date: |
Tue, 05 Aug 2008 15:12:46 +0200 |
User-agent: |
Mozilla Thunderbird 1.0 (Windows/20041206) |
> For many years I had the following statement in my .emacs file:
>
> (defun show-tabs () "Show tabs with a slightly changed background"
> (font-lock-add-keywords nil '(("\t" (0 'tab-face t))) t))
> (add-hook 'font-lock-mode-hook 'show-tabs)
>
> This has worked without any problems up to 22.1.
> In version 22.2 and 23 I do have problems with syntax highlighting due
> to these few lines above in some modes, e.g. when I try M-x list-faces-display
> all colors are gone.
The behavior you observe seems due to the change
2007-06-11 Stefan Monnier <monnier@iro.umontreal.ca>
* font-lock.el (font-lock-add-keywords): In case font-lock was only
half-activated, forcefully activate it completely.
which added the following lines to `font-lock-add-keywords'
(when (and font-lock-mode
(not (or font-lock-keywords font-lock-defaults)))
;; The major mode has not set any keywords, so when we enabled
;; font-lock-mode it only enabled the font-core.el part, not the
;; font-lock-mode-internal. Try again.
(font-lock-mode -1)
(set (make-local-variable 'font-lock-defaults) '(nil t))
(font-lock-mode 1))
What happens appears to be that in any mode that does not specify
`font-lock-keywords' (like `help-mode' or `view-mode' in your case),
(font-lock-mode -1) unfontifies the entire buffer thus removing any
faces assigned earlier by, for example, `list-faces-display'. Since
these faces are not reassigned by font-lock you won't get them back
either :-(
AFAICT, this change also broke `hi-lock-mode' in such buffers.
Get your original behavior back by writing something like
(defun show-tabs () "Show tabs with a slightly changed background"
(unless (or font-lock-keywords font-lock-defaults)
(set (make-local-variable 'font-lock-defaults) '(nil t)))
(font-lock-add-keywords nil '(("\t" (0 'tab-face t))) t))
(add-hook 'font-lock-mode-hook 'show-tabs)
or by removing the offending lines from font-lock.el ;-(
martin