You can use
font-lock-add-keywords to add additional
search-based fontification rules to a major mode, and
font-lock-remove-keywords to remove rules.
font-lock-add-keywordsmode keywords &optional how
This function adds highlighting keywords, for the current buffer or for major mode mode. The argument keywords should be a list with the same format as the variable font-lock-keywords.
If mode is a symbol which is a major mode command name, such as
c-mode, the effect is that enabling Font Lock mode in
mode will add keywords to font-lock-keywords.
Calling with a non-
nil value of mode is correct only in
your ~/.emacs file.
If mode is
nil, this function adds keywords to
font-lock-keywords in the current buffer. This way of calling
font-lock-add-keywords is usually used in mode hook functions.
By default, keywords are added at the beginning of
font-lock-keywords. If the optional argument how is
set, they are used to replace the value of
font-lock-keywords. If how is any other non-
value, they are added at the end of font-lock-keywords.
Some modes provide specialized support you can use in additional
highlighting patterns. See the variables
and java-font-lock-extra-types, for example.
Warning: Major mode commands must not call
font-lock-add-keywords under any circumstances, either directly
or indirectly, except through their mode hooks. (Doing so would lead to
incorrect behavior for some minor modes.) They should set up their
rules for search-based fontification by setting
This function removes keywords from font-lock-keywords
for the current buffer or for major mode mode. As in
font-lock-add-keywords, mode should be a major mode
command name or
nil. All the caveats and requirements for
font-lock-add-keywords apply here too.
For example, the following code adds two fontification patterns for C mode: one to fontify the word ‘FIXME’, even in comments, and another to fontify the words ‘and’, ‘or’ and ‘not’ as keywords.
(font-lock-add-keywords 'c-mode '(("\\<\\(FIXME\\):" 1 font-lock-warning-face prepend) ("\\<\\(and\\|or\\|not\\)\\>" . font-lock-keyword-face)))
This example affects only C mode proper. To add the same patterns to C mode and all modes derived from it, do this instead:
(add-hook 'c-mode-hook (lambda () (font-lock-add-keywords nil '(("\\<\\(FIXME\\):" 1 font-lock-warning-face prepend) ("\\<\\(and\\|or\\|not\\)\\>" . font-lock-keyword-face)))))