Re: How to make font lock work with comments?

[Pascal J. Bourguignon]

rusi <rustompmody@gmail.com> writes:

> Im hacking on an apl mode
> In other words emacs sees this as a comment-type char (similar to what
> it says for semicolon in elisp buffers
>
> And yet in an elisp buffer the ; to EOL is red
> but here it is not.

Font locking is a tricky matter. 

(font-lock-add-keywords nil
    '(("⍝.*"                          0 font-lock-comment-face prepend)
     ("[^\\]\"\\([^\"\\]*\\|\\.\\)\"" 0 font-lock-string-face  prepend)))

The main problem is that it uses regular expressions to find the
"keywords", but you want syntax coloring.  However, there's a way to use
it for syntax coloring, since instead of a regular expression, you can
use a function here, which will have to set the "matched regions".

For example, for an assembler, I wrote a function to parse
(syntactically) an assembler line, and matching the fields.  It is
configured with font-lock-add-keywords as:

 (font-lock-add-keywords 
   nil
   (list
    (list
     (function search-asm7090-fields)
     '(1 font-lock-function-name-face)       ; labels
     '(2 font-lock-keyword-face)             ; operation codes
     '(3 font-lock-reference-face)           ; arguments
     '(4 font-lock-comment-face)             ; comments
     '(5 font-lock-preprocessor-face)        ; ibsys
     '(6 font-lock-type-face)                ; cols 72-80
     )))

Of course, you can also implement buffer-wide syntax analysis, and have
these functions just report the findings.

-- 
__Pascal Bourguignon__                     http://www.informatimago.com/
A bad day in () is better than a good day in {}.