Re: How to make font lock work with comments?

["Pascal J. Bourguignon" <pjb@informatimago.com>]

rusi <rustompmody@gmail.com> writes:

> On Dec 30, 7:09 pm, "Pascal J. Bourguignon" <p...@informatimago.com>
> wrote:
>> rusi <rustompm...@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)))
>
> Thanks Pascal.  I gave this (\x235 is that char) and it works

\x235d actually.

> [Else I get some unicode-related messages when I try ot save the el
> file]

I save my files encoded in utf-8.  To be sure, you can add on the first
(or second) line a comment containing "-*- coding:utf-8 -*-".
See File Local Variables in emacs documentation.



> (font-lock-add-keywords 'inferior-apl-mode
>     '(("\x235d.*"     0 font-lock-comment-face prepend)))
>
> I guess the second line is for strings?

Yes.  I wanted to avoid strings containing that character to be colorized
as comments.  The order in font-lock-keywords is important.


> Where do I get all the (typical) faces that should be set up for a
> progmode?

One way to find all the existing faces is to type:

M-x customize-face RET TAB

You can use one of the "standard" font-lock-*-face faces, or you can
also create apl specific faces.


> Ive been trying to copy stuff from scheme.el -- is there a better
> model?


>> 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
>>      )))
>
>
> I dont think I really understand this...  

Check the documentation of the function font-lock-add-keywords:
      C-h f font-lock-add-keywords RET
and the variable font-lock-keywords:
      C-h v font-lock-keywords RET

The numbers refers to the regular expression groups.

For example, if you have a regexpp that matches three different parts,
identified by three regexp groups, you can colorize them differently
with:

(font-lock-add-keywords nil
    '("\\(procedure\\) +\\([A-Za-z0-9]+\\) *(\\(.*\\));"
       (1 font-lock-keyword-face)
       (2 font-lock-function-name-face)
       (3 font-lock-type-face)))


> In any case I guess I dont need much parsing (for apl)

Right.

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