Re: changing visuals of code in emacs

[Pascal J. Bourguignon]

Andrei Alexandrescu <SeeWebsiteForEmail@erdani.org> writes:

> Pascal J. Bourguignon wrote:
>> Andrei Alexandrescu <SeeWebsiteForEmail@erdani.org> writes:
>> 
>>> Hello,
>>>
>>>
>>> I'd like to change code visuals for the D programming language as
>>> follows. I'd like the construct:
>>>
>>> Symbol!(balanced_parens)
>>>
>>> to be visualized as:
>>>
>>> Symbol«balanced_parens»
>>>
>>> The chevrons should appear electrically when I type the closing
>>> ")". Note that balanced_parens could in turn nested use of "!()", as
>>> in A!(B!(C)), and they should all be paired using chevrons. The
>>> underlying file should not contain the chevrons, just the ASCII
>>> representation using "!(" and ")".
>>>
>>> I haven't done much elisp programming beyond the common .emacs
>>> configuration tricks, so I don't know where to start. A few searches
>>> suggested that overlays may be what I'm looking for... any ideas and
>>> pointers? Thank you.
>> If you didn't ask for recursion, this could have be done with
>> font-locking.
>> (font-lock-add-keywords nil
>>   '(("\\(!(\\)[^()]*\\()\\)"      0 (progn
>>          (compose-region (match-beginning 1) (match-end 1) ?« 
>> 'decompose-region)
>>          (compose-region (match-beginning 2) (match-end 2) ?» 
>> 'decompose-region)
>>          nil))))
>> But since this uses regular expressions, it won't work for recursive
>> !(...).
>> You can still use compose-region, but you'll have to implement the
>> parsing yourself.  Perhaps this could be hooked on the code doing the
>> parenthesis balancing?
>
> I think I'd be happy with a nonrecursive region to get my feet
> wet. How do I use your font-lock-add-keywords code? I added it to both
> my .emacs and my d-mode.el file, to no avail.

You could run it from a d-mode-hook if it exists, ensuring that
font-lock-mode is enabled.

(add-hook 'd-mode-hook 
          (lambda () 
            (font-lock-add-keywords nil
              '(("\\(!(\\)[^()]*\\()\\)"      0 (progn
                     (compose-region (match-beginning 1) (match-end 1) ?« 
'decompose-region)
                     (compose-region (match-beginning 2) (match-end 2) ?» 
'decompose-region)
                     nil))))
            (font-lock-mode 1)))

-- 
__Pascal Bourguignon__                     http://www.informatimago.com/

Pour moi, la grande question n'a jamais été: «Qui suis-je? Où vais-je?» 
comme l'a formulé si adroitement notre ami Pascal, mais plutôt: 
«Comment vais-je m'en tirer?» -- Jean Yanne