Re: changing visuals of code in emacs

[Andrei Alexandrescu <SeeWebsiteForEmail@erdani.org>]

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.

Thank you,

Andrei