Re: progmodes cc: addition of builtin def-const

[Alan Mackenzie <acm@muc.de>]

Hi, Vincent.

Sorry for the delay in answering your proposal.  I've been swithering a
fair bit over it.

On Mon, Dec 03, 2012 at 09:01:54PM +0100, Vincent Belaïche wrote:
> Hello,

> DXL has a number of language specific functions which I think would be
> better to fontify like builtins, similar to what is done in AWK.

As a matter of interest, what is DXL?  All I found on the web was a
language based on XML, not C-like at all.

> On the other hand DXL is more typed than AWK, so the 3 level
> fontification of cc-fonts.el is better to use than do a specific
> fontification like in AWK mode.

OK.

> In order to achieve this goal of reusing cc-fonts, I propose the
> addition of a new lang constant c-builtin-kwds. This allows the
> dxl-mode.el which I am elaborating to plug more readily on EMACS CC
> progmode.

> If nobody objects I would commit the change the patch thereof is herein
> attached.

My first reaction was negative - do we really want extensive use of
c-preprocessor-face-name for builtin functions?  I know AWK Mode does
precisely this, but is it a good thing to encourage?

Then, on the other hand, the new code does nothing which isn't already
inside CC Mode.

To answer my own question, I don't feel we really should encourage this
use of c-preprocessor-face-name.  As a matter of interest, have you tried
using font-lock-add-keywords to get the new keywords fontified?  If so,
how easy/neat is it to do this?  Could you try to persuade me a new
general facility is better than a one-off for DXL Mode?

There were one or two little things about the patch which weren't quite
optimal, see below.

> VBR,
>   Vincent.


> === modified file 'lisp/ChangeLog'
> --- lisp/ChangeLog	2012-12-03 17:23:42 +0000
> +++ lisp/ChangeLog	2012-12-03 19:55:20 +0000
> @@ -1,3 +1,12 @@
> +2012-12-03  Vincent Belaïche  <vincentb1@users.sourceforge.net>
> +
> +	* progmodes/cc-fonts.el (c-basic-matchers-before): Use new lang
> +	constant `c-builtin-kwds' for handling language specific keyword
> +	fontification.
> +
> +	* progmodes/cc-langs.el (c-builtin-kwds): New lang constant for
> +	handling language specific keyword fontification.
> +
>  2012-12-03  Agustín Martín Domingo  <agustin.martin@hispalinux.es>

>  	* textmodes/ispell.el (ispell-init-process)

> === modified file 'lisp/progmodes/cc-langs.el'
> --- lisp/progmodes/cc-langs.el	2012-09-13 18:41:21 +0000
> +++ lisp/progmodes/cc-langs.el	2012-12-03 17:24:59 +0000
> @@ -649,6 +649,15 @@
>  	 (prefix "::")
>  	 (left-assoc ".")))

> +(c-lang-defconst c-builtin-kwds
> +  "Keywords for builtin keywords constants."
> +  ;; This is for functions that are not part of a library but builtin in the
> +  ;; language. AWK mode does not use this constant but could have done
> +  ;; so. Currently this is used only as a hook for languages not yes part of
> +  ;; cc-xxx progmode, like DXL.
> +  t       nil
> +  )
> +
>  (c-lang-defconst c-opt-identifier-concat-key
>    ;; Appendable adorned regexp matching the operators that join
>    ;; symbols to fully qualified identifiers, or nil in languages that

c-builtin-kwds really needs a fuller doc string, since unlike
c-constant-kwds, it doesn't have examples to guide other hackers in its
use.  The comment is really too vague - nowhere does it say what is done
with the supplied functions.  I don't think the offhand remark about AWK
is really helpful.  Something like the following would be better:

"A list of keywords which will get fontified with c-preprocessor-face-name."
;; This is intended for built-in function names in modes derived from CC
;; Mode.

> === modified file 'lisp/progmodes/cc-fonts.el'
> --- lisp/progmodes/cc-fonts.el	2012-01-19 07:21:25 +0000
> +++ lisp/progmodes/cc-fonts.el	2012-12-03 17:26:28 +0000
> @@ -763,6 +763,12 @@
>  	      `((eval . (list ,(concat "\\<\\(" re "\\)\\>")
>  			      1 c-constant-face-name))))))

> +      ;; Fontify builtins keyword constants.
> +      ,@(when (c-lang-const c-builtin-kwds)
> +	  (let ((re (c-make-keywords-re nil (c-lang-const c-builtin-kwds))))
> +	      `((eval . (list ,(concat "\\<\\(" re "\\)\\>")
> +			      1 c-preprocessor-face-name)))))
> +
>        ;; Fontify all keywords except the primitive types.
>        ,(if (c-major-mode-is 'pike-mode)
>  	   ;; No symbol is a keyword after "->" in Pike.

But as I said, I'm not quite convinced that the general facility you've
implemented is a good idea, as compared with each mode (how many are
therre?) which needs it implementing it specially.  What is your feeling
about how many derived modes would benefit from it?

-- 
Alan Mackenzie (Nuremberg, Germany).