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Extending lua-mode syntax table

From: Niels Aan de Brugh
Subject: Extending lua-mode syntax table
Date: Sun, 4 Apr 2010 22:01:27 +0200


Today I decided to try and improve a little on the handling of long
strings in lua-mode (and possibly long comments after that).
Unfortunately I'm new to Emacs and I'm not sure whether I'm on the
right track.

Needless to say I didn't succeed in my goals and I'm seeking guru-help.

Some context: Long strings in Lua are started by [[ and closed by ]].
Between the brackets the programmer can type zero or more = signs to
make the string delimiter unique.

Reuben Thomas already made a regexp that works fine:


I can use that regexp to highlight the string (font-lock-string-face),
but I'd rather convince Emacs that this text element belongs to the
string class. Lua-mode uses parse-partial-sexp to detect strings. That
information is in turn used to determine indentation, etc.

The first of two questions. I'm trying to assign the right character
class like so:

(defun lua-mode ()
  ;; ....
    (set (make-local-variable 'font-lock-defaults)
                        '(lua-font-lock-keywords nil nil ((?_ . "w"))))

(defvar lua-font-lock-keywords
    ;; .....
     ;; Long strings.
       (1 "\""))

I see no visual impact on the rendering of long strings (i.e. they
don't use the same highlighting as regular strings). Am I doing this

Second, the function that determines whether something is a string
looks like this:

(defun lua-syntax-status ()
  "Returns the syntactic status of the character after the point."
  (parse-partial-sexp (save-excursion (beginning-of-line) (point))

(defun lua-string-p ()
  "Returns true if the point is in a string."
  (elt (lua-syntax-status) 3))

As you can see, the parse-partial-sexp function gets a range of text
from the start of the line until the point. The long strings can span
multiple lines (in fact, that's the whole point). So I'm worried that
the parse-partial-sexp doesn't have enough context to work with. Is
this true? If so, is there a work-around (other than parsing from the
start of the buffer), or do I need to implement something clever and

Any help would be greatly appreciated.


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