nxml (was Re: Re: Callbacks?)

Martin Duerst wrote:
> At 22:13 05/11/30, Gregg Reynolds wrote:
>  >Have you taken a look at the source for nxml mode?  You might be able 
> to hack it up do do something like this.  As I understand it, in Emacs 
> you can set whatever properties you like on each character in a buffer.  
> See node 32.19, "Text Properties", of the Elisp manual.
> 
> I haven't looked at the actual nxml source, but otherwise,
> that's very much what I have thought about.
> 
Take a look at xmltok.el, starting at "defun xmltok-r".  It uses a 
clever but somewhat hairy method using "symbolic regexp"s and macros to 
handle regexps and get at match data for parsing.  Make sure you 
understand what a "symbolic regexp" is (explained in the code). Pay 
special attention to xmltok+, xmltok-g, and especially xmltok-defregexp. 
  The key macro definition for parsing attributes is

(xmltok-defregexp
  xmltok-attribute
  (let* ...

This creates the symbolic regexp "xmltok-attribute" which is used for 
parsing.  Note that where it is used, it looks like a function e.g.

	(xmltok-attribute regexp)

but it's actually a macro thingee.

My hunch is that we could set some bidi-related text properties for 
att-val delimiters here:

(defun xmltok-scan-attributes ()
   (let ((recovering nil)
	(atts-needing-normalization nil))
     (while (cond ((or (looking-at (xmltok-attribute regexp)) ;GAR: add 
bidi attrs here?
		      ;; use non-greedy group

I hope that helps; I haven't looked much beyond that.  You mentioned 
your students; I'm a lightweight when it comes to Elisp, but studying 
nxml looks like a very good way to become a master elisp hacker.  It 
exercises lots of elisp stuff in interesting ways.  There's also an nxml 
list somewhere.

-gregg