Re: diary font-lock issue

[martin rudalics]

>>`foo-font-lock-keywords' will fail to find a match when the end of
>>`font-lock-fontify-region' is positioned as indicated above.
[...]
>
> Just looking at this quickly, it looks to be doing the same job as the
> regexp I originally quoted, but using a function instead to do the
> match. Setting font-lock-multiline to t in the buffer means that it
> gets added as a property to all fontified regions, so yours is more
> elegant (only adding the property where needed), but the two ought to
> be equivalent, right?

Not really, I put a question mark at the end of the regexp.  Hence I
also match date lines not followed by a =[=]* line.  To handle that very
case - which is the cause of your problem - I use a function.  You
probably could do that more elegantly with anchored matches.

> This all seems very complex. According to:
>
> <http://lists.gnu.org/archive/html/emacs-devel/2006-04/msg00881.html>
>
> "the font-lock-multiline property should be enough in all cases to
> make it unnecessary to use an after-change-function hook."

Indeed, it *should*, eventually ...

> That's a long thread, but AFAICS, it seems that for simple keyword
> fontification, setting font-lock-multiline for the buffer ought to be
> enough.
>
> (Though later on I find:
>
> <http://lists.gnu.org/archive/html/emacs-devel/2006-04/msg01130.html>
>
>     > (i) The matching of keywords which span line breaks;
>     ... setting the font-lock-multiline variable... won't reliably
>     take care of (i)
>
> which confuses me.)

You might have to solve the following problem: Suppose you have the
single line

Friday, May 5, 2006

in your buffer and you type a "=" on the next line as in

Friday, May 5, 2006
=

There's no multiline property around before you type the "=" but you
probably want to highlight the date line after.  That's what my ugly
after-change-hook is for.

> I'm also confused as to why the initial fontification is not working
> as it should. There are no "changes" involved in this instance.
> (Indeed, the fancy diary buffer is not something one edits, so this is
> about as simple as multiline font-lockign can get.)

I explained that at the very beginning of this message.  If you never
edit the buffer you obviously don't need font-lock-multiline and you
don't need the after-change hook either, just use a simplified version
of foo-bar like

(defun foo-bar (bound)
  (and (re-search-forward
        
"\\(\\(?:\\(?:Fri\\|Mon\\|S\\(?:atur\\|un\\)\\|\\(?:T\\(?:hur\\|ue\\)\\|Wedne\\)s\\)day\\)\
, 
\\(?:A\\(?:pril\\|ugust\\)\\|December\\|February\\|J\\(?:anuary\\|u\\(?:ly\\|ne\\)\\)\
\\|Ma\\(?:rch\\|y\\)\\|\\(?:Novem\\|Octo\\|Septem\\)ber\\) [0-9]+, 
-?[0-9]+\n\\)\\(=+\n\\)?" bound t)
       (or (> (match-end 0) (match-end 1))
           (and (= (match-end 1) bound)
                (save-match-data
                  (looking-at "=+\n"))))))

But never try to match things that span two or more lines the way you
did.  It will always fail at boundaries of jit-lock chunks.